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Full-wave rectifiers are kind of rectifiers that converts ac to dc that is alternating current to direct current. This type of rectifier allows both halves of the ac input voltage to pass through the circuit. Two diodes are necessary to make a full-wave rectifier.
Full Wave Rectifier Working & Circuit
A full-wave rectifier is shown in the below circuit.
There is a transformer T on the input side. The transformer T steps up or steps down the AC voltage supplied at the primary side. It is a center-tapped transformer. An ac input voltage of V = nVoSinwt is applied in the circuit. N is the turn ratio of the center-tapped transformer. Two diodes are connected to the course. Current flows through one diode for the first half of the cycle and flows through the other diode for the next half of the process. That is how a unidirectional current flow towards the load.
This is a modified and also an improved version of the half-wave rectifier. We use a center-tapped transformer. Each half of the transformer’s secondary has an equal number of turns; the voltage induced in each half of the secondary is equal in values and opposite in phase.
Now for any instance of the input half-cycle, point A has a positive voltage concerning O (center). The lower point B has an equal voltage but negative in magnitude (It is the center-tapped transformer). So, diode D1 conducts current, and diode D2 does not appear at this half of the cycle. For the next half of the process, diode D1 is at revere biased, and diode D2 is forward biased. So, diode D1 does not conduct the current while D2 does for this half of the input cycle. The load current is the sum of current from diode D1 and diode D2 from both the input voltage cycles.
Diodes D1 and D2 are identical, so the average value of load current for a full-wave rectifier circuit is double that of a half-wave rectifier.
As both halves of the cycle passed through the circuit, this is known as a Half wave rectifier.
The significance of the RMS value is that it is equivalent to DC Value.
Provided that RMS value is ≤ Peak Value
Peak Inverse Voltage (PIV):
Peak inverse voltage or PIV is an important parameter. It is defined as the maximum reverse bias voltage applied across the diode before entering the Zenner Region or Breakdown Region.
For a full-wave rectifier. Peak inverse voltage is given as PIV >= 2Vm
If, at any point, PIV<Vm, the diode will be damaged.
The load current of a rectifier circuit is fluctuating and unidirectional. The output is a periodic function of time. Using the Fourier theorem, it can be concluded that the load current has an average value superimposed on which are sinusoidal currents having harmonically related frequencies. The average of the dc amount of the load current is – Idc = 1/2π *∫02πIload d(ωt)
Iload is the instantaneous load current at time t, and is the source sinusoidal voltage’s angular frequency. A more excellent value of Idc implies better performance by the rectifier circuit.
Full Wave Rectifier graph
The following diagram represents the input and output graph.
The form factor of a full-wave rectifier can be defined as RMS’s ratio (Root Means Square) Value of load voltage to the average value load Voltage.
Form Factor = Vrms / Vav
Vrms = Vm/2
Vav = Vm / π
Form Factor = (Vm/√2) / (2*Vm/ π) = π/2√2=1.11
So, we can write, Vrms = 1.11 * Vav.
Ripple Factor
Ripple factor is given as the RMS (Root Means Square) Value of AC Component to the Average value of the output. The output current consists of both the AC and DC components. The ripple factor measures the percentage of AC components present in the rectified output. The symbol represents the ripple factor – γ
The transformer utilisation factor is defined as the DC power ratio supplied to the transformer’s AC power rating load.
TUF = Pdc/ Pac(rated)
Now, to find the Transformer Utilisation Factor, we need the rated secondary voltage. Let us say that Vs. / √2. RMS current through the winding is Im/2.
The average transformer utilization factor comes as =
(0.574 + 0.812)/2 = 0.693
Increase in Transformer utilisation factor suggests a better performance of the full wave rectifier.
Full Wave Rectifier Efficiency
Efficiency of Full Wave Rectifier is defined as the ratio of the DC power available at the load to the input AC power. It is represented by the symbol – η
η = Pload / Pin *100
or, η = Idc2 * R/ Irms2 * R , as P = VI, & V= IR
Now, Irms = Im/√2 and Idc = 2*Im/π
So, η = (4Im2/ π2) / (Im2/2)
η = 8 / π2 * 100% = 81.2%
Efficiency of a ideal Full Wave Rectifier Circuit is = 81.2%
Difference Between Half Wave and Full Wave Rectifier
Subject of Comparison
Half Wave Rectifier
Full Wave Rectifier
No. of diodes used
Only One diode is used
Two diodes are used
Current flow
Current flows in the circuit for only the positive half of the input cycle.
Current flows in the circuit for all half of the input cycle.
The frequency of the load current in the half-wave rectifier is the same as the input frequency supply.
The frequency of the load current is twice the input power supply.
Ripple Factor
Ripple factor is 1.21
Ripple factor is 0.482
Transformer Utilization Factors
Transformer Utilization Factor is 0.287
For a full-wave transformer, TUF is = 0.693
Efficiency
The efficiency of a half-wave rectifier is less than a full-wave rectifier and is = 40.56%
Efficiency is more than half-wave rectifier and is = 81.2%
Problems with Full Wave Rectifiers
1. A full-wave rectifier has a load of 1 kilo- ohm. The applied AC voltage is 220 V (RMS value). If the diodes’ internal resistances are neglected, what will be ripple voltage across the load resistance?
a. 0.542 V
b. 0.585 V
c. 0.919 V
d. 0.945 V
The ripple voltage is = γ * Vdc / 100
Vdc = 0.636 * Vrms * √2 = 0.636*220*√2 = 198 V.
The ripple factor of a full wave rectifier is 0.482
Hence the ripple voltage = 0.482*198/100 = 0.945 V
2. If the peak voltage of a full-wave rectifier circuit is 5 V and the diode is silicon diode, what will be the peak inverse voltage on the diode?
Peak inverse voltage is an important parameter defined as the maximum reverse bias voltage applied across the diode before entering the breakdown region. If the peak inverse voltage rating is less than the value, then breakdown may occur. The diode’s peak inverse voltage is twice the peak voltage = 2Vm -Vd for a full-wave rectifier. Vd is the diode cut-in voltage. Now for a silicon diode, the cut-in voltage = 0.7 v. So, peak inverse voltage =2* 5 -0.7volts = 9.3 volts.
3. A input of 200Sin 100 πt volt is applied to a full-wave rectifier. What is the output ripple frequency?
V= VmSinωt
Here, ω= 100
Frequency is given as – ω/2 = 100/2 = 50 Hz.
The output frequency of a center-tapped frequency is doubled the input frequency. Thus the output frequency = 50*2 = 100 Hz.
4. What is the main application of a rectifier? Which device does the opposite operation?
A rectifier transforms the AC voltage to the DC voltage. An oscillator converts a DC voltage to AC voltage.
Rectifiers play a crucial role in the field of electrical engineering and power electronics. They are essential components in electronic circuits that convert alternating current (AC) to direct current (DC). In this section, we will explore the definition of rectification and the role of rectifiers in changing AC to DC.
Rectification is the process of converting an AC electrical signal into a DC signal. AC voltage and current change direction periodically, while DC voltage and current flow in only one direction. Rectifiers are electronic devices that enable this conversion by utilizing the properties of semiconductor diodes.
Role of Rectifiers in changing AC to DC
The primary function of a rectifier is to convert the alternating current (AC) waveform into a direct current (DC) waveform. AC voltage and current oscillate between positive and negative values, while DC voltage and current maintain a constant polarity and direction. Rectifiers ensure that the output waveform has a unidirectional flow, allowing for the consistent supply of power to electrical devices.
Rectifiers are widely used in various applications, including power supplies, battery chargers, and electronic devices. They are especially important in situations where a constant and steady DC voltage is required. By converting AC to DC, rectifiers enable the efficient utilization of electrical energy and power in electrical systems.
There are different types of rectifiers, including half wave rectifiers and full wave rectifiers. In this article, we will focus on the half wave rectifier, which is a simple and commonly used rectifier circuit.
In the next section, we will delve into the working principle of a half wave rectifier and understand how it converts AC to DC.
Half Wave Rectifier
The half wave rectifier is a fundamental electronic circuit used in power electronics and electrical engineering. It is a simple yet important component that converts alternating current (AC) into direct current (DC). In this section, we will explore the explanation, circuit diagram, working principle, derivation of formulas and equations, graphical representation, and calculations associated with the half wave rectifier.
Explanation of Half Wave Rectification
Half wave rectification is the process of converting an AC waveform into a unidirectional DC waveform. It is achieved by using a diode, which is a semiconductor device that allows current to flow in only one direction. The diode acts as a switch, allowing current to pass through when it is forward-biased and blocking current when it is reverse-biased.
Circuit Diagram of Half Wave Rectifier
The circuit diagram of a half wave rectifier is quite simple. It consists of a diode, a load resistor, and an AC input source. The diode is connected in series with the load resistor, and the AC input source is connected across the diode. The load resistor is used to limit the current flowing through the circuit.
Working Principle of Half Wave Rectifier
The working principle of a half wave rectifier is based on the fact that a diode allows current to flow in only one direction. When the AC input signal is positive, the diode is forward-biased and conducts current. This positive half-cycle of the AC waveform appears across the load resistor, resulting in a positive half-cycle of the output waveform. However, when the AC input signal is negative, the diode is reverse-biased and blocks current flow. As a result, the negative half-cycle of the AC waveform is suppressed, and no output is obtained during this period.
Derivation of Half Wave Rectifier Formula and Equations
The formulas and equations associated with the half wave rectifier can be derived by analyzing the circuit. The key parameters to consider are the peak value of the input voltage, the peak value of the output voltage, and the average value of the output voltage. By applying basic principles of electrical circuits and diode characteristics, these values can be calculated.
Graphical Representation of Half Wave Rectifier
A graphical representation of the half wave rectifier waveform helps visualize the conversion process. The input waveform, which is an AC signal, is transformed into a unidirectional output waveform. The positive half-cycle of the input waveform appears as the positive half-cycle of the output waveform, while the negative half-cycle is suppressed.
Calculation of Average Output Voltage
The average output voltage of a half wave rectifier can be calculated using the formula:
[ V_{text{avg}} = frac{V_{text{p}}}{pi} ]
where ( V_{text{avg}} ) is the average output voltage and ( V_{text{p}} ) is the peak value of the input voltage.
Calculation of RMS Value of Current
The RMS value of the current flowing through the load resistor in a half wave rectifier can be calculated using the formula:
[ I_{text{rms}} = frac{I_{text{p}}}{sqrt{2}} ]
where ( I_{text{rms}} ) is the RMS value of the current and ( I_{text{p}} ) is the peak value of the input current.
Calculation of Peak Inverse Voltage (PIV)
The peak inverse voltage (PIV) is the maximum voltage that appears across the diode when it is reverse-biased. In a half wave rectifier, the PIV is equal to the peak value of the input voltage.
In conclusion, the half wave rectifier is a fundamental component in power electronics and electrical engineering. It converts AC into DC by utilizing the properties of a diode. Understanding the circuit diagram, working principle, and calculations associated with the half wave rectifier is essential for designing and analyzing electronic circuits.
Form Factor of Half Wave Rectifier
The form factor of a half wave rectifier is a measure of how closely the rectified waveform resembles a pure DC (direct current) waveform. It is an important parameter to consider when designing and analyzing rectifier circuits. The form factor is defined as the ratio of the RMS (root mean square) value of the output voltage to the average value of the output voltage.
The form factor of a half wave rectifier can be calculated using the following formula:
Form Factor = (Vrms) / (Vavg)
where Vrms is the RMS value of the output voltage and Vavg is the average value of the output voltage.
The form factor provides an indication of the quality of rectification achieved by the half wave rectifier. A perfect rectifier would have a form factor of 1, indicating that the output waveform is a pure DC voltage with no ripple. However, in practice, the form factor of a half wave rectifier is always greater than 1 due to the presence of ripple in the output waveform.
Ripple Factor of Half Wave Rectifier
The ripple factor of a half wave rectifier is a measure of the amount of AC (alternating current) ripple present in the rectified output waveform. It is defined as the ratio of the RMS value of the AC component of the output voltage to the average value of the output voltage.
The ripple factor can be calculated using the following formula:
Ripple Factor = (Vrms(ac)) / (Vavg)
where Vrms(ac) is the RMS value of the AC component of the output voltage and Vavg is the average value of the output voltage.
The ripple factor provides an indication of the amount of ripple present in the output waveform. A lower ripple factor indicates a smoother output waveform with less AC ripple, while a higher ripple factor indicates a more distorted waveform with greater AC ripple.
In a half wave rectifier, the ripple factor is relatively high compared to other rectifier configurations. This is because the rectification process only utilizes one half of the input waveform, resulting in a higher amount of ripple in the output waveform. To reduce the ripple factor and achieve a smoother output waveform, additional filtering techniques such as the use of capacitors can be employed.
Overall, the form factor and ripple factor are important parameters to consider when designing and analyzing half wave rectifier circuits. They provide valuable insights into the quality of rectification achieved and the amount of ripple present in the output waveform. By understanding and optimizing these factors, engineers can design more efficient and reliable rectifier circuits for various applications.
Full Wave Rectifier
A full wave rectifier is a type of rectifier that converts alternating current (AC) into direct current (DC). It is an essential component in power electronics and is widely used in various electronic circuits. In this section, we will explore the introduction, circuit diagram, working principle, advantages over half wave rectifier, and the importance of a center-tapped transformer in a full wave rectifier.
Introduction to Full Wave Rectification
Full wave rectification is the process of converting the entire cycle of an AC waveform into a unidirectional DC waveform. Unlike a half wave rectifier, which only utilizes one half of the input waveform, a full wave rectifier makes use of both halves. This results in a more efficient conversion of AC to DC.
Circuit Diagram of Full Wave Rectifier
The circuit diagram of a full wave rectifier consists of a transformer, two diodes, and a load resistor. The transformer is used to step down the input voltage to a suitable level. The diodes, which are semiconductor devices, allow the flow of current in only one direction. The load resistor is connected in parallel with the diodes to provide a path for the current to flow.
Working Principle of Full Wave Rectifier
The working principle of a full wave rectifier is based on the concept of diode rectification. When the inputAC voltage is applied to the primary winding of the transformer, it induces a voltage in the secondary winding. This induced voltage is then applied to the diodes, which conduct current in only one direction. As a result, the negative half-cycle of the input waveform is rectified by one diode, while the positive half-cycle is rectified by the other diode. This ensures that both halves of the input waveform are converted into a unidirectional DC waveform.
Advantages of Full Wave Rectifier over Half Wave Rectifier
A full wave rectifier offers several advantages over a half wave rectifier. Firstly, it provides a higher average output voltage compared to a half wave rectifier. This is because a full wave rectifier utilizes both halves of the input waveform, resulting in a higher overall rectification efficiency. Secondly, a full wave rectifier produces a smoother output waveform with less ripple. This is due to the fact that the rectification occurs during both the positive and negative half-cycles of the input waveform. Lastly, a full wave rectifier has a higher efficiency compared to a half wave rectifier, as it utilizes the entire input waveform.
Importance of Center Tapped Transformer in Full Wave Rectifier
A center-tapped transformer is an essential component in a full wave rectifier. It provides a means of obtaining two equal and opposite voltages, which are required for the rectification process. The center tap of the transformer is connected to the ground, while the two ends are connected to the diodes. This allows the diodes to conduct current in opposite directions during each half-cycle of the input waveform. The center-tapped transformer ensures that the rectification process is carried out effectively, resulting in a smooth and efficient conversion of AC to DC.
In conclusion, a full wave rectifier is a crucial component in power electronics and electronic circuits. It offers advantages over a half wave rectifier, such as higher average output voltage, smoother output waveform, and higher efficiency. The presence of a center-tapped transformer is essential for the proper functioning of a full wave rectifier. By understanding the working principle and circuit diagram of a full wave rectifier, we can appreciate its importance in converting AC to DC for various electrical applications.
Comparison between Half Wave and Full Wave Rectifiers
Rectifiers are electronic circuits used to convert alternating current (AC) into direct current (DC). They are essential components in various electrical devices and systems. Two commonly used rectifiers are the half wave rectifier and the full wave rectifier. While both serve the purpose of converting AC to DC, there are significant differences between the two. Let’s explore these differences and understand the advantages and disadvantages of each.
Key Differences between Half Wave and Full Wave Rectifiers
Half Wave Rectifier
A half wave rectifier is the simplest form of rectifier circuit. It uses a single diode to convert the positive half of the AC waveform into DC. The negative half of the waveform is blocked, resulting in an output waveform that contains only the positive half cycles. Here are the key differences between a half wave rectifier and a full wave rectifier:
Efficiency: The efficiency of a rectifier refers to how effectively it converts AC to DC. In this aspect, the half wave rectifier falls short. It has lower efficiency compared to a full wave rectifier due to the fact that it utilizes only half of the input waveform.
Output Waveform: The output waveform of a half wave rectifier is characterized by a pulsating DC signal. It contains only the positive half cycles of the input waveform. As a result, the output voltage is not constant and has a higher ripple factor compared to a full wave rectifier.
Voltage Ripple: The voltage ripple is a measure of the variation in the output voltage. In a half wave rectifier, the voltage ripple is higher due to the absence of the negative half cycles. This can lead to fluctuations in the output voltage, which may not be suitable for certain applications.
Full Wave Rectifier
A full wave rectifier, on the other hand, utilizes both halves of the input waveform to produce a smoother DC output. It employs either two diodes or a bridge rectifier circuit to achieve this. Here are the key differences between a half wave rectifier and a full wave rectifier:
Efficiency: The full wave rectifier is more efficient than the half wave rectifier. By utilizing both halves of the input waveform, it effectively doubles the output voltage and reduces the voltage ripple. This makes it more suitable for applications that require a stable and constant DC voltage.
Output Waveform: Unlike the half wave rectifier, the full wave rectifier produces a continuous DC output waveform. It contains both the positive and negative half cycles of the input waveform, resulting in a smoother output voltage.
Voltage Ripple: The full wave rectifier has a lower voltage ripple compared to the half wave rectifier. This is because it utilizes both halves of the input waveform, reducing the fluctuations in the output voltage.
Advantages and Disadvantages of Half Wave Rectifier
Advantages:
– Simple and inexpensive circuit design
– Requires fewer components compared to a full wave rectifier
– Suitable for applications where a low output voltage is acceptable
Disadvantages: – Lower efficiency compared to a full wave rectifier
– Higher voltage ripple
– Not suitable for applications that require a stable and constant DC voltage
Advantages and Disadvantages of Full Wave Rectifier
Advantages: – Higher efficiency compared to a half wave rectifier
– Lower voltage ripple
– Suitable for applications that require a stable and constant DC voltage
Disadvantages:
– More complex circuit design compared to a half wave rectifier
– Requires additional components such as diodes or a bridge rectifier circuit
– Relatively higher cost compared to a half wave rectifier
In conclusion, both the half wave rectifier and the full wave rectifier have their own advantages and disadvantages. The choice between the two depends on the specific requirements of the application. While the half wave rectifier is simpler and cheaper, it has lower efficiency and higher voltage ripple. On the other hand, the full wave rectifier offers higher efficiency and lower voltage ripple, but at the cost of a more complex circuit design.
Applications of Half Wave Rectifier
The half wave rectifier is a fundamental component in electrical engineering and power electronics. It finds numerous applications in various electronic devices and circuits. Let’s explore some common uses and the significance of the half wave rectifier in these applications.
Common Uses of Half Wave Rectifier
The half wave rectifier is widely used in electronic circuits where the conversion of alternating current (AC) to direct current (DC) is required. Here are some common applications of the half wave rectifier:
Battery Chargers: Half wave rectifiers are commonly used in battery chargers to convert the AC voltage from the power source into DC voltage suitable for charging batteries. The rectifier ensures that the battery receives a steady and constant flow of current in one direction, enabling efficient charging.
Power Supplies: Half wave rectifiers are used in power supplies to convert the AC voltage from the mains into a DC voltage that can be used to power electronic devices. The rectifier ensures a smooth and constant DC output, which is essential for the proper functioning of electronic components.
Voltage Multipliers: Half wave rectifiers are also used in voltage multiplier circuits, where they help increase the voltage level. These circuits are commonly used in applications such as cathode ray tubes (CRTs), X-ray machines, and other high-voltage applications.
Signal Demodulation: In communication systems, the half wave rectifier is used for signal demodulation. It extracts the original modulating signal from the carrier wave by rectifying the amplitude variations of the modulated signal.
Significance of Half Wave Rectifier in Electronic Devices
The half wave rectifier plays a crucial role in various electronic devices and circuits. Here are some key reasons why it is significant:
Conversion of AC to DC: The primary function of the half wave rectifier is to convert the AC voltage into DC voltage. This conversion is essential for powering electronic devices that require a constant and steady DC supply.
Simplicity and Cost-effectiveness: The half wave rectifier is a simple circuit consisting of only one diode and a load resistor. Its simplicity makes it cost-effective and easy to implement in electronic devices and circuits.
Efficiency: While the half wave rectifier is not as efficient as full wave rectifiers, it still offers reasonable efficiency in converting AC to DC. The rectifier allows only half of the input waveform to appear at the output, resulting in a lower average DC voltage. However, for applications where high efficiency is not critical, such as low-power devices, the half wave rectifier is a suitable choice.
Waveform Filtering: The output waveform of a half wave rectifier contains significant ripple due to the absence of a smoothing capacitor. However, in some applications where a small amount of ripple is acceptable, the half wave rectifier can be used without a filter capacitor, reducing the complexity and cost of the circuit.
In conclusion, the half wave rectifier finds a wide range of applications in electronic devices and circuits. Its simplicity, cost-effectiveness, and ability to convert AC to DC make it an essential component in power supplies, battery chargers, voltage multipliers, and signal demodulation circuits. While it may not offer the same level of efficiency as full wave rectifiers, its significance in various applications cannot be overlooked.
Precision Half Wave Rectifier
A precision half wave rectifier is a type of electronic circuit used to convert an alternating current (AC) electrical signal into a direct current (DC) signal. It is commonly used in various applications, including audio amplifiers, power supplies, and signal processing circuits. In this section, we will explore the definition and purpose of a precision half wave rectifier, as well as its circuit diagram and working principle.
Definition and Purpose of Precision Half Wave Rectifier
A precision half wave rectifier is designed to rectify only the positive half cycles of an AC waveform while blocking the negative half cycles. Unlike a standard half wave rectifier, which uses a diode and a capacitor to rectify the waveform, a precision half wave rectifier provides a more accurate and precise rectification process.
The purpose of a precision half wave rectifier is to ensure that the rectified output waveform closely follows the positive half cycles of the input waveform. This is particularly useful in applications where a precise and accurate rectification is required, such as in instrumentation and measurement systems.
Circuit Diagram and Working Principle of Precision Half Wave Rectifier
The circuit diagram of a precision half wave rectifier typically consists of an operational amplifier (op-amp), a diode, and a feedback resistor. The op-amp is configured in an inverting amplifier configuration, with the diode connected in the feedback loop.
The working principle of a precision half wave rectifier is as follows:
During the positive half cycle of the input waveform, the diode conducts and allows the current to flow through the feedback resistor and into the inverting input of the op-amp. This causes the op-amp to amplify the voltage across the feedback resistor.
The amplified voltage is then fed back to the non-inverting input of the op-amp, which causes the op-amp to output a negative voltage. This negative voltage effectively cancels out the positive half cycle of the input waveform, resulting in a rectified output waveform that closely follows the positive half cycles.
During the negative half cycle of the input waveform, the diode blocks the current flow, preventing any feedback to the op-amp. As a result, the op-amp does not produce any output voltage during the negative half cycles, effectively blocking them from the rectified output waveform.
By utilizing the feedback resistor and the inverting amplifier configuration of the op-amp, a precision half wave rectifier ensures that the rectified output waveform closely follows the positive half cycles of the input waveform, providing a precise and accurate rectification process.
In conclusion, a precision half wave rectifier is a specialized electronic circuit used to accurately rectify the positive half cycles of an AC waveform. By utilizing an operational amplifier, a diode, and a feedback resistor, it provides a precise and accurate rectification process, making it suitable for applications where precise rectification is required.
Half Wave Rectifier Efficiency
A half wave rectifier is an electronic circuit that converts alternating current (AC) into direct current (DC). It is a simple and commonly used circuit in power electronics and is widely used in various applications. One important aspect to consider when analyzing the performance of a half wave rectifier is its efficiency.
Calculation of Efficiency for Half Wave Rectifier
Efficiency is a measure of how effectively a device converts input power into useful output power. In the case of a half wave rectifier, efficiency is calculated by comparing the DC power delivered to the load with the AC power supplied to the rectifier. The formula for calculating efficiency is as follows:
Efficiency = (DC power output / AC power input) * 100%
To calculate the DC power output, we need to determine the average value of the rectified waveform. Since a half wave rectifier only conducts during the positive half cycle of the input waveform, the average value can be calculated by taking the integral of the positive half cycle and dividing it by the time period. This can be expressed as:
DC power output = (Vp / π) * (1 - cos(π))
Where Vp is the peak value of the input voltage waveform.
The AC power input can be calculated by multiplying the RMS value of the input voltage waveform with the RMS value of the input current waveform. For a half wave rectifier, the RMS value of the input current can be calculated as:
Irms = (Im / √2)
Where Im is the peak value of the input current waveform.
Once we have the DC power output and the AC power input, we can substitute these values into the efficiency formula to determine the efficiency of the half wave rectifier.
It is important to note that the efficiency of a half wave rectifier is relatively low compared to other rectifier configurations, such as full wave rectifiers. This is because a half wave rectifier only utilizes half of the input waveform, resulting in a lower average output power. However, despite its lower efficiency, a half wave rectifier is still widely used in applications where cost and simplicity are more important factors than efficiency.
In summary, the efficiency of a half wave rectifier can be calculated by comparing the DC power output to the AC power input. Despite its lower efficiency compared to other rectifier configurations, the half wave rectifier remains a popular choice in various applications. Conclusion
In conclusion, the half wave rectifier is a simple and commonly used circuit that converts an alternating current (AC) input signal into a pulsating direct current (DC) output signal. It utilizes a diode to allow only the positive half cycles of the input signal to pass through, while blocking the negative half cycles. This results in a rectified output waveform with a significant amount of ripple. Despite its simplicity, the half wave rectifier has certain limitations, such as low efficiency and high ripple content. However, it still finds applications in various electronic devices where a low-cost and basic rectification is sufficient. Overall, the half wave rectifier serves as a fundamental building block for more complex rectifier circuits and provides a basic understanding of rectification principles.
Frequently Asked Questions
Q: What is a half wave rectifier and how does it work?
A: A half wave rectifier is an electronic circuit that converts alternating current (AC) into direct current (DC) by allowing only one half of the input waveform to pass through. It uses a diode to block the negative half of the waveform, resulting in a pulsating DC output.
Q: What is the derivation of a half wave rectifier?
A: The derivation of a half wave rectifier involves analyzing the circuit and understanding the behavior of the diode. It includes calculations of voltage and current waveforms, as well as the average and peak values of the rectified output.
Q: What is the difference between a half wave rectifier and a full wave rectifier?
A: A half wave rectifier allows only one half of the input waveform to pass through, while a full wave rectifier allows both halves of the waveform to be utilized. This makes a full wave rectifier more efficient in converting AC to DC compared to a half wave rectifier.
Q: Why is a full wave rectifier center tapped?
A: A full wave rectifier is center tapped to provide a balanced output waveform. The center tap allows the use of two diodes in a bridge configuration, which ensures that both halves of the input waveform are rectified, resulting in a smoother DC output.
Q: What is the circuit diagram of a full wave rectifier?
A: The circuit diagram of a full wave rectifier consists of a transformer, a center-tapped secondary winding, and four diodes arranged in a bridge configuration. This arrangement allows for full wave rectification of the input AC waveform.
Q: What is the efficiency of a half wave rectifier?
A: The efficiency of a half wave rectifier is the ratio of DC power output to the AC power input. It is typically lower than that of a full wave rectifier due to the fact that only half of the input waveform is utilized.
Q: How can I calculate the output voltage of a half wave rectifier?
A: The output voltage of a half wave rectifier can be calculated by multiplying the peak value of the input voltage by the rectification factor, which is typically around 0.5.
Q: What is the symbol for a half wave rectifier?
A: The symbol for a half wave rectifier is a triangle with a vertical line intersecting it, representing the diode used in the rectification process.
Q: When is a half wave rectifier used?
A: A half wave rectifier is used in applications where a lower DC output voltage is acceptable, such as in battery charging circuits or low power applications.
Q: What is the purpose of a capacitor in a wave rectifier circuit?
A: The capacitor in a wave rectifier circuit is used to smooth out the pulsating DC output by storing electrical energy during the positive half of the waveform and releasing it during the negative half. This helps in reducing the ripple voltage.
Frequently asked questions on step up transformers.
Definition of Step up Transformer
A transformer transfers electrical energy. Step up transformer is one type of electrical transformer. A step-up transformer increases the input voltage and provides increased voltage as the output. In the process of transferring the power, the power and the frequency of the power remains constant.
Step-up transformer construction means the construction of core and construction of the windings.
Core Construction:
Transformer’s core is a specially build part which is created with spongy metals. The reason behind choosing the spongy metals for core is that magnetic flux can pass through those types of metals. The core is surrounded by the coils. The design of the wrapping decides the types of the core.
A transformer core will be called as a Closed core transformer if the core is bounded by the coils from the outside.
A transformer is called Shell core transformer if the core is surrounded by the coils from inside.
For industry purpose a shell type of core is being chosen over a core type because a core type has the shortcoming of ‘leakage Flux’.
Windings:
Windings are another important part of transformer which are basically coils of wire and carries current. The Primary and secondary windings are made up of copper and Aluminium. Primary windings take the input voltage and the secondary voltage provides the output voltage. The classification of step-up or step-down is done here. Now, for a step-up transformer the number of turns in secondary windings is more than the number of turns in secondary windings.
Step Up Transformer Working principle
Step up transformer has the same principle as a normal transformer. Step-up transformers take a lower voltage and provides a higher voltage. Their working is based upon the laws of Faraday and the turn ratio theory.
Inside a step-up transformer, current flows due to the input voltage. The current flow induces a magnetic flux around the windings and the flux passes through the core of the transformer.
The voltage in the secondary windings is induced by the secondary-winding.
The next working principle is the turn ratio. Turn ratio is given as the ratio of primary winding’s turn number to the secondary winding’s turn ratio. It is also described as the ratio of the input voltage to the output voltage.
Turns ratio = Nprimary/Nsecondary =Vprimary/Vsecondary ———————- (i)
Using the (ii) marked equation we try to calculate the secondary voltage. It is clear that the input voltage is constant. Now changing the turn ratio, we can get the wanted output voltage. A step-up transformer is used to produce a higher voltage at the output side. That is why the Ratio of (Nsecondary/Nprimary) is fixed to greater than 1.
Now, from the equations, we can observe that the Nsecondary will be greater unlike step-down transformer. That is why a step-up transformer consists of higher number of turns in the secondary windings.
Applications in Power Systems: Step-up transformer is one of the most important part of power distribution system. A step-up transformer helps to step-up the supplied voltage as per the need.
Electronics device and Instruments: Step-up transformers is used inside numerous electronics devices and instruments. Devices like rectifiers, ADC and DAC converters use this type of transformer.
Electric motor and generators, microwave ovens, X-Ray machines and various home appliances use to step up transformers.
Frequently asked questions on step up transformers
1. How do you identify a step up and step down transformer?
A step up transformer supplies increased voltages on the load whereas a step down transformer supplies reduced voltages on the load. Measuring the input voltage at the primary winding and output voltage at the secondary windings, one can identify the type of transformer. One can check the current value of input and output also. If the current value is more than the supplied, then that is step up type, else that is step down. This was a process. Another process will be to check the turn ratio. If the turn ratio is less than one, then it is step up else it is step down transformer.
Checking the types of wire will be another way. For a step up transformers, primary windings have thicker wire density than the wire density of secondary windings.
A small step up transformer
2. What is the need of a step-up transformer?
A step-up transformer delivers increased supplied voltages to its load. So, if there is a need to step-up or increase the supplied voltage for our workings, then it is advised to use a step-up transformer. But that the current value gets decreased. So if we need a higher voltage source with the same current, then a step up transformer would not serve our purposes.
3. What is the purpose of a step up transformer?
Step up transformer helps to increase the voltage. So, the purpose is relatively straight, that is to step up the voltage supplied to it.
4. What is the turn ratio for a step up transformer?
Turn’s ratio is an important parameter of electrical transformers. It is given by the ratio of the primary winding’s number of turns to the secondary winding’s number of turns.
Turns ratio = Nprimary/Nsecondary
Nprimary is the primary winding’s number of turn and Nsecondary is the secondary winding’s number of turns.
Step up transformer has no ideal turns ratio. But in general, the turn ratio is less than 1 in case of a step-up transformer.
5. Write about practical significances of Step-Up Transformers
Step up transformers are very much important for our daily life. It is quite impossible to supply electric if there are no step-up transformers. In a power distribution system, when power is supplied from the power stations, the supplied voltage gets decreased due to the resistance of the supplying conductors. Step-up transformers are required at this time to increase the voltage again keeping the power constant. That is the practical significance of a step-up transformer.
6. Differences between a step-up transformer and step-down transformer?
The objective of step-up and step-down transformer differentiates the transformers. The objective of step-up transformer is that it step-up the voltage provided and step-down transformer provides the decreased supplied voltage. Some other differences are given below.
7. Does a step up transformer increase current?
No, a step up transformer does not increase current. Instead, it increases the voltage and decreases current. The power of the signal remains constant, though.
8. Number of turns of a winding of an Electrical transformer is 3000. Another winding has number of turns = 1500 where an AC voltage of 50 volts is applied. Find out the voltage at the lesser number of turns. Find out the type of transformer.
Voltage is applied at the 1500 turn side. So, that is the primary winding and the number of turns of wire = 1500. Let’s say that is Np.
3000 turn side is the secondary side. So this is the secondary winding and the number of turns of wire = 3000. Let’s say that is ns.
50 volt is supplied at the primary side, so that is primary voltage and let’s say that = Vp
We have to calculate the voltage at the secondary side; let’s say that = Vs.
We know that turn ratio = Np/Ns
That is also= Vp/Vs
So, Np/Ns = Vp/Vs
Or, Vs = (Ns/Np) * Vp
Substituting the values, we get-
Vs = (3000/1500) * 50
Or, Vs = 100 volt
The voltage at the secondary side will be = 100 volt.
Now as we can see, the voltage is higher than the supplied voltage, so this is a step up transformer.
A transformer transfers electrical energy. Step down transformer is one kind of it. A step-down transformer decreases the voltage applied on primary windings and supplies reduced voltage on the secondary side. However, the power and frequency remain constant in the process.
The construction process of a step-down transformer lies in its core and windings, and it is very much similar to a step-up transformer.
Construction of Core of a Transformer:
Core of a transformer is made of soft iron-like metals. It allows the magnetic flux to pass through it. The coils of both the windings are wrapped around the core. The core can be of two types based on the wrapping up of the locks. If the coils are wrapped outside the body, then that is Closed Core Transformer. If the windings are inside the iron core, then that will be Shell Core Structure. A closed core type transformer suffers a problem of ‘Leakage Flux’ while a shell type does not. That’s why a shell core structure is more preferred rather than a closed core.
Windings are the conductors of current inside the transformer. They are made of a coil of wires. The material of the wire is copper or aluminium. Windings are of two types – Primary windings and Secondary windings. Primary windings receive the applied voltage, and the secondary windings supply the induced voltage to load. Though electrical energy transfers from the primary side to secondary windings without metallic contacts—the main classification parameter to decide whether a transformer is a step up or step down lies here.
In case of a step-down transformer, the number of turns in primary windings is more than the number of turns in the secondary windings. However, the density of wire is thinner in primary windings than the thickness of the secondary windings.
The working principle of a step-down transformer is the same as a typical transformer. A step-down transformer gives higher output voltages than a lower input voltage and works on Faraday’s law and Turn Ratio.
Due to the applied voltage in the primary windings, the current flows through the wires. The flow of alternating current generates magnetic flux around the windings. The core of the transformer allows this magnetic flux to flow through it.
Change in magnetic flux further induces a voltage in the secondary windings.
Now the turn ratio factor comes into action.
Turns ratio = Np/Ns =Vp/Vs ———————- (i)
Or, Vs = Vp *(Ns /Np) ——————— (ii)
Here, Np = number of turns in the primary windings.
Ns = number of turns in the secondary windings
Vp = voltage at the primary side
Vs = voltage at the secondary side.
Now in the equation (ii), we are calculating Vs – the secondary voltage. We can see Vp is constant as the applied voltage is constant. Now increasing or decreasing the (Ns/Np) ratio, we will able to get our desire voltage at the output side. While using a step-up transformer, our motive is to generate lesser voltage than the input. So, we have to keep the Ratio of (Ns/Np) less than 1.
That means the value of Np should be higher than the magnitude of Ns. As we know, Np is the number of turns in the primary windings, that’s why a step-down transformer is designed with higher no. of turns in the primary winding side. As mentioned earlier, the power of the electrical signal remains the same. The voltage gets reduced, and to keep the power constant, the current gets increased. The frequency of energy also remains unchanged.
Transformers have various applications. Step down transformer is designed to do some specific tasks and has a wide range of applications in both electrical and electronics circuitries.
Power System: Step down transformers are used in power distribution systems. In a various phase of supplying power, step down transformers is used to reduce voltage whenever necessary.
Electronic devices: Step-up transformers are used in various electronics device where the device works on lower voltages than the supplied voltage. Tools like adapters of different electronic devices and low voltage applications use this type of transformers.
Transformers, which we found at streets near our home step down transformers.
Frequently asked questions on a step down transformer
1. Does a step down transformer decrease current?
No, a step down transformer does not decrease or reduce current. Instead, it reduces the voltage and increases current. The power of the signal remains constant, though.
2. Why do we need to step-up transformers?
The name of the transformer helps us to find out what it does. A step-down transformer delivers reduced supplied voltages to its load. So, when we need to step down or reduce the voltage provided for our workings, then we should use a step-down transformer. But that the current value gets increased. So if we need to minimise voltage source with the same current, then a step-down transformer would not serve our purposes.
3. A transformer has 2000 turns of copper wire wrapped in a side, and 1000 turns of copper wire surrounded at another side. If an AC voltage of 440 volts is applied at 2000 turn side, what will be the voltage at the 1000 turn side? Also what type of transformer is this?
Voltage is applied at the 2000 turn side. So, that is the primary winding and the number of turns of wire = 2000. Let’s say that is Np.
1000 turn side is the secondary side. So this is the secondary winding and the number of turns of wire = 1000. Let’s say that is ns.
440 volt is supplied at the primary side, so that is primary voltage and let’s say that = Vp
We have to calculate the voltage at the secondary side; let’s say that = Vs.
We know that turn ratio = Np/Ns
That is also= Vp/Vs
So, Np/Ns = Vp/Vs
Or, Vs = (Ns/Np) * Vp
Substituting the values, we get-
Vs = (1000/2000) * 440
Or, Vs = 220 volt
The voltage at the secondary side will be = 220 volt.
Now, as we can see, the voltage is lower than the supplied voltage, so this is a step-down transformer.
4. Write some differences between step up and step down transformers
The fundamental difference of step up and step down transformers lies in their working. Step-up transformers increase the supplied voltage, whereas step down transformers reduces that. Here are some of the more differences. Click Here!
5. Practical Significance of Step-Down transformers
Step down transformers have impacts on our day to day life. The power which generates at a power station is of high voltages (Range of Megawatt to Gigawatt). If there are no step-down transformers, then there would not be electricity in households. When we need to transfer power from power stations to the home, then it is necessary to use a step-down transformer. Using a step-down transformer, we can reduce the high voltage and can be supplied to houses.
6. What is the turn ratio for a step-up transformer?
The turn’s ratio of a transformer is an essential parameter for the calculation of power. It is given by the balance of the number of turns of the wire in primary windings to the number of the arches of the wire in secondary windings. The equation gives the ratio –
Turns ratio = Np/Ns
Np is the number of turn in the primary windings, and Ns is the number of bend in the secondary windings.
Step down transformer has no ideal turn’s ratio. It varies as per the need. But to work as a step-down transformer, the turn ratio must be greater than unity.
A typical transformer can be defined as “A device that transfers electrical energy between electrical circuits.” It is a passive and static device. A power transformer is one of its kind. Power transformers are used to interface step down and step up voltages in the power distribution system.
A typical power transformer has a life span of around 30 years.
A power transformer has the same components as a normal one. Additionally, it has a cooling system and a metallic skeleton, which is laminated with sheets. Depending on the core structure, a power transformer may be either shell type or core type. This may also be three-phase or single phase-type. A three-phase can be made from three single-phase transformer.
Primary and secondary windings are wrapped using conductors either from inside or from outside the core. Single-phase and three-phase both the transformers need ‘bank’ to place the windings. If we use three single-phase transformers, then it is necessary to identify each bank isolated from others. If one of the banks fails, then also the transformer will ensure continuous service. But in the case of a single three-phase transformer, it won’t work if a bank fails.
All these settings with the core are kept inside a skeleton. The skeleton is absorbed inside a fire-protected oil. The oil both does the job of isolation and cooling. There is busing (isolators), which allows the conductor to do their job without interfering with the outer structure. Transformers need a cooling device too. A fan or some other process may serve the process.
Transformers are rated based on the power it can deliver to the load. If a transformer gives 5 volts and 4 amperes current as output, then the transformer’s rating will be 5*4 = 20-volt ampere. That’s why transformers are rated in Volt – Ampere (VA) or Kilovolt – Ampere (kVA). It usually work for higher voltages and are rated in kilovolt ampere.
A power transformer is a costly part of a distribution system. If the power rating isn’t done correctly, then the transformer may be burnt out. So, it is necessary to rate a power transformer accurately. The current value can be calculated using the diameter of the coil of the windings. The voltage can be calculated using the number of turns or using the turns ratio.
Power transformer losses
A power transformer suffers loss as it is not an ideal transformer. A transformer loss means loss of power. Losses of the transformer can be divided into four categories. They are –
A. Core Loss / Iron Loss (Hysteresis Loss & Eddy Current Loss)
B. Dielectric Loss
C. Copper loss or Ohmic Loss
D. Stray Loss
A. Core Loss / Iron Loss:
These losses are also termed as “No Load Losses”. This transformers suffer such losses whenever it is plugged in with power even it has no load connected with it on the secondary side. These types of losses are constant and do not fluctuate. Iron loss is also of two kind –
a. Hysteresis losses
b. Eddy current losses
a. Hysteresis losses:
An alternating magnetizing force occurs inside the core of the transformer. Due to the magnetizing leverage, a hysteresis loop traced out and power dissipated in the form of heat. Hysteresis losses cause a 50% to 80% no-load loss.
Ph = η * Bmax * n * f * V
Ph = Hysteresis Loss
η = Steinmetz hysteresis coefficient
Bmax = Maximum flux density
n = Steinmetz exponenet
f = frequency of magnetic reversals per second
V = volume of magnetic material
b. Eddy Current Loss:
Eddy current loss occurs due to Faraday’s law of induction. An emf is induced in the core circuit due to the magnetic flux. This emf cause flow of current through the core structure as it is made up of iron. This current is known as Eddy Current. Eddy current is not useful for working in this circuit. So, the power loss due to this current is known as eddy current loss. Eddy current losses are accountable for 20% to 50% no-load loss.
The loss is given by –
Pe = Ke * Bmax2 * f * V * t2
Pe = Eddy Current loss
Ke = Eddy current constant
Bmax = Maximum flux density
f = frequency of magnetic reversals per second
V = volume of magnetic material
t = magnetic thickness
B. Dielectric Losses:
Insulators placed inside transformers are the reason behind this loss. It is not a significant loss and contributes 1% of the total no-load losses.
C. Copper loss or Ohomic loss:
This type of loss in a power transformer can be called Load Losses as transformers suffer this type of loss due to short circuit conditions or when connected with the load. The resistance of the wire’s windings is the source of this loss. As most of the cables are made up of copper, the loss is named after that.
D. Stray Loss:
This loss occurs due to the leakage flux. The leakage flux depends on several parameters like – winding’s geometrical structure, the tank’s size, etc. Changing these parameters can also reduce loss. It is a negligible loss.
There are some other losses too. One of them is Auxiliary losses. The cooling system of the transformer causes this type of loss. Also, imbalanced and distorted power results in some extra losses.
Power Transformer Efficiency
The efficiency of an Electrical device is given as the ratio of output power to the input power. It is given by – η.
η = Output / Input * 100%
In a practical scenario, a transformer has losses, as mentioned earlier. This loss is numerically equal to the difference between the Input power and Output power, that is –
Loss = Input Power – Output Power
Or, Output Power = Input Power – Loss
Now, efficiency can be written –
η = (Input Power-Loss) / Input Power * 100%
η = 1- (Loss / Input Power) * 100%
It can also be written as –
η = (V2I2Cosϕ / ( V2I2Cosϕ+ Pi+ Pc ))* 100%
Where,
V2 = Secondary voltage
I2 = Secondary current
Cos ϕ = Power Factor
Pi = Iron Loss / Core Loss
Pc = Copper Loss
A large power transformer can achieve efficiency by up to 99.75%, and a small one can achieve efficiency by up to 97.50 %. If a power transformer’s efficiency stays in a range of 98 to 99.50%, it will be considered good.
The need for power is increasing by leaps and bound. In the case of the distribution of power, a power transformer is one of the essential tools needed. Though these are designed for higher efficiency, the need is high for more efficiency with a concern towards the environment and reduced usage of power. The reduction of losses is the way towards this goal.
Power transformer Application (Power transformer in a substation)
Transformers are one of the essential and most incredible innovations in the field of Electrical Engineering. Power transformers have the most use in the power distribution system. Some of the applications are –
Power transformers are used in power generation and distribution systems.
Power transformers are used in Sub-stations. A substation transforms higher electrically voltages to lower voltages, and a power transformer does this work. these are the most critical device of a power substation.
To reduce power losses in power transmission. Transformers help to minimize power, and thus electricity can be supplied throughout the areas.
To step up and step-down voltages as per the need.
Power transformers work continuously, ensuring supply for 24 * 7. Thus, when we need to do always, a transformer can be used.
These are also find application in Earthing transformers, isolation transformers.
Power transformer maintenance
Power transformers are expensive, bulky, and an essential part of a power distribution system. So, a transformer needs a high quality of maintenance. Maintenance can be two types – a daily basis and at the time of emergency. Regular maintenance is highly recommended for this type of transformer, which is placed in a substation. Some maintenance types are given below –
Regular Maintenance:
Checking of oil level
To keep the oil level at the desired level.
To seal up leakage if any detected.
To replace the silica gel if the colour changes to pink.
Monthly Maintenance:
Oil level to avoid damage.
To check up the bushings.
Cleaning of the skeleton.
Half Yearly Maintenance:
To check the IFT, DDA, flashpoints.
To check acidity, water content, and dielectric strength.
Annual Maintenance:
Check the condition of the oil—the situation in terms of moisture content and dielectric strength.
To check up on all alarm and control switches.
Measuring and checking the earthing connection.
Checking of bushings and cleaning them up.
To check a press release device.
Power transformer failure
A typical electrical transformer is quite complex in its circuitries. A power transformer is more complicated as it has some additional elements. A transformer fails by burning out or shut down of a transformer. A transformer’s failure may occur due to several reasons. Mechanical faults, periodic maintenance, natural calamity like lightning may lead a transformer to destruction.
Transformers generates heat during operation. If there are low-quality material for isolation, then the generated heat would lead towards burning.
Overloaded condition is another cause for transformers.
Old transformers can cause failure. Mechanical faults are prominent for old transformers.
If the oil’s moisture content fluctuates from the rated values, that may also lead to failure.
The power failure may be prevented by doing regular maintenance. Information based on previous failures also helps to detect signs of a power failure before the incident occurs.
Difference between Step up and step down transformer
Difference between single phase and three phase transformer
Types of Transformers
There are many types of transformers based on classification parameters described below. We will discuss some of the transformer types and their workings. List of transformers we will discuss are the followings –
There are different types of transformer classification parameters based on which we can classify the transformer. Some of them are –
Voltage Class: Transformer can be classified based on the voltage used by them. From a few volts to megavolt amount of voltage can be used by transformers.
Power Rating: Transformers have ratings range from few Volt-Amperes to mega Volt-Amperes.
The number of turns in primary and secondary windings: Step down transformer, step-up transformer.
Construction of core: Depending on the transformer’s core construction, they can be classified into two types. They are shell types and core types.
Cooling Type: Transformers can be classified upon the cooling types. There are several types of transformer – self-cooled, oil-cooled, forced cooled, etc.
Application type: Based on transformer’s various applications like – energy transfer, power distribution, voltage-current stabilizer, isolation, etc., they can be classified into enormous kinds.
Ideal Transformer
Ideal transformers are theoretical transformer that suffer no losses and provides 100% efficiency. An ideal transformer can not be made in reality and present only in imagination.
Real Transformers
Every transformer which we can use in the real world is real transformer.
A real transformer can not achieve 100% efficiency as it will suffer some loss of power. There are many types of transformer power-loss can be found. Some of them are – Eddy current loss, Hysteresis loss, dielectric loss, etc.
Step-up transformers
This types of transformer increases voltage, which is applied to primary windings. The secondary windings supply the higher voltage.
The number of turns of the secondary transformer is higher than the number of turns in the primary windings.
Step-up transformers found its application in transmission line carrying high voltage.
Step-down transformers
This types of transformers does the opposite of a step-up transformer.
Step-down transformers reduce the voltage that is applied to its primary windings. The secondary windings supply the lower voltage. Many home appliances, power distribution systems, and many other electrical fields use this type of transformer.
Power transformers
Power transformer is the one particularised for the distribution of power. They are very high rated transformers and are designed for 100% efficiency. They are extensive and useful for delivering needed and limited power for consumers.
Transformer working on faraday’s law and having two windings are single-phase transformers. The windings are known as primary and secondary windings. Without varying the frequency and power, this transformer transfers AC energy.
Three single-phase transformers are connected to form a three-phase transformer. All three primary windings are combined to form a single primary winding, and also all three secondary windings are combined to form a single secondary winding. Star and delta are the types for primary and secondary connections. The combination of primary and secondary windings are all possible combination of star and delta type.
This types of transformer is generally used for industrial purposes.
Assembling of three single-phase transformer is less costly than buying a three-phase transformer.
A centre tapped transformer works almost in the same way a normal transformer works. The only difference is that its secondary windings has two parts and from that individual voltages can be acquired. The tapping point lies in the centre of the secondary windings and that divides the secondary windings. The tapping point provides a common connection for opposite and equal secondary voltages.
Diagrammatic Representation of a Centre Tapped Transformer
Instrument transformers
Instrument transformer is a special type of transformer used for transforming or isolation of current and voltage. It is a high accuracy device. An instrument transformer’s main use is to isolate high voltage connected primary windings from the meter connected with the secondary windings.
It has two types. The series-connected type is known as the current transformer, while the parallel-connected transformer is known as potential or voltage transformer. Current transformer steps down the current while the voltage transformers do the same for voltage of a supplied power.
Some advantages of using Instrument transformer are that – large current and voltage of Alternating Current power can be measured by using a low power rated instrument transformer, many measuring instruments can be connected using a single instrument transformer to power system, measuring instruments can also be standardized.
Another special type of transformer is the pulse transformer. It is used for transmitting rectangular electrical pulses. It transmits pulse of voltages between load and the windings. It has high open-circuit inductance, distributed capacitance, and low leakage induction. Depending on the types, it has several applications. Small versions are used in digital logic circuits. Medium versions are used in power-controlling systems. In contrast, larger versions are used in the power distribution system. Various pulse transformers have a wide range of applications like radar, power semiconductors, and high energy power applications.
There are some parameters which measures the performance of a pulse transformer. Some of them are – repetition rate, pulse width, duty cycle, current, frequency, input – output voltages, etc.
The main advantages of a pulse transformers includes that they are small in size, less costly, provides a high isolation voltage and operates at high frequency. The disadvantage includes – saturation current of the core can get reduced because of the direct current through the primary windings.
The transformers used in the radio frequency domain is known as RF transformer. This devices transfers energy in circuits with the help of electromagnetic induction. Steel as a core structure is prohibited in this type of transformer. It has several types too. Air core(low inductance, PCB use), Ferrite core(baluns for TV and radios), and transmission line transformers are some types. Low power circuit is ideal for the use of this transformers. Some important specifications of a RF transformers are – range of operating frequency, bandwidth, unbalance amplitude and phase, operating temperatures etc.
Audio Transformers
The transformers used in audio circuits are known as audio transformer. Audio transformer has various applications.
Previously audio transformers were made to isolate different telephone systems while keeping their power supplies isolated. Carrying an audio signal is its main objective. It can be used to match impedance like low impedance loudspeaker can be matched with high impedance amplifiers.
Audio transformers also do interconnection of professional audio system components, elimination of buzz and hum. Loudspeaker transformer, inter-stage and coupling transformers, small-signal transformers are some of its types.
A transactor is a combined device of the reactor (inductor or choke coil) and a transformer. Air – core present in the device used to limit the coupling between windings.
Difference between Step up and Step down transformer
Subject of Comparison
Step down transformer
Step up transformer
Number of turns in windings
Higher no. of turns in primary windings, lower no. of turns in secondary windings.
Lower no. of turns in primary windings, higher no. of turns in secondary windings.
Working
Reduce the input voltage applied in the primary windings.
Increases the input voltage applied in the primary windings.
Voltage -Current
High input voltage, Low output voltage and high current in the secondary side.
Low input voltage, high output voltage and low current in the secondary side.
Size of conductor
Secondary windings are made up of thick insulated copper wire.
Primary windings are made up of thick insulated copper wire.
Power Rating
Comparatively lower than Step-up transformer. The range lies under 110 volts.
Comparatively higher than step down transformers. Rated above 11,000 volts.
Uses
Many home appliances, voltage converters.
Power distribution system, X-Ray machines etc.
Types of Transformer, Table – 1
Difference between Single phase and three phase transformer
““Any changes in the coil of wires’ magnetic-fields, will cause an induction of emf. The magnitude of the induced potential is identical to the flux’s changing rate.
It can be written as –
E = – N * dϕ/dt
E is the induced emf, & N, ϕ is the number of turns and the magnetic flux produced, respectively.
The negative sign represents that the change in the magnetic field’s direction is opposite to induced emf. It is also known as Lenz’s law.
Now, we know that transformers have two windings. The alternating power is applied to the primary windings. The flow of current causes generation of a magnetic field around it. This property is known as mutual inductance. Now the current flows according to Faraday’s Law. The maximum strength of the magnetic field will be equal to d ‘phi’/dt. Magnetic lines of force now expand outside from the coil. The soft iron core concentrates the field lines and forms a path. The magnetic fluxes connect the primary windings as well as the secondary windings.
Now, as the flux also passes through the secondary windings, a voltage generates there. The induced emf’s magnitude will be given according to Faraday’s law. It will be = N * dϕ /dt.
The frequency and power of the supplied voltage never change in the whole process.
f is the frequency of the flux and N is the number of turns
Now, E = N * dϕ/dt
or, E = N * d (ϕm sin (2 * π * f * t)) /dt
or, E = N * 2 * π * f * ϕm * cos (2 * π * f * t)
For E =Emax, cos (2 * π * f * t) = 1
Emax = N * 2 * π * f * ϕ m
Now, Erms = Emax / √ 2
Erms = N * 2 * π * f * ϕm / √2
Erms = 4.44 f * N * ϕm
This is known as Transformer EMF Equation.
Losses of a Transformer
Loss in an electrical device or circuit means loss of power. A real transformer has different types of losses, but an ideal transformers never suffers a loss. There are several types of loss inside a transformer. Some of them are –
A. Core Loss / Iron Loss
B. Copper loss or Ohmic Loss
C. Stray Loss
D. Dielectric Loss
A. Core loss / Iron Losses:
The loss occurs due to alternating flux, inside the iron core is known as Core Loss or Iron loss. This type of losses are known as No Load Losses.
There are two categories of core loss. They are –
i) Hysteresis Loss
ii) Eddy Current Loss
i) Hysteresis Loss –
An alternative magnetic force generates in the core of the transformer. That magnetizing force causes a hysteresis loop and that causes hysteresis loss.
Ph = η * Bmax * n * f * V
Ph = Hysteresis Loss
η = Steinmetz hysteresis coefficient
Bmax = Maximum flux density
n = Steinmetz exponenet
f represents the magnetic reversal per second
V = volume of magnetic material
Hysteresis loss contributes 50% of no load loss.
ii) Eddy Current Loss –
Faraday’s Laws are behind the cause of Eddy Current Loss. The magnetic-fluxes cause a potential in the core. Now, due to this emf, current flows. This current is termed as Eddy Current and it is an undesired current. Loss due to this current is Eddy Current Loss.
The eddy current loss is expressed as –
Pe = Ke * Bmax2 * f * V * t2
Pe = Eddy Current loss
Ke = Eddy current constant
Bmax refers to the maximum flux density and f is the frequency of the magnetic reversal per second.
V = volume of magnetic material
t = magnetic thickness
B. Copper loss or Ohomic Loss:
This type of loss occurs due to the windings’ wire resistance. If Ip, Rp is current and resistance of primary winding and Is, Rs is current and resistance of secondary windings, then the loss will be given by the equation –
Po = Ip2Rp + Is2Rs
As the wires are of coppers’, the loss is termed as Copper loss. This type of loss is also known as Load Losses because this loss occurs only when load is connected with the secondary windings.
C. Stray Loss:
The reason behind such losses is the leakage field. It is a negligible loss.
D. Dielectric Loss:
The transformer’s insulator causes this type of loss.
There are also losses due to distorted voltage and currents.
The efficiency is the ratio of the produced power in the input to the supplied power of the output. It is represented as – η.
η = Output power /Input Power * 100%
In an ideal transformer, η comes as 1, which means Output power is equal to the input power. But in reality, a transformer suffers losses.
Loss = Input Power – Output Power
Or, Output Power = Input Power – Loss
So, Efficiency –
η = (Input Power – Loss) / Input Power * 100%
η = 1 – loss/ Input Power * 100%
Frequently Asked Questions
1. How is a transformer rated?
Transformers are rated in volt-amperes or kilo-volt-amperes (kVA). This rating indicates that the primary windings and the secondary windings are designed to tolerate the rated power.
2. How many types of Transformers are there?
There are many types of transformers based on different parameters. Some of them are –
3. A transformer has a turn’s ratio of 16 to 4 or 4. If the transformer secondary voltage is 220 V, determine the primary voltage.
We know that
Turns ratio =NpNs =VpVs
Here, Np = 16
Ns =4
Vs = 220 v
we have to find Vp
so Vp = Np*Vs/Ns = 16 * 220 / 4
Vp = 480 volt.
So the primary voltage was 480 volt.
4. What is the Reversibility of Transformer Operation?
Reversibility of Transformer Operation means using the transformer from backward. That is, giving the secondary windings an input voltage and connecting load at the primary windings.
5. Do the transformers perform in DC voltage?
No, a transformer does not perform in DC voltage. Applying Dc voltage will cause over hitting of the primary windings as the signal finds it a short-circuit.
6. What is Impedance matching?
The concept of impedance matching is that when a source voltage is connected to load, the load get the maximum power if the impedance of load is equal to the impedance of the impedance of the fixed internal source .It is one of the application of transformers.
7. A single phase transformer is with a rating of 2 kilo volt ampere has a 400v at primary windings and a 150v at secondary windings. Find out the primary and secondary full load current of the transformer.
Primary full-load current = 2kVA x 1000 / 400 V = 5 A
Secondary full-load current = 2kVA x 1000 / 150 V = 13.33 A
8. A transformer has 500 turns in the primary windings and 20 turns in the secondary windings. Find out –
a) The secondary voltage if the secondary circuit is open and the primary voltage is 100 v
b) Find out the current in primary and secondary windings when the secondary winding is connected to a resistance load of 16 ohms.
We know that turns ratio is given by
Turns ratio = Np/Ns = Vp/Vs
Np is the number of turns in primary windings.
Ns is the number of turns in secondary windings.
Vp is the voltage at primary side.
Vs is the voltage at secondary side.
Now we can write
Vs = (Ns * Vp) / Np
Or, Vs = (20*100)/500 V
Or, Vs = 4 V
Now for the second case, we know that power remains unchanged while transferring energy through a transformer.
We can write,
Pp = Ps
Where Pp is the power in primary side and Ps is the power from secondary side.
Pp = Vp * Ip
Ps = Vs * Is
Ip is the current in primary side and Is is the current in secondary side.
So, Vp *Ip = Vs * Is
Or, Ip = (Vs * Is) / Vp
Or, Ip = ((Vs*(Vs/Rs) / VpFrom ohm’s law V= IR, thus I = V/R, Here Rs is the resistance of the secondary coil.
Or, Ip = (Vs * Vs )/ (Vs * Rs)
Or, Ip = 4*4 / 100*16, Substituting the values and Rs = 16 ohm was given in the question.
So, Ip = 10 mili – ampere.
And, Is = Vs/ Rs
Is = 4/16 A = 0.25 A
To know more about transformers and electronics click here
As the name suggests, an Electrical transformer transfers energy. A formal transformer definition will be –
“It is a device that transfers electrical energy between electrical circuits.”
It is a passive device. It uses Faraday’s law to transfer energy without any metallic contact. Electrical transformers are one of the useful and needed device for the power distribution.
History related to transformers
Miksa Deri, Otto Blathy and Karoly Zipernowsky are considered to be first designer of the first transformer. They also implemented transformer for commercial systems. Though the Law of induction was given by Faraday in 1830’s and Rev. The induction coil was invented by Nicholas Callan in the year 1836. In the meantime Thomas Alva Edison came up with the idea of Electric Bulb in the year 1882.
Basic Structure of Electrical transformers
A single phase electrical transformer consists of three main components. They are – Primary Windings, Secondary Windings & the Magnetic Core.
Primary Windings – It is the part that is connected with the source. It is made up of coils of wire. Magnetic flux initially produces here.
Secondary Windings – It is the part that is connected with the load. It is also made up of coils. There is a turn’s ratio that defines the number of turns of the wire to make both the windings’ coils. There is no metallic connection between primary windings and secondary windings, as mentioned before.
Magnetic Core – It is the iron structure that wraps up both the primary and secondary windings. It is a soft iron core, made up of small elements to reduce the core’s losses.
The construction of Electrical transformers depends on how the primary and secondary windings are wrapped around the iron core structure.
There are two categories of transformers. One is Closed-core type and another is Shell-core type.
A. Closed Core Transformer –
Here, both the windings are wrapped from outside of the core. (Both windings means – Primary Windings and Secondary Windings). In this construction, windings wrap-up every legs of the core. Half of the primary windings and half of the secondary windings are kept on over other densely on each leg. Magnetic flux passes by this process and increases magnetic coupling. This type of transformer has a drawback, known as – ‘leakage flux.’
Structures of of core type transformers
B. Shell Core Transformer –
In this type, both the primary and secondary windings are inside the iron core. Here, the iron core forms a shell-like Structure for the windings, that’s why it is known as Shell Core Transformer. The windings share the same center leg, which has a cross-sectional area twice as the outer legs. This type of transformers overcome the issue of ‘leakage flux.’
Windings: Windings are the current-carrying part of the transformer. Mainly copper or aluminium wire is used to make the coil of the windings. Transformer coils and windings can be classified into two main categories. They are – Concentric Coils and Sandwich Coils. Sandwich Coils are generally used in Shell Type Transformer. Alternate discs are made to spiral form.
There are also Helical Windings, which are used in low voltage, high power applications. There are some insulators inside every type of windings. Insulators are one of the important elements for electrical transformers.
Cooling: Cooling of a device helps the machine to operate more years flawlessly. Some electrical transformers need forced cooling, and some are self-cooling types. Forced cooling includes cooling by oil, water, or both. Large transformers with high power ratings are filled with transformer oils, which cool and insulate windings. Some transformers are filled with gases for cooling.
Insulation: Insulation is necessary between turns of windings, between two windings, between core and windings. Layers of papers and polymer films are used as insulators. Large insulators use transformer oil as insulation purposes.
Bushing: Bushing is a hollow electrical insulator that allows a conductor to pass through a barrier. Large, high rated transformers has bashings made up of porcelain or polymers.
The polarity check of Electrical Transformers
An Electrical transformer’s polarity is defined as the direction of induced emf in both the primary and secondary windings. It is of two types –
A. Additive Polarity
B. Subtractive Polarity
A. Additive Polarity
-In this type of polarity, the same polarity terminals are connected in both the windings.
B. Subtractive Polarity
– In this type of polarity, different polarity terminals are connected in both the windings.
What does the transformer do?
Electric transformers increases or decreases the supplied voltage and current. It does not change the frequency or the power of the supplied electrical signal. The need for using a transformer is that electrical appliances need a certain amount of voltage, which is lower or higher than the supplied power. For example, a LED which works on 1.5 volts – 2 volts will blow out if we connect it to a normal household rated power supply. So we need to use a step down transformer to use the LED.
Click hereto know about Working Principles, Efficiency and Losses of a transformer.
Application of a Transformer
Transformers has a lot of applications in today’s world. Some of them are –
i) Power Distribution:
A large amount of voltage is produced in the power stations. But we cannot use that voltage directly for our household applications. In this time, a transformer comes into action. Transformers stepped down the voltage to our required voltage. This type of transformer is known as power transformers. There are also transformers which steps up the voltage. Because of this type of transformer it is possible to provide electricity to houses.
This type of transformers allows telephonic circuits to allow a two-way conversation over a single pair of wire. They also interconnections between audio systems. It can be used to match impedance like low impedance loudspeaker can be matched with high impedance amplifiers.
Three phase transformers have wide use in industrial purposes where single phase transformers can not serve the purposes.
Instrument transformers can isolate two device or system using its properties.
Radio frequency transformers or RF transformers are used in Radar like devices and has application in radio frequency domain.
Pulse transformers are used for transferring electric pulses in electronic circuits, digital circuits and in power distribution and controlling system.
Advantages & disadvantages of using a Transformer
Advantages of Electrical transformers
Transformers are used for various purposes because of its advantages. Some of the advantages are –
Transmits Power: Transformers allow transmitting of electrical signal over long distance. The resistance of the transmission line get reduced after increasing the voltage and that is possible only by transformers. Thus, the power loss is less and electricity can be supplied to every household. Otherwise the resistance would be so high that it is quite impossible to supply.
Continuous workings: Transformers can work continuously over long times. It does not need to switch off in a day or give rest.
Low Maintenance: Transformers not only works continuously but also they need not high maintenance. Checking oil, cleaning the parts are the only maintenance a transformer needs. Also, the maintenance does not cost much and also not time consuming.
No delay: Transformers has no delay while starting. It starts operation immediately. Once a transformer is implemented, it starts immediately.
Efficient: Though transformers suffer losses but they are efficient enough for distribution economically. Almost 95% efficiency is achievable.
Disadvantages of using Electrical Transformers
Few disadvantages are –
Larger in size : Though there are transistors that are small in size but as the voltage rating increases the transformer size get increased too. Not only the basic structure increases, the cooling system size get increased too. So it takes a lot of space to accommodate.
Requires a cooling system: Transformers operates continuously and it produces a lot of heat. So to operate in a efficient way, a transformer need a cooling system attached with it.
AC working only: Transformer works only for alternating current or AC voltages as it need time varying current to produce magnetic flux. Connecting with a DC voltage will burn out the transformer.
To define a rheostat, we need to know what is Resistor or Resistance. Resistors are electrical devices that are to controls the flow of current. A formal rheostat’s definition will be –
“Rheostat is an element of an electrical circuit whose resistance value can be changed whenever needed, that means a variable resistor.”
It is a three-terminal device, of which two are usable. There is a slider as a moving terminal, and only one is usable out of two fixed terminals. A typical rheostat also consists of a resistive material and a slider.
What does a rheostat do
The basic principle of this device is simple. In electrical circuits, whenever we need to change the resistance value, a rheostat comes into action. If we need to increase the flow of current – we will increase the resistance of the device. When we need to decrease the current flow in the circuit, we will raise the resistance value.
How does a rheostat work
Rheostat works on the property of resistance. The resistance of a material (let’s say wire) depends linearly with the length and inversely with the cross-section area.
R∝L/A
R=?L/A,
?is the resistivity of the material
Thus, if we keep the cross-section area constant, increasing the length will increase the resistance. As shown in the figure, the slider- is moved through the resistive element for linear rheostats. It moves either from input to output or vice-versa. The effective length changes accordingly. While moving the wiper towards the output port, the effective length decreases, causing a fall in resistance, increasing the current.
Working of a Rheostat
Rheostat symbol
Institute of Electrical and Electronics Engineers(IEEE) and the International Electrotechnical Commission(IEC), has defined two different rheostat’s symbols.
The IEEE standard Rheostat symbol
The IEC standard Rheostat symbol
Rheostat Switch
Rheostats control current of a circuit by controlling the resistance of the circuit. A rheostat, thus, can be used as as switch to vary the resistance as well as the current of the circuit. That is why a rheostat is used as switch.
RheostatsApplications
A rheostat has its application in an electrical circuit. When there’s a need to control the flow of current with a change of time. Based on the property of current controlling, some of the purpose of rheostat is given below.
Why is a rheostat connected in series?
To connect rheostat in the circuit, we must place it in series, not in parallel. The flow of current is much in a lesser resistive path. Thus, when it finds an option between a less resistive path and a more resistive path, it always chooses the lesser one.
Now, a rheostat is a device that has some variable resistance value. If we connect it to the parallel path, that path gains some more resistance than the other way available. When current flows in the circuit, electrons will never choose the parallel-path instead- they will flow straight through the series path. So, the rheostat will not function at all. It needs the current flow to work as a rheostat.
Series Connection
Type of Rheostat
Though there are several types of rheostat available, three main types are –
Linear Rheostats
Rotary Rheostats
Preset Rheostats
A. Linear Rheostats:
This type of rheostat consists of a cylindrical resistive element. The slider is moved linearly along the resistive element. It has two fixed terminals; one- is used, and another connects the slider. This type of rheostats is mostly used – in laboratories and experiment purposes.
This type of rheostat has a resistive element, which is circular. To use it, one needs to move the slider in a rotary way. They find applications in power electronics and also, they are used widely because of their smaller size than linear types. As the wiper needs to rotate to change the value, that’s why it is called a rotary rheostat.
When it is needed to implement a rheostat in a PCB (Printed Circuit Board), one should use preset rheostats or trimmers. It provides fine-tuning, that’s why they have found application in calibration circuits. This types of rheostats are suitable for industrial uses.
Differences between rheostat and potentiometer
There is a misconception that a rheostats and potentiometer are the same things, but there are some differences. Let us discuss some of them –
Rheostats are rated – in Amperes and Watts. There is also a resistance value. For example – 50W – 0.15 A, 100k Ohm. It means the maximum amount of current that can be measured is 0.15A. The resistance offered by the rheostat will be in the range of 0 to 100k Ohm.
2. How to select a rheostat based on rating?
While selecting a rheostat, the current rating is more important than the power rating.
It is the current that limits what power the device will generate provided for any resistance value. One should select rheostats with a current rating more than or equal to the actual need of current in the circuit.
3. What are the differences between resistors and rheostats?
A resistor is a passive electronic component that reduces the flow of current by providing resistance. On the other hand, rheostats are – variable resistors, which gives different values of resistances as per the need.
4. What is the function of a rheostat in the circuit?
A. It decreases the current
B. It increases the current
C. It limits the current
D. It makes the current constant in the circuit
E. All of the above
The correct option will be E. All of the above. Using Ohm’s law, we can find the answer to the question. As the ohm law states, V = IR, where V is the applied voltage, I is current, and R is the resistance. Rheostat provides variable resistances value; thus, it can increase, decrease, and limits the current. Keeping the resistance value constant will keep the current steady. So, all the options are correct.
5. Can rheostats be used as a potentiometer?
The answer is no, but there is some way to do this. A rheostat is a two-terminal device, while a potentiometer is a three-terminal device, so it seems impossible. But if a rheostat has inbuilt three terminals, the unused terminal can be joined to the circuit to use it as a potentiometer.
6. Can potentiometers be used as a rheostat?
Yes, a potentiometer is usable as a rheostat. A potentiometer controls voltage in a circuit. A potentiometer has three terminals. One terminal should connect the wiper while another should leave unconnected.
7. What are the drawbacks of using a rheostat?
There are few drawbacks of using this device. Some of them are –
A. The main drawback of this device is that it produces excessive heat causing loss of power.
B. It is bigger & does not fit into modern devices. That’s why rheostats are not used – in modern technologies. Though in rotors and various laboratory experiments, they are irreplaceable. Some of the replacements of rheostats are – triacs, SRCs, etc.
8. What type of taper a rheostat has?
Rheostat has linear types of taper. A taper is a relationship between resistance and sliding position. It is one of the most important parts of the device.
9. What is the use of a rheostat in a Wheatstone Bridge?
A Wheatstone bridge is used in labs to measure mean value resistances. Rheostats find its application in a Wheatstone Bridge to determine the value of unknown resistance in imbalanced conditions. The maximum resistance a rheostat can offer is the maximum resistance that a mounted Wheatstone Bridge can measure.
10. Why is choke of a coil preferred over a rheostat in AC circuits?
A rheostat is a resistive element. It provides resistance and produces an excessive amount of heat. So it causes a loss of electricity. On the other hand, a choke coil is an inductive element by nature. It maintains the same power but changes voltage according to Faraday’s Law. That is why a choke coil is preferred more.
11. Does a Rheostat change voltage?
No, a rheostat doesn’t change the voltage of the circuit. One of the conditions for working of a Rheostat is to keep the voltage constant. As the Ohm’s law states- V= IR, where V is the voltage, I is current, R is resistance. Using a rheostat, we change the current. One of the conditions for working of a Rheostat is to keep the voltage constant. Then only it can change the current of the circuit.
12. Does a rheostat’s terminal have polarity?
A rheostat is a three-terminal device of which two are fixed, and one is a moving terminal. The terminals have no polarity. So, any terminal can be connected.
“Band reject filter is combined of low pass and high pass filter which eliminates frequencies or stop a particular band of frequencies.”
Band rejection is obtained by the parallel connection of a high pass section with a low pass section. Now, the general rule is that, the cutoff frequency should be higher than the cut-off frequency of the low-pass area.
There is another way to create it. If a multiple feedback system is incorporated with an adder, then that functions like the desired operation. It is called as notch.
The Frequency response of a bandstop filter is calculated by considering the frequency and gain.
The bandwidth is chosen through the lesser and greater cut-off frequency. Notch filter is used to remove the single frequency. From this frequency response, we can also obtain Passband ripple and stopband ripple.
Where ∂p= magnitude response of the passband filter
∂s= magnitude response of the stopband filter
The frequency response of a band-stop filter
Why It is called band stop filter ?
Bandstop filter rejects a certain band of frequency and allows another frequency component of the primary signal. If the band of the frequency is narrow, the stopband filter is known as Notch Filter. The filter attenuates the specific band. The filter has several applications.
For example, a band-stop filter is designed to reject frequencies between 2.5 GHz to 3.5 GHz. The filter will allow frequency components lower than 2.5 GHz and above 3.5 GHz. The filter will We will explore the filter in the below sections.
Passband and stopband of a filter
Before diving into a band-reject or bandpass details, let us understand what pass band and stop band means. A passband is the frequency bandwidth that is allowed by a filter. On the other hand, a stopband is the band of frequency which one filter hasn’t allowed to pass. For a bandstop filter, there are two passbands and one stopband.
What does a band-stop filter do?
As the name suggests, a band-stop filter simply ‘stops band.’ That means a band-stop filter resistor doesn’t allow a certain band of frequency to pass through the
What is a band-stop filter used for
When there is a need to attenuate a certain band of frequency and pass other frequency components, a band-stop filter is used. Bandstop filters are useful in various applications.
Band stop filter applications
Being a very important type of filter, bandstop filters has several applications. Let us find out some of the applications.
Medical Engineering: Bandstop filters are used in medical engineering. Like – in ECG machine. 60 Hz bandstop filters are used to remove the supply frequency from the output.
Audio Engineering: Bandstop filters have huge applications in audio engineering. They remove the unwanted spikes and noises from the score and provides a good quality of audio.
Telecommunication: Bandstop filters are used in telephonic connections to remove the internal noise from the lines.
Radio communication: Band rejects filters are widely used in radio stations to transmit a better audio quality.
Optical filters: Band-stop filters are used to block certain wavelengths of light in an optical communication system.
Digital Image Processing: Bandstop filters are also used in digital image processing to remove certain periodic noises.
Miscellaneous: Whenever there is a need to remove the noise of a certain frequency, a band-stop filter is used.
Band stop filter diagram
This article explains the bandstop filter with various circuit diagrams, block diagrams, and graphs. This article includes a block diagram, band reject-with op-amp, frequency response of band stop, passive circuits, bode plots.
Circuit diagram of band-stop filter
The bandstop filter can be designed in several ways. It can be active types (which has op-amp). It can be for passive kinds (without op-amp). Active types have several varieties, too as well as passive filters have different styles too. That is why there are several circuits available also. In this article, almost all possible courses are given below. Check out the needed one.
Band stop filter block diagram
The bandstop filter is a combination of both high pass filters as well as low pass filters and another amplification factor for the filter. The block diagram is given below.
Narrow band stop filter
If the freq. of the bandstop filter is narrowed than general, the filter is often known as a Notch filter(hyperlink) or narrow bandstop filter.
Simple band stop filter
Unlike notch filter or higher-order filters, the simple bandstop filter is a basic filter which attenuates certain band of frequency allowing other bands.
Band stop filter using op-amp
Active bandstop filters are designed using operational amplifiers. Op-amp is one of the most important devices in making a filter. In passive filters, as there is no op-amp, there is no amplification. Thus, using the op-amp as a circuit element gives amplification.
Bandstop filter circuit using op-amp
This filter consists of a high-pass filter, a low-pass filter, and a summing amplifier to summation the lpf and hpf’s o/p, The circuit is shown below.
Band pass filter vs Band stop filter
There are fundamental differences between bandpass and bandstop filter.
The main principle of a bandpass filter is that it allows a certain band of frequency. At the same time, the main tenet of the bandstop filter is that it blocks a certain band of frequency.
Let us take an example to demonstrate. Let us say there is a lower cutoff frequency of Flow and a higher cutoff frequency high. Now, for a bandpass filter, the frequency in between the lower cutoff and higher cutoff will only pass, and other components below the Flow and above the fhigh will not pass.
Now, for a band-stop filter, the frequency band lower Flow, and above fhigh will pass. But the band in between the frequency limit will not pass.
Band stop filter vs notch filter
A notch filter is one type of bandstop filter. The main difference between them is that a notch filter attenuates a narrower band of frequency than a bandstop filter. In other words, bandstop filters have a wider band of frequency to attenuate.
Band stop filter RLC circuit
The band stop filter can be designed using basic components like resistor, capacitor, and inductor. There are two ways of developing the filter – 1. RLC parallel band-reject filter or Parallel resonant band-reject filter, & 2. RLC series resonant band-reject filter. As we are using passive elements, so both the filters will be of passive types.
Parallel RLC band stop filter
As mentioned earlier, a bandstop filter can be designed with basic components like – resistor, capacitor, and inductor. There are two ways of developing the circuits. The methods are discussed below.
Parallel RLC band stop filter
A Parallel RLC bandstop filter is a tank circuit. It also works fine as a frequency attenuator as the tank circuit is providing a lot of impedance. The below image shows the circuit diagram of a parallel rlc bandstop filter.
The parallel resonant band stop filter
The parallel resonant bandstop filter is also known as the parallel rlc bandstop filter. The details of the circuit and filter are given previously.
Series resonant bandstop filter
The main instruments for this filter are – capacitor and inductor. As the name suggests, the inductor and capacitor are kept in series. This part is the filter. At resonance, the circuit can attenuate certain frequencies before reaching the load. The below image shows the circuit diagram of the series resonant circuit.
Passive bandstop filter circuit
The passive bandstop filter is made of passive components, such as – resistor, inductor, and capacitor etc. Previously given circuits are an example of such filters. These filters do not have any operational amplifiers. Thus, there is no amplification process. A passive band stop filter consists of both passive hpf and passive lpf.
Active band stop filter
Unlike passive bandstop filters, active band-reject filters come with active components. The most important active part is the operational amplifier which also introduces amplification. Circuit using op-amp or the functional bandstop filter diagrams are given previously in this article.
Active bandstop filter design
Let us design a band stop filter. The center frequency will be 2 KHz. The bandwidth will be -3 dB of 200 Hz. Take capacitor value as one uF.
The depth in decibel comes as: 20log (0.1) = -20 db.
Band stop filter transfer function
The transfer function of a device refers to a mathematical function that provides output for every input. The transfer function of a band-stop filter is given below.
The second-order band-stop filter transfer function
The transfer function expression for the second-order band-stop filter transfer function is given below.
Band stop filter graph
The phase response stands for the phase output of the bandstop filter, bottom one represented the phase response.
The bandwidth of the bandstop filter depends on the requirement. The band-width is the range of freq. in which the filter will attenuate. In general, the bandwidth is referred to as the specification of a filter.
The impulse response of band-stop filter
Bandstop or band-reject filter can be designed digitally. There are two types of digital band-reject filters, They are – Infinite Impulse Response(IIR) and Finite Impulse Response(FIR). FIR method is more popular.
There are two design methods of FIR filter. They are also known as non-recursive filters. The methods are – 1. Window method & 2. Weighted-Chebyshev method.
Sallen key band stop filter
Low pass filters allow the lower frequency components of a filter and reject the higher frequency components. So, for the low pass filter, the stopband is the high-frequency component.
Sallen key is another topology of designing filters. The bandstop filter can also be created using the topology. Sallen key topology is designed using operational amplifiers for creating higher-order filters. Thus, we can understand this topology is for active filters.
Basic Sallen Key topology comes with one non-inverting op-amp and two resisters. It creates a Voltage Control Voltage Source or VCVS circuit. The circuit provides high input impedance and low output impedance which useful for filter analogy.
This Sallen Key topology also provides good stability of the system, which is highly suggested. The circuit is also very simple. They are connected one after another to achieve the higher-order filters. The circuit diagram of the band-reject filter using Sallen key topology is given below.
Band stop filter formula
There are some important equations for designing a band stop filter. Using these equations, we can find out important parameters. But one of the values of the parameter should be supplied as it is needed to design the filter.
The Normal Frequency Equation:
The Lower Frequency Cut-off:
The Higher Frequency Cutoff:
Here, the RL is lower resistance, and RH is higher resistance.
The center frequency:
The bandwidth: fBW = fH – fL
The Q Factor of the filter: Q = fC/fBW
Band stop filter example
The bandstop filter is an important concept that has several applications. That is why there are several examples as well. There is a band stop filter for blocking certain frequencies. Like – 2.4 GHz Band Stop filter. There is a band-reject filter for blocking narrower frequency bands, like the Notch filter, which has several applications. Audio bandstop filters, optical band-reject filters, digital-analog filters are some of its examples.
60 Hz band stop filter
From the filter’s name, we can understand that this bandstop filter is designed for attenuate frequency bands of 60 Hz. Now, the question comes why the 60 Hz band reject filter is so popular. It is because, in the USA, their supply frequency is 60 Hz. So, in most cases, when there is an interference of the supply frequency with the working signal, a 60 Hz bandstop filter is used to remove the frequency band from the output.
Band stop filter bode plot
At first, let us understand what the abode plot means. Abode plot refers to the graph of the frequency response of a device. The freq. response of the band-reject filter is presented below.
The cutoff frequency of a band-reject filter refers to the frequency of the band to be attenuated. There are formulas for lower frequency cutoff and higher frequency cutoff.
The lower cutoff frequency: fL = 1 / 2π RL C
The higher cutoff frequency: fH = 1 / 2π RH C
Band stop filter image processing
The bandstop filter is used in image processing. There are some different kinds of noises. The noises are repetitive. They have certain frequencies. A band-stop filter omits such noises. At first, the frequency is matched with the noise frequency. Then the bandstop filter removes the noises and makes the image a better one.
Band stop filter pole-zero plot
A band-reject filter can be designed using two zeros placed at ±jω0. These types of designs don’t have a unity gain at zero frequency. A notch filter can be developed by putting two poles close to the zeros.
Bandstop filter using op-amp 741
As mentioned earlier, band-reject filters can be designed using operational amplifiers. That is known as creating active band-reject filters. The band-reject filters consist of both low pass and high pass filters. Both these filters require operational amplifiers to design. Op-amp 741 is used here. Another summing op-amp is also necessary to sum the outputs of the previous filters and provide amplification. Op-amp 741 can be used in all those cases.
Band stop notch filter
A bandstop notch filter is just a special type of band-reject filter. Bandstop notch filter has a narrower bandwidth than usual band-reject filters. To know more about the notch filter, check out my article on Notch filter.
Band stop vs. Bandpass filter
The name of both the filters explains the difference between them. Here band means the range of frequency. Bandpass filter allows the specific band to pass through the filter and attenuates other components. At the same time, band-reject filters attenuate the particular band of frequency while it will enable other parts.
Characteristics of band stop filter
The bandstop filter has several characteristics. Some of them are listed below.
It has two passbands and one stopband.
It comes with a combination of lpf and a hpf.
If the bandstop filter has a narrow bandwidth, it is a notch filter that has great depth.
Bandstop filters are also known as band-reject filters as it ‘rejects’ the specified band.
Constant k band stop filter
Constant k filter is another topology of designing a filter. It is quite a simple topology, but it has a shortcoming. Here, the ‘k’ is referred to as the impedance level of the filter. It is also known as the nominal impedance. The terminating resistance is also considered as ‘k’ ohms (Rk2 = k2). The bandstop filter using constant k topology is shown below.
Design Procedure: At first, the center frequency, the bandwidth, and the intended characteristic impedance should be specified. Then follow the steps.
Calculate C2 using wH -wL = RkC2w02/2.
Calculate L2 using L2 = 1/w02C2.
Calculate L1 using L1 = k2C2, as L1/C2= k2.
Calculate C1 using C1 = 1/w02L1.
FIR band stop filter
FIR or Finite Impulse Response Filter is a digital bandstop filter. The formula for an FIR bandstop filter is given below.
N signifies the dimension of the filter. F1 and F0 are the cut off freq and Fs is the sampling freq.
lC band stop filter
A passive band-reject filter can be designed with an LC circuit. The working of the LC filter is quite simple. Inductors come with a reactance as well as capacitors also come with capacitive reactance. Now an increase in the frequency causes the decrease in capacitive reactance and increase in inductive reactance. This is the primary principle behind LC bandstop filter.
Notch band stop filter
As mentioned earlier, the notch bandstop filter is a normal bandstop filter that has a narrower bandwidth. It has several applications as it has great depth and performance than a band-reject filter. To know more about notch band-reject filters, check here. <link>.
Optical band stop filter
Optical band-reject filters block a certain wavelength of light and allow other components to pass. Just like normal band-reject filters, an optical filter rejects a certain wavelength. For example, there is a 532nm optical bandstop filter. Now, it will block the light, which has a wavelength of 532 nanometers.
RC band stop filter
The bandstop filter can also be designed using resistance and capacitors. Such band-reject filters are known as RC band top Filter. The circuit is shown below. It is a first-order filter. The resistors and capacitors are connected in parallel at first; then, they are connected in series. The frequency components are trapped in between them.
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RF band stop filter
The bandstop filter has several applications in Radio Frequency Domain. For example, during the measurement of non-linearities of a power amplifier. Also, when radio signals are transmitted from stations, band-reject filters are used to remove interfering noises.
Twin-t band stop filter
It is another method of implementing a higher-order filter and provide great depth and accuracy in performance. That is why this method is popular for notch filters. The twin t filter is made of two T networks, there is an RCR circuit, and another is the CRC network
Mathematical Expression for a Band Stop Filter:
Band Reject Filter can also be obtained by using the multiple -feedback bandpass filter with an adder. A notch filter is created using a circuit which eliminates the output of a bandpass filter from the unmodified signal.
Characteristics of a Band Reject Filter:
A band-stop filter works a frequency remover which is not within a specific range, reason it is called a rejection filter.
A band-stop filter passes frequencies of a particular bandwidth with maximum attenuation.
Different types of band-stop filters produce a maximum rate of roll-off rate for a given order and flat frequency response in the passband.
Applications of a Band Stop Filter:
An active Band Pass filter is used in the public addressing system and speakers for enhancing the quality.
A bandstop filter is also used in telecommunication technology as a noise reducer from different channels.
BSF is used in radio signals to remove static on the radio devices for better and clear communications.
Besides radios and amplification, this filter is also used in many other electronic devices to decrease a specific range of frequencies, known as ‘noise.’
In the medical field, BSF is used in making many useful devices like ECG machines, etc.
It also plays a vital role in image processing.
What is a Notch filter?
Notch filters find applications when there is a need to attenuate the undesirable frequencies while passing the necessary frequencies.
Advantages & Disadvantages of a band stop filter:
A bandstop filter attenuates the frequencies that are below the cut off range, so key advantage of using this filter is, it eliminates the external and unwanted noise or signals as well as gives us a stable output.
On the other hand, due to some certain limitations a band stop filter does not function properly under sustainable conditions. The parallel arrangement between the high pass and low pass filter my vary about the change of frequencies.
Frequently Asked Questions :
What is the Q factor or ‘Quality Factor’?
Q is given by the ratio between the resonant frequency to the bandwidth. It is an important parameter and it helps us to calculate the selectivity.
The higher the value Q, the more selective is the filter, i.e., narrower is the bandwidth.
How do a Band stop filter work?
A band stop or band reject filter always cuts or rejects frequencies that are not within a certain range, as the name implies. Besides this, it also gives easy passage to the frequencies to pass which are not in the range. These types of filters are often termed as ‘Band Elimination Filters’.
How to design a Band Reject Filter?
To make a Band Stop/reject filter we always need a Low Pass Filter(LPF) & a High Pass Filter(HPF). Therefore we combine them and make a ‘parallel’ connection with both the filters to create a band reject filter.
What does a Notch Filter do?
Notch Filter is also band reject filter. They can be used to fix frequency noise sources which are from the line frequency within a certain limit. Notch filter is also used to remove resonances from a system. Like a Low pass filter, notch filter creates less phase lag in a control loop.
Find out the differences between between a band reject filter & a notch filter?
A band reject filter or band stop filter is a filter that carries or passes the frequencies without altering and attenuates them in a specific range to low level. This is the opposite of a band pass filter.
On other hand, a notch filter is a bandstop filter which has a narrow stop band and has good high ‘Quality factor’(Q-factor).
What is Ideal Filter & Real Filter?
Sometimes, for the reason of simplification, we often use the active filters to approximate ways. We upgrade them into an ideal and theoretical model, which is called ‘Ideal Filter.’
The use of these standards is insufficient, leading to errors; then, the filter should be treated based on accurate real behaviour, For example, the Real filters.
The characteristics of an ideal filter are:
The response transits between zones in a sudden way.
It does not create any distortion when the signal passes through the transit zone.
