Transformers Increase Voltage To Decrease Current: 3 Facts


This article elaborates on How Do Transformers Increase Voltage To Decrease Current, keeping the total power intact. We shall discuss some frequently asked questions as well.

We know the basic principle of transformers is to transfer power by transforming the voltage to the current ratio. Power is the combination of two electrical quantities-the voltage and the current. Therefore, if we increase the voltage in a transformer, we have to bring the current down by some amount to draw constant power. 

How Do Transformers Increase Voltage To Decrease Current Obeying Ohm’s Law?

Ohm’s law states that the amount of current passing through a conductor material between any two points is directly proportional to the voltage across them. So, when the voltage becomes more significant, the current also must be increased. 

In the case of transformers, we see that the current is reduced to maintain the total power when the voltage goes up. So, quite naturally, a question strikes us- do transformers contradict Ohm’s Law? Well, the transformers, as a whole, cannot obey Ohm’s law. But the internal circuits of the transformers, of course, obey Ohm’s law. The statement of Ohm’s law is valid for the parameters of a single circuit. A transformer splits the entire circuitry into two halves that act as two different circuits. So, Ohm’s law individually validates for each of the circuits. Let us elucidate more in this regard. 

Step-up transformers: There are more turns in the secondary coil than in the primary coil. So the ratio Ns/Np is greater than 1. By the transformation phenomenon, we can say that the secondary resistance is much greater than the primary. This secondary inductor is attached to the transmission line. 

Step-down transformers: Just the opposite incident takes place in step-down transformers. As the primary coil turns are higher than the secondary coil turns, the primary resistance is huge. 

In both cases, we can see that the resistance value is analogous to the voltage amount. So quite evidently, the current will be low(in step-up) or high(in step-down) to keep the balance. Therefore, we can say that Ohm’s law suits perfectly for the individual circuits. 

How Do Transformers Increase Voltage To Decrease Current and help in saving power? Exemplify.

Transformers are employed to effectively minimize the losses during long-distance power transmission. 

Power stations send the generated power to distribution systems via transmission lines. At the power stations, a step-up transformer is applied to boost the voltage. The voltage passes through the transmission line and finally reaches the distribution systems, where a step-down transformer is present. The function of this transformer is to downgrade the voltage so that it works fine in smaller systems.

For any distribution system, the current depends upon the quantity of load. It is evident that a system consisting of two lights and two fans would draw much less power than a system with two lights, two fans, an air-conditioner, and a refrigerator.

Now, let us understand better how the transformers cope up with losses with two scenarios.

In the first case, the transmission voltage is 220 volts. So if the system draws a current of 10 amp, the electrical power, P = VI = 220 x 10 = 2200 Watt. If the resistance of Tx is 0.5 ohm, the loss= I2R = 102 x 0.5= 50 watt.

In the second case, we use a transformer of 10 kV/220 volt at the transmission line. So if the system draws a secondary current of 10 amp, the primary current Ip= Is x Vs/Vp = 10 x 220/10000 = 0.22 amp. If the resistance of Tx is 0.5 ohm, the loss= I2R = (0.22)2 x 0.5=0.0242 watt.

Therefore, we notice that if we use a transformer, we can save (50-0.0242) = 49.9758 watt power just for a single system. So, transformers are incredibly efficient as power savers.

How Do Transformers Increase Voltage To Decrease Current- FAQs

Do transformers reduce current or voltage?

Transformers are electrical devices capable of reducing the voltage or current according to the requirement of a particular circuit. 

The transformers are responsible for leveling or stepping up the voltage in transmission lines and stepping down the voltage in distribution systems for power supply. Obviously, to maintain constant power, it is necessary to bring down the current level when we are using the step-up transformer. Similarly, the voltage gets lowered in a step-down transformer. 

How do Transformers change current?

Transformers are classified as electromagnetic devices. They make use of the concepts of electromagnetic induction in order to change the current.

Every transformer comprises two circuits- a primary inductor circuit and a secondary inductor circuit. When the primary inductor coil is subjected to an AC voltage, the current is produced. This current varies and generates a varying magnetic field. Now the variable magnetic field causes an electromotive force to develop in the secondary inductor coil. Subsequently, this EMF generates a current in the secondary coil as the number of turns is different in both the coils. The current value either increases( step-down transformer) or decreases( step-up transformer).

What happens to current when voltage is stepped down?

A step-down transformer is known to elevate the current while bringing down the voltage.

A step-down transformer curtails the voltage from the primary inductor in the secondary inductor. The secondary winding count is less than the primary winding count, which helps in voltage reduction. But the principle of the transformers says that the power must remain unchanged throughout the process. Therefore, for lower voltage, the current level has to increase proportionally. So current goes up when voltage is stepped down.

How much voltage can a step up transformer increase?

The step-up transformers are designed to elevate the voltage from its primary winding to secondary winding. The quantity of elevation depends upon the turns of both the windings.

Let us illustrate with an example. Suppose the turn counts in the primary, and the secondary inductor is 10 and 100, respectively. So the voltage transformation ratio= Ns/Np = 1/10. Therefore, the primary voltage will be stepped up 10 times in the secondary coil. This ratio isn’t fixed, it varies for each transformer, and thus the stepped-up secondary voltage also differs.

Do transformers increase resistance?

A transformer is a voltage regulating instrument, so it doesn’t deal with resistors.

A transformer is utilized in the circuits just to regulate the voltage keeping the power unharmed. So the quantities responsible for this phenomenon are the current and the voltage. Where the voltage is being increased, the current goes down and vice-versa. So, the resistances or impedances don’t get counted on. The primary effect of resistances or impedances in a transformer is various kinds of losses

File:Pole mounted Transformer.jpg - Wikimedia Commons
BidgeePole mounted Transformer, size and dimensions by Using for my blog, CC BY 3.0

Can a step-down transformer be reversed?

A step-down transformer can be carefully operated to make it function like a step-up transformer. 

A step-down transformer is simply reverse fed by interchanging its input and output. Though this method is acceptable for temporary use, it should not be deployed in greater set-ups. We should never exceed the voltage margin mentioned in the transformer. Otherwise, electrical hazards can occur. 

Kaushikee Banerjee

I am an electronics enthusiast and currently devoted towards the field of Electronics and Communications . My interest lies in exploring the cutting edge technologies. I'm an enthusiastic learner and I tinker around with open-source electronics. LinkedIn ID- https://www.linkedin.com/in/kaushikee-banerjee-538321175

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