Convert Step Down To Step Up Transformer: 5 Important Facts


We can convert the step-down transformer to a step-up transformer by simply swapping the primary and the secondary windings. We shall now discuss the technique on How To Convert Step Down To Step Up Transformer along with some relevant frequently asked questions in detail.

A step-down transformer implies that it has fewer turns in its secondary coil than its primary coil. If we connect the transformer in a reverse manner, the primary coil becomes secondary, and the secondary coil becomes primary. Therefore, the behaviour of the transformer becomes analogous to that of a step-up transformer. 

How To Convert Step Down To Step Up Transformer- Related Topics

How To Convert Step Down To Step Up Transformer

Step-up transformer – working principle and diagram

A step-up transformer is said to be an electrical apparatus that enlarges the voltage from the primary coil to the secondary coil. It is generally used in power plants where voltage generation and transmission take place. 

 A step-up transformer has two major parts- the core and the windings. The core of the transformer is built with a material having permeability higher than the vacuum. The reason behind using a highly permeable substance is to restrict the magnetic field lines and reduce the losses. Silicon steel or ferrite is used to prevent the transformer from excess eddy current and hysteresis loss. So, the magnetic flux can easily flow through the core, and the efficiency of the transformer increases. 

The transformer windings are fabricated with copper. Copper has huge rigidity and is perfectly suited for carrying a large amount of current. These are covered with insulators to provide safety and endurance for better performance. The windings are coiled over the transformer core. The primary coil consists of fewer windings with thicker wires, specifically designed to carry low voltage and high current. The exact opposite phenomenon takes place for the secondary coil. The wires are thinner this time with more turns. These wires are good carrers of substantial voltage and small current. 

The primary winding is composed of fewer turns than the secondary winding. So, Ns>Np where,

Ns=number of turns in the secondary coil.

Np=number of turns in the primary coil

We know from the properties of an ideal transformer,

[Latex]\frac{N_{p}}{N_{s}}=\frac{V_{p}}{V_{s}}[/Latex]

Therefore, the more the number of turns in the secondary coil, the more the induced voltage.

But the power should be fixed for a transformer. Therefore, the step-up transformer steps the voltage up and reduces the current so that the power remains unchanged. 

Step-up transformers are an integral part of power systems. Transmission lines use step-up transformers to transfer voltage through long distances. The voltage produced in power plants steps up, transmits through them, and reaches the domestic systems. A step-down transformer lowers the voltage and makes it safe to use in households.

Step-up transformer coil
Step-up transformer winding

Step-down transformer – working principle and diagram 

An electrical device that brings down the voltage from the primary winding to the secondary winding is known as a step-down transformer. The function of a step-down transformer is exactly opposite to the operation of a step-up transformer. 

A step-down transformer core is typically made up of soft iron. The construction is similar to that of the step-up transformer—the ferromagnetic properties of the core help in magnetization and energy transfer. 

The insulator-covered copper wires are employed for the inductor coils. The primary coil is joined with a voltage source, and the secondary coil is joined with the load resistance. The voltage provided as input to the primary coil generates magnetic flux and induces EMF in the secondary coil. The load connected to the secondary coil draws required a “stepped down” alternating voltage. 

We know, in a step-down transformer, the number of turns in the primary winding is more than the number of turns in the secondary winding. So, Np>Ns where,

Ns=number of turns in the secondary coil

Np=number of turns in the primary coil

We know, [Latex]\frac{N_{p}}{N_{s}}=\frac{V_{p}}{V_{s}}[/Latex]

Therefore, [Latex]V_{s}=\frac{N_{p}}{N_{s}}\times V_{p}[/Latex]

As the ratio [Latex]\frac{N_{s}}{N_{p}}<1\: ,\: V_{s}<V_{p}[/Latex]. So, we can conclude that the step-down transformer reduces the voltage.

Just like the step-up transformer, the power is kept constant in the case of the step-down transformer as well. As the voltage level drops, the current at the secondary coil is increased to maintain the balance. 

For houses or other distribution systems, step-down transformers are an essential component.

Step-down transformer winding

How To Convert Step Down To Step Up Transformer-FAQs

What are the differences between a step-up and a step-down transformer?

Step-up transformer Step-down transformer 
A step-up transformer steps the primary voltage up to the secondary coil.A step-down transformer steps the primary voltage down to the secondary coil.
The quantity of turns within the secondary inductor coil of a step-up transformer is higher than the quantity of turns within the primary inductor coil.The quantity of turns within the primary inductor coil of a step-up transformer is higher than the quantity of turns inside the secondary inductor coil.
The value of the output voltage is greater than the input voltage value.The value of the output voltage is lower than the input voltage value.
Thick copper wires are used in primary and thin wires are used in the secondary winding.Thin copper wires are used in primary and thick wires are used in the secondary winding.
Step-up transformers are essential components of electrical substations, power plants etc.Step-down transformers are essential components of distribution systems, adapters, CD players etc.
Transformer Power-Line Electricity - Free photo on Pixabay
Transmission lines make use of step-up transformer

How to use a step-down transformer as a step-up transformer?

A step-down transformer can sufficiently work as a step-up transformer by reversing the operation.

The voltage source and the load resistor are attached to the primary winding and the secondary winding in case of a step-down transformer, respectively. If we power the secondary winding with the voltage and connect the load to the primary winding, the secondary coil acts as primary and vice-versa. So we can say, now the step-down transformer behaves as a step-up transformer and produces an elevated voltage at the secondary coil.

If a step-down Transformer is connected with its output and input interchanged, does it work as a step-up transformer?

It is possible to interchange the input and the output of a step-down transformer to make it work like a step-up transformer.

While we can perform this reverse operation, we have to keep in mind that it is good for temporary uses. We must maintain the original transformer ratings; otherwise, serious hazards may occur. 

What are the conditions while converting a step-down to a step-up transformer?

There are some points that we need to remember when we are going to use a step-down transformer as a step-up transformer. 

  • Theoretically, this method looks easy and plausible. In reality, it is a challenging job and has limitations. When we’re connecting the transformer backward, we change polarity, but the number of turns remains the same as previous. So the turns ratio also doesn’t change. Therefore, the voltage level must be increased in order to keep everything balanced. Let us take an example. Suppose we have a step-down transformer that yields 100 Volt secondary voltage when 200 Volt input voltage is supplied. Turns ratio, Np/Ns= Vp/Vs = 200/100= 2. If we want to use the transformer as a step-up, the same 200-volt input voltage will produce 400 volts of stepped-up output. Therefore, we can say that this conversion is fine for low ratings. Otherwise, the circuit can be shorted, and the set-up would be destroyed.
  • ‌Another important side of this method is the use of highly durable core and insulation materials. If materials with weak magnetic properties are used, the high voltage would harm the material and eventually lead to severe damage. 
  • ‌ The turns ratio must not be high. If the factor is 10, the output voltage gets multiplied by ten times and exceeds the limit of the transformer. So, it is better to have a turns ratio <=3.

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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