# Transformer: Definition and Working Principle A transformer is a static device that transfers alternating power from one electric circuit to another. The process of transferring power is done without any rotating parts. In the construction of the transformer, all parts are static. That’s why this device is known as a static device.

The alternating power has a frequency when power transfers from one circuit to another circuit, the frequency of the alternating power is not changing. So why is frequency not changing? Let’s get an answer from the principle of transformer. We can see that there are two electrical circuits (winding) and one magnetic circuit. Both electrical circuits are not connected physically. But these circuits are connected by one common magnetic circuit.

By this magnetic circuit, the transformer is capable of transferring the power. The transformer works on the principle of electromagnetic induction.

This phenomenon says that if we apply the alternating current across the coil, alternating flux is induced in the coil.

The magnitude of the flux is directly proportional to the current induced in the coil, and the direction of flux depends on the current direction. Therefore, we can determine the direction of flux by the right-hand rule.

When an alternating voltage (V1) source applies to the electric circuit and an alternating current flow, this alternating current produces an alternating flux in the magnetic circuit.

The frequency of this alternating flux is the same as the supply frequency, and that will never change. This alternating flux links with another electrical circuit with that same frequency.

I hope you got your answer, still, if you have a problem, you can comment on your problem, and I’ll try to solve it.

### Principle of Transformer

Now, this flux induces EMF in the coil. This induced EMF is caused because of the alternating current. According to Lenz’s law, the causes always oppose the effect. Here, the EMF’s effect and this induced EMF opposes the supply voltage. This means the polarity of induced EMF is opposite to the supply voltage. Let us consider that the second coil is placed near the alternating flux of the first coil. So, according to the Faraday law of electromagnetic induction, the EMF is induced in the second coil.

Because of the induced EMF, a small amount of current is produced in the second coil. The magnitude of the current depends on the reluctance of the magnetic path.

As shown in the above figure, if the air is used as a medium, the reluctance of air is much higher. So, a very small amount of current will flow.

But, in the case of a transformer, we use a core with low reluctance material like steel. Hence, the total flux produced in the first coil is linked with the second coil, and an equal magnitude of current will flow through the second coil.

### Working of Transformer

The transformer has two main parts; core and winding. The core is made from laminated silicon steel. This provides a low reluctance path to the magnetic flux.

In the transformer, we have two winding; primary winding and secondary winding. The winding through which we supply input is known as the primary winding. The winding through which we connect the load is known as the secondary winding.

When we give the alternating supply to the primary winding, an alternating current will flow through the primary winding. Because of this current, the flux induces in the winding.

According to the self-induction phenomena, the EMF is induced in the primary winding. As discussed in principle, the induced EMF is the opposite polarity of the supply voltage (according to Lenz’s law).

Because of the mutual-induction phenomena, the flux induces the primary winding link with the secondary winding. The EMF is induced in the secondary winding. The current is following through the secondary winding because of this EMF.

The magnitude of the secondary current is almost the same as the primary current. This happens because we use a low reluctance path. In this case, nearly all flux is induced in the primary links with the secondary winding.

The ratio of primary to secondary turns (T1/T2) equals the ratio of primary to secondary induced voltage (E1/E2). This ratio is nothing but the transformation ratio, denoted by ‘a’.

a = E1/E2 = T1/T2

Hence, you can achieve input and output voltage by selecting the turn ratio.

### Step-up and Step-down Transformers

The output voltage (secondary voltage) is more significant than its input voltage (primary voltage). These transformers are step-up transformers. The output voltage (secondary voltage) is lower than its input voltage (primary voltage). These transformers are step-down transformers.

The same transformer can use as a step-up and step-down transformer. The low voltage winding is primary when the transformer is used as a step-up transformer. When the transformer is used as a step-down transformer, the high voltage winding is primary.

If the turn ratio is the same, both winding have the same number of turns. In this condition, the transformer uses to isolate two circuits.

## Related Article:

Transformer: Construction and Classification

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