Transformer basics

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Transformer is electromagnetic device .There are two parts of transformer .First part is electrical domain and other part is magnetic domain.

The input is given in electrical domain that passes through magnetic domain and then we take the output in electrical domain

There are two types of transformer.

  • Step up
  • Step down

In the step up transformer the secondary number of turns is greater than primary turns. In this kind of transformer, we take greater output voltage at secondary than primary input voltage.

In step down transformer, the primary number of turns is greater than secondary number of turns. So, voltage at primary or input is greater than voltage of secondary at output.

Transformer Principle:-

Transformer principle is based on faraday’s law of electromagnetic induction.

According to this law, voltage induced is equal to number of turns and rate of change of flux.


               eind =   Ndɸ/dt

When voltage is applied at input terminal vp. It produced primary current Ip that flow through the rate of change of flux in core. So, induced voltage at primary is,

                     ep =   Npdɸp/dt

This rate of change of flux also links with Ns secondary winding. So, induce the voltage at secondary.

                     es   =   Nsdɸs/dt

Now relation becomes as

                     ep/es   = Np/Ns

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