What is Transformer and its Working Principle?

The transformer is a static device (no rotating part in it) which is used to transfer electrical energy from one ac circuit to another ac circuit. It increase or decrease the value of voltage or current, without any change in frequency. Input and output quantity of Xer is always AC (Alternating) quantity.


Basic construction :

Basically transformer is design as single phase or three phase supply, according to their area of application. A single Xer is used as a step up or as step down depending on application.

Basic construction of a single phase Xer is as shown in figure.  It consists of two highly inductive coils called as winding of Xer wound on a core made up of iron or steel material.

The winding connected to the ac supply is called as primary winding. Whereas the other one on output side is called as the secondary winding. Or say ac supply is connected to the primary winding and the load is connected to the secondary winding


There is no electrical contact between primary and secondary windings as well as winding and iron core. In other word, there is no physical connection between the primary and secondary windings.

Flux produce by primary winding is linked with secondary winding through core path and EMF is induced in secondary windings.

Operating principle of a transformer

Question: State principle of operation of transformer.

Transformer operates on the principle of mutual induction as the primary winding (coil) is connected to the single-phase ac supply, and AC current starts flowing through it.

The ac primary current produces an alternating flux (Φ) in the core and the varying flux gets linked with the secondary winding (coil) through the core.

These varying flux will induce voltage (mutually induced EMF) into the secondary winding (coil) according to the Faraday’s laws of electromagnetic induction.

Transformer can work on DC supply?

Answer is no.

Transformer cannot operate on DC supply, because DC primary current cannot produce alternating flux and this zero frequency flux link with secondary winding produce zero EMF.

 Key Points :

  • It is a static device.
  • Xer work on AC Quantity Only.

  • Transformer cannot change frequency.
  • Its weight vary from few Grams to hundred of Tonnes.

Watch MCQ Questions of Transformer on YouTube.

1 thought on “What is Transformer and its Working Principle?”

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