20th September 2020




The transformer is a static device which transfers electrical energy from one circuit to another circuit without a change in frequency. It works on the principle of Faraday’s Law of Electromagnetic induction.

Before the transformer was invented, the electricity was generated and distributed as DC at low voltages. The voltage drop of lines limited the use to small areas where the generating centers are located.

The invention of transformers revolutionized the electrical industry,  After the invention of the transformer, generation, transmission, and distribution of electricity at a different voltage level become possible.

The transformer plays an important part in electrical power systems, as they  made Transmission of electricity possible to a large distance by stepping up the electricity to high voltage or extra high voltage, which reduces transmission losses and voltage drop and by stepping down to a voltage suitable for distribution and consumption.

Definition as per IS / IEC

A static piece of apparatus with two or more windings which, by electromagnetic induction, transforms a system of alternating voltage and current into another system of voltage and current usually of different values and at the same frequency for the purpose of transmitting electrical power.

Principle and Ideal Transformer

The working principle of the transformer is the law of electromagnetic induction which states that “ if a coil links with a flux varying with time then the voltage is induced in the coil”. The ideal transformer consists of two windings i.e primary and secondary, and core which helps in completing the magnetic circuit. An ideal transformer with windings and core is shown in fig.

When the primary of the transformer gets connected to an alternating voltage source, this results in the generation of mutual flux(Φm) . The value of the alternating flux depends on the alternating voltage and the number of turns in the primary winding. 

The generated alternating flux links with secondary winding which induces a voltage in the secondary winding.  The value of voltage depends on the alternating flux and the no. of turns in the secondary winding.

Let the voltage of primary winding V1, the flux(Φ) will get generated such that it induces counter EMF e1 in primary winding equal to the primary voltage V1. Thus the equation can be written as Here N1 is the number of turns in the primary winding.

Real Transformer

In Ideal Transformer resistance of winding is zero and the core permeability is infinite, such a transformer does not exist.  The Real/ Practical transformer have both resistance and inductance.

Types of Transformers

Transformers can be classified in different types on basis of many parameters such as use, construction etc.

  1. On the Basis of Voltage Ratio.
    1. Step-Up Transformers
    2. Step-down Transformers
  2. On the Basis of Construction
    1. Core Type Transformers
    2.  Shell Type Transformer
  3. On the Basis of Uses
    1. Power Transformers
    2. Distribution Transformers
    3. Instrument Transformers
  4.   On the Basis of Phases
    1. Single Phase Transformers
    2. Three Phase Transformers

Components of Transformers



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