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2. Perceive the emf equation, transformation ratio and Losses of transformer.

2.1. Define emf equation, transformation ratio of transformer

EMF Equation of a Transformer
When a sinusoidal voltage is applied to the primary winding of a transformer, alternating flux ϕm sets up in the iron core of the transformer. This sinusoidal flux links with both primary and secondary winding. The function of flux is a sine function.

emf = turns x rate of change
This is known as the Transformer EMF Equation. For the primary winding emf, N will be the number of primary turns, ( NP ) and for the secondary winding emf, N will be the number of secondary turns, ( NS ).

As the magnetic flux varies sinusoidally, Φ = Φmax sinωt, then the basic relationship between induced emf, ( E ) in a coil winding of N turns is given by:

emf = turns x rate of change

transformer emf equation

  • Where:
  •   ƒ  –  is the flux frequency in Hertz,  = ω/2π
  •   Ν  –  is the number of coil windings.
  •   Φ  –  is the amount of flux in webers

This is known as the Transformer EMF Equation. For the primary winding emf, N will be the number of primary turns, ( NP ) and for the secondary winding emf, N will be the number of secondary turns, ( NS ).


The transformer transformation ratio or transformer turns ratio (K) is the quotient value obtained by dividing the number of turns of the primary winding (N1) and the number of turns of the secondary winding (N2). Then K = N1/N2.

The turns ratio is defined as the ratio of turns of wire in the primary winding to the number of turns of wire in the secondary winding.

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