Ideal Transformer

Ideal transformer characteristics

(1) Windings have zero resistance. It means there is no ohmic power loss and no resistive voltage drop.

(2) The core loss (hysteresis as well as eddy-current loss) is zero.

(3) There is no leakage flux. i.e all the flux is confined to the core and links both the windings.

(4) The core has infinite permeability i.e No magnetizing current is needed to estaiblish the required amount of flux.

Ideal transformer equivalent circuit

Below shown is the equivalent circuit of a practical transformer.

Lets apply ideal transformer characteristics into this circuit to get equivalent circuit for ideal transformer.

(1) Windings have zero resistance i.e R₁=R₂=0

(2) Core loss is zero i.e Core loss component of current is zero or R_Cis infinite.  

(3) There is no leakage flux i.e X₁=X₂=0

(4) Core has infinite permeability i.e magnetizing component of current is zero or X_m=0.

We get the equivalent circuit of ideal transformer as shown below.

From above circuit, we can write equations of ideal transformer as

Ideal transformer on no load

Above diagram shows ideal transformer with secondary open and its phasor diagram.

Ideal transformer on load

Let a lagging power factor load ( let impedance angle be ϴ₂ ) be connected to ideal transformer shown below. Corresponding phasor diagram is also shown.

It is clear from phasor diagram that the source power factor angle ϴ₁ is decided by the load power factor angle ϴ₂  and is always equal to it.

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