Ideal Transformer

Definition of Ideal Transformer

An ideal transformer is an imaginary transformer which does not have any loss in it, means no core losses, copper losses and any other losses in transformer. Efficiency of this transformer is considered as 100%.

Ideal Transformer Model

Ideal transformer model is developed by considering a transformer which does not have any loss. That means the windings of the transformer are purely inductive and the core of transformer is loss free. There is zero leakage reactance of transformer. As we said, whenever we place a low reluctance core inside the windings, maximum amount of flux passes through this core, but still there is some flux which does not pass through the core but passes through the insulation used in the transformer. This flux does not take part in the transformation action of the transformer. This flux is called leakage flux of transformer. In an ideal transformer, this leakage flux is also considered nil. That means, 100% flux passes through the core and links with both the primary and secondary windings of transformer. Although every winding is desired to be purely inductive but it has some resistance in it which causes voltage drop and I²R loss in it. In such ideal transformer model, the windings are also considered ideal, that means resistance of the winding is zero.

Now if an alternating source voltage V₁ is applied in the primary winding of that ideal transformer, there will be a counter self emf E₁ induced in the primary winding which is purely 180° in phase opposition with supply voltage V₁.

For developing counter emf E₁ across the primary winding, it draws current from the source to produce required magnetizing flux. As the primary winding is purely inductive, that current 90° lags from the supply voltage. This current is called magnetizing current of transformer I_μ.