# What is an Ideal Transformer? Properties, Working, and Phasor diagram

An ideal transformer is a transformer that has no winding resistance(no copper loss), no core loss, no magnetic leakage, and zero magnetizing currents.

But in existence, there is no such ideal transformer, that is, a transformer with ideal properties is hypothetical.

However, it is important to know about the ideal transformer for a better understanding and an easier explanation of a practical transformer. In an ideal transformer, certain assumptions are made which are close approximations for a práctical transformer.

## Properties of Ideal transformer

In an ideal transformer, the windings are purely inductive and there will be no loss in the transformer core. A purely inductive circuit will have zero resistance, which indicates that there will be no voltage drop and no copper loss in the windings. An ideal transformer has 100% efficiency.

The following are the properties of an ideal transformer.

**No winding resistance**– It means the primary and secondary windings have zero resistance. The ideal transformer will have no ohmic power loss and no resistive voltage drop in an ideal transformer.**No magnetic leakage**– there is no leakage flux and all the flux set up is confined to the core and links both the windings.**No iron loss**– hysteresis and eddy current losses in the transformer core are zero.**Zero magnetizing current**– the core has infinite permeability and zero reluctance so zero magnetizing current is required to establish the requisite amount of flux in the core.

## Working of Ideal transformer

Consider the below given ideal transformer. An alternating voltage source V_{1} is connected to the primary winding of the transformer and the secondary is kept open.

When the voltage V_{1} is applied, the transformer draws a very small current. This current merely magnetizes the core and is hence called the magnetizing current I_{m}. Since the coil is purely inductive, the current I_{m} lags behind the applied voltage V_{1} by 90^{0}.

This current when flowing through the primary coil establishes the flux φ in the core. The flux produced is always proportional to the flow of current and hence both are in phase with each other.

This alternating flux φ links the primary and secondary windings magnetically. It produces a self-induced emf E_{1} in the primary winding and mutually induced emf E_{2} in the secondary winding.

The EMF induced in the primary winding E_{1} is equal and opposite to the applied voltage V_{1}. Thus it is called counter emf or back emf.

The EMF E_{2} is induced as a result of flux φ linking with the secondary winding through the core of the transformer. This emf is antiphase with V_{1} and its magnitude is proportional to the rate of change of flux and the number of turns in the secondary winding.

## Phasor diagram of Ideal transformer

The phasor diagram of the ideal transformer on no-load is drawn as shown below.

Since the flux φ is common to both the windings of a transformer, it is taken as the reference phasor to draw the phasor diagram.

The magnetizing current I_{m} is drawn on the same phase as φ, as both are in phase with each other. As the magnetizing current I_{m} lags behind the V_{1} by 90^{0}, it is drawn at 90^{0} in the anti-clockwise direction.

Also, the induced EMFs E_{1} and E_{2} in the primary and secondary windings respectively are in phase with each other. It is drawn exactly opposite to that of V_{1} phasor.

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