No load vector diagram of transformer

Introduction:- Electrical quantities like voltages and currents are represented by vectors. A no load vector diagram of  a transformer is used to indicate no load data of a transformer in vector form.
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No load test:- No load test of a transformer is done to determine no load losses of transformer. Which is mainly consist of iron losses that is hysteresis loss and eddy current loss.  Short circuit test is carried out to find copper losses. For no load test a volt meter, ampere meter and a watt meter is required. All meters and transformer is connected as shown in circuit diagram below.

Rated primary voltage is applied to primary winding. Readings of volt meter ampere meter and watt meter is note down to draw vector diagram.. The secondary voltage is also measured. Now the power factor is calculated by formula
Power factor  cosΦ = watt/ voltage × current

Angle between voltage and current Φ = Cos^-1Φ

Current shown in meter is known as no load  current denoted by Io. It can be resolved in phase with voltage ie Io cosΦ  known as Iw watt full component of Io. It represent iron losses, which is given by watt meter. Second part of Io is  90 degree lagging to voltage is known as magnetizing current ie Io sinΦ  it is watt less component of no load current.

Here V1 is applied voltage to primary winding which causes Io current to flow through primary winding. Im is magnetizing component of Io which sets up alternating magnetic field in transformer core. Iw is watt full component of Io which supplies for iron losses. E1 is induced emf in primary winding which acts in opposite direction to applied voltage works as back emf to control primary current. E2 is secondary voltage depends on transformation ratio. E2=E1/k where k is transformation ratio.