Figure 1.30 shows a transformer having resistances R1 and R2 of primary and secondary windings respectively, and leakage reactances X1 and X2 of primary and secondary windings respectively. The primary impedance is given by
and the secondary impedance is given by
The applied voltage V1 on primary side is given by
If V2 be the secondary terminal voltage during load, the secondary induced emf (E2) is given by
Figure 1.31 shows the phasor diagram of the transformer for unity power factor, lagging power factor and leading power factor respectively.