...Contd from previous slide...

The equivalent circuit is shown in Fig. 1.16. Let the current i_a lag the internal emf e_a by θ_a . The stator currents are then

	(1.109)
	(1.110)
	(1.111)

Fig. 1.16 Three-phase equivalent circuit of a synchronous generator.

The single-phase equivalent circuit is shown in Fig. 1.17. The phase angle θ_abetween e_aand i_a is rather difficult to measure under load as e_a is the no load voltage. To avoid this, we define the phase angle between ν_a and i_a to be θ . We assume that e_a leads ν_aby δ . Therefore we can write

(1.112)

Then the voltages and currents shown in Fig. 1.17 are given as

	(1.113)
	(1.114)
	(1.115)

Equations (1.113) to (1.115) imply that

(1.116)

The synchronous impedance is then defined as

(1.117)

The terminal voltage equation is then

(1.118)

Fig. 1.17 Single-phase equivalent circuit of a synchronous generator.