A separately excited dc machine is coupled to a 50 Hz, three-phase,

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A separately excited dc machine is coupled to a 50 Hz, three-phase, 4-pole induction machine as shown in the figure. The dc machine is energized first and the machines rotate at 160 rpm. Subsequently the induction machine is also connected to a 50 Hz, three-phase source, the phase sequence being consistent with the direction of rotation. In steady state,

1. both machines act as generators
2. the dc machine acts as a generator, and the induction machine acts as a motor
3. the dc machine acts as a motor, and the induction machine acts as a generator
4. both machines act as motors

Correct Option: C

Synchronus speed of induction machine,

=	120 × f	=	120 × 50	= 1500 rpm
	P		4

Speed of d.c. machine, N_r = 1600 rpm = actual speed of IM

∴ Slip =	N_s - N_r	=	1500 - 1600	= negative
	N_s		1500

Hence induction machine acts as induction generator and dc machine acts as motor.