A 250 V dc shunt machine has armature circuit resistance

A 250 V dc shunt machine has armature circuit resistance of 0.6 Ω. and field circuit resistance of 125 Ω. The machine is connected to 250 V supply mains. The motor is operated as a generator and then as a motor separately. The line current of the machine in both the cases is 50 A. The ratio of the speed as a generator to the speed as a motor is ___.

When running as a motor,

I_f =	250	= 2 A
	125

E_m = V_t – I_a r_a
= 250 – 48 × 0.6 = 221.2 Volt
When running as a generator,

E_g = 52 × 0.6 + 250
= 281.2 Volt

Now, As , E =	φ n z			P
	60			A

Then	E_m	=	n_m	[φ remain constant]
	E_g		n_g

Ratio of generator to motor speed,

⇒	n_g	=	281.2	= 1.271
	n_m		212.2