Question

For a DC motor taking 10kW power from 230V mains, having armature resistance and field resistance equal to 0.08Ω and 115Ω resp. The value of armature current is_____

(a) 45.68 A

(b) 43.48 a

(c) 41.48 A

(d) Data insufficient

I had been asked this question by my college professor while I was bunking the class.

The query is from Electromagnetic Power and Circuit Models in division Circuit Model, Emf and Torque of DC Machines

Answer 1

Correct option is (c) 41.48 A

Best explanation: Field current is equal to 230/115 = 2A, by Ohm’s law. When running as a motor line current IL= 10k/230= 43.48A. Since power is taken from 230V mains, Ia=IL- If = 43.48-2 =41.48A. For generating mode Ia= IL+ If.