Question

What is the armature current for a DC generator if terminal voltage is observed to be 245V and open circuit voltage is equal to 250V, where armature resistance is 0.05Ω?

(a) 10A

(b) 100A

(c) 1KA

(d) 1A

This question was posed to me by my college professor while I was bunking the class.

Question is taken from Electromagnetic Power and Circuit Models topic in division Circuit Model, Emf and Torque of DC Machines

Answer 1

Right choice is (b) 100A

Explanation: Open circuit voltage means the voltage at armature current equal to 0, i.e. Vt=Ea= 250V. Actual Vt at loaded condition is 245V. For motoring mode, Ea – Vt= Ia*Ra. By substituting all the given values, we get Ia= 100A.