Question

For a DC machine, given Diameter of the commutator= 0.48 m, Speed = 600 rpm. What is the voltage across the commutator?

(a) 15 V

(b) 15.5 V

(c) 15.2 V

(d) 15.1 V

The question was asked in an internship interview.

This interesting question is from Design of Commutator and Brushes topic in division Thermal Design Aspects of Electrical Machines & D.C of Design of Electrical Machines

Answer 1

The correct answer is (d) 15.1 V

The best I can explain: Voltage across the commutator = 3.14*(Diameter of the commutator)*Speed

Voltage = 3.14*0.48*600 = 15.1 V.