Question

For a universal motor, the rated supply current is 10A giving a rated torque of 100 N-m. If a current of 5A is applied, what will be generated torque vary to?

(a) 250 N-m

(b) 400 N-m

(c) 500 N-m

(d) 1000 N-m

This question was addressed to me in quiz.

The doubt is from Torque in DC Machines topic in division Electromechanical Energy Conversions of Electrical Machines

Answer 1

Correct option is (b) 400 N-m

The best I can explain: The torque is proportional to the square of the current.

             So the new torque will be  100*(2^2) = 400 N-m.