Question

A 6-pole lap wound DC generator has a developed power of P watts and brush voltage of E volts. Three adjacent brushes of the machine had been found worn out and got open circuited. If the machine is operated with the remaining brushes, voltage and power that could be obtained from the machine are _________

(a) E, P

(b) E, 2P/3

(c) E/P, 2P/3

(d) E, P/3

I had been asked this question in an international level competition.

Enquiry is from Armature Windings topic in portion Armature Windings of Electrical Machines

Answer 1

Correct answer is (a) E, P

Explanation: Taking Kirchoff’s law into study here, the voltage across the winding will remain same.

             But the current will reduce in the overall winding as the resistance has increased, so power will decrease by 1/3.