Electrical Machines
Resistance commutation is used generally in case of

 DC machines above 10 kW.
  fractional kW DC machines.
None of these
 DC machines bellow 5 kW.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

 field system lost residual magnetism
 field resistance was higher than critical resistance
 field winding was wrongly connected
 there was a break in the armature circuit

ANSWER DOWNLOAD EXAMIANS APP