Electrical Machines
The armature mmf in a dc machine is 1. stationary with respect to field poles 2. stationary with respect to armature 3. rotating with respect to field poles 4. rotating with respect to armature From these, the correct answer is

 2, 3
 1, 3
 2, 4
 1, 4

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
In dc machines, the field system has to be provided on stator unlike synchronous machines Where in it could be on any member, because

 it gives more uniform air-gap flux distribution
 dc machines are comparatively low rating machines.
 commutator action is not possible otherwise
 it reduces field structure iron losses

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
In a DC machine the armature mmf is

 rotating with respect to field poles.
  stationary with respect to armature.
  stationary with respect to field poles.
  rotating with respect to field poles as well as armature.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
In a star - delta starting of an IM

  applied voltage per stator phase is 57.7 % of a line volt
  resistance is inserted in the rotor.
  line voltage is 57.7 % of stator voltage.
  reduced voltage is applied to the stator.

ANSWER DOWNLOAD EXAMIANS APP