Electrical Machines
DC generators are usually designed to develop armature voltages not exceeding 650 V because of the limitations imposed by

 armature winding
 starters
 commutator
 field winding

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Electrical Machines
The mmf produced by rotor currents of a 3 - Φ induction motor

  is at standstill with respect to stator mmf.
  rotates at the speed of rotor in the air gap.
  rotates at slip speed with respect to stator mmf.
  rotates at synchronous speed with respect to rotor.

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