Electrical Machines
The residual magnetism of a self-excited dc generator is lost. To build up its emf again

 the field winding must be replaced
 the field winding connection must be reversed
 field winding must be excited by low voltage dc supply
 the armature connection must be reversed

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Electrical Machines
Skewing of the rotor in a 3 - Φ squirrel cage induction motor reduces

  noise and parasitic torque, but increase starting and pull-out torque.
  noise, parasitic and starting torque, but increase pull out torque.
  noise, parasitic torque, starting torque and pull out torque.
  noise and pullout torque, but increase parasitic and starting torque.

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