Electrical Machines
Autotransformer makes effective saving on copper and copper losses, when its transformation ratio is equal to

  less than one.
  approx to one.
  greater than one.
  very low

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

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

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