Electrical Machines
The field system of an alternator is usually excited

  250 / 250 V DC.
  230 V AC.
  110 / 220 V AC.
  3 - Φ, 50 Hz and 400 V.

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Electrical Machines
Two dc machines A and B, using the same conductor material, have armature circuit resistances of 0.4 Ω and 1.2 Ω respectively. Of the two machines,

 B is bigger than A for the same current rating
 both are of the same size for the same current rating
 A is bigger than B for the same current rating
 A is bigger than B for the same voltage rating

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