Electrical Machines
The armature core of a DC machine is laminated to minimise

 temperature rise
 hysteresis loss
 eddy-current loss
 mechanical loss

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Electrical Machines
A 3-φ alternator has negligible stator resistance. A short circuit test is conducted on this alternator. At a particular speed, a field current of If1 is required to drive the rated armature current. If the speed of the alternator is reduced to half, the field current required to maintain rated armature current

 Would be equal to If1/2.
  Cannot be predicted due to insufficient data.
 Woud be equal to 2If1.
 Would be equal to If1.

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