Electrical Machines
Consider the following statements: To control the speed of a dc shunt motor above the base speed over a reasonably wide range, the motor must 1. have compensating winding 2. have interpole winding 3. be started using a 3-point starter 4. be started using a 4-point starter Of these statements

 2 and 4 are correct
 1, 2 and 4 are correct
 1, 2 and 3 are correct
 1 and 3 are correct

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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

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

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