Electrical Machines
Which of the following is done in speed control of DC motor by field flux control?

 Inserting an additional resistance in the field circuit.
 Any of above.
 Inserting an additional resistance in the armature circuit.
 Inserting resistance to armature circuit and field circuit.

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Electrical Machines
Interpoles in a DC motor must be

 Series excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.

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