Electrical Machines
The air gap between the yoke and armature is dc machine is kept very small

 to achieve a stronger magnetic field.
 to avoid locking of the armature.
All of these
 to avoid over heating.

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Electrical Machines
The result of slip test on a 3-phase, 20 KVA, 400 V, 50 Hz connected salient pole alternator is given below- Phase value: Vmax = 100 V, Vmin = 96 V, Imax = 10 A and I min = 7 A. The direct and quadranature axis reactances are respectively

 14.28 and 9.60 Ω.
  14.28 and 5.54 Ω.
 8.248 and 9.60 Ω.
 8.248 and 5.54 Ω.

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

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

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