Electrical Machines
A 3- phase synchronous motor can operate over a wide range of power factors i.e. from lagging to leading power factor. This is achieved by

 varying the speed.
 changing the field excitation.
 changing the load.
 varying the applied voltage.

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Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

 there was a break in the armature circuit
 field resistance was higher than critical resistance
 field system lost residual magnetism
 field winding was wrongly connected

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