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 system lost residual magnetism
 field winding was wrongly connected
 field resistance was higher than critical resistance

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Electrical Machines
An inverted V curve of synchronous motor shows variation of

  power factor and DC excitation at constant load.
 supply voltage and excitation current at constant load.
 supply voltage and field current at constant excitation.
 power factor and supply voltage during hunting.

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