DGVCL Exam Paper (11-12-2011)
The efficiency of a transformer at full load, 0.8 p.f. lag is 90%. Its efficiency at full load, 0.8 p.f. lead will be

More than 90%
80 %
Less than 90%
90 %

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DGVCL Exam Paper (11-12-2011)
DC series motors are best suited for traction work because

Torque and speed are inversely proportional to the square of the armature current
Its torque is proportional to the square of the armature current and speed is directional proporational to torque
Torque and speed are proportional to the square of the armature current
Its torque is proportional to the square of the armature current and speed is inversely proportional to torque

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DGVCL Exam Paper (11-12-2011)
The main advantage of using fractional pitch winding is to refuce

Size of the machine
Harmonics in the generated emf
Cost of the machine
Amount of copper in the winding

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DGVCL Exam Paper (11-12-2011)
The purpose of embedding the damper winding in the pole face of a synchronous motor is to

Eliminate losses on account of fair friction
Reduce winding losses
Reduce bearing friction
Eliminate hunting and provide adequate starting torque

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