ELECTRICAL MACHINES QUIZ

An induction motor is, in general analogous to

None of these

auto transformer.

two winding transformer with secondary open circuited.

two winding transformer with secondary short circuited.

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A 220 V, DC shunt motor is operating at a speed of 1440 rpm. The armature resistance is 1.0 Ω and armature current is 10 A. of the excitation of the machine is reduced by 10%, the extra resistance to be put in the armature circuit to maintain the same speed and torque will be

3.1 Ω

2 .1 Ω

1.8 9 Ω

1.79 Ω

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In an induction motor, what is the ratio of rotor input to rotor copper loss?

1-S

S

1/(1-S)

1/S

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The polarity of a DC generator can be reversed by

increasing field current.

reversing the field current.

any of above.

reversing field electric current as well as direction of rotation.

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In which of the following, voltage regulation may be zero or negative

lagging power factor

unity power factor

leading power factor

All of these

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The current drawn by the armature of DC motor is directly proportional to

The speed of motor.

The torque required.

None of above.

The voltage across the terminals.

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The emf induced in the dc generator armature winding is

DC

AC

AC and DC

None of these

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In a DC Shunt Motor if the load current increases then field flux

remains constant.

decreases.

decreases

increases.

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Armature of DC machine is made of

silicon steel.

conducting material.

insulating material.

non-ferrous material.

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Eb/Vt ratio of a DC motor is an indication of

efficiency.

speed regulation.

running torque.

starting torque.

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