ELECTRICAL MACHINES QUIZ

In DC machines internal characteristics are plotted between

Eg vs Ia

Eg vs load current

Vt vs Ia

Vt vs load current

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Which of the following motor is expensive for same Kw output rates?

Synchronous motor.

Induction motor.

AC single phase motor.

DC Shunt Motor

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In DC machines shape of net flux density is?

saddle shape

peaky in nature

flat tapped or trapezoidal

sine wave

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which of the following type of brush and their application is/are correct

carbon brush → normal ratings

All of these

copper graphite → low voltage high current density

electro graphite → large ratings

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A motor armature conductor of length 0.5 m is exposed to a flux density of 4 Wb / m2. Calculate the force experienced by the conductor, when the armature current is 5 Amp?

Can't be determined.

20 N.

15 N.

None of these.

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The torque speed characteristics of a AC servomotor is approximately

linearised

any of the above

parabola

hyperbola

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In V/f speed control of 3-phase induction motor, with increase in frequency, the slip at which maximum torque occurs

None of these

increase.

either of these.

decrease.

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What is/are the necessary conditions for parallel operation of alternators?

Both 1and 2

Frequency should be same

Speed of alternators should be same

Terminal voltage is same

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Which motor used in Lathe machine?

D.C. shunt motor.

None of these

D.C . series motor.

D.C. cumulative compound motor.

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Transformer action requires a

constant magnetic flux.

alternating magnetic lux.

alternating electric flux.

increasing magnetic flux.

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