ELECTRICAL MACHINES QUIZ

Generators work on the principle of production of

dynamically and statically induced emf.

None of these

statically induced emf.

dynamically induced emf.

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A 500 V, 55 kVA single phase alternator has an effective resistance of 0.5 ÃŽÂ©. An excitation current of 10 A produces 200 A armature current on short circuit and an emf of 450 V on per circuit. The synchronous reactance will be

25.564 ÃŽÂ©.

2.781 ÃŽÂ©.

2.241 ÃŽÂ©.

2.74 ÃŽÂ©.

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A shaded pole single phase induction motor can be used for

food mixers

personal computers as cooling fan

wet grinders

tape recorders

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Essential conditions for two DC generators are connecting for parallel operation is/are

polarities should be same.

both A and B.

terminal voltage should be same.

rating of generators should be same.

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The field system of an alternator is usually excited

3 - ÃŽÂ¦, 50 Hz and 400 V.

250 / 250 V DC.

230 V AC.

110 / 220 V AC.

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The demagnetising component of armature reaction in a DC generator

reduces inter poles flux density.

increases armature speed.

results in sparking trouble.

reduces generator emf.

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Flux density under trailing pole tips in case of generator will

either increase or decrease

increase

decrease

None of these

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In DC generators brushes are used for

convert ac armature current in to dc

collecting of current without any sparkings

reduce eddy current loss

collecting of voltage

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A voltmeter gives 120 oscillations per minute when connected to the rotor of an induction motor. The frequency is 50Hz. The slip of the motor is

4%

2%

5%

25%

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Total core loss is also called as -------------?

Copper loss

Hysteresis loss

Eddy current loss

Magnetic loss

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