ELECTRICAL MACHINES QUIZ

What is the frequency of rotor current of 50 Hz induction motor operating at 4% slip?

50Hz

1 Hz

2HZ

2.5Hz

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The power input to a 3 - φ induction motor is 60 kW and stator loss is 1 kW the rotor cu loss per phase is

slip X 59 / 3.

slip X 69 / 3.

slip X 50 / 3.

1.

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If an induction machine is run at above the synchronous speed it acts as

a synchronous motor

None of these

an induction generator

an induction motor

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If terminal voltage of one 1000 rpm shunt motor is reduced to half the speed of the motor will be

2000 rpm

250 rpm

1000 rpm

500 rpm

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In a 3 - ÃŽÂ¦ induction motor

power factor at starting is high as compared to that while running.

power factor at starting is low as compared to that while running.

power factor at starting in the same as that while running.

none of them.

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Two identical loss less series motors connected in series across a dc supply voltage, runs at speed of N1 and N2, then ratio of their output power is

1 : 1.

none.

N1 : N2.

N12 : N22.

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The efficiency of a transformer is mainly dependent on

core losses.

dielectric losses.

stray losses.

copper losses.

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Maximum power developed by a synchronous motor depends on

supply voltage and load angle

supply voltage and excitation

supply voltage, load angle and excitation

excitation and load angle

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A shunt generator has a critical field resistance of 300 Ω at a speed of 800 rpm if the speed is raised to 1000 rpm the critical field resistance is

225 Ω.

145 Ω.

150 Ω.

375 Ω.

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Hopkinson test is conducted under which of the following condition?

no load

full load

half load

any of the above

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