Electrical Engineering MCQs

Page No. 267

Blocked rotor test on induction motors is used to find out?


aleakage reactance

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bpower factor on short circuit

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cshort-circuit current under rated voltage

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dall of the above

✓


View Answer all of the above

The complete circle diagram of induetion motor can be drawn with the help of data found from__________?


anoload test

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bblocked rotor test

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cstator resistance test

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d all of the above

✓


View Answer all of the above

In the squirrel-cage induction motor the rotor slots are usually given slight skew__________?


ato reduce the magnetic hum and locking tendency of the rotor

✓


bto increase the tensile strength of the rotor bars

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cto ensure easy fabrication

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dnone of the above

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The torque of a rotor in an induction motor under running condition is maximum__________?


a at the unit value of slip

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bat the zero value of slip

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c at the value of the slip which makes rotor reactance per phase equal to the resistance per phase

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dat the value of the slip which makes the rotor reactance half of the rotor

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What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?


aThe slip of the motor will be 5%

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bThe rotor will not run

✓


cThe rotor will run at very high speed

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dThe torque produced will be very large

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The stating torque of the slip ring induction motor can be increased by adding__________?


aexternal inductance to the rotor

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bexternal resistance to the rotor

✓


cexternal capacitance to the rotor

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dboth resistance and inductance to rotor

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A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6 poles. The slip of the machine will be__________?


a 0.01

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b0.02

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c0.03

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d0.04

✓


View Answer 0.04

The power scale of circle diagram of an induction motor can be found from__________?


astator resistance test

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bno-load test only

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cshort-circuit test only

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dnoue of the above

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A change of 4% of supply voltage to an induction motor will produce a change of approximately ________?


a4% in the rotor torque

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b8% in the rotor torque

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c12% in the rotor torque

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d16% in the rotor torque

✓



The shape of the torque/slip curve of induction motor is__________?


aparabola

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b hyperbola

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crectangular parabola

✓


d straigth line

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View Answer rectangular parabola

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