3 Phase Induction Motors solved MCQs

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Which of the following component is usually fabricated out of silicon steel ? Which of the following component is usually fabricated out of silicon steel ? Bearings Shaft Statorcore None of the above discuss The answer is: C. Statorcore
The frame of an induction motor is usually made of The frame of an induction motor is usually made of silicon steel cast iron aluminium bronze discuss The answer is: B. cast iron
The shaft of an induction motor is made of The shaft of an induction motor is made of stiff flexible hollow any of the above discuss The answer is: A. stiff
The shaft of an induction motor is made of The shaft of an induction motor is made of high speed steel stainless steel carbon steel cast iron discuss The answer is: C. carbon steel
In an induction motor, no-load the slip is generally In an induction motor, no-load the slip is generally less than 1% 1.5% 2% 4% discuss The answer is: A. less than 1%
In medium sized induction motors, the slip is generally around In medium sized induction motors, the slip is generally around 0.04% 0.4% 4% 14% discuss The answer is: C. 4%
In squirrel cage induction motors, the rotor slots are usually given slight skew in orderto In squirrel cage induction motors, the rotor slots are usually given slight skew in orderto reduce windage losses reduce eddy currents reduce accumulation of dirt and dust reduce magnetic hum discuss The answer is: D. reduce magnetic hum
In case the air gap in an induction motor is increased In case the air gap in an induction motor is increased the magnetising current of the rotor will decrease the power factor will decrease speed of motor will increase the windage losses will increase discuss The answer is: B. the power factor will decrease
Slip rings are usually made of Slip rings are usually made of copper carbon phospor bronze aluminium discuss The answer is: C. phospor bronze
A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. willbe A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. willbe 200 Hz 50 Hz 2 Hz 0.2 Hz discuss The answer is: C. 2 Hz
In Ns is the synchronous speed and s the slip, then actual running speed of aninduction motor will be In Ns is the synchronous speed and s the slip, then actual running speed of aninduction motor will be Ns s.N, (l-s)Ns (Ns-l)s discuss The answer is: C. (l-s)Ns
The efficiency of an induction motor can be expected to be nearly The efficiency of an induction motor can be expected to be nearly 60 to 90% 80 to 90% 95 to 98% 99% discuss The answer is: B. 80 to 90%
The number of slip rings on a squirrel cage induction motor is usually The number of slip rings on a squirrel cage induction motor is usually two three four none discuss The answer is: D. none
The starting torque of a squirrel-cage induction motor is The starting torque of a squirrel-cage induction motor is low negligible same as full-load torque slightly more than full-load torque discuss The answer is: A. low
A double squirrel-cage induction motor has A double squirrel-cage induction motor has two rotors moving in oppsite direction two parallel windings in stator two parallel windings in rotor two series windings in stator discuss The answer is: C. two parallel windings in rotor
Star-delta starting of motors is not possible in case of Star-delta starting of motors is not possible in case of single phase motors variable speed motors low horse power motors high speed motors discuss The answer is: A. single phase motors
The term 'cogging' is associated with The term 'cogging' is associated with three phase transformers compound generators D.C. series motors induction motors discuss The answer is: D. induction motors
In case of the induction motors the torque is In case of the induction motors the torque is inversely proportional to (Vslip) directly proportional to (slip)2 inversely proportional to slip directly proportional to slip discuss The answer is: D. directly proportional to slip
An induction motor with 1000 r.p.m. speed will have An induction motor with 1000 r.p.m. speed will have 8 poles 6 poles 4 poles 2 poles discuss The answer is: B. 6 poles
The good power factor of an induction motor can be achieved if the average fluxdensity in the air gap is The good power factor of an induction motor can be achieved if the average fluxdensity in the air gap is absent small large infinity discuss The answer is: B. small

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