300 Important Three Phase Induction Motor MCQ Question and Answer | PDF Free Download
1.Circle diagram of an induction motor can be used to determine its
- APower factor
- BEfficiency
- COutput and Slip
- DAll of the above
2.An induction motor is said to be crawling when
- AIt runs at one seventh of rated speed
- BIt accelerates too fast
- CIt is subjected to fluctuating loads
- DIt is started on full load
3.Zero sequence impedance of a 3-phase cage induction motor is due to
- AStator circuit 3rd time harmonic
- BStator circuit 3rd space harmonic
- CRotor circuit 3rd time harmonic
- DRotor circuit 3rd space harmonic
4.An induction motor when started on load does not accelerate up to full speed but run at 1/7th of the rated speed. The motor is said to be
- ALocking
- BPlugging
- CCrawling
- DCogging
5.Crawling in an induction motor is due to
- ATime harmonics in supply
- BSlip ring rotor
- CSpace harmonics produced by winding currents
- DInsufficient starting torque
6.The crawling in the induction motor is caused by
- AImproper design of stator laminations
- BLow voltage supply
- CHigh loads
- DHarmonics developed in motor
7.The phenomenon of crawling in a 3-phase induction motor may be due to
- AUnbalanced supply voltage
- B7th space harmonics of air gap filed
- C7-time harmonics of voltage wave
- D5th space harmonics
8.In an induction motor, when the number of stator slots is equal to an integral multiple of rotor slots
- AThere may be a discontinuity in torque slip characteristic
- BA high starting torque will be available
- CThe maximum torque will be high
- DThe machine will fail to start
9.Crawling of induction motor occurs due to
- AHarmonic synchronous torques
- BHarmonic induction torques
- CVibration torques
- DBoth (a) and (b)
10.Presence of 5th harmonics in induction motor causes
- ACogging
- BCrawling
- CSmall reverse braking torque
- DHunting
11.The cogging occurs in induction motors due to
- Aharmonic induction torques
- Bharmonic synchronous torques
- Cvibration torques
- Dboth (a) and (b)
12.Cogging of induction motors occurs at
- AHigh voltage and when the number of stator teeth and rotor teeth are equal
- BHigh voltage and when the number of stator teeth and rotor teeth are not equal
- CLow voltage and when the number of stator teeth and rotor teeth are equal
- DLow voltage and when the number of stator teeth and rotor teeth are not equal
13.An increase in number of poles of an induction motor results in
- ADecrease in maximum PF
- BIncrease in maximum PF
- CNo change in maximum PF
- DCannot be predicted
14.Increase in length of air gap in an induction motor causes
- ADecrease in power factor
- BDecrease in pulsation losses
- CIncrease the ampere turns required to produce same flux density in the air gap
- DAll of the above
15.An induction motor with larger number of slots has ____overload capacity
- ALow
- BLarge
- CNo effect on
- DNone of these
16.The induction motors which are provided with open slots have
- AReduced leakage reactance
- BIncreased starting current, starting torque and breakdown torque
- CBetter PF
- DBoth (a) and (b)
17.Semi closed or totally closed slots are used in induction motors to
- AImprove pull out torque
- BIncrease pull out torque
- CIncrease efficiency
- DReduce magnetizing current and improve power factor
18.The stator of a small (up to 5hp) induction motor is provided with
- AOpen slots with parallel teeth
- BOpen slots with tapered teeth
- CSemi closed slots with parallel teeth
- DTotally closed slots with parallel teeth
19.“Cogging” in induction motor occurs when
- ANumber of stator teeth-number of rotor teeth=odd number
- BNumber of stator teeth-number of rotor teeth=even number
- CNumber of stator teeth-number of rotor teeth =0
- DNumber of stator teeth-number of rotor teeth=negative
20.In a 3-phase induction motor, the stator slots are
- AEqual to rotor slots
- BExact multiple of rotor slots
- CNot exact multiple of rotor slots
- DNone of the above