300 Important Three Phase Induction Motor MCQ Question and Answer | PDF Free Download
1.In a 3-phase induction motor, the number of slots on stator is not kept an exact multiple of the number of rotor slots because it
- AFacilitates cooling
- BAvoids magnetic locking between stator field and rotor
- CImproves efficiency
- DImproves PF
2.The difference between the number of stator slots and that of rotor slots in an induction motor should not be equal to P, 2P or 5P. It is essential in order to avoid
- ASynchronous cusps
- BCrawling
- CMagnetic locking
- Dnoise and vibrations
3.The rotor slots in a 3-phase induction motor are kept inclined. This phenomenon is known as
- ASkewing
- BCrawling
- CCogging
- DNone of these
4.In an induction motor, skewing of motor bars reduces
- AEddy currents and copper requirement
- BNoise, vibrations and synchronous cusps
- CBoth (a) and (b)
- DNone of these
5.Skew of rotor bar eliminates
- AThe effect of space harmonics
- BThe entire effects of crawling
- CMagnetic noise
- DVibration due to unequal force developed on rotor
6.Jogging of an induction motor is
- AEnergizing a motor once or repeatedly to have small movement for mechanisms
- BA process of synchronization
- CA method of braking
- DNone of the above
7.In 3-phase induction motors, sometimes copper bars are placed deep in the rotor. It is done in order to improve
- AEfficiency
- BStarting torque
- CPower factor
- DNone of these
8.In a squirrel cage induction motor high starting torque is achieved by using
- AHigh resistance in series with the rotor circuit
- BLow resistance across the rotor circuit
- CDouble cage rotor
- DNone of these
9.The outer cage of a double squirrel rotor consists of
- AManganese brass
- BRed copper
- CBronze
- DSteel
10.In double cage induction motor, the inner cage has
- AHigh resistance and high leakage reactance
- BHigh resistance and low leakage reactance
- CLow resistance and high leakage reactance
- DLow resistance and low leakage reactance
11.In the equivalent circuit of a double cage induction motor, the two rotor cages can be considered
- ATo be in parallel
- BTo be in series parallel
- CTo be in series
- DTo be parallel with stator
12.The advantage of the double squirrel cage induction motor over single cage rotor is that its
- AEfficiency is higher
- BPower factor is higher
- CSlip is larger
- DStarting current is lower
13.In a double squirrel cage induction motor, the resistance of upper cage is ____that of inner cage.
- AEqual to
- B4 to 5 time of
- COne fourth of
- DNone of these
14.The deep bar rotors of double cage rotors are employed to
- AIncrease starting torque
- BImprove efficiency
- CIncrease pull out torque
- DReduce rotor core loss
15.For high starting torque, the most suitable 3-phsae induction motor is ___induction motor
- ASlip ring
- BSquirrel cage
- CDouble cage
- DDeep bar squirrel cage
16.Which of the following AC motor is widely used?
- ASquirrel cage induction motor
- BSlip ring induction motor
- CDouble cage induction motor
- DSynchronous motor
17.A squirrel cage induction motor is not favored when ______ in the main consideration.
- AInitial cost
- BMaintenance cost
- CHigh starting torque
- DHigher efficiency and higher power factor
18.A slip ring induction motor is recommended for application requiring
- AHigh starting torque
- BVariable speed operation
- CFrequent starting, stopping and reversing operation
- DAll of the above features
19.Unbalanced 3-phase voltage supply to an induction motor causes excessive heating of
- ARotor
- BStator
- CRotor shaft
- DNone of these
20.Unbalance supply voltage given to a 3- phase delta connected induction motor will cause
- AZero sequence currents
- BLess heating of motor
- CNegative sequence component current
- DAll the above