300 Important Three Phase Induction Motor MCQ Question and Answer | PDF Free Download
1.An induction motor works with
- ADC only
- BAC Only
- CBoth AC & DC
- DNone of these
2.The stator frame in an induction motor is used to
- AHold the armature stampings in position
- BVentilate the armature
- CProtect the whole machine
- DProvide return path for the flux
3.The frame of an induction motor is made of
- AAluminum
- BSilicon steel
- CClosed grained cast iron
- DStainless steel
4.The stator core of a 3- phase induction motor is laminated in order to reduce the
- AEddy current loss
- BHysteresis loss
- CBoth eddy current and hysteresis I loss
- DWeight of the stator
5.Use of fractional pitch winding
- AResults in reduced leakage reactance
- BResults in reduced axial length of the machine
- CMakes it stiffer
- DAll of the above
6.If all the stator coils of an induction motor are connected for the same magnetic polarity, there will be formed an equal number of
- ARotor poles with same polarity
- BRotor poles with opposite polarity
- CConsequent pole with opposite polarity
- DConsequent poles with same polarity
7.The induction motor shaft should be
- AHollow
- BStiff
- CFlexible
- DAny of these
8.The induction motor shaft is made of
- AMild steel
- BCast iron
- CHigh speed steel
- DStainless steel
9.Induction motors normally use die cast aluminum rotor because aluminum is
- ACheaper in cost
- BLighter in weight
- CEasy to cast owing to its low melting point and is easily available
- DOf low resistivity
10.In a 3-phase squirrel cage induction motor
- ARotor conductors are short circuited through end rings
- BRotor conductor ends are short circuited through slip rings
- CRotor conductors are kept open
- DNone of the above
11.The squirrel cage rotor of a 6-pole induction motor can be used for ____induction motor
- AOnly 6-pole
- B6 or 12 poles
- CAny number of poles in an
- DNone of the above
12.The squirrel cage induction motors are provided with blades in order to
- AFacilitate cooling of rotor
- BBalance the rotor dynamically
- CEliminate noise
- DNone of these
13.The rotor of a 3-phase wound rotor induction motor is provided with
- ASingle phase winding
- BThree phase winding
- CHeavy copper or aluminum bars placed in rotor slots
- DHeavy short-circuited end rings
14.In a 3-phase slip ring induction motor, the rotor winding terminals are brought out through slip rings to
- AConnect extra resistance across them during starting
- BConnect them either in star or in delta as per need
- CConnect to 3-phase ac supply
- DClose the rotor circuit externally
15.The rotor winding for a 3-phase slip ring induction motor having delta connected stator must be connected in
- ADelta
- BStar
- CDelta or star according to need
- DNone of the above
16.In a 3-phase slip ring induction motor, brushes are connected to
- AExternal star connected resistors
- BDC supply
- C3 ? Phase AC supply
- DEqualizing coils
17.In a 3-phase wound rotor induction motor the short circuit gear is used to short circuit the
- AStator phases of the motor
- BRotor at slip rings
- CStarting resistance in the starter
- DNone of the above
18.Uneven gap in an induction motor is likely to cause
- AHeating of motor
- BUnbalancing of motor shaft
- CBoth (a) and (b)
- DNone of these
19.A smaller air gap in a poly phase induction motor helps to
- AReduce the chance of crawling
- BIncrease the starting torque
- CReduce the chance of cogging
- DReduce the magnetizing current
20.In an induction motor, if the air gap is increased
- A Its speed will reduce
- BIts efficiency will improve
- CIts power facts will reduce
- DIts breakdown torque will reduce