Single Phase Induction Motor MCQ Question & Answer
1.A single-phase induction motor is
- ASelf-starting
- BNot self-starting
- CSelf-starting with the help of an auxiliary winding
- DNone of the above
2.A single-phase induction motor is running at N rpm. Its synchronous speed is Ns. If its slip with respect to forward field is s, what is the slip with respect to the backward field?
- As
- B? s
- C(1 ? s)
- D(2 ? s)
3.A rotating magnetic field is produced by current is two windings displaced by 90 electrical degrees. This is the principle of
- APhase sequence
- BPhase splitting
- CPhase timing
- DNone of these
4.The torque developed by a single-phase induction motor drop to zero at
- ASynchronous speed
- BA speed slightly above synchronous speed
- CA speed slightly below synchronous speed
- DNone of the above
5.The no load current of a single-phase induction motor is around ____% of full load current
- A10
- B20
- C40
- D80
6.The power factor at which single phase induction motors usually operate is
- A0.7 lag
- B0.8 lag
- C0.7 lead
- DUnity
7.Which of the following tests are performed on single phase ac motors?
- AStator winding resistance test
- BBlocked rotor test
- CNo load test
- DAll of the above
8.Single phase induction motors are made self-starting by
- AIncreasing rotor resistance
- BUsing an external starting device
- CProviding an additional winding on the stator called the auxiliary winding
- DAny of the above methods
9.The two windings provided on the stator of a single-phase induction motor, one main winding and the other auxiliary winding are connected
- AIn parallel
- BIn series
- CEither in series or in parallel depending on the design of the motor
- DThrough inductive coupling
10.The stator winding of a single-phase induction motor is splatted into two parts in order to
- AImprove efficiency
- BImprove power factor
- CDevelop starting torque
- DIncrease speed
11.In a single-phase induction motor
- ABoth the main and auxiliary windings are placed on stator
- BBoth the main and auxiliary windings are placed on rotor
- CMain winding is placed on stator and auxiliary winding on rotor
- DAuxiliary winding is placed on stator and main winding on rotor
12.Phase splitting can be accomplished in a single-phase induction motor.
- AOnly by adding capacitor in series with the auxiliary winding
- BOnly by causing the auxiliary winding to have high reactance
- COnly by causing the auxiliary winding to have low resistance
- DBy any one of the above three methods
13.In a split phase motor, the ratio of number of turns of auxiliary winding to that on main winding is
- AUnity
- BLess than one
- CMore than one
- DTwo
14.Why is a centrifugal switch used in a single-phase induction motor?
- ATo protect the motor from overloading
- BTo improve the starting performance of the motor
- CTo cut off the starting winding at an appropriate instant
- DTo cut in the capacitor during running conditions.
15.Centrifugal switch fitted on the rotor will operate when
- ARotor speed reaches its rated conditions
- BRotor speed exceeds 70 per cent of its rated value
- CRotor speed exceeds synchronous speed
- DRotor speed exceeds 40 per cent of its rated value
16.The torque speed characteristic of two-phase induction motor is largely affected by
- AVoltage
- BSpeed
- CX/R ratio
- DSupply frequency
17.The direction of rotation of a split phase induction motor can be reversed by reversing the connections to the supply of
- AAuxiliary winding only
- BMain winding only
- CWither (a) and (b)
- DBoth (a) and (b) simultaneously
18.The capacitor in a capacitor start induction run ac motor is connected in series with
- AStarting winding
- BRunning winding
- CSquirrel cage winding
- DCompensating winding
19.A single-phase induction motor is provided with a 3- phase slip ring rotor connected to starting resistances. The motor would
- ANot start
- BResult in more starting torque
- CProduce no difference in the starting torque
- DRun at half the synchronous speed
20.Capacitor in a single-phase induction motor is used for
- AImproving the power factor
- BImproving the starting torque
- CStarting the motor
- DReducing the harmonics