Home » Electrical Engineering » Electrical Engineering MCQ » Single Phase Induction Motor

### 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

Self-starting with the help of an auxiliary winding

Explanation:

A single-phase induction motor is Self-starting with the help of an auxiliary winding.

• As
• B? s
• C(1 ? s)
• D(2 ? s)

(2 ? s)

Explanation:

### 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

Phase splitting

Explanation:

### 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

A speed slightly below synchronous speed

Explanation:

The torque developed by a single-phase induction motor drop to zero at a speed slightly below synchronous speed.

• A10
• B20
• C40
• D80

40

Explanation:

• A0.7 lag
• B0.8 lag
• DUnity

0.7 lag

Explanation:

### 7.Which of the following tests are performed on single phase ac motors?

• AStator winding resistance test
• BBlocked rotor test
• DAll of the above

All of the above

Explanation:

### 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

Providing an additional winding on the stator called the auxiliary winding

Explanation:

### 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

In parallel

Explanation:

### 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

Develop starting torque

Explanation:

### 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

Both the main and auxiliary windings are placed on stator

Explanation:

In a single-phase induction motor both the main and auxiliary windings are placed on stator.

### 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

By any one of the above three methods

Explanation:

### 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

Less than one

Explanation:

### 14.Why is a centrifugal switch used in a single-phase induction motor?

• 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.

To cut off the starting winding at an appropriate instant

Explanation:

### 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

Rotor speed exceeds 70 per cent of its rated value

Explanation:

### 16.The torque speed characteristic of two-phase induction motor is largely affected by

• AVoltage
• BSpeed
• CX/R ratio
• DSupply frequency

X/R ratio

Explanation:

### 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

Wither (a) and (b)

Explanation:

### 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

Starting winding

Explanation:

The capacitor in a capacitor start induction run ac motor is connected in series with Starting 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

Result in more starting torque

Explanation:

### 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