1. Which of the following statements regarding a reluctance motor is incorrect ?

It cannot be reversed, ordinarily

It requires no D.C. field excitation for its operation

It is nothing else but a single-phase, salient pole synchronous-induction motor

Its squirrel cage-rotor is of unsymmetrical magnetic construction in order to vary reluctance path between stator and rotor

Answer: It cannot be reversed, ordinarily

Explanation:


2. Hysteresis motor is particularly useful for high-quality record players and tape-recorders because ?

it revolves synchronously

it is not subject to any magnetic or mechanical vibrations

it can be easily manufactured in extremely small sizes of upto 1 W output

it develops hysteresis torque which is extremely steady both in amplitude and phase

Answer: it develops hysteresis torque which is extremely steady both in amplitude and phase

Explanation:


3. In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will ?

become unstable

draw excessive armature current and may burn out

fall out of synchronism and come to stand still

Run as induction motor

Answer: Run as induction motor

Explanation:


4. Which of the following motors has highest starting torque ?

Repulsion motor

Shaped pole motor

Capacitor-start motor

Split-phase motor

Answer: Capacitor-start motor

Explanation:


5. The repulsion-start induction-run motor is used because of ?

good power factor

high efficiency

minimum cost

High starting torque

Answer: High starting torque

Explanation:


6. The speed of a universal motor is generally reduced by using ?

gear trains

V-belts

brakes

chains

Answer: gear trains

Explanation:


7. In a hysteresis motor, the rotor must have ?

retentivity

resistivity

susceptibility

none of the above

Answer: retentivity

Explanation:


8. The speed control of universal motor used for sewing machines is by ?

friction

varying the resistance

tapping the field

centrifugal mechanism

Answer: varying the resistance

Explanation:


9. In repulsion motor, maximum torque is developed when ?

Brush axis is at 45º electrical to the field axis

brush axis coincides with the field axis

brush axis is at 90º electrical to the field axis

none of the above

Answer: Brush axis is at 45º electrical to the field axis

Explanation:


10. Which of the following single-phase motors is suitable for timing and control purposes ?

Reluctance motor

Series motor

Repulsion motor

Universal motor

Answer: Reluctance motor

Explanation: