Three Phase Induction Motor MCQs

A three-phase induction motor is widely employed in electrical industries. An induction motor is named so because the rotor voltage is induced in rotor windings rather than being physically connected by wires. Given below are top 10 Three Phase Induction Motor MCQs.

The 3-phase induction motor is

The 3-phase induction motor is

1. Almost a constant-speed motor
2. Highly variable speed motor
3. Very expensive motor
4. Not easily maintainable

Correct answer: 1. Almost a constant-speed motor

The slip of three phase induction motor at no-load is

The slip of three phase induction motor at no-load is:

1. Practically zero
2. 0.4
3. 0.525
4. 1

Correct answer: 1. Practically zero

For a three-phase induction motor the reactance of rotor circuit is maximum at

For a three-phase induction motor the reactance of rotor circuit is maximum at:

1. No load
2. Half load
3. Full load
4. Starting

Correct answer: 4. Starting

Explanation:

Rotor reactance = s * Rotor reactance at standstill position Under starting condition s = 1, Hence the rotor reactance will be maximum at starting

The maximum torque developed under running condition in squirrel cage induction motor is

The maximum torque developed under running condition in squirrel cage induction motor is:

1. Less than starting torque
2. Equal to starting torque
3. Full load torque
4. Much high than full-load torque

Correct answer: 4. Much high than full-load torque

If one of the lines of a 3 phase induction motor is interchanged, next to that

If one of the lines of a 3 phase induction motor is interchanged, next to that

1. Flux speed increases
2. Flux speed decreases
3. Flux speed remains keeping same direction
4. Flux speed remains same but direction is reversed

Correct answer: 4. Flux speed remains same but direction is reversed