Induction motor MCQs Part 6

Contents

- 1 The outer cage winding in the double squirrel cage induction motor has
- 2 For a 3-phase induction motor, the mechanical power developed in terms of air gap power (Pag) is expressed mathematically by the equation
- 3 As compared to rotor resistance, the rotor reactance of three phase induction motor at starting is
- 4 When rotor of three-phase induction motor is blocked, the value of slip is
- 5 One of the major advantages of wound rotor induction motor is that
- 6 Friction and windage losses of 3 phase induction motor are
- 7 A pump induction motor is switched on to a supply 30% lower than its rated voltage and the pump runs. What will ultimately happen
- 8 Cogging in an induction motor can be avoided using
- 9 In equivalent circuit diagram of double squirrel-cage induction motor is constructed the two cages can be considered
- 10 Reduced voltage starter can be used for which of following type of induction motors

## The outer cage winding in the double squirrel cage induction motor has

The outer cage winding in double squirrel cage induction motor has:

- Low resistance
- High resistance
- High inductance
- None of these

Correct answer: 2. High resistance

## For a 3-phase induction motor, the mechanical power developed in terms of air gap power (Pag) is expressed mathematically by the equation

For a 3-phase induction motor, the mechanical power developed in terms of air gap power (Pag) is expressed mathematically by the equation:

- Pag/(1 – s)
- Pag * (1 – s)
- Pag * s
- Pag / s

Correct answer: 2. Pag * (1 – s)

## As compared to rotor resistance, the rotor reactance of three phase induction motor at starting is

As compared to rotor resistance, the rotor reactance of three phase induction motor at starting is:

- Smaller
- Larger
- Just identical
- None of above

Correct answer: 2. Larger

## When rotor of three-phase induction motor is blocked, the value of slip is

When rotor of three-phase induction motor is blocked, the value of slip is:

- 0.1
- 0.5
- 1
- Zero

Correct answer: 3. 1

Explanation: When rotor is blocked N = 0 and s = Ns/Ns = 1

## One of the major advantages of wound rotor induction motor is that

One of the major advantages of wound rotor induction motor is that:

- It requires less maintenance
- External resistance can be inserted in rotor circuit
- It is inexpensive
- None of these

Correct answer: 2. External resistance can be inserted in rotor circuit

## Friction and windage losses of 3 phase induction motor are

Friction and windage losses of 3 phase induction motor are:

- Minimum at no-load
- Maximum at no-load
- Same for all loads
- None of above

Correct answer: 2. Maximum at no-load

## A pump induction motor is switched on to a supply 30% lower than its rated voltage and the pump runs. What will ultimately happen

A pump induction motor is switched on to a supply 30% lower than its rated voltage and the pump runs. What will ultimately happen:

- Get heated and subsequently get damaged
- Continue to run at lower speed without damage
- Stalling immediately
- Stalling after sometime

Correct answer: 1. Get heated and subsequently get damaged

## Cogging in an induction motor can be avoided using

Cogging in an induction motor can be avoided using:

- Number of rotor slots more or less than the number of stator slots (not equal)
- Autotransformer starter
- Using dol starter
- Proper ventilation

Correct answer: 1. Number of rotor slots more or less than the number of stator slots (not equal)

## In equivalent circuit diagram of double squirrel-cage induction motor is constructed the two cages can be considered

In equivalent circuit diagram of double squirrel-cage induction motor is constructed the two cages can be considered:

- In parallel
- In series
- In parallel with stator
- In series-parallel

Correct answer: 1. In parallel

## Reduced voltage starter can be used for which of following type of induction motors

Reduced voltage starter can be used for which of following type of induction motors:

- None of the above
- Squirrel cage as well as slip ring induction motor
- Squirrel cage induction motor only but not with slip ring motor
- Slip ring motor only but not with squirrel cage induction motor

Correct answer: 2. Squirrel cage as well as slip ring induction motor