Explore topic-wise MCQs in Electrical Machines.

This section includes 14 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.

1.

Reactor method of starting is preferred over resistance method because _________

A. III, IV
B. I, II, III
C. II, III, IV
D. I, IIView Answer
Answer» B. I, II, III
Discussion
2.

During the blocked rotor test the wattmeter reading will be _________

A. I, V
B. II, III, IV
C. I, III, II, IV
D. II, IVView Answer
Answer» B. II, III, IV
Discussion
3.

If use auto transformer method starting to start an induction motor to replace star-delta method, then the required tapping on the transformer will be _________

A. 57.73%
B. 86.7%
C. 57%
D. 66.66%
Answer» B. 86.7%
Discussion
4.

During no load test the wattmeter reading will be _________

A. I, II, IV
B. II, III, IV
C. I, III, II, IV
D. II, IVView Answer
Answer» B. II, III, IV
Discussion
5.

A three phase induction motor is sometimes called a generalized transformer in so far as voltage and frequency transformation has been concerned. Then the rotor emf E2 and the rotor current I2 are zero at _________

A. Ns
B. 2Ns
C. Zero
D. Slip of 50%
Answer» B. 2Ns
Discussion
6.

A_THREE_PHASE_INDUCTION_MOTOR_IS_SOMETIMES_CALLED_A_GENERALIZED_TRANSFORMER_IN_SO_FAR_AS_VOLTAGE_AND_FREQUENCY_TRANSFORMATION_HAS_BEEN_CONCERNED._THEN_THE_ROTOR_EMF_E2_AND_THE_ROTOR_CURRENT_I2_ARE_ZERO_AT?$

A. Ns
B. 2Ns
C. zero
D. slip of 50%
Answer» B. 2Ns
Discussion
7.

A_THREE_PHASE_INDUCTION_MOTOR_IS_SOMETIMES_CALLED_A_GENERALIZED_TRANSFORMER_IN_SO_FAR_AS_VOLTAGE_AND_FREQUENCY_TRANSFORMATION_HAS_BEEN_CONCERNED._HOW_A_THREE_PHASE_INDUCTION_MOTOR_OPERATES_WHEN_ROTOR_FREQUENCY_IS_LESS_THAN_STATOR_FREQUENCY??$

A. It operates as induction motor
B. Emf is induced in rotor
C. Rmf will rotate at synchronous speed
D. All of the mentioned
Answer» E.
Discussion
8.

If use auto transformer method starting to start an induction motor to replace star-delta method, then the required tapping on the transformer will be$

A. 57.73%
B. 86.7%
C. 57%
D. 66.66%
Answer» B. 86.7%
Discussion
9.

The starting method for a 3-phase squirrel-cage induction motor which is inferior in view of poor starting torque per ampere of line current drawn,

A. series-inductor method of starting
B. direct-on-line starting
C. auto-transformer method
D. star-delta method
Answer» B. direct-on-line starting
Discussion
10.

A three phase induction motor is sometimes called a generalized transformer in so far as voltage and frequency transformation has been concerned. How a three phase induction motor operates when rotor frequency is greater than stator frequency?

A. Rotor will be driven against rmf
B. Rotor will be driven in direction of rmf
C. No emf will be induced
D. The losses will be maximum
Answer» B. Rotor will be driven in direction of rmf
Discussion
11.

A three phase induction motor is sometimes calles a generalized transformer in so far as voltage and frequency transformation has been concerned. How a three phase induction motor operates when rotor frequency is equal to stator frequency?

A. It will not operate
B. It will operate as induction motor only
C. It will operate as induction generator
D. It will operate in braking mode
Answer» B. It will operate as induction motor only
Discussion
12.

Two three phase induction motors A and B are identical in all respects except that motor A has a larger air-gap than motor B. Which motor will have more no load current?

A. A
B. B
C. Both A and B
D. Neither A nor B
Answer» B. B
Discussion
13.

The direction of rmf when a single phase supply is given to stator of three phase induction motor is

A. zero
B. Ns
C. 2Ns
D. -Ns
Answer» B. Ns
Discussion
14.

The rotor of a three phase induction motor can never attain synchronous speed.

A. True
B. False
Answer» B. False
Discussion