Electrical Machines MCQ

Welcome to your Electrical Machines MCQ

Can an induction motor be said analogous?

Transformer

Synchronous motor

Universal motor

Stepper motor

None

What does a 3-phase induction motor with its rotor blocked behave similar to?

Transformer under short circuit of secondary terminals

Transformer under open circuit of secondary

Synchronous motor under slip test

Synchronous motor under open circuit

None

Which of the following represents the commutator pitch?

Number of conductors spanned by one coil at the back end of the armature.

Number of conductors spanned by one coil at the front end of the armature.

The distance between the staring of first coil and its next successive coil

Number of commutator segments between two successive coils.

None

Consider a 4 pole lap winding used in a DC machine and What is the number of parallel paths?

None

Consider a 6 pole lap winding used in a DC machine and What is the number of parallel paths?

None

Lap winding is prefered for which type of machines?

low current and low voltage

high current and high voltage

high current and low voltage

low current and high voltage

None

Equalizer rings are used in which of the followings?

Lap winding

Wave winding

Both 1 and 2

None of the above

None

Wave winding is prefered for which of the following rating?

low current and low voltage

high current and high voltage

high current and low voltage

low current and high voltage

None

What are dummy coils used for?

Increasing efficiency

Reducing armature reaction

Mechanical balancing

All of the above

None

10.

What are the shunt resistance & armature resistance values for a DC machine?

high and high

high and low

low and low

low and high

None

11.

What is/are the necessary conditions for voltage build up in self excited generator?

Poles should contain residual flux.

Field winding should be properly connected to armature winding.

Field winding resistance should be less than critical resistance.

All of the above.

None

12.

No load saturation characteristics are plotted between

No load voltage and field current

No load voltage and armature current

Short circuit current and field current

Short circuit current and armature current

None

13.

Cross magnetization effects which of the following?

Commutation

Reduction in main field flux

Reduces the terminal voltage

Both 2 and 3

None

14.

Demagnetization effects which of the following?

Commutation

Reduction in main field flux

Reduces the terminal voltage

Both B and C

None

15.

Which of the following is/are effects of armature reaction?

Increase the iron loss

Increase the maintenance and repair

Increases the design cost

All of the above

None

16.

In DC machine torque depends on which of the following?

flux (φ)

Armature current (I)

Both A and B

Speed

None

17.

In DC machine shape of main field flux distribution is?

Triangular

Flat tapped or trapezoidal

Saddle shape

Peaky in nature

None

18.

In DC machine shape of armature MMF wave is?

Triangular and directed towards brush axis

Triangular and directed towards main pole

Saddle shape

Peaky in nature

None

19.

Series generators are used in which of the following applications?

Air crafts

Arc welding

Used as boosters in dc distribution or transmission

All of the above

None

20.

Which of the following generators are used in arc welding?

Shunt generators

Series generators

Cumulative compound generators

Differential compound generators

None

21.

Ideal value of voltage regulation of a device is?

∞

A positive finite value

A finite negative value

None

22.

Which motor cannot be started on no load?

Shunt motors

Series motors

Cumulative compound motors

Both B and C

None

23.

Which of the following motors has negative speed regulation?

Shunt motors

Series motors

Differential compound motors

Both B and C

None

24.

Armature reaction effect is more in which of the following methods?

Field weakening method

Armature resistance control

Same in both methods

None of the above

None

25.

Induction motor operation depends on

Rotating magnetic field

Stationary magnetic field

Either of these

None of the above

None

1 out of 25

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