Synchronous motor Mcqs

01. Synchronous motor for power factor correction operates at

No load with over-excited fields

No load with under-excited fields

Normal load with minimum excitation

Normal load with zero excitation


02. What happens if field winding of the synchronous motor is short circuited?

First, starts as induction motor then run as synchronous motor

Not start

Motor will burn out

Run as induction motor


03. When the field winding of an unloaded salient pole synchronous motor is open circuited the motor will

Burn

Not start

Run as induction Motor

Run as variable reluctance motor


04. The speed regulation of a synchronous motor is

100%

50%

25%

0%


05. The negative phase sequence in a three phase synchronous motor exists when the motor is

Supplied with an unbalanced voltage

Supplied with an unbalanced load

Unbalanced system fault

All of the above


06. In 3 -Φ synchronous motor if one of the phases is short circuited the motor will

1 point

Run as before

Overheated and eventually burn

Not start

Burn


07. For a synchronous motor, the breakdown torque will be proportional to

1 point

Applied voltage V

V^2

1/V

1/V^2


08. In a synchronous motor, during hunting when the rotor speed exceeds the synchronous speed then damper bar develop

Induction generator torque

Harmonic

DC motor torque

Synchronous motor torque


09. In a synchronous motor, at no load condition, and with normal excitation the armature current drawn by a synchronous motor is

Zero

Lagging applied voltage by 90°

Leading Applied voltage by 90°

In phase with applied voltage


10. In a synchronous motor, “hunting” may be due to variation in any of the following EXCEPT

Winding friction

Frequency

Load

Supply voltage


11. What happens to the synchronous motor when the excitation of an unloaded salient-pole synchronous motor suddenly gets disconnected?

Run as variable reluctance motor

Run as induction motor

Motor will stop

None of the above


12. A synchronous motor working at leading power factor can be used as

1 point

Synchronous induction motor

Static condenser

Synchronous condenser

None of the above

13. Which of the following motor is not self-starting?

1 point

Wound rotor induction motor

Squirrel cage induction motor

DC series motor

Synchronous motor


14. Which of the following motor can operate on lagging as well as leading power factor?

1 point

DC series motor

Wound rotor induction motor

Squirrel cage induction motor

Synchronous motor

15. A synchronous motor is switched on to supply with its field windings short circuited. It will run as

1 point

DC series motor

Induction motor

Induction motor then run as synchronous motor

None of the above

16. The back emf in the stator of a synchronous motor depends on

1 point

Flux density

DC excitation

Load on the motor

Speed of the rotor

17. The maximum value of torque that a synchronous motor, can develop without losing its synchronism, is known as

1 point

Pull out torque

Breaking torque

Slip torque

Non-synchronizing torque


18. The construction of a synchronous motor resembles which of the following machine

Differential compound motor

Alternator

Dc series motor

Induction motor


19. The synchronous motors are not self-starting because

1 point

The direction of torque on the rotor reverses after every half cycle.

Slip is not present in synchronous machine

Starting winding is not present in synchronous machine

DC excitation is used

20. The direction of rotation of synchronous motor can be reversed by reversing

1 point

Field winding

Polarity of the rotor poles

Supply phase sequence

None of the above

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