Synchronous Motors MCQs

1.What is the primary application of an over-excited synchronous motor?

Loads with varying power demandsLoads requiring adjustable speedsLoads that need minimal torqueImproving power factor in electrical systemsNone of the above

2.At what operating condition can a synchronous motor generate synchronous torque?

Only when it is carrying a loadWhen it is over-excitedExclusively at synchronous speedAt speeds either below or above synchronous speed

3.What factors determine the maximum power output of a synchronous motor?

Only the excitation of the rotorOnly the input voltage from the supplyBoth the rotor excitation and the supply voltageThe rotor excitation, supply voltage, and the maximum coupling angle of 90°None of the above

4.For a synchronous motor, the breakdown torque is proportional to which of the following?

Proportional to the square of the voltage appliedProportional to the voltage appliedInversely proportional to the voltage appliedNone of the given options

5.What is the term for a synchronous motor operating at a leading power factor without any mechanical load?

6.When a synchronous motor is correctly synchronized with the power supply, operating without any load and experiencing negligible losses, what will be the condition of the stator current?

The stator current will be zeroThe stator current will be minimalThe stator current will be extremely highThe back electromotive force will exceed the supply voltageNone of the above

7.What does the coupling angle, also known as the load angle, of a synchronous motor represent?

The angle between the rotor and the stator teethThe angle formed between the rotor and stator poles having opposite magnetic polarityThe angle between the rotor and stator poles with identical polarityNone of the aboveThe angle between the rotor shaft and stator core

8.What is the term for the highest torque a synchronous motor can produce while stationary, regardless of the rotor's angular position, at rated stator voltage and frequency?

locked-rotor torquesynchronous torquepull-up torquereluctance torque

9.What will happen to an unloaded salient pole synchronous motor if its field winding becomes open circuited?

It will come to a haltIt will operate like an induction motorIt will act as a static capacitorIt will emit thick smoke and burn

10.What characteristic does a synchronous machine with a low short-circuit ratio exhibit?

11.What is the term for the highest steady load torque at which a synchronous motor can achieve synchronism at its rated rotor voltage and frequency?

torque required to accelerate into synchronismpull-in torquemaximum torque before losing synchronismno applicable term

12.Which machine's design is most similar to that of a synchronous motor?

a series-wound motoran induction-type motoran alternatora rotary type converter

13.At what operating condition do synchronous motors function to achieve power factor correction?

Running without load and with heavily over-excited fieldsRunning without load and with under-excited fieldsOperating under normal load with minimal excitationOperating under normal load with no excitation

14.Which type of loss does not occur on the surface of the stator core in a synchronous motor?

Eddy current losses within the conductorsIron losses occurring in the stator coreCopper losses inside the conductor slotsWindage losses caused by air frictionAll of the above losses occur on the stator core surface

15.As which parameter increases does the size of a synchronous motor reduce?

magnetic flux densitypower output ratingrotational speedevery one of the above

16.In a synchronous motor, which type of loss remains constant regardless of the load applied?

Windage lossCopper lossesAll of the aboveNone of these

17.In a synchronous motor, when does the armature current reach significantly high levels?

18.On what factor does the back electromotive force (e.m.f.) in the stator of a synchronous motor primarily rely?

19.What happens to the power factor of a synchronous motor when its field excitation is below the required level?

20.What is the primary purpose of the damping winding in a synchronous motor?

Minimize the noise generated during operationDecrease the formation of eddy currentsSupply only the initial starting torquePrevent hunting and supply the starting torqueNone of the mentioned purposes