Question 1

The armature current of the synchronous motor

Accepted Answer

A) has large values for low excitation i niy 
B) has large values for high excitation only 
C) has large values for low and high excitation 
D) any of the above 
A) has large values for low excitation i niy 
B) has large values for high excitation only 
C) has large values for low and high excitation 
D) any of the above C

Question 2

If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then

Accepted Answer

A) the stator current will be zero 
B) the stator current will be very small 
C) the stator current will be very high 
D) the back e.m.f. will be more than the supply voltage 
A) the stator current will be zero 
B) the stator current will be very small 
C) the stator current will be very high 
D) the back e.m.f. will be more than the supply voltage A

Question 3

Which of the following losses, in a synchronous motor, does not vary with load?

Accepted Answer

A) Windage loss 
B) Copper losses 
C) Any of the above 
D) None of the above 
A) Windage loss 
B) Copper losses 
C) Any of the above 
D) None of the above A

Question 4

Exciters of synchronous machines are

Accepted Answer

A) d.c. shunt machines 
B) d.c. series machines 
C) d.c. compound machines 
D) any of the above 
A) d.c. shunt machines 
B) d.c. series machines 
C) d.c. compound machines 
D) any of the above

Question 5

If the field of a synchronous motor is underexcited, the power factor will be

Accepted Answer

A) zero 
B) unity 
C) lagging 
D) leading 
A) zero 
B) unity 
C) lagging 
D) leading

Question 6

A synchronous motor develops maximum power when load angle is

Accepted Answer

A) 45° 
B) 60° 
C) 90° 
D) 120° 
A) 45° 
B) 60° 
C) 90° 
D) 120°

Question 7

Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?

Accepted Answer

A) Eddy current losses in the conductors 
B) Iron losses in the stator 
C) Copper losses in the slot portion of the conductors 
D) Windage losses 
A) Eddy current losses in the conductors 
B) Iron losses in the stator 
C) Copper losses in the slot portion of the conductors 
D) Windage losses

Question 8

For power factor correction, synchronous motors operate at

Accepted Answer

A) no-load and greatly over-excited fields 
B) no-load and under-excited fields 
C) normal load with minimum excitation 
D) normal load with zero excitation 
A) no-load and greatly over-excited fields 
B) no-load and under-excited fields 
C) normal load with minimum excitation 
D) normal load with zero excitation

Question 9

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as

Accepted Answer

A) locked-rotor torque 
B) synchronous torque 
C) pull up torque 
D) reluctance torque 
A) locked-rotor torque 
B) synchronous torque 
C) pull up torque 
D) reluctance torque

Question 10

The construction of a synchronous motor resembles

Accepted Answer

A) a series motor 
B) an induction motor 
C) an alternator 
D) a rotary converter 
A) a series motor 
B) an induction motor 
C) an alternator 
D) a rotary converter

Question 11

The duration of sudden snort-circuit test on a synchronous motor is usually about

Accepted Answer

A) one hour 
B) one minute 
C) one second 
D) none of the above 
A) one hour 
B) one minute 
C) one second 
D) none of the above

Question 12

The back e.m.f. in the stator of a synchronous motor depends on

Accepted Answer

A) number of poles 
B) flux density 
C) rotor speed 
D) rotor excitation 
A) number of poles 
B) flux density 
C) rotor speed 
D) rotor excitation

Question 13

In a synchronous motor, the armature current has large values for

Accepted Answer

A) high excitation only 
B) low excitation only 
C) both high and low excitation 
D) none of the above 
A) high excitation only 
B) low excitation only 
C) both high and low excitation 
D) none of the above

Question 14

A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as

Accepted Answer

A) static condenser 
B) condenser 
C) synchronous condenser 
D) none of the above 
A) static condenser 
B) condenser 
C) synchronous condenser 
D) none of the above

Question 15

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

Accepted Answer

A) slip torque 
B) pull-out torque 
C) breaking torque 
D) synchronising torque 
A) slip torque 
B) pull-out torque 
C) breaking torque 
D) synchronising torque

Question 16

The maximum power developed in a synchronous motor will depend on

Accepted Answer

A) the rotor excitation only 
B) the supply voltage only 
C) the rotor excitation and supply volt-age both 
D) the rotor excitation, supply voltage and maximum value of coupling angle (90°) 
A) the rotor excitation only 
B) the supply voltage only 
C) the rotor excitation and supply volt-age both 
D) the rotor excitation, supply voltage and maximum value of coupling angle (90°)

Question 17

A synchronous machine with low value of short-circuit ratio has

Accepted Answer

A) lower stability limit 
B) high stability limit 
C) good speed regulation 
D) good voltage regulation 
A) lower stability limit 
B) high stability limit 
C) good speed regulation 
D) good voltage regulation

Question 18

The coupling angle or load angle of synchronous motor is defined as the angle between the

Accepted Answer

A) rotor and stator teeth 
B) rotor and the stator poles of opposite polarity 
C) rotor and the stator poles of the same polarity 
D) none of the above 
A) rotor and stator teeth 
B) rotor and the stator poles of opposite polarity 
C) rotor and the stator poles of the same polarity 
D) none of the above

Question 19

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will

Accepted Answer

A) stop 
B) run as induction motor 
C) function as static condenser 
D) burn with dense smoke 
A) stop 
B) run as induction motor 
C) function as static condenser 
D) burn with dense smoke

Question 20

In a synchronous motor, the breakdown torque is

Accepted Answer

A) directly proportional to applied voltage 
B) directly proportional to the square of the applied voltage 
C) inversely proportional to applied voltage 
D) none of the above 
A) directly proportional to applied voltage 
B) directly proportional to the square of the applied voltage 
C) inversely proportional to applied voltage 
D) none of the above

The armature current of the synchronous motor

If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then

Which of the following losses, in a synchronous motor, does not vary with load?

Exciters of synchronous machines are

If the field of a synchronous motor is underexcited, the power factor will be

A synchronous motor develops maximum power when load angle is

Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?

For power factor correction, synchronous motors operate at

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as

The construction of a synchronous motor resembles

The duration of sudden snort-circuit test on a synchronous motor is usually about

The back e.m.f. in the stator of a synchronous motor depends on

In a synchronous motor, the armature current has large values for

A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as

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

The maximum power developed in a synchronous motor will depend on

A synchronous machine with low value of short-circuit ratio has

The coupling angle or load angle of synchronous motor is defined as the angle between the

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will

In a synchronous motor, the breakdown torque is

Synchronous Motors: Part A

Synchronous Motor: Part B

Synchronous Motors and Their Operation

Synchronous Motor Characteristics and Applications

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Exam 5: Synchronous Motor: Power Factor, Back EMF, Torque, Losses

The armature current of the synchronous motor

If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then

Which of the following losses, in a synchronous motor, does not vary with load?

Exciters of synchronous machines are

If the field of a synchronous motor is underexcited, the power factor will be

A synchronous motor develops maximum power when load angle is

Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?

For power factor correction, synchronous motors operate at

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as

The construction of a synchronous motor resembles

The duration of sudden snort-circuit test on a synchronous motor is usually about

The back e.m.f. in the stator of a synchronous motor depends on

In a synchronous motor, the armature current has large values for

A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as

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

The maximum power developed in a synchronous motor will depend on

A synchronous machine with low value of short-circuit ratio has

The coupling angle or load angle of synchronous motor is defined as the angle between the

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will

In a synchronous motor, the breakdown torque is

Synchronous Motors: Part A

Synchronous Motor: Part B

Synchronous Motors and Their Operation

Synchronous Motor Characteristics and Applications

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