Question 1

A synchronous motor will always stop when

Accepted Answer

A) supply voltage fluctuates 
B) load in motor varies 
C) excitation winding gets disconnected 
D) supply voltage frequency changes 
A) supply voltage fluctuates 
B) load in motor varies 
C) excitation winding gets disconnected 
D) supply voltage frequency changes C

Question 2

The efficiency of a properly designed synchronous motor will usually fall in range

Accepted Answer

A) 60 to 70% 
B) 75 to 80% 
C) 85 to 95% 
D) 99 to 99.5% 
A) 60 to 70% 
B) 75 to 80% 
C) 85 to 95% 
D) 99 to 99.5% C

Question 3

To limit the operating temperature an electrical machine should have proper

Accepted Answer

A) voltage rating 
B) current rating 
C) power factor 
D) speed 
A) voltage rating 
B) current rating 
C) power factor 
D) speed B

Question 4

The shaft of synchronous motor is made of

Accepted Answer

A) mild steel 
B) chrome steel 
C) alnico 
D) stainless steel 
A) mild steel 
B) chrome steel 
C) alnico 
D) stainless steel

Question 5

The speed regulation of a synchronous motor is always

Accepted Answer

A) 1% 
B) 0.5% 
C) positive 
D) zero 
A) 1% 
B) 0.5% 
C) positive 
D) zero

Question 6

The percentage slip in case of a synchronous motor is

Accepted Answer

A) 1% 
B) 100% 
C) 0.5% 
D) zero 
A) 1% 
B) 100% 
C) 0.5% 
D) zero

Question 7

Synchronsizingpower of a synchronous machine is

Accepted Answer

A) direcly proportional to the synchronous reactance 
B) inversely proportional to the synchronous reactance 
C) equal to the synchronous reactance 
D) none of the above 
A) direcly proportional to the synchronous reactance 
B) inversely proportional to the synchronous reactance 
C) equal to the synchronous reactance 
D) none of the above

Question 8

When the field of a synchronous motor is under-excited, the power factor will be

Accepted Answer

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

Question 9

The rotor copper losses, in a synchronous motor, are met by

Accepted Answer

A) d.c. source 
B) armature input 
C) motor input 
D) supply lines 
A) d.c. source 
B) armature input 
C) motor input 
D) supply lines

Question 10

When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is

Accepted Answer

A) more 
B) less 
C) equal 
D) twice 
A) more 
B) less 
C) equal 
D) twice

Question 11

Slip rings are usually made of

Accepted Answer

A) carbon or graphite 
B) brass or steel 
C) silver or gold 
D) copper or aluminium 
A) carbon or graphite 
B) brass or steel 
C) silver or gold 
D) copper or aluminium

Question 12

A synchronous motor can be made self starting by providing

Accepted Answer

A) damper winding on rotor poles 
B) damper winding on stator 
C) damper winding on stator as well as rotor poles 
D) none of the above 
A) damper winding on rotor poles 
B) damper winding on stator 
C) damper winding on stator as well as rotor poles 
D) none of the above

Question 13

The maximum power developed in a synchronous motor occurs at a coupling angle of

Accepted Answer

A) 30° 
B) 60° 
C) 90° 
D) 180° 
A) 30° 
B) 60° 
C) 90° 
D) 180°

Question 14

When the voltage applied to a synchronous motor is increased, which of the following will reduce ?

Accepted Answer

A) Stator flux 
B) Pull in torque 
C) Both (a) and (b) 
D) None of the above 
A) Stator flux 
B) Pull in torque 
C) Both (a) and (b) 
D) None of the above

Question 15

The oscillations in a synchronous motor can be damped out by

Accepted Answer

A) maintaining constant excitation 
B) running the motor on leading power factors 
C) providing damper bars in the rotor pole faces 
D) oscillations cannot be damped 
A) maintaining constant excitation 
B) running the motor on leading power factors 
C) providing damper bars in the rotor pole faces 
D) oscillations cannot be damped

Question 16

riunting in a synchronous motor takes place

Accepted Answer

A) when supply voltage fluctuates 
B) when load varies 
C) when power factor is unity 
D) motor is under loaded 
A) when supply voltage fluctuates 
B) when load varies 
C) when power factor is unity 
D) motor is under loaded

Question 17

In which of the following motors the stator and rotor magnetic field rotate at the same speed ?

Accepted Answer

A) Universal motor 
B) Synchronous motor 
C) Induction motor 
D) Reluctance motor 
A) Universal motor 
B) Synchronous motor 
C) Induction motor 
D) Reluctance motor

Question 18

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because

Accepted Answer

A) synchronous motor has no slip 
B) stator supply is not required to produce magnetic field 
C) mechanical load on the rotor remains constant 
D) synchronous motor has large airgap 
A) synchronous motor has no slip 
B) stator supply is not required to produce magnetic field 
C) mechanical load on the rotor remains constant 
D) synchronous motor has large airgap

Question 19

A synchronous motor running with normal excitation adjusts to load increases essentially by increase in

Accepted Answer

A) back e.m.f. 
B) armature current 
C) power factor 
D) torque angle 
A) back e.m.f. 
B) armature current 
C) power factor 
D) torque angle

Question 20

The standard full-load power factor ratings for synchronous motors are

Accepted Answer

A) zero or 0.8 leading 
B) unity or 0.8 lagging 
C) unity or 0.8 leading 
D) unity or zero 
A) zero or 0.8 leading 
B) unity or 0.8 lagging 
C) unity or 0.8 leading 
D) unity or zero

A synchronous motor will always stop when

The efficiency of a properly designed synchronous motor will usually fall in range

To limit the operating temperature an electrical machine should have proper

The shaft of synchronous motor is made of

The speed regulation of a synchronous motor is always

The percentage slip in case of a synchronous motor is

Synchronsizingpower of a synchronous machine is

When the field of a synchronous motor is under-excited, the power factor will be

The rotor copper losses, in a synchronous motor, are met by

When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is

Slip rings are usually made of

A synchronous motor can be made self starting by providing

The maximum power developed in a synchronous motor occurs at a coupling angle of

When the voltage applied to a synchronous motor is increased, which of the following will reduce ?

The oscillations in a synchronous motor can be damped out by

riunting in a synchronous motor takes place

In which of the following motors the stator and rotor magnetic field rotate at the same speed ?

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because

A synchronous motor running with normal excitation adjusts to load increases essentially by increase in

The standard full-load power factor ratings for synchronous motors are

Synchronous Motors: Part A

Synchronous Motor: Part B

Synchronous Motors and Their Operation

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

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Exam 4: Synchronous Motor Characteristics and Applications

A synchronous motor will always stop when

The efficiency of a properly designed synchronous motor will usually fall in range

To limit the operating temperature an electrical machine should have proper

The shaft of synchronous motor is made of

The speed regulation of a synchronous motor is always

The percentage slip in case of a synchronous motor is

Synchronsizingpower of a synchronous machine is

When the field of a synchronous motor is under-excited, the power factor will be

The rotor copper losses, in a synchronous motor, are met by

When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is

Slip rings are usually made of

A synchronous motor can be made self starting by providing

The maximum power developed in a synchronous motor occurs at a coupling angle of

When the voltage applied to a synchronous motor is increased, which of the following will reduce ?

The oscillations in a synchronous motor can be damped out by

riunting in a synchronous motor takes place

In which of the following motors the stator and rotor magnetic field rotate at the same speed ?

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because

A synchronous motor running with normal excitation adjusts to load increases essentially by increase in

The standard full-load power factor ratings for synchronous motors are

Synchronous Motors: Part A

Synchronous Motor: Part B

Synchronous Motors and Their Operation

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

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