Question 1

In a synchronous motor which loss varies with load ?

Accepted Answer

A) Windage loss 
B) Bearing friction loss 
C) Copper loss 
D) Core loss 
A) Windage loss 
B) Bearing friction loss 
C) Copper loss 
D) Core loss C

Question 2

A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

Accepted Answer

A) power factor as well as armature current will decrease 
B) power factor as well as armature current will increase 
C) power factor will increase but armature current will decrease 
D) power factor will decrease and armature current will increase 
A) power factor as well as armature current will decrease 
B) power factor as well as armature current will increase 
C) power factor will increase but armature current will decrease 
D) power factor will decrease and armature current will increase D

Question 3

When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected

Accepted Answer

A) the motor stops 
B) it runs as a reluctance motor at the same speed 
C) it runs as a reluctance motor at a lower speed 
D) none of the above 
A) the motor stops 
B) it runs as a reluctance motor at the same speed 
C) it runs as a reluctance motor at a lower speed 
D) none of the above A

Question 4

A synchronous motor can be started by

Accepted Answer

A) pony motor 
B) D.C. compound motor 
C) providing damper winding 
D) any of the above 
A) pony motor 
B) D.C. compound motor 
C) providing damper winding 
D) any of the above

Question 5

The power developed by a synchronous motor will be maximum when the load angle is

Accepted Answer

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

Question 6

Mostly, synchronous motors are of

Accepted Answer

A) alternator type machines 
B) induction type machines 
C) salient pole type machines 
D) smooth cylindrical type machines 
A) alternator type machines 
B) induction type machines 
C) salient pole type machines 
D) smooth cylindrical type machines

Question 7

A synchronous motor can develop synchronous torque

Accepted Answer

A) when under loaded 
B) while over-excited 
C) only at synchronous speed 
D) below or above synchronous speed 
A) when under loaded 
B) while over-excited 
C) only at synchronous speed 
D) below or above synchronous speed

Question 8

As the load is applied to a synchronous motor, the motor takes more armature current because

Accepted Answer

A) the increased load has to take more current 
B) the rotor by shifting its phase backward causes motor to take more current 
C) the back e.m.f. decreases causing an increase in motor current 
D) the rotor strengthens the rotating field casuing more motor current 
A) the increased load has to take more current 
B) the rotor by shifting its phase backward causes motor to take more current 
C) the back e.m.f. decreases causing an increase in motor current 
D) the rotor strengthens the rotating field casuing more motor current

Question 9

In a synchronous motor, the magnitude of stator back e.m.f. £& depends on

Accepted Answer

A) d.c. excitation only 
B) speed of the motor 
C) load on the motor 
D) both the speed and rotor flux 
A) d.c. excitation only 
B) speed of the motor 
C) load on the motor 
D) both the speed and rotor flux

Question 10

When V is the applied voltage, then the breakdown torque of a synchronous motor varies as

Accepted Answer

A) V 
B) V3/2 
C) V2 
D) 1/V 
A) V 
B) V3/2 
C) V2 
D) 1/V

Question 11

The working of a synchronous motor is similar to

Accepted Answer

A) gear train arrangement 
B) transmission of mechancial power by shaft 
C) distribution transformer 
D) turbine 
A) gear train arrangement 
B) transmission of mechancial power by shaft 
C) distribution transformer 
D) turbine

Question 12

Synchronous motor always runs at

Accepted Answer

A) the synchronous speed 
B) less than synchronous speed 
C) more than synchronous speed 
D) none of the above 
A) the synchronous speed 
B) less than synchronous speed 
C) more than synchronous speed 
D) none of the above

Question 13

A synchronous motor can operate at

Accepted Answer

A) lagging power factor only 
B) leading power factor only 
C) unity power factor only 
D) lagging, leading and unity power factors 
A) lagging power factor only 
B) leading power factor only 
C) unity power factor only 
D) lagging, leading and unity power factors

Question 14

In case one phase of a three-phase synchronous motor is short-circuited the motor will

Accepted Answer

A) not start 
B) run at 2/3 of synchronous speed 
C) run with excessive vibrations 
D) take less than the rated load 
A) not start 
B) run at 2/3 of synchronous speed 
C) run with excessive vibrations 
D) take less than the rated load

Question 15

For V-curves for a synchronous motor the graph is drawn between

Accepted Answer

A) field current and armature current 
B) terminal voltage and load factor 
C) power factor and field current 
D) armature current and power factor 
A) field current and armature current 
B) terminal voltage and load factor 
C) power factor and field current 
D) armature current and power factor

Question 16

A synchronous motor can be used as a synchronous capacitor when it is

Accepted Answer

A) under-loaded 
B) over-loaded 
C) under-excited 
D) over-excited 
A) under-loaded 
B) over-loaded 
C) under-excited 
D) over-excited

Question 17

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

Accepted Answer

A) speed 
B) load 
C) load angle 
D) all of the above 
A) speed 
B) load 
C) load angle 
D) all of the above

Question 18

A pony motor is basically a

Accepted Answer

A) small induction motor 
B) D.C. series motor 
C) D.C. shunt motor 
D) double winding A.C./D.C. motor 
A) small induction motor 
B) D.C. series motor 
C) D.C. shunt motor 
D) double winding A.C./D.C. motor

Question 19

An over-excited synchronous motor takes

Accepted Answer

A) leading current 
B) lagging current 
C) both (a) and (b) 
D) none of the above 
A) leading current 
B) lagging current 
C) both (a) and (b) 
D) none of the above

Question 20

Synchronous motors are generally not self-starting because

Accepted Answer

A) the direction of rotation is not fixed 
B) the direction of instantaneous torque reverses after half cycle 
C) startes cannot be used on these machines 
D) starting winding is not provided on the machines 
A) the direction of rotation is not fixed 
B) the direction of instantaneous torque reverses after half cycle 
C) startes cannot be used on these machines 
D) starting winding is not provided on the machines

In a synchronous motor which loss varies with load ?

A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected

A synchronous motor can be started by

The power developed by a synchronous motor will be maximum when the load angle is

Mostly, synchronous motors are of

A synchronous motor can develop synchronous torque

As the load is applied to a synchronous motor, the motor takes more armature current because

In a synchronous motor, the magnitude of stator back e.m.f. £& depends on

When V is the applied voltage, then the breakdown torque of a synchronous motor varies as

The working of a synchronous motor is similar to

Synchronous motor always runs at

A synchronous motor can operate at

In case one phase of a three-phase synchronous motor is short-circuited the motor will

For V-curves for a synchronous motor the graph is drawn between

A synchronous motor can be used as a synchronous capacitor when it is

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

A pony motor is basically a

An over-excited synchronous motor takes

Synchronous motors are generally not self-starting because

Synchronous Motor: Part B

Synchronous Motors and Their Operation

Synchronous Motor Characteristics and Applications

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

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Exam 1: Synchronous Motors: Part A

In a synchronous motor which loss varies with load ?

A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected

A synchronous motor can be started by

The power developed by a synchronous motor will be maximum when the load angle is

Mostly, synchronous motors are of

A synchronous motor can develop synchronous torque

As the load is applied to a synchronous motor, the motor takes more armature current because

In a synchronous motor, the magnitude of stator back e.m.f. £& depends on

When V is the applied voltage, then the breakdown torque of a synchronous motor varies as

The working of a synchronous motor is similar to

Synchronous motor always runs at

A synchronous motor can operate at

In case one phase of a three-phase synchronous motor is short-circuited the motor will

For V-curves for a synchronous motor the graph is drawn between

A synchronous motor can be used as a synchronous capacitor when it is

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

A pony motor is basically a

An over-excited synchronous motor takes

Synchronous motors are generally not self-starting because

Synchronous Motor: Part B

Synchronous Motors and Their Operation

Synchronous Motor Characteristics and Applications

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

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