Practice Synchronous Motors Multiple Choice Questions Quiz-4 - MCQGeeks.com

Q.1

A pony motor is basically a

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

Q.2

The maximum power developed in a synchronous motor will depend on

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

Q.3

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

static condenser
condenser
synchronous condenser
none of the above

Q.4

Which of the following methods is used to start a synchronous motor ?

Damper winding
Star-delta starter
Damper winding in conjunction with star-delta starter
Resistance starter in the armature circuit

Q.5

Armature of a synchronous machine is

Of reducing number of slip rings on the rotor
Armature is associated with large power as compared to the field circuits
Of difficulty of providing high voltage insulation on rotor
All of the above reasons

Q.6

Synchronsizingpower of a synchronous machine is

direcly proportional to the synchronous reactance
inversely proportional to the synchronous reactance
equal to the synchronous reactance
none of the above

Q.7

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

field current and armature current
terminal voltage and load factor
power factor and field current
armature current and power factor

Q.8

The armature current of the synchronous motor has higher values for

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

Q.9

In which of the following motors the stator and rotor fields rotate simultaneously ?

D.C. motor
Reluctance motor
Universal motor
Synchronous motor

Q.10

Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?

Phase to phase winding resistance
Stator winding to earthed frame
Rotor winding to earthed shaft
All of the above

Q.11

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

Eddy current losses in the conductors
Iron losses in the stator
Copper losses in the slot portion of the conductors
Windage losses

Q.12

Power factor of a synchronous motor is unity when

the armature current is maximum
the armature current is minimum
the armature current is zero
none of the above

Q.13

In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be

3000 r.p.m.
1500 r.p.m.
750 r.p.m.
none of the above

Q.14

The angle between the rotating stator flux and rotor poles is called _____ angle.

torque
obtuse
synchronizing
power factor

Q.15

A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed

the motor will stop
the motor continue to run in the same direction
the winding of the motor will burn
the motor will run in the reverse direction

Q.16

A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will

remain same
go down
improve
none of the above

Q.17

A rotory converter can also be run as a

d.c. shunt motor
d.c. series motor
d.c. compound motor
induction motor
synchronous motor

Q.18

The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of

zero degree
two degrees
five degrees
ten degrees

Q.19

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

voltage booster
phase advancer
noise generator
mechanical synchronizer

Q.20

Which of the following motors is non-self starting ?

D.C. series motor
synchronous motor
Squirrel cage induction motor
Wound round induction motor

Q.21

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

Windage loss
Copper losses
Any of the above
None of the above

Q.22

Stability of a synchronous machine

decreases with increase in its excitation
increases with increase in its excitation
remains unaffected with increase in excitation
any of the above

Q.23

Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?

High field current
Low short circuit ratio
High core losses
Low field current

Q.24

When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop

inductor motor torque
induction generator torque
synchronous motor torque
d.c. motor toque

Q.25

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

30°
60°
90°
180°

Q.26

When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor

remains same as the original value
decreases to half the original value
tends to becomes zero
increases to two times the original value

Q.27

The working of a synchronous motor is similar to

gear train arrangement
transmission of mechancial power by shaft
distribution transformer
turbine

Q.28

The speed of a synchronous motor

increases as the load increases
decreases as the load decreases
always remains constant
none of the above

Q.29

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

Universal motor
Synchronous motor
Induction motor
Reluctance motor

Q.30

In a synchronous motor, the breakdown torque is

directly proportional to applied voltage
directly proportional to the square of the applied voltage
inversely proportional to applied voltage
none of the above

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