When the field of a synchronous motor is under-excited, the power factor will be
leading
lagging
unity
zero
Q.2.
The speed regulation of a synchronous motor is always
1%
0.5%
positive
zero
Q.3.
The percentage slip in case of a synchronous motor is
1%
100%
0.5%
zero
Q.4.
The operating speed of a synchronous motor can be changed to new fixed value by
changing the load
changing the supply voltage
changing frequency
using brakes
Q.5.
When load on an over-excited or under excited synchronous*motor is increased, rateof change of its armature current as compared with that of power factor is
more
less
equal
twice
Q.6.
The rotor copper losses, in a synchronous motor, are met by
source
armature input
motor input
supply lines
Q.7.
Synchronous motors are
not-self starting
self-starting
essentially self-starting
none of the above
Q.8.
An over excited synchronous motor is used for
fluctuating loads
variable speed loads
low torque loads
power factor corrections
Q.9.
The efficiency of a properly designed synchronous motor will usually fall in range
60 to 70%
75 to 80%
85 to 95%
99 to 99.5%
Q.10.
Riunting in a synchronous motor takes place
when supply voltage fluctuates
when load varies
when power factor is unity
motor is under loaded
Q.11.
A three-phase synchronous motor will have
no slip-rings
one slip-ring
two slip-rings
three slip-rings
Q.12.
In case one phase of a three-phase synchronous motor is short-circuited the motor will
not start
run at 2/3 of synchronous speed
run with excessive vibrations
take less than the rated load
Q.13.
A synchronous motor can develop synchronous torque
when under loaded
while over-excited
only at synchronous speed
below or above synchronous speed
Q.14.
A synchronous motor can be started by
pony motor
compound motor
providing damper winding
any of the above
Q.15.
When V is the applied voltage, then the breakdown torque of a synchronous motorvaries as
V
V312
V2
1/V
Q.16.
The back e.m.f. of a synchronous motor depends on
speed
load
load angle
all of the above
Q.17.
Mostly, synchronous motors are of
alternator type machines
induction type machines
salient pole type machines
smooth cylindrical type machines
Q.18.
In a synchronous motor which loss varies with load ?
Windage loss
Bearing friction loss
Copper loss
Core loss
Q.19.
The minimum armature current of the synchronous motor corresponds to operation at
zero power factor leading
unity power factor
0.707 power factor lagging
0.707 power factor leading
Q.20.
As the load is applied to a synchronous motor, the motor takes more armature currentbecause
the increased load has to take more current
the rotor by shifting its phase backward causes motor to take more current
the back m.f. decreases causing an increase in motor current
the rotor strengthens the rotating field casuing more motor current
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