MCQs on Electrical Machines

Page 83 of 114. Go to page
01․ The speed of a 4-pole, 60 Hz synchronous machine will be
1800 rpm.
2400 rpm.
3000 rpm.
3600 rpm.

Under construction.
02․ The speed of a p-pole synchronous machine in rpm is given by
120f / p.
120p / f.
120fp.
none of the above.

Under construction.
03․ The aircraft alternators are designed to generate emf of high frequency of 400 Hz in order to
compensate for high speeds.
reduce the bulk.
make the system free from external disturbances.
all of above.

Under construction.
04․ The angle between induced emf and terminal voltage on no-load for a single phase alternator is
180°.
90°.
0°.
none of them.

Under construction.
05․ Three phase alternators are invariably connected in star so as to
reduce magnetic losses.
reduce the size of stator conductors used.
increase the terminal voltage.
all of the above.

Under construction.
06․ The armature of a single phase alternator is completely wound with T turn coils distributed uniformly. The induce voltage in each turn is 2 V ( rms ). The emf of the whole winding is
2T Volts.
1.11T Volts.
1.414T Volts.
1.273T Volts.

Under construction.
07․ The maximum electric current that can be supplied by an alternator depends upon
speed of exciter.
number of poles.
exciter current.
strength of the magnetic field.

Under construction.
08․ Two alternators A and B are sharing an inductive load equally. If the excitation of alternator A is increased
alternator B will deliver more
alternator A will deliver more electric current and than B.
both will deliver more current.
both will continue to share load equally.

Under construction.
09․ Three phase alternators are invariably star-connected because
magnetic losses are the minimum.
small conductors can be used.
less turns of wire are required.
higher terminal voltage is obtain.

Under construction.
10․ Modern 3-phase alternator of a central power station will have generated voltage of
132 kV.
400 V.
11 kV.
230 V.

Under construction.
<<<8182838485>>>