MULTIPLE CHOICE QUESTIONS
Q.1 A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be
(A) 800 rpm.
(B) more than 800 rpm.
(C) less than 800 rpm.
(D)
both higher or lower than 800 rpm.
Q.2 A 50 Hz, 3-phase induction motor has a full
load speed of 1440 r.p.m. The number of poles of the motor are
(A)
4.
(B) 6.
(C)
12.
(D) 8.
Q. 3 In a 3-phase synchronous motor
(A) the speed of stator MMF is always more
than that of rotor MMF.
(B)
the speed of stator MMF is always less than that of rotor MMF.
(C)
the speed of stator MMF is synchronous speed while that of rotor MMF is
zero.
(D)
rotor and stator MMF are stationary with respect to each other.
Q.4 In a capacitor start single-phase induction
motor, the capacitor is connected
(A) in series with main winding.
(B) in series with auxiliary winding.
(C) in series with both the windings.
(D) in parallel with auxiliary
winding.
Q.5 A synchro has
(A)
a 3-phase winding on rotor and a single-phase winding on stator.
(B)
a 3-phase winding on stator and a commutator winding on rotor.
(C)
a 3-phase winding on stator and a single-phase winding on rotor.
(D) a single-phase winding on stator and a
commutator winding on rotor.
Q.6 In a three phase transformer, if the primary
side is connected in star and secondary side is connected in delta, what is the
angle difference between phase voltage in the two cases.
(A)
delta side lags by -30°.
(B) star side lags by -30°.
(C) delta side leads by 30°.
(D)
star side leads by -30°.
Q.7 To achieve low PT error, the burden value
should be ____________.
(A) low
(B)
high
(C)
medium
(D) none of the above
Q.8 Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will be the frequency of the rotor induced emf?
(A)
10 Hz.
(B) 50 Hz.
(C)
1 Hz.
(D) 2500 Hz.
Q.9 A 4 pole lap wound dc shunt motor rotates at
the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors
are 1000. What is the value of emf?
(A) 100 Volts.
(B) 0.1 Volts.
(C)
1 Volts.
(D) 10 Volts.
Q.10 The synchronous reactance of the synchronous machine is
(A)
Ratio between open circuit voltage and short circuit current at constant
field current
(B)
Ratio between short circuit voltage and open circuit current at constant
field current
(C)
Ratio between open circuit voltage and short circuit current at
different field current
(D)
Ratio between short circuit voltage and open circuit current at
different field current
