1. Imbalance in shaft of the induction motor occurs due to
a) air gap is not uniform
b) overheating of the winding
c) rugged construction
d) slip rings.
ans. a
2. The noise and tooth pulsation losses can be minimized by using
a) large number of open slots in stator
b) small number of open slots in stator
c) large number of narrow slots in stator
d) small number of narrow slots in stator
ans. c
3. Dispersion coefficient σ is the ratio of
a) magnetizing current to supply voltage
b) magnetizing current to ideal short circuit current
c) open circuit voltage to short circuit for the same excitation
d) none of these
ans. b
4. If two phases open accidentally of 3-phase supply of a running 3-phase induction motor, the motor will
a) stop
b) run at high speed
c) continue to run depending on load
d) none of these
ans. c
5. If 3-phase induction motor is switched on with one phase disconnected, it
a) is likely to burn out
b) will run at very low speed
c) will not run at all
d) none of these
ans. a
6. In squirrel-cage induction motor, if the rotor is open, the rotor
a) will not run
b) will make noise
c) will run at very slow speed
d) will run at very high speed
ans. a
7. If the input voltage and the frequency of supply is halved, to the 3-phase induction motor
a) the maximum torque is halved
b) the maximum torque remains the same
c) the air-gap flux is halved
d) none of these
ans. a
8. An induction motor crawls at lower speed. This is due to
a) skewing
b) harmonic induction torques
c) high secondary reactance
d) low secondary reactance
ans. b
9. Semi-closed stator slot and not open slot is used in induction motor
a) to increase the pull out torque
b) to decrease the slot reactance
c) to decrease magnetizing current
d) both a and b are correct
ans. c
10. In an induction motor, skew of the rotor bar reduces
a) noise
b) vibration
c) synchronous cusps
d) all of the these
ans. d
a) air gap is not uniform
b) overheating of the winding
c) rugged construction
d) slip rings.
ans. a
2. The noise and tooth pulsation losses can be minimized by using
a) large number of open slots in stator
b) small number of open slots in stator
c) large number of narrow slots in stator
d) small number of narrow slots in stator
ans. c
3. Dispersion coefficient σ is the ratio of
a) magnetizing current to supply voltage
b) magnetizing current to ideal short circuit current
c) open circuit voltage to short circuit for the same excitation
d) none of these
ans. b
4. If two phases open accidentally of 3-phase supply of a running 3-phase induction motor, the motor will
a) stop
b) run at high speed
c) continue to run depending on load
d) none of these
ans. c
5. If 3-phase induction motor is switched on with one phase disconnected, it
a) is likely to burn out
b) will run at very low speed
c) will not run at all
d) none of these
ans. a
6. In squirrel-cage induction motor, if the rotor is open, the rotor
a) will not run
b) will make noise
c) will run at very slow speed
d) will run at very high speed
ans. a
7. If the input voltage and the frequency of supply is halved, to the 3-phase induction motor
a) the maximum torque is halved
b) the maximum torque remains the same
c) the air-gap flux is halved
d) none of these
ans. a
8. An induction motor crawls at lower speed. This is due to
a) skewing
b) harmonic induction torques
c) high secondary reactance
d) low secondary reactance
ans. b
9. Semi-closed stator slot and not open slot is used in induction motor
a) to increase the pull out torque
b) to decrease the slot reactance
c) to decrease magnetizing current
d) both a and b are correct
ans. c
10. In an induction motor, skew of the rotor bar reduces
a) noise
b) vibration
c) synchronous cusps
d) all of the these
ans. d
