91. Zero sequence impedance off a 3-phase cage induction motor is due to
- stator circuit 3rd time harmonic
- stator circuit 3rd space harmonic
- rotor circuit 3rd time harmonic
- rotor circuit 3rd space harmonic
92. An induction motor when started on load does not accelerate up to full speed but runs at 1/7th of the rated speed. The motor is said to be
- locking
- plugging
- crawling
- cogging
93. Crawling in an induction motor is due to
- time harmonics in supply
- slip ring rotor
- space harmonics produced by winding currents
- insufficient starting torque
94. The phenomenon of crawling in a three phase induction motor may be due to
- Unbalanced supply voltage
- 7th space harmonics of air-gap field
- 7th time harmonics of voltage wave
- 5th space harmonics
95. In an induction motor, when the number of stator slots is equal to an integral multiple of rotor slots,
- there may be a discontinuity in torque-slip characteristics
- a high starting torque will be available
- the maximum torque will be high
- the machine will fail to start
96. Presence of 5th harmonics in induction motor causes
- cogging
- crawling
- small reverse braking torque
- hunting
97. The cogging occurs in induction motors due to
- harmonic induction torques
- harmonic synchronous torque
- vibration torques
- both a and b
98. Cogging of induction motors occurs at
- high voltage and when the number of stator teeth and rotor teeth are equal
- high voltage and when the number of stator teeth and rotor teeth are not equal
- low voltage and when the number of stator teeth and rotor teeth are equal
- low voltage and when the number of stator teeth and rotor teeth are not equal
99. An increase in number of poles of an induction motor results in
- decrease in maximum pf
- increase in maximum pf
- no change in maximum pf
- cannot be predicted
100. Increase in length of air gap in an induction motor causes
- decrease in power factor
- decrease in pulsation losses
- increase in ampere-turns required to produce same flux density in the air gap
- all of the above