81. What is the shunt resistance component in equivalent circuit obtained by no-load test of an induction motor representative of?
- windage and frictional losses only
- core losses only
- core, windage and frictional losses
- copper losses
82. Under no- load conditions, if the applied voltage to an induction motor is reduced from the rated voltage to half the rated value
- The speed decreases and the stator current increases
- Both the speed and the stator current decreases
- The speed and the stator current remain practically constant
- There is negligible change in the speed but the stator current decreases
83. The core losses, and friction and windage losses in case of an induction motor and determined in the ________ test
- no-load
- blocked rotor
- load
- stator resistance
84. Short-circuit test is performed on an induction motor to determine
- short-circuit current under rated voltage
- equivalent resistance and reactance
- transformation ratio
- power factor on short-circuit
- all of the above
85. Circle diagram is employed to determine the performance on a
- Synchronous motor
- Induction motor
- DC motor
- Transformer
86. The power scale of circle diagram of an induction motor is determined from _________ test data only.
- open circuit
- stator resistance
- short-circuit
- slip
87. In the circle diagram of an induction motor, the diameter of the circle represents the
- rotor current
- line voltage
- operating torque
- maximum torque
88. Circle diagram of the induction motor can be used to determine its
- power factor
- efficiency
- output
- slip
- all of the above
89. A three-phase induction motor when started picks up speed but runs stably at about half of normal speed. This is because of
- unbalance in the supply voltages
- non-sinusoidal nature of the supply voltage
- stator circuit asymmetry
- rotor circuit asymmetry
90. An induction motor is said to be crawling when
- it runs at one-seventh of rated speed
- it accelerates too fast
- it is subjected to fluctuating loads
- it is stated on full load