81. The synchronous motor can be started by
- pony motor
- DC compound motor
- providing damper winding
- any of the above
82. When a synchronous motor is started, the field winding is energized
- in the very beginning
- when the motor attains a speed slightly less than the synchronous speed
- after the motor has attained the synchronous speed and synchronized
- any time
83. A 3-phase synchronous motor provided with damper winding is started as a 3-phase
- synchronous motor
- synchronous alternator
- induction motor
- induction generator
84. The number of poles on a pony motor employed for starting of a 3-phase synchronous motor should be _______ that on the synchronous motor.
- equal to
- more than
- lesser than
- none of these
85. While starting a synchronous motor, its field winding should be
- kept open
- short circuited
- connected to a dc source
- none of the above
86. A cylindrical rotor synchronous motor is switched on to the dc supply with its field winding shorted on themselves. It will
- not start
- start but not run at synchronous speed
- start as an induction motor and then run as a synchronous motor
- start and run as a synchronous motor
87. If the field winding of a synchronous motor is short circuited and the motor stator is connected to 3-phase ac supply through an auto-transformer, the motor will
- start and run as a 3-phase induction motor
- crawl
- hunt
- not start
- start and run as a 3-phase synchronous motor
88. Which of the following methods is employed for starting a 3-phase synchronous motor?
- Star-delta starter
- Damper winding
- Resistance starter in the stator circuit
- Damper winding in conjunction with a star-delta starter or an auto-transformer starter
89. While starting a 3-phase synchronous motor by induction motor action, very high emf is induced in the field winding. The damage to the insulation of field winding and slip rings can be avoided by
- splitting the field winding in several sections
- short circuiting the field winding through field discharge resistance
- either (1) or (2)
- none of these
90. A 3-phase synchronous motor hunts due to
- fluctuating load
- fluctuating supply voltage
- excessive field current
- faulty connections
- either fluctuating load or fluctuating supply voltage