Objective Questions on Synchronous Motor & MG Set for Electrician Trade
| Sr. No. | Questions with options |
| 1 | Why D.C supply is necessary for synchronous motor operation?
(a) Reduce the losses (b) Start the motor initially (c) Run the motor without over load (d) Run the motor at synchronous speed Ans – (d) |
| 2 | Which acts as both inverter and converter?
(a) Metal rectifier (b) Mercury arc rectifier (c) Semi conductor diode (d) Synchronous converter Ans – (d) |
| 3 | What is the function of inverter?
(a) Convert A.C to D.C (b) Convert D.C to A.C (c) Smoothening A.C sine wave (d) Convert pulsating DC into pure DC Ans –(b) |
| 4 | Which converting device can be over loaded?
(a) Rectifier unit (b) Rotary converter (c) Motor generator set (d) Mercury arc rectifier Ans – (a) |
| 5 | Why exciter is essential to run a synchronous motor?
(a) Carry more load in motor (b) Improve the power factor (c) Reduce the losses in motor (d) Run the motor at synchronous speed Ans – (d) |
| 6 | Which application requires only DC?
(a) Electroplating (b) Stepping up of voltage (c) Operating induction motor (d) Operating repulsion motor Ans – (a) |
| 7 | Why the LED’s are avoided as converters in rectifier diodes?
(a) Heavily doped device (b) Very low power device (c) Designed for light emitting (d) Very sensitive to temperature Ans – (b) |
| 8 | Which is the main application of synchronous motor?
(a) Elevators (b) Paper rolling mills (c) AC to DC converter (d) Power factor correction device Ans – (d) |
| 9 | What is the advantage of motor generator set?
(a) Noiseless (b) High efficiency (c) Low maintenance required (d) DC output voltage can be easily controlled Ans – (d) |
| 10 | What is the purpose of damper winding in a synchronous motor at starting?
(a) Produce high voltage to initiate the rotation (b) Produce high current to start rotate the motor (c) Produces torque and runs near in synchronous speed (d) Produce a high magnetic –field to maintain a constant speed Ans – (d) |
| 11 | Why the synchronous motor fails to run at synchronous speed?
(a) Insufficient excitation (b) Defective pony motor (c) Open in damper winding (d) Short in damper winding Ans –(a) |
| 12 | How the synchronous motor is used as a synchronous condenser?
(a) Varying the motor load (b) Varying the rotor excitation (c) Varying stator voltage in motor (d) Varying stator current in motor Ans – (b) |
| 13 | What is the function of damper windings in synchronous motor?
(a) Maintain power factor (b) Excite the field winding (c) Maintain constant speed (d) Start the synchronous motor Ans –(d) |
| 14 | Which converter is having high efficiency?
(a) SCR converter (b) Rotary converter (c) Motor generator set (d) Mercury arc rectifier Ans – (a) |
| 15 | How synchronous motor works as a power factor corrector?
(a) Varying the line voltage (b) Varying the field excitation (c) Increasing the speed of motor (d) Decreasing the speed of motor Ans – (b) |
| Published On – 8th June 2022 | |
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