A. carbon or graphite
B. brass or steel
C. silver or gold
D. copper or aluminium
Related Mcqs:
- Slip-rings in a synchronous motor carry____________?
A. direct current
B. alternating current
C. no current
D. all of the above - The percentage slip in case of a synchronous motor is____________?
A. 1%
B. 100%
C. 0.5%
D. zero - The duration of sudden snort-circuit test on a synchronous motor is usually about_____________?
A. one hour
B. one minute
C. one second
D. none of the above - The efficiency of a properly designed synchronous motor will usually fall in range___________?
A. 60 to 70%
B. 75 to 80%
C. 85 to 95%
D. 99 to 99.5% - If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor__________?
A. become more
B. become less
C. remain constant
D. none of the above - The armature current of the synchronous motor
A. has large values for low excitation i niy
B. has large values for high excitation only
C. has large values for low and high excitation
D. any of the above - The operating speed of a synchronous motor can be changed to new fixed value by___________?
A. changing the load
B. changing the supply voltage
C. changing frequency
D. using brakes - Under which of the following conditions hunting of synchronous motor is likely to occur?
A. Periodic variation of load
B. Over-excitation
C. Over-loading for long periods
D. Small and constant load - In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
A. one-third
B. twice
C. thrice
D. six times
E. nine times - A synchronous machine with low value of short-circuit ratio has___________?
A. lower stability limit
B. high stability limit
C. good speed regulation
D. good voltage regulation
E. none of the above
