Class 2 (2nd Engineer) MET 📅 Sep 2023

Exam Question

(a) State the necessary conditions required prior to the synchronizing of electrical alternators (4)

(b) Describe the type of cumulative damage that may be caused when alternators are incorrectly synchronized (4)

(d) For two alternators operating in parallel the consequence of: (4)

(i) Reduced torque from the prime mover of one machine

(ii) Reduced excitation on one machine

Reference Answer

(a) Necessary Conditions Required Before Synchronizing Alternators:
Voltage: Voltage should be equal to or slightly higher than the busbar voltage. This is checked using a voltmeter.
Frequency: The frequency should be equal to or slightly higher than the busbar frequency. In practice, the frequency of the incoming alternator is kept slightly higher so that when load is applied, it matches the busbar frequency. The synchroscope should move clockwise at a slow speed.
Phase Angle: There should be no phase angle between the incoming and running generator. The synchroscope pointer should be at 12 o'clock, indicating a zero or acceptable phase angle difference between the incoming alternator and the busbar.

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