Correct Answer - Option 3 : steam supply to their prime movers
Concept:
The alternators to be operated in parallel should meet some requirements so as to make their operation proper.
- They must have the same output voltage rating.
- The rated speeds of the machines should be such as to give the same frequency (f being equal to PN/120).
- The alternators should be of the same type so as to generate voltages of the same waveform. They may differ in their kVA ratings.
- The prime movers of the alternators should have same speed-load characteristics, which of course must be drooping ones, so as to load the generators in proportion to their output ratings.
- The alternators should have reactance in their armatures; otherwise they will not operate in parallel successfully.
Explanation:
Two steam driven alternators are operating in parallel. The load sharing between them will be varied based on the steam supply to the prime movers.
