Question:-
Common data For Question 48 & 49:

Two 20 MVA alternators operate in parallel. The governor of the first machine is such that the
frequency drops uniformly from 50 Hz on no-load to 48 Hz on full-load. The uniform frequency
drop of the second machine from no-load to full-load is 50 Hz to 47 Hz.

Q. 48. How will the two machines share a total load of 30 MW ?
Option (A)
1st machine will have 12 MW while2nd one will have 18MW
Option (B)
1st machine will have 14 MW while2nd one will have 16MW
Option(C)
1st machine will have 18 MW while2nd one will have 12MW
Option(D)
1st machine will have 16 MW while2nd one will have 14MW
Correct Option:
(C)
Question Solution:
The two machines must run at the same frequency as they are in parallel. Let x MW be the load of the first machine, then the second machine supplies 30 - x MW. The common frequency is
50 – (x/20) x 2 = 50 – ((30-x)/20) x 3
or ((1/10) + (3/20)) x = 4.5 . so x = 18 MW , the load of the other machine = 30 - x = 30 - 18 = 12 MW.
question-answer-faq-1645