Two 10 MVA 3 phase alternators operate in parallel to supply at 0.8 power factor with lagging load of 15 MVA. If output of one alternator is 8 MVA at 0.9 lagging.
1) Calculate the output of second alternator2) Calculate the value of power factor of second alternator
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Given
MVAtotal = 15 MVA
Φtotal = 0.8 ; sin Φtotal = 0.6
For Alternator 1
MVA1 = 8 MVA
Φ1 = 0.9 ; SinΦ1 = 0.436
To find
1. MVA2
2. Φ2
Solution
Total load MWtotal = MVAtotal x cos Φtotal
= 15 x 0.8
= 12 MW
Total Reactive load MVARtotal = MVAtotal x sin Φtotal
= 15 x 0.6
= 9 MVA
Alternator 1 load MW1 = MVA1 x cos Φ1
= 8 x 0.9
= 7.2 MW
Alternator 1 Reactive load MVAR1 = MVA1 x sin Φ1
= 8 x 0.436
= 3.49 MVAR
For Alternator 2 Load MW2 = MWtotal - MW1
= 12 - 7.2
= 4.8 MW
Alternator 2 Reactive load MVAR2 = MVARtotal - MVAR1
= 9 - 3.49
= 5.51 MVAR
1. MVA22 = MW22 + MVAR22
MVA2 = Square root of (MW2 + MVAR2)
= Square root of (4.82 + 5.512)
MVA2 = 7.3 MVA
2. Cos Φ2 = MW2 / MVA2
= 4.8 / 7.3
Cos Φ2 = 0.66 (lag)
In diesel ship MVA 2 GIVEN AS 7MVA
ReplyDeleteBYT HERE 7.3..
do all the calculation by ur own. its depend upto how many decimal no. the person who solving consider
DeleteIn Diesel ship they directly subtract the apparent power from total apparent power, so you will get that answer, but you cannot add or subtract apparent power directly, so 7.3 MVA will be the correct answer as per calculations.
Delete