Recently asked questions in Kochi mmd and Class 2 Numerical solutions

Search

11 February 2019

31.MET January 2019 Q.7(B)

February 11, 2019 Posted by AK No comments
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 alternator
2) Calculate the value of power factor of second alternator

              If you are noticing some error in problems kindly comment below.Thanks

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)
   

   

0 comments:

Post a Comment