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13 February 2019

32.MET January 2019 Q.9(B)

February 13, 2019 Posted by AK 3 comments
A 3phase, 4pole 24 slot alternator has its armature coils short pitched by one slot. Find the distribution factor and pitch factor

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

Given 

No of pole = 4
No of slot = 24

To find

1. Distribution factor
2. Pitch factor

Solution

No of slot per pole, n = 24 / 4 
                                  = 6

Angular displacement between slots β = 180 / n
                                                              = 180 / 6
                                                              = 30 deg

No of slot/phase/pole, m = 24 / (3 x 4)
                                        = 2

1. Distribution factor Kd = (Sin mβ/2) / (m sin β/2)
                                      = (Sin 2 x 30/2) / (2 x Sin 30/2)
                                      = 0.965

Armature coils are short pitched by one slot. Therefore angle a is same as that of B.

2. Pitch factor Kc = cos α /2
                            = cos 30/2
                            = 0.965

3 comments:

  1. sir I think Distribution factor calculation is wrong, If not plz explain how to calculate.

    ReplyDelete
  2. Even pitch factor answer is also different if putting given data in cos (30/2)

    ReplyDelete
  3. U got right answer by wrong method, distribution factor is correct, for pitch factor alpha=180*(1/6) = 30 deg, as short pitch by 1 slot, and hence kc or pitch factor will be cos(alpha/2)=cos(30/2)= 0.9659...cheers

    ReplyDelete