RE: Looking for run caps, urgent

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mike Wood by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mike.wood-at-opennw-dot-com>

Hiya

>I'm at the office so I can't quote the original formula I used but it was
>from the pupman archives doing a search on PFC.

I found the same problem - searching pupman for pfc stuff gave me a hit on
math.txt, which includes the following:

=======================================================================
EQUATION 10: POWER FACTOR CORRECTION FOR NEON SIGN TRANSFORMERS

    Neons typically have an efficiency of about 50%, in that they
    draw twice as much power as they put out. This problem can be
    resolved with the use of power factor correction (pfc) capaci-
    tance across the line. The pfc capacitors used are the same as
    for capacitor starting motors. The voltage rating should be at
    least twice the line current used, and I like a 4x voltage margin
    for long life. The formula used to determine ballpark pfc is as
    follows:
                                    9
                                  10^
              C = Corrected kVA  ------ 2
                                 2(pi)fe^

    This should read C = Corrected kVA times (10 to the ninth power)
                         over, (2 pi times f times e squared)

    C = required capacitance in microfarads
    f = frequency of applied voltage
    e = applied voltage

    CORRECTED KVA is determined by dividing the volt*amps (watts)
    output of the neon sign xfrmr by 1000

    Equation courtesy of Richard Quick
    
=======================================================================


and which gave me suggested pfc results so far away from the "known ok"
system specifications that everyone's kind enough to post that I went
looking for why.  It turns out the chunk above is just an extract from an
earlier posting to the list, but which has lost an important something in
the translation.  The last bit originally read:

    CORRECTED KVA is determined by dividing the corrected power factor
    output of the neon sign xfrmr (below) by 1000
   
                 Corrected Power Factor
 
        Secondary Rating         Volt-Amps
             kV,mA

             15,120                 900
             15,60                  450
             15,30                  250
             12,120                 775
             12,60                  400
             12,30                  200
              9,120                 600
              9,60                  300
              9,30                  150
            7.5,120                 500
            7.5,60                  250
            7.5,30                  125
              6,60                  200
              6,30                  100

	Equation courtesy of Richard Quick

=======================================================================


which makes a big difference.


>I think there is some serious discrepency for the PFC calculation. 

apologies for lengthy post, but yes, I think so too!

Cheers anyway

Mike 
Wellington, NZ