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RE: TRANSFORMERS

 * Carbons Sent to: Esondrmn-at-aol-dot-com


 > From: Esondrmn-at-aol-dot-com
 > Subject: Re: TRANSFORMERS

 ES> Richard,

 ES> I finally found some transformers. I got one 12kv at 60ma    
 ES> and one 12kv at 120ma - both for $50.

Sounds good to me! You can run them in parallel for over 2 kVA!

 ES> I tried to calculate the pfc capacitors from your formula    
 ES> and get 265 for the 1.44kva unit.  I know this is not        
 ES> correct.  I would expect it to be in the range of one to     
 ES> five or so microfarads. Can you figure out what I'm doing    
 ES> wrong?    Thanks, Ed Sonderman

I sat and work on this for awhile. I worked, re-worked, thought,
and then pulled out the reference books.

I made a mistake. In over a year since I made the mistake, you
are the first person to catch it. The problem is with the
corrected kVA. In neon sign transformers with 15,000 and 12,000
volt secondary ratings the corrected kVA figure needs to be
divided by 2. Corrected kVA for your transformer should be about
.72 . I reworked the math using .72 for the corrected kVA and
came up with 132 microFarads which is much closer. In practice
I found that about 150 - 170 microFarads on my 12 kV 1.4 KVA
power supply worked best. The figure you are looking for, one to
five microFarads, is much too small, though my truely flawed
formula gave a number much too large.

I am really sorry about the mistake. I try to go through and
check everthing, but being humbly human, stuff does slip by. 
I put this together from several references patched together,
rather than working it all out from scratch over and over like 
I usually do (and math is not my forte). Even using the proper
figure for corrected kVA, my experiments show the formula is only
good for putting you in the ballpark, not necessarily in the
strike zone. I apologize for any inconvienience I may have
caused.

Richard Quick


... If all else fails... Throw another megavolt across it!
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