Neon sign transformer power factor correction

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Neon sign transformer power factor correction
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 15 Sep 1997 16:55:38 -0500
Approved: tesla-at-stic-dot-net

From: 	Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Sent: 	Sunday, September 14, 1997 9:21 AM
To: 	Tesla List
Cc: 	LINEMAN23K-at-aol-dot-com
Subject: 	Neon sign transformer power factor correction

On Thursday, September 11, 1997 12:35 AM Rusty Duncan
[SMTP:LINEMAN23K-at-aol-dot-com] wrote;

> All,
> 
> I tried to post on this subject but the mail must have gotten lost so I will
> try again.
> What size PFC cap should be used on a 15KV-at-60mA NST?  Also, how do you
> calculate this?  
> 
> It seems to me that at 900VA output there would be 900VA input to the NST
> (probably more input, assuming losses of the transformer).  From my
> calculations, ignoring losses, I come up with 7.5A input and Zpri = 16ohms.
>  Using the equation 
> C = 1/(2*pi*F*Z) I get 166uF.  
> 
> This seems like too large a value for the PFC cap.  If so, where is my logic
> flawed?  How much of an improvement to the system can I expect with the PFC
> cap in place?
> 
> All comments will be appreciated

Hi Rusty, neon sign transformers typically are only about 50%  
efficient thus drawing twice as much power as they put out. This 
problem can be resolved with the use of power factor correction (pfc) 
capacitance across the line, efficiency can be improved upwards to 
90%! The pfc capacitors used are the same as for alternating current 
motors. The voltage rating should be at least twice the line current 
used, 4x voltage is even better!. The formula used to determine 
ballpark pfc is as follows:

                  Corrected KVA  x  10^9
          C =  ----------------------------
                       2  pi  x  f  x  e^2

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

Corrected KVA is determined by dividing the volt x amps (watts)
output of the neon sign transformer by 1000.
			       Sincerely

				\\\|///
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			   Alfred A. Skrocki
		  Alfred.Skrocki-at-CyberNetworking-dot-com
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