Re: What size PFC should i use with my 15/30 NST?

["Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

You can't specify a PFC just with VARs.  You also need Volts and frequency
...you need both to uniquely specify it....  Or just uF...

VAR = I(reactive) * Volts

Since Ir = E/X   and X = 1/(2*pi*f*C), then Ir = E * 2 * pi * f * C

VAR = E^2*2*pi*f*C

Granted, most PFC's are running at a standard line voltage of some sort
(120, 240, 480, 2200, etc.), but you need to know the system voltage to
figure it out.
-----Original Message-----
From: Tesla list <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Friday, September 01, 2000 11:57 AM
Subject: RE: What size PFC should i use with my 15/30 NST?


>Original poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>
>
>This equation is incorrect. The Vo and Io are in volt amps. This PFC
>equation is on several web sites and I am amazed it is still being shown.
>You need to find the reactive volt amps (VAR). I showed how to do this in a
>past post that I cannot find now. This is why manufacturers rate their PFC
>caps in VARs.


>
>John Couture
>
>----------------------------
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Wednesday, August 30, 2000 8:24 PM
>To: tesla-at-pupman-dot-com
>Subject: Re: What size PFC should i use with my 15/30 NST?
>
>
>Original poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net>
>
>Hi John M., Terry,
>
>Tesla list wrote:
>>
>> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>>
>> At 10:50 PM 8/29/00 -0500, you wrote:
>> >
>> >Hi again,
>> >
>> >I do have another question.  I would like to put a PFC on my NST but
>don't
>> >know what size cap to use.  It is a 15/30 stock NST.  I'm using a 13nf
>MMC
>> >with a 120 bps SRGS (if that makes any differenc).  Any recomendations
>out
>> >there?  If so, is there a formula or rule of thumb to use to determine
>what
>> >size PFC to use?
>> >
>> >Thanks in advance,
>> >John M.
>> >
>>
>> I think this is correct.  It was posted awhile back and needed about
three
>> typo corrections but this should be right.
>>
>> Cpfc = ( Vo x Io ) / ( 2 x pi x f x Vi^2 )
>
>
>This is correct. I posted a few days ago as Cpfc(uF) = (KVA *
>10^9)/(2*pi*f*Vi^2).
>That was wrong. The 10^9 should be 10^6. Anyway, the value is uF. PFC's due
>to
>their size are typically rated in uF.
>
>Just wanted to correct my previous blunder.
>
>Bart
>>
>>
>>  Where
>>         Cpfc = Power factor cap value in Farads
>>         Vo = Rated NST output voltage in volts
>>         Io = Rated NST output current in amps
>>         pi = 3.14159...
>>         f = AC line frequency (50 or 60Hz)
>>         Vi = AC input voltage (120 VAC)
>>
>> Cheers,
>>
>>         Terry
>
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>
>
>
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>