# RE: What size PFC ...

```Hi John,

At 12:42 PM 9/2/00 -0700, you wrote:
>
>Terry -
>
>The rearranged equation is still incorrect when used with active volt amps.
>The equation is correct only when used with reactive volt amps. To convert
>active to reactive amps you need to use complex numbers or trig functions. I
>prefer to use trig functions as I show in my post to the Tesla List 7-14-96
>"PFC for Neons". Can it be that long ago?
>
>Note that using your "close enough" equation will always give you a leading
>power factor which is worst that a lagging power factor. It would be
>interesting to see what a model by microSim would show.
>
>To properly meter the TC load you need at least 4 meters, volts, amps,
>watts, power factor. The power factor meter is required to tell you if the
>load is leading or lagging. A VAR meter would help and save you having to do
>the necessary calculations.
>
>Bart I am glad to hear that you are researching the problem. As Terry
>pointed out there may be other issues and your work may shed more light on
>the subject.
>
>John Couture
>
>------------------------------
>

I pulled up your old post:
==============================================
PFC for Neons

·	To: Tesla List
·	Subject: PFC for Neons
·	From: "John H. Couture"
·	Date: Sun, 14 Jul 1996 17:55:23 GMT

Uncorrected neon transformers are usually 50% power factor. To correct them
for 90% power factor add a capacitor calculated as follows:

For 120 volts    c uf = .079 V A
For 240 volts    c uf = .020 V A
V = neon secondary volts     A = neon secondary amps

The factors       K1 = sin(arccos(LPF)-sin(arccos(HPF))
K1 = .43 for 50% to 90% power factor

For 120 volts     K2 = (.43 x 10^6)/(6.283 F V)           F = 60 Hz
K2 = (.43 x 10^6)/(377 x 120^2) = .079
For 240 volts     K2 = .0198 or .02

Example:   Neon 15000 volts  60 ma  120 volts  60 Hz

C = .079 x 15000 x .06 = 71.1 uf

sniped efficiency text...
======================================

So your saying I should have a 71.1 uF cap instead of my present 200uF on
my 15/60 coil...

Let's look at the RMS current draw of my 15/60 coil with various PFC caps
using MicroSim:

Cap size	AC line current		Notes
0uF 		11.16 ARMS		No PFC cap
71.1uF		9.19 ARMS		John's equation
165.8uF	7.75 Arms		"Terry's" equation
200uF		7.72 ARMS  		The "real" best PFC cap size

Cheers,

Terry

```