No Subject

Hi All,

	I am not the biggest expert in the world on power factor correction so I
may be just reinventing the wheel or be totally off track...

	I looked at my coils and the PFC caps I use and the basic principle behind
Adam's test seems to be a useful way of selecting PFC cap values.
Basically just correct for the transformer's VA rating.  In the non-linear
operation of a TC there are a few inaccuracies but they do not seem very
significant.

The VA rating on my big coil is 900VA, which implies a PFC cap value of
166uF.  The actual value is 200uF.  On my little coil the VA rating gives
49.7uF where the actual value is about 60uF.  Not exact but close enough.
Thus, I would propose the following equation (unless everyone has been
using it for years and I am the last person on earth the figure it out ;-))

Cpfc = ( Vo x Vi ) / ( 2 x pi x f x Vi^2 )

Where
	Cpfc = Power factor cap value in Farads
	Vo = Rated NST output voltage in volts
	Vi = Rated NST output current in amps
	pi = 3.14159...
	f = AC line frequency (50 or 60Hz)
	Vi = AC input voltage (120 VAC)

For a 15kV/60mA transformer you get:

( 15000 x 0.06 ) / ( 2 x 3.14159 x 60 x 120 x 120 ) = 165.8uF

To get "exact" you have to take all the non linearities, timing, and such
into account which is a few orders of magnitude harder but this equation
seems to do fine...

Comments, suggestions,...

Cheers,

	Terry