High voltage side PFC caps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Marc,

Normally, there is nothing wrong with using PFC caps on the secondary side
of HV transformers.  This is often done by utility companies since high
voltage, but far lower value, caps are easier to make and they can easily
install them on poles as needed.

However, if you have a big cap on the output of and NST, when the main gap
fires it would tend to short the cap directly and perhaps waste a lot of
power and mess with the gap firing.  A high side PFC cap is not isolated
from the main gap by the NST current limiting.  A filter network "may" fix
that problem so perhaps there is some merit to the idea.  I don't know
right off how such a PFC cap would affect LTR charging and other charging
circuit operations.  The arc may stay lit until the PFC cap discharges
since there is nothing to stop the current flow once the arc starts (rotary
gap?).

A 100uF cap on the input of a 15/60 NST is equivalent to a:

100uF / (15000/120)^2 = 6.4nF    (someone check me on this ;-))

cap on the output side.  This cap would not have to be a high current pulse
cap or anything other than a very typical high voltage cap.  Although MMC
type caps are probably the easiest to use and you would only need one
string since there should not be any high currents like a main cap would see.

So it is an interesting idea but it is not obvious what the "answer" is.  I
have never heard of this idea before so it would be new as far as I know.

Cheers,

	Terry



At 12:59 AM 11/28/2001 -0500, you wrote:

>
>I could be showing some more of my ignorance here, but couldn't an mot
>system use Pfc. on the secondary side?
>Take care,
>Marc M.
>
>