Re: Calculation of PFC Capacitors using LTR Capacitor

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Ed,

Tesla list wrote:

> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>
>
> Tesla list wrote:
> >
> > Original poster: "Barton B. Anderson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>
> >
> > Hi Dan,
> >
> > The tank cap won't affect the PFC value.
>
>         Why not?  Please explain.

The transformer is the reactive load we (they) are concerned with. The tank
circuit downstream
should only be of concern if it was greatly inductive or capacitive in
nature. However, it's
resonant. It's the magnetizing current in the transformer which causes the
reactive component.
The reactive component is current which is circulating around doing nothing
"useful" (but it is
still working, that is, working at heating up wire upstream in the form of
I2R losses while it
sloshes around). The PF capacitor of course brings the PF back into or near
unity (W/VA). The
coil itself still uses the same amount of power regardless. When we measure
current (before the
transformer) we also measure the reactive portion along with the portion
that is doing
something useful (entertainment mostly).

Often when we compare our coils, we think of it in terms of Watts to coil
output. In reality,
we compare reactive + real power to coil output. Because the reactive
component differs form
transformer to transformer, we really can't do a good job at output
comparison without first
correcting the PF. Once done, then we get a real comparison of Watts to
coil output.

The funny thing about all this PFC business is that the transformer and
coil still use the same
amount of real power regardless of PFC use. It's  really only important to
everything upstream
from the transformer and the current we read on the meter. This to me is
one of those areas I
still don't quite understand why we worry about it so much. Yes,
transformers cause reactive
power, but, I see little use of a PFC (except to identify how much real
power is entertaining
us). Just my opinion.

Take care,
Bart