PFC questions

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

Original poster: DRIEBEN-at-midsouth.rr-dot-com 

Hello coilers,

I have some questions regarding using PFC caps w/ the primary of a pole pig.
I have a 14,400 volt, 15 kVA distribution transformer that I am currently
just driving a Jacob's ladder with. The ballasting is provided by the
guts of a 225 amp Lincoln arc welder that has been submerged in SAE 30
non-detergent motor oil as well as (2) seriesed MOTs w/ their secondaries
shorted. The MOTs are also submerged in motor oil. The rotory current
selector switch of the arc welder is mounted where it's accessable so
as to have some control over the current to the pig. Today, I had a
little spare time so I decided to measure the input to the LV terminals
of the pig as well as the output of the HV bushings. Also, I have 200
uFD of PFC cap in parallel w/ the LV input lugs to the pig. I noticed
that when I run the pig w/ PFC caps in place, the LV input and HV output
of the pig increases. Here is a chart of the input/output measurements
of the pig (the voltage regulation is provided by (2) seriesed 1156
style 120/140 volt -at- 50 amp powerstats set up for 0 - 280 volts output)

First with 200 uFD PFC                    without PFC

Vin     Vout                              Vin      Vout

100     6400                              100      6570
150     9550                              150      9760
200    12,750                             200     12,980
240    15,400                             240     15,650
250    16,000                             250     16,350
270    17,650 (variac dial at 73)         270     17,840 (variac dial
280    18,450 (variac dial at 76)                is maxed out at 100)
300    20,340 (variac dial at 82)

The arc welder current selector switch is set at 175 amps, I believe
(don't have the marked dial guage anymore) and is paralleled with the
two MOTs. MOTs are pretty beefy but don't know what kind of microwave
oven that they come out of. Oh yeah, the HV output was obviously mea-
sured open circuit with no load. The voltage measurements were made
with a standard Sperry DVM (low voltage) and the HV measurements were
made with a Radio Shack 10Mohm impedance DVM that is taken through
an ebay special 40 kV (28 kVAC) HV probe. BTW, the variac's maxed
output (measured at the ballasted input to the LV lugs of the pig)
will reach nearly 320 volts with the 200 uFD primary PFC. Without
the PFC cap, this same voltage point only reaches 270 volts with
the variac(s) maxed out.

My question is how much PFC capacitance would I need for this setup
if I were going to use it to power a big Tesla coil? I suppose it's
no surprise that the voltage increases with the PFC caps in place
as there is probably resonance rise involved.

Another problem is that this setup will trip out a 60 amp breaker
in about 30 to 45 seconds if i run the Jacob's ladder. The 200 uFD
PFC seems to reduce the current draw a little but I figure that I
would probably need more capacitance to optimally reduce the current
draw. Would a further increase in PFC capacitance cause a dangerous
resonant rise in the voltage? I know the pig started humming loudly
with the PFC caps in place when the input voltage starts to exceed
290 volts.

I'm sorry for such a long post but I was just a little curious about
these observations.

Thanks,
David Rieben