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PFC Question



Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Hey guys,

I have a question about power factor correction of
the input to a pole pig transformer. I tried adding
700 uFd of PFC to the input to my 15 kVA pig for
my Tesla system, which can be seen at:
<http://dawntreader.net/hvgroup/david/gm.html>http://dawntreader.net/hvgroup/david/gm.html
After I added the (7) 100uFd, 370 VAC PFC caps
in series with the output of the variac/input to the
transformer, I noticed that it pushes up the voltage
a bit and actually causes the variac to start satu-
rating when I turn the variac control knob up to
near 100 (max). This is noted by the dramatic in-
crease in the audible "hum" in the variac once
the control knob is turned past about 90 on the
variac dial. Also, the output of the coil starts to
become erratic when I really turn up the variac
knob past about 80 on the dial. Even the #10
AWG lead wire from the PFCs to the variac ter-
minals gets warm to the touch, even without any
load on the system. Also, the output voltage of
the variac assembly is notably higher (~5%) at
a given variac setting with the PFCs than without
them. The PFC'd output at 100% on the variac
dial is measure 325 volts with PFC but about 302
volts without PFC. The variac is (2) paralleled 1256D
Powerstats w/ 240 input and set for 0 - 280 volts
ouput.

Once I removed the PFC caps, the loud humming
ceased, even with the variac knob turned all the way
up to 100. I just removed the PFCs this afternoon
and I haven't had a chance to fire up the coil since
PFC removal, but I have a sneaking suspicion that the
"erratic" coil output along with the matching "thumping"
of the variac/ballast assembly will now be absent. I've
heard that PFCs aren't even necessary with large pole
pig systems. Until now, I never used PFC with large
systems and they seemed to work fine. Once I tried
adding PFC I started having ferroresonant problems
so I think I'm just going to leave out the PFCs in my
big coils from now on. Comments, anyone?

David Rieben