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Re: [TCML] PFC Question (again)
Hi Gary,
Even if you are "talking through your hat" I would feel pretty confident
that you
still have a better grasp of this than I do :^) Ed Phillips also brings up a
good
point about whether any program can truly compute a correct PFC value on
low reactance transformers, and I'm assuming that by "low reactance" he is
referring to the non-internal ballasted transformers like PTs, pigs, radar
trans-
fomers, ect. As I originally stated, the line current draw does actually
start to
drop when I turn the voltage beyond a certain point. Also, the fan for the
air blast gap will run at a much higher RPM when the variac is still turned
to
low voltage input to the PT (like 35 volts or so) than it will at the same
input
voltage w/out the PFCs. I think maybe I'm beginning to see the picture a
wee bit clearer now but further comments are still welcome ;^)
David R.
----- Original Message -----
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, May 20, 2008 12:33 PM
Subject: RE: [TCML] PFC Question (again)
Let me see if I understand this. You added a 700 uF PFC cap to the primary
side of the unloaded PT.
I don't think this is surprising. Since the PT is unloaded, it should
present only a small reactive load, but the huge PFC cap presents a huge
reactive load. Maybe if the PT was capacitively loaded, driving a TC, it
might cancel? Can you tell that I'm talking just a little bit through my
hat ;-) ?
Regards, Gary Lau
MA, USA
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of David Rieben
Sent: Tuesday, May 20, 2008 12:18 PM
To: Tesla list
Subject: [TCML] PFC Question (again)
Hi all,
I have already posted this question once about four days ago
and as of yet I have not received a single response to it. I am
going to try posting it once again and see if it blips on anyone's
radar screen this time araound :^) ...............
Hi all,
I ran the specs of my medium PT powered coil through JavaTC
and came up with something like 675 uFd for suggested PFC.
I tied in (7) paralleled 100 uFd run caps in parallel with the
main input to the PT and the saturable reactor ballast. The
added 700 uFd actually caused the transformer/sat reactor
to draw about 40 to 45 amps with 120 volts input before I
even started gradually ramping up the voltage to the control
coil of the sat. reactor. The only "real" load was the insigni-
ficant SG cooling fan. Now what was really strange is that
as I cranked the input voltage to the PT/sat. reactor (not
the control voltage) to beyond about 140 volts, the current
draw suddenly begun to DECREASE and if I kept increasing
the voltage beyond this point, the coil would start to spit
out sparks without any voltage into the sat. reactor's control
coil. Normally, the PT cannot pass enough current to fire
the coil when there is zero voltage to the control coil of the
saturable reactor, even with 140 volts of input. Of course the
abrupt sparking would cause the current to once again increase.
Question - can anyone explain these effects and should I
only parallel the PFC with the input of the PT only and not
the main input to the PT and its ballast? Do PFCs really work
for non-shunted transformers in SG driven Tesla coil circuits?
The PT is a 120:1 (14,400 volt) 1.5 kVA @ 30*C GE instrument
transformer and the saturable reactor is rated at 12 kVA and was
originally paired with a 15 kVA, 240V/20 KV dry neon bombarder
transformer (which I in fact still have ;^). Sorry but I don't really
know the exact inductance ratings of the transformer or reactor.
The secondary coil is wound with about 28" on a 6.5" OD PVC
pipe with #22 AWG magnet wire. The primary C is .04 uFd driven
through an air-cooled stationary SG and the topload is a 6 x 30"
dryerduct donut.
Thanks in advance for any advice,
David R.
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