Re: PFC Question

["Tesla list" <tesla@xxxxxxxxxx>]

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

Hi Ed,

I must not have explained myself properly.
My PFC caps were directly across the out-
put terminals of the variac and consequently
across the input terminals to the transformer.
That's in parallel with the input terminnals of
the transformer, isn't it? And the variac would
start the resonant saturation hum even with the trans-
former disconnected from it, or with no load.
I even tried removing one of the 100 uFd
caps to make it 600 uFd PFC but that didn't
really seem to help so at that point, I just decided
remove them altogether.

David Rieben



----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, November 02, 2005 2:49 PM
Subject: Re: PFC Question


> Original poster: Esondrmn@xxxxxxx
> David,
>
> I think your caps in series with the transformer are acting like a 
> capacitive ballast, and possibly causing a 60 hz resonance 
> problem.  Pfc caps should be connected directly across the input 
> terminals (in parallel) to the transformer.
>
> Ed Sonderman
>
> In a message dated 11/2/2005 7:48:19 AM Pacific Standard Time, 
> tesla@xxxxxxxxxx writes:
> 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