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[TCML] Homemade ballast - was: 100kVA trannies as salvage?



Hi Roger, all,

I have heard of running air-cored inductors for ballasting.
However, "I" now use the core of a dismantled 125 kVp,
500 mA x-ray transformer for the core of my inductive
ballast. It has about an 11 sq. inch cross section and it
is comprised of 2 separate  "UP" shaped pieces instead of
the typical "E" and "I" interleaved laminations. Of course,
each of the "U's" is still made of many thin laminations
glued together, but there are only 2 pieces and they are
much easier to deal with than trying to disassemble and
reassemble those tedious "E" and "I" laminations. The 2
"U's" stand about 14" tall together and probably weigh
over 50 lbs. I wrapped 110 turns of #8 THHN building
wire around each leg of the deeper "U" piece in opposing
directions (220 turns total) in opposing directions, in pa-
rallel with each other. It took 4 layers on each leg to get
110 turns on each leg and I spaced each of the 4 layers
with 1/4" thick shims. This allows for plenty of air circu-
lation between each layer and with 2 paralleled #8 copper
conductors, it should be good for at least 80 continuous
amps of current flow.

In placement of the top shallow "U" core piece over the
lower, deeper "U" piece on which the wire is wound, I
had to space the opposing core face surfaces to properly
adjust the ballasting. The more spacing between the two
core piece faces, the less ballasting i.e. the more current
flow. I wanted the ballasting to allow about 100 amps
max at 280 volts input from the maxed out variac into
a shorted output pig. I found that 5/8" thick spacers
between each of the opposing pole faces allowed for
the proper magnetic leakage for about this much current
flow into a dead short. Works like a champ and with a
fan blowing across the windings of this homemade ballast,
they hardly get warm when pushing 80 to 90 amps for se-
veral minutes non-stop at a time :^)

I wonder if a large PFC like you have with your setup
would help reduce the wallplug draw of my setup? I
have tried about 700 uFd PFC before with my con-
trol panel but it seemed to just cause a resonant rise in
the input voltage from the variac without any reduction
of the current draw.

David Rieben



----- Original Message ----- From: "Roger Smith" <rwsmith@xxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, October 30, 2008 10:56 PM
Subject: Re: [TCML] 100kVA trannies as salvage?


I have my 10kva pig hooked up to run a Jacobs latter right now. It is ballasted with an air core inductor that lets it draw about 140 amps. I also use a 1200 uf capacitor bank with it for power factor correction which reduces the current at the mains to about 65 amps.

The inductor I use is a winding from a large transformer with the core removed. After a few minutes of running it starts to get very warm.

Roger
----- Original Message ----- From: "david baehr" <dfb25@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, October 30, 2008 9:03 PM
Subject: RE: [TCML] 100kVA trannies as salvage?




Hi!,


       I have a  10kva pig that Id like to push 'up to' 70+ amps


i now use a short peice of electric dryer element ( approx 3-3.5 ohms ) in a 5 gal bucket of water, it doesnt take long for the water to boil !!





I have a bunch of transformer ' E ' & 'I' laminations . The winding window is close to 6" tall, so i thought of using 4" wide flashing. It comes in .012" - .014" thick ??? .....not sure how much current 4" / .012" aluminum could handle ?





             Thanks!! ,dave B







From: dh@xxxxxxxxxxxxxx
To: tesla@xxxxxxxxxx
Subject: RE: [TCML] 100kVA trannies as salvage?
Date: Wed, 29 Oct 2008 21:53:31 -0700
CC:

Tell me how many amps you are looking at dealing with?

Also, spot surplus price of copper (as well as most metals) has tanked in
the last couple months. Another @#$% bubble...

Retail price has yet to fall into place but it will eventually (if they
don't run up another @#$% bubble).

Dave (who is getting @#$% tired of "economic" bubbles!)



-----Original Message-----
From: tesla-bounces@xxxxxxxxxx
[mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of david baehr
Sent: Monday, October 27, 2008 6:30 PM
To: Tesla Coil Mailing List
Subject: RE: [TCML] 100kVA trannies as salvage?



Hmmm, i was just thinkin' about winding a J. Ladder ballast
with alum. flashing from da home depot, (with the high $ of copper )








what could I use between turns ,..maybe heavy cardboard
soaked with polyurthane ? would it work ??























From: rwsmith@xxxxxxxxxxxxxx
Subject: RE: [TCML] 100kVA trannies as salvage?
To: "Tesla Coil Mailing List"
Date: Monday, October 27, 2008, 3:49 PM

Yes, there is a pretty cool video on youtube that shows how
pole pigs are made and they do show the low side being wound
with aluminum sheet.




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