Re: Ballasting Primer (was: Help Me Prepare for a BIG Coil)

[Tesla729-at-cs-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 8/17/00 8:45:39 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

<< I know that there is inductive ballasting and resistive ballasting, and
 that a combination of both is usually known as the best method, but not
 necessary >>

Hi Ryan,

I use inductive ballast only (225 amp Lincoln Arc Welder) for my large
"Medusa" 10 KVA pig powered Tesla system. Yes, you do short the
secondary leads from the welder and place the input to it in series with
the 240V winding of the pig. I assume you will also be using a large var-
iac in series with your pig/ballast set-up to control the input voltage to 
the pig? 

A lot of coilers like to use resistance in combo with the inductance for
a ballast. I personally don't like using resistance to ballast at this kind 
of power as I2R losses are manifest as heat, and plenty of it. This also
introduces fire-proof mounting problems and waste a lot of power. I get
excellent performance from my big coil system with only inductive bal-
lasting. Of course, this is just my personal opinion and there are plenty
of coilers more knowledgable than myself that would swear by the I/R 
ballast combo saying it gives more stability and control, but like I said,
I get excellent results with inductance-only ballasting (8 to 10 ft+ arcs).

I know that you are on a very limited budget, but I would try to go to a
rotory gap set-up as soon as I possibly could for this kind of power. 
Tyring to properly quech these kind of power levels would be a real
nightmare with a static gap IMHO. A lot of coilers like the SRSG
(synchronous) gap systems, but these are more of a design challenge
and with a 10 KVA pig power source, you will have plenty of power
to spare with just an asynchronous RSG. My RSG is asynchronous
and I get outstanding performance. If you were operating with the
limited power of a frail NST xfmr, then you would definitely need to 
consider SRSG for max efficiency and to keep from killing your NST(s).
However, a pole pig is built like the "Rock of Gibraltar" and will pro-
bably NEVER die in Tesla service.

Yes, you can use the selector of the welder to have some control
over the input current to the pig. Setting it to say 75 amps does NOT
mean that you are going to pump 75 amps into your pig, however.
Remember, the amperage settings on a welder are the approximate
amperages for the secondary LV outputs of the welder. The input amp-
erage at 240V would obviously be proportionately lower. I generally
leave mine set on 150 or 175 amps. Hope this helps you out.

Finally, please be VERY CAREFUL with that pole pig as one little
mistake can cost you your life! I'm sure you alredy know this, but
you can't be too careful with this stuff.



Good, Safe Coiln,
David R.