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Re: to Bert Hickman




From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Saturday, July 26, 1997 9:58 AM
To: 	Tesla List
Subject: 	Re: to Bert Hickman

Tesla List wrote:
> 
> From:   Rodney Stapivic[SMTP:rstapivic-at-sprynet-dot-com]
> Reply To:       rstapivic-at-sprynet-dot-com
> Sent:   Thursday, July 24, 1997 8:28 PM
> To:     tesla
> Subject:        to Bert Hickman
> 
>  That is very true,  you would definitely draw 3x more current than rated.
> I want to thank everybody for their inputs. Anyway have you priced what it
> would cost to construct  a .19 Henries ballast? You sound like you're in
> the same boat I'm in...no arc welder and trying to do this project on a low
> budget. Let me know what you find out and  I'll try to look into the
> inductive ballast method myself.
> 
> Thank you
> Rodney

Rodney,

You may have confused me with Rodney Davies who also responded to your
earlier post. I have a 225A arc welder and also a big 7 KVA tappable
ballast I picked up at a junkyard for inductive ballasting on the pig.
Others on this list have made their own inductive ballasts by using
heavy gauge (#6 or 8 AWG THHN or similar housewire) wound around a 2 or
3 foot length of 3-4" PVC with a movable core made from transformer
laminations or even welding rods! Inductive ballasting runs much more
efficiently and delivers much better coil performance than simple
resistive ballasting. The best overall solution appears to be a
combination of both. 

I'd recommend scanning the local want-ads and scouting the junk yards
for old welders or inductive reactors. You can usually get these for
about the average of the going rate for the copper and iron - my big
reactor ran about $20, and weighs over 54 pounds. The welder was more
($75.00) since it worked, and I got it through a want-ad in the local
Trading Times newspaper. 

If you decide to wind your own, you'll still need to obtain the copper
wire from somewhere, and it'll take a fair amount of fairly heavy gauge
wire to do it. Simple THHN Housewire is not very expensive, and you can
often find it very inexpensively at junkyards. You'll probably need at
least 20-30 pounds worth. Make sure to bring out taps periodically, or
have a method to vary how much iron is in the solenoid. Perhaps those
who've actually wound their own can give you some more pointers.

BTW, 0.19 Henries, or 190 MilliHenries, sounds much too large - the
ballast inductance should be in the range of 3-5 mH (for max current) to
20-25 mH (minimum current) if you're running off 60 Hz and a 240 V
source. However, this is _good_ news, since it significantly reduces the
size of the inductive ballast you'll need. In any regard, chokes capable
of handing 50+ amps tend to get quite large and heavy!

Safe ballasting to you!

-- Bert --