Re: simple question about ballast cores

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Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bigfoo39-at-telocity-dot-com>

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Pyrotrons-at-aol-dot-com>
>
> Aron and I have HAD it with current limiting inductors, variacs,
> transformers, etc. etc.!! Nothing has seemed to work: but nothing gets us
> down in the hobby. (we were using an arc welder - - but its such a nice
> welder - - it's made for welding)
>

SNIPPERZ>>>


Hi Justin....

what you are contemplating is more frustrating than all the other items you
mentioned
in your post. True you will have a non saturating "inductor" with the
design in mind
but you should take into consideration that the thickness of the wire
needed for this
will be a # 8 or smaller for 10KVA application.

When it comes to inductors, you have to take into consideration the amount of
amperage flowing thru the inductor. Even tho a #10 can handle 30- 38 amps (
depending
upon insulation qualities), this is considering the cooling factor allowed.
Most
applications of a # 10 wire carrying 25+ amps is considered in an open air
enviroment, not coiled upon itself ( where the heat generated from the
inner coils
cant get out and thus melts the insulation and shorting occurs)

My best advice is to find the BIGGEST  EI core that you can ( 20+ square
inch middle
leg ) that you can find. use about 200 - 250 wraps to make it about 1 -
1.25 Volts
per turn. Try to use a solid core ( not stranded) wire of # 6 or  # 8...
if you cant
get either of those, then use 3 # 10 THHN insulated wire to wind on the EI core
center leg.

If you want to "control" the amperage, place a variable thickness spacer
between the
E and the I part of the core ( more space more amps before saturation (( up
to a
point))  )

If you use a variac to control voltage to the piggie.... then design an EI
core and
windings to handle the maximum amount of current flow you want to the piggie -at-
maximum voltage ( as you reduce voltage the amps will drop in perspective).
Say you
have a 10KVA piggie which runs approximately 42 amps -at- 240V and you run a
variac that
can supply 280V then make the inductor to be able to handle 60A.

To be on the safe side ...  a # 6 wire will handle 60 A   2 # 8 or 3 # 10
will all
behaive the same as current handling capacity.



Scot D