Re: Ballasting

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 5/30/01 12:04:32 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

> 
>  I am facing that thorny issue when using a pole transformer and that is 
how 
> to
>  ballast. I have read that one can ballast a pole transformer with a 
suitably
>  rated variac configured as a variable inductor. I have also read that this
>  method is not ideal because the variac core does not have an air gap and is
>  thus liable to saturate. Also, since the maximum number of variac wire 
turns
>  may not be used, this does not fully utilize all of the core. I have read 
> that
>  other people use this method and it works fine. I have also read that 
using 
> a
>  constant-current arc welder is an ideal ballast. If so, how is it 
connected? 
> Is
>  the secondary left open or shorted? I assume that the pole transformer 
power 
> is
>  drawn through the arc welder primary in a series connection. Facts, not
>  conjecture, would be greatly appreciated.
>  

Steve,

Many folks have had excellent results using a welder as a ballast.
The secondary is shorted, and yes, the welder primary is used in
series with the pig primary.  It is also true that a variac is best used
with a slot cut in the core.  Some folks said they had good results
using a variac without a slot, but when I tried it, the system drew
double the current compared with my other (homemade) ballast. 
This may be because I was only able to use a few of the variac
turns as you suggested.

Some folks also like to add some resistive ballast, perhaps
a couple of ohms in series or parallel with the welder to smooth
out the operation.  Other folks have found no difference either way.
Much depends on the break-rate, capacitor size, sync or non-sync
rotary, etc.

John Freau