Re: Transformer Question

To: tesla-at-pupman-dot-com
Subject: Re: Transformer Question
From: Richard Hull <hullr-at-whitlock-dot-com>
Date: Tue, 17 Sep 1996 10:46:06 -0700
Tesla List wrote:
> 
> >From jparisse-at-ddlabs-dot-comSun Sep 15 21:44:06 1996
> Date: Sun, 15 Sep 1996 13:30:05 -0700
> From: "Jeff W. Parisse" <jparisse-at-ddlabs-dot-com>
> To: tesla-at-pupman-dot-com
> Cc: swan-at-d2-dot-com
> Subject: Transformer Question
> 
> I've been using two 4500VAC 400ma plate transformers pulled from copy
> machines. These transformers (GE) have an extra winding that is
> connected to a 660VAC 10uf capacitor.
> 
> Questions: What is the purpose of this capacitor? Power factor
> correction? Current limiting? What effect would result by changing or
> removing the capacitor?
> 
>    0---------) || (----------0
>              ) || (
>   LV In      ) || (
>              ) || (
>    0---------) || (
>                || (
>     |--------) || (   HV Out
>     |        ) || (
>    ---       ) || (
>    --- 10uf  ) || (
>     |        ) || (
>     |--------) || (-----------0
> 
> Thanks...   ...Jeff Parisse


Jeff, 

You have a ferro-resonant transformer.  It is a cheap cop-out for people 
too cheap to use real copper!  These things do work, albeit in a stable 
environment of constant load.  They can be quite efficient and stable 
when precisely applied to a given purpose.

 For Tesla coil usage, you are asking for an early demise.  The capacitor 
can be blown by the swings of the coil under heavy loads and kickbacks.  
As a matter of fact, the whole business can be very unstable.  I have two 
of these and used them for a short period in 1990.  They sucked - big 
time!  You might have a more survivable system if you used a 
polypropelene snubber cap of very high voltage rating in the resonant 
winding.  If what you have works for you, then OK.  But I wouldn't change 
much or go up in power or they will be wiped out.

Richard Hull, TCBOR