Re: Primary Transformer Question (fwd)

---------- Forwarded message ----------
Date: Thu, 21 May 98 08:38:12 EDT
From: Gary Lau  21-May-1998 0812 <lau-at-hdecad.ENET.dec-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re: Primary Transformer Question (fwd)

>Date: Wed, 20 May 1998 08:59:11 -0400
>From: John Heck <jkh-at-lexis-nexis-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Primary Transformer Question
>Here's a real newbie question for someone. I set out to Mendelsons
>Surplus to look for a neon sign transformer, being informed by a
>friend who works there that they had some around, and what I found
>was a huge transformer that looks like it could light broadway. 
>What I had in mind was a small one like what one would find on a
>bar window beer sign, etc. The books/plans I read just call for
>a neon sign transformer, and don't seem to make mention of size.
>What's going on here? What size ttranny do I need for a, say, 250 KV
>coil project? Thanks very much.
> Regards,
>John Heck, KC8ETS
>1009 Donson Drive
>Dayton, Ohio 45429

You weren't too specific on the "huge" transformer you found.  Just how
big is it?  A 12-15kV/30mA NST is about 4"x5"x10", a 60mA job is about
5"x6"X12" (from memory).  Most plans are non-specific because people
generally have to use what they can find, and almost any size NST can be
used.  Either the label on the unit will state the ratings, or you can
measure the short-circuit secondary current. This assumes the transformer
is an NST and is current limited!  Then hook the secondary to 120VAC and
measure the primary voltage to determine the turns ratio and normal
secondary voltage rating.

As far as what's needed for a "250 KV coil project", coil performance is
not generally measured by voltage because it's not possible to make this
measurement with commonly available equipment.  Usually coils are
described by the power (VA) rating of their power supply.

Gary Lau
Waltham, MA USA