Re: 7 kv -at- 1 amp transformer

tesla-at-grendel.objinc-dot-com wrote:
> >From richard.quick-at-slug-dot-org Wed Apr 10 01:23 MDT 1996
> >Received: from uustar.starnet-dot-net (root-at-uustar.starnet-dot-net []) by uucp-1.csn-dot-net (8.6.12/8.6.12) with SMTP id WAA25770 
for <tesla-at-grendel.objinc
> From: richard.quick-at-slug-dot-org (Richard Quick)
> Subject: 7 kv -at- 1 amp transformer
> Date: Wed, 10 Apr 1996 01:37:00 GMT
> To: tesla-at-grendel.objinc-dot-com
> Quoting Skip Greiner <sgreiner-at-mail.wwnet-dot-com>:
> > I have a chance to pick up a 7 kv -at- 1 amp plate transformer at
> > a very good price. I wonder if anyone in the group has
> > attempted to work with this low a voltage transformer....
> > successfully?
> I have fired with single plate transformers in the 5-6 kV range
> but it is not something you can do easily and reliably. You need
> external current limiting and a rotary gap. Because the input
> voltage is so low the rotary electrodes needs to be practically
> contacting the stationary electrodes in order to get the gap to
> fire. At one point I tried replacing the stationary electrodes
> with a soft bristle brass brush and actually allowed contact
> to the rotary wheel electrodes: while it worked I would not
> recommend doing this for reasons that should be obvious.
> Tesla's liquid mercury break would be ideal for operating in this
> voltage range. Anybody aware of any reproduction units in
> existence? I have looked at the patent diagrams carefully and
> this looks like it would be a major bear to reproduce a large
> unit capable of switching any real power.
> However, and this is key, if you can lay your hands on two of
> these type transformers they can be ganged with the primaries
> in parallel and the secondaries in series and they will serve
> well. Being a pack-rat I would definately pick one of these up
> if the price were right in the hopes of running across a second
> transformer of the same or similar type.
> Large plate transformers of this type fall into the "boat-anchor"
> category at some HAMfests. If you spot one laying out, you can
> frequently come back at the end of the day (they are not "hot"
> sellers with the solid state crowd) and walk away with one for
> next to nothing (after you pay the bill for the hernia repair).
> The other thing I guess I could mention, is running the variac up
> at 280 volts input and pushing the 7kV plate transformer up to
> rotary gap set very close.
> Richard Quick
> ... If all else fails... Throw another megavolt across it!
> ___ Blue Wave/QWK v2.12

Thanks for the in depth reply. I do have a question. I have only been on 
the list a short time but on several occassions a recommendation has been 
made to parallel primaries and series up the secondaries to obtain higher 
output voltages. It seems to me that a 7kv xformer would have insulaion 
capable of handling 7kv plus a safety factor, maybe 25 to 50% or say 10kv 
at the most. If the two secondaries are series connected, we are going to 
have 14 kv floating around both xformers, each having 10kv insulation. 
Where am I wrong? Or are we making an assumption that the insulation is 
really good for much higher voltages than the nameplate may imply?
Yours for bigger and better sparks

Skip Greiner