7 kv -at- 1 amp transformer

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
~8200 volts, high enough to get your foot in the door with a
rotary gap set very close. 

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12