Re: good catch?? Wiring the transformers

The first thing you want to do is determine which secondary wire is
closest to the core. Once you have determined this, connect the
secondary inner wires of the two transformers together. This forms
a center tap that during operation will tend to reside at zero volts
relative to the core. 

Since you have just connected the secondaries in what might be called
an anti-series connection, you want to connect your two primaries
in anti-parallel. (if you don't like the terms anti-series and
anti-parallel, then call them reverse series and reverse parallel)

Assuming identical transformers with primary wires labelled A and B,
connect A of the first transformer to B of the second transformer,
and B of the first transformer to A of the second transformer.
The AB and BA connections become the new primary connections.

I strongly recommend tying the center tap and the core together
and then to ground. This reduces the chance of an accidental
flashover between ground and the core to zero.

So, when might an accidental flashover to the core occur when 
the center tap is not connected to the core? Well, if either
HV side of the secondary is brought near ground, then the
voltage at the center tap will rise to 9,000 volts. Flashover.

Many commercial HV transformers use this center tap method
to allow very high voltages without having to worry about
flashover to the core. It is a wise choice. Of course you can
only do this with your 9KV transformers if they do not
already have their secondaries center tapped. A simple 
ohmmeter check will tell you if the core is connected to
the secondary.

Fr. Tom McGahee
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: good catch??
> Date: Saturday, August 21, 1999 2:11 PM
> Original Poster: arwin wijnschenk <solva-at-xs4all.nl> 
> Dear All,
> bought two 9 KV, 700 mA transformers for 350 US together. Can I use them
> and is it possible to isolate the cores (=not grounding them!) parallel
> the primaries and serie the secondairies to get 18 KV output??? Who can
> tell me???
> Arwin Wijnschenk, The Netherlands