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Re: Tesla!

> I know that this can't be done with a neon sign transformer,
> because the input windings arent' made to handle that kind of 
voltage.
> On yours I don't know.  But I would be real careful.....those
> transformers aren't current limited, so you will need some form of
> external current limiting to prevent a power arc in your AC supply.
> 
The reason that neon sign transformers don't work this way is that the 
secondaries are center-tapped and grounded to the case.  There's no 
way to wire them together in series to increase the voltage; you would 
simply be shorting out half of each transformer if you tried it.  I imagine 
this would be a pretty good way to toast your transformers, though.

I finally wired my microwave oven transformers together last night and 
tried it out at low voltage, and everything seemed to work as 
advertised!

Since my transformers have two input terminals and two output 
terminals with nothing grounded, I used the two transformers together 
to effectively make a single center-tapped transformer.  By tying
one output terminal from each transformer together and grounding 
them, each transformer is still putting out the rated voltage (4kV AC) 
relative to ground.  But wired in series, depending on the phase 
difference between the two voltages, the maximum voltage difference 
between the ungrounded output terminals can be either 0 V (when the 
voltages are in phase, i.e. - one terminal's voltage goes up and down 
relative to ground just like the other terminal's), or 8kV (when the 
voltages are 180 degrees out of phase, i.e. - one terminal's voltage is 
+V relative to ground and the voltage on the other terminal is -V relative 
to ground, giving a 2V difference).

You can get a 180 degree shift in the output voltage by simply 
reversing the input leads, so if you wire everything up and the voltage 
difference is 0 V, then just reverse the120 V wires on one of the 
transformers and you should have it made.


Steven Roys (sroys-at-anchorage.ab.umd.edu)