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Re: Volltage Multipliers/DC supplies
> I noticed that using transformers in phase, you can place the primary in
>parallel, and the secondarys in series, which will produce the output
>voltage of Ts1+Ts2 if the model, and make of the transformers are the same.
>If you were using auto-transformers there would be a phase relationship
>problem in respect to ground where Ts1+Ts2 = 0 because the outputs of the
>secondarys would be out of phase using a proper grounding scheme on both
>transformers.
There are problems with this setup which have been pointed out
several times on the list. First of all, as the voltage increases, the
need for insulation needed to prevent core to coil breakdown also
increases--so above a certain level oil immersion is needed. Second, neons
would be out of the question, since the potting makes accessing the bottom
turn impossible. If you simply connect the high voltage to the grounded
case (which is connected then to the core and the bottom turn) you will
almost certainly get core to coil breakdown.
Thirdly, if you double the voltage being fed into the transformer, the
core will quickly saturate, melting the windings. This occurs for the same
reason that
you cannot power a 120v-7kv potential transformer with 220 and expect it to
put out 14 kv-- if you increase the voltage on either winding, you must
increase the core
mass proportionally or the inductance proportionally, or both, in order to
handle the increase in power.
So there are three problems in building staged transformer
multipliers: insulation breakdown, configuration, and saturation. The
first is accomplished by submerging the array in oil or parraffin. The
second you can take care of by using MOTS or other potential transformers
which can be staged. The third is accomplished by increasing the inductance
or core area of each successive stage in your power supply. So, for
example, if you were to try to build a rock solid MOT supply the first
stage would consist of one MOT, the second would consist of two MOTS with
primaries and secondaries in series, the third would consist of three MOTS
arranged similarly, and so on. Each stage would have more and more
inductance and more and more core mass, each individual transformer
stepping up the high voltage in decreasing increments, and handling less
and less current, and more and more voltage. At some point (the third
stage, I think) it becomes more economical to double the voltage by means
of a voltage doubler than use transformers, because the number of
transformers needed is so great.
--Mike