Re: Why people don't use MOTs in a TC

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:

> >         Every time I read about MOT's in series I keep wondering about
> primary
> > to secondary breakdown.  Don't see how this can be avoided, considering
> > the construction.  Any other thoughts?
> 
> Several techniques are of use:
> 1) Sink it in oil... Assuming the sucker was good for 2.5 kV before, it's
> now good for 7.5 kV, or so.  What sort of hipot testing do they do from
> primary to core?
> 2) Various back to back cascades, using the MOT as an isolation transformer
> (heavy, but it will work...)
> 3) A healthy dose of hoping..
> >
> > Ed


[1.] This won't help the internal breakdown, as all the ones I've seen
have encapsulated windings.  Hipot testing doesn't tell you much about
long term breakdown, particularly if the potting has any voids in it
where corona can form.  One way of checking that is to look for RF noise
due to corona at the same time as the hi pot test is run.  When I worked
at Hughes we had a group which built high-voltage capacitors for radar
pulse-forming network.  If they saw (or heard) any evidence of corona
they'd pitch the part.

[2.] I've wondered about that, but it would take a lot of transformers
in cascade if you're going to series vary many, and the ones at the
input side have to carry all of the current for all subsequent ones. 
Has anyone really tried it?   

[3.] This seems like the most realistic one, especially if you have a
lot of transformers to sacrifice.

Ed