Re: new rotary and cap problem

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

Original poster: "R.E.Burnett by way of Terry Fritz <twftesla-at-uswest-dot-net>" <R.E.Burnett-at-newcastle.ac.uk>


Hi Bob, all.

I think this problem is caused by surging with your asynchronous
rotary.  It really is not practical to run an ASYNC gap down to
200BPS in my opinion.  The beating with the line frequency
becomes severe,  and the tank voltages can ring up to very high
voltages (25kv+ with ease)  Your ten caps in series are only
"rated" for 15kv peak !

What have you got your safety gap set at ???  Mine is at 6mm
(1/4" inch) and fires reliably at around 20kV. Your safety gap
should have fired well before you got down to 200BPS, and this
would have protected the tank capacitor.

I don't think more capacitors in a string will help much, as
the tank voltage will ring-up until something "fires" if the
rotary phasing is wrong.  Your safety gap should catch this
occurence however.

I would not run the async gap again until your safety gap is
set correctly,  and then keep the BPS above 300 or so to
prevent severe surging.  If you want to run at 200BPS then you
need a synchronous gap or HVDC supply in my opinion.

I hope this helps to identify the problem.
                                                Cheers,

                                                -Richie,

> Original poster: "bob golding"
>
> Hi All,
>     Did some more tests with the rotary tonight, and blew another cap. I
> set the cap bank up were I could get a good view of what was going on
> and started the coil up. all was well until I got down to  200 bps. I
> noticed that the caps were starting to flash over. One bank suffered a
> failure in the middle of the string again. Time to make the strings....
>
> <snip>
>
> cheers
> bob golding