Re: new rotary and cap problem

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

Original poster: "bob golding by way of Terry Fritz <twftesla-at-uswest-dot-net>" <yubba-at-clara-dot-net>

Hi Richie,all
    I am sure you are right about the surging problem. I have my safety gap
set to 6 mm so It should have
fired. I think I will move it to somewhere were I can see it. At the moment
it is inside the safety cover of
the rotary. I have noticed that the longest sparks seem to be just before
the caps start to flash over. This
is at around 2000 RPM. I will try setting the safety gap at 4 mm and run
with strings of 20 caps. I can't
seem to get any more than 4 ft sparks at the moment so I don't know if I
have killed the caps. They are
reading a bit low 4 .1 to 4.4 nF from the nominal 4.7nF. I should have the
ERO cap bank finished by Sunday
so I will try it out. I will make sure I don't go below 300 BPS. I think
the problems are of my own making
rather than any failure of the Arcotronics caps. Hope this reassures people
who have just brought them! As I
said in my previous post I have been using them for at least a year on a
regular basis with no problems
whatsoever with my static gap. Pushing the bleeding edge of cap voltage
limits.

cheers
bob golding

Tesla list wrote:

> 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,