RE: HV Arc Resistance
Subject: RE: HV Arc Resistance
From: Terry Fritz <twftesla-at-uswest-dot-net>
Date: Mon, 12 Jul 1999 18:01:22 -0600
In-Reply-To: <D5210908318AD211A3F20000F8062CCD5D8213-at-excpko-02.pko.dec.c om>
The diameter of the rotor points is 6.5 inches and the speed is 1800 RPM.
The firing cycle lasts about 280uS so the points move 0.17 inches during
the firing cycle. On my gap, that puts the points to within about 0.1
inches of each other at the end of the cycle which is almost the minimum
gap spacing (0.05 inch). So as the burst dies down, the gaps move
significantly closer to each other. The gap spacing does seem to make a
difference. Perhaps the closer spacing helps keep the system going in the
final stages of the burst were the streamers are established and even the
low energy at the end of the cycle can help the streamers a bit. My
stationary electrodes are large 1/2 inch acorn nuts but the spinning
electrodes are just brass bolt ends. Perhaps if I used rounded nuts on
them too the resistance and loss would be even lower?
These days, I always use rounded electrodes on at least one set of points
so that if the points crash they will deflect away more gracefully than if
two solid edges hit. If all the electrodes are rounded, then the fields
would be much more likely to fire the gap close and with the least
resistance. My gap isn't quite finished yet (despite the fact I use it all
the time) but it seems like using rounded electrodes on all the points
would be a good idea.
At 07:31 AM 7/12/99 -0500, you wrote:
>Perhaps I'm missing something. If a rotary gap fires 1/4 inch before
>electrode alignment, of what value is close electrode spacing? It seems to
>me that arcing distance is determined by electrode radius of curvature and
>Vcap, and that aligned-electrode-spacing wouldn't matter, since quench would
>probably have been achieved before alignment.
>Regards, Gary Lau
>Waltham, MA USA
>In a message dated 99-07-11 05:42:21 EDT, you write:
>> Forgetting all the sync effects, I have been
>> going for as few gaps as possible with very close spacing and not worrying
>> much about quenching. My rotary arcs about 1/4 inch before the gaps align
>> so the quenching should be very poor. Yet my systems does not seem to
>> that as long as the primary resistance is lowered.