From: Bert Hickman
Date: Tue, 08 Oct 2002 07:12:31 -0500
Subject: Re: [TSSP] TOPV breakout threashoul
Marc and all, I remember that post. Do you have a filter circuit between your main gap and the safety gap? Perhaps the effective Q of the primary was much lower due to the presence of filter resistors in the discharge path? I'm not really satisfied that we have any explanation... add it to a growing pile of discharge physics mysteries for now. Space charge undoubtedly plays a very important part in the breakout and discharge propagation behavior of a Tesla Coil. If partial discharges are occurring during voltage peaks, "waves" of space charge are continually being created near the toroid (longer lived positive and negative ions - any "free" electrons quickly attach themselves to air molecules). Let's assume that a previous voltage peak was positive, and that positive corona, streamers, and arrested leader discharges have injected a positive space charge into the region nearest the toroid. If we now swing the toroid polarity to the following negative voltage peak before the residual space charge has a chance to dissipate through diffusion and recombination, the effective E-field seen at the surface of the toroid will be significantly increased. This should lower the "observed" voltage necessary for subsequent breakouts (referenced from the toroid to ground). Under these circumstances, current can be injected into, and extracted out of, the surrounding region on alternate half cycles as we swing towards successive voltage peaks. Discharge current measurements seem to show both positive and negative discharges between the toroid and the surrounding air. Best regards, -- Bert -- -- Bert Hickman Stoneridge Engineering "Electromagically" (TM) Shrunken Coins! http://www.teslamania.com marc metlicka wrote: > > Bert, all > The space charge is a very strong field i think. > In one of the early videos i made of the triggered gap firing my little > test coil, I noticed something very strange. When the safety gap would > fire the normal 2' or so leaders all of the sudden turned into a series > of very faint short streamers, many, many of them equally spaced around > the toroid. This baffled me because i assumed that any tank charge would > be dumped into ground? > I looked and looked at this without any good explanations coming to > mind, I mean it happened every time the safety fired. > Then i got to thinking, Maybe this charge isn't coming from the toroid > at all, maybe it is the surrounding space charge being drained into the > toroid to ground somehow? > It sounded like such a far fetched idea that i never posted it, but it > does seem some of them were actually dissociated from the toroid. > I know this really doesn't help us any, but i thought i'd toss it out > for review. > Take care, > Marc > > Bert Hickman wrote: > > > > Marco.Denicolai@tellabs.com wrote: > > > > > Hi Marco, > > > > I'm probably the guilty party. You're correct - a single number fails to > > adequately describe the complexity of the situation, especially for very > > fast rising pulses or where there's significant field enhancement > > through interactions with preexisting space charge.
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.