From: Bert Hickman
Date: Thu, 31 Oct 2002 07:49:22 -0600
Subject: Re: [TSSP] Top Voltage
Hi Boris, all, Comments interspersed below... boris petkovic wrote: > Hi All, > Bert wrote: > >>Unfortunately, the rapid polarity reversals seen in >>a Tesla Coil are >>simply not very common in lightning research or in >>power distribution. >>So, unfortunately, there's not a lot of research >>material available, or >>being done, for long RF sparks. > > --- > Thanks for your inputs.However,considering polarities > of terminal and acompanied spark elongation I find > that negative polarity semicycles,especially if really > high TC voltages involved,could play very important > role in fast development of a long transient rf spark. > One way or another,and as stated in previous > posts,there's still a lot of work ahead before we come > to the points relevant to spark propagation > considerations. > --- I agree, especially if a previous negative voltage excursion and partial discharge has deposited negative space charge near the terminal, field enhancement (and enhanced breakout) could then occur during the next positive half cycle and vice versa. It would be very useful to have a way to ring up to an equal magnitude positive or negative peak (perhaps sequentially measuring with two otherwise identical secondaries with opposite winding directions in OLTC?). This would help differentiate breakout preference under controlled single-shot conditions... > > I wrote: > > ,I think some > >>>preliminary scoping tests under obvious breakout >> >>would >> >>>come in handy.Only problem here is the requirement >> >>of >> >>>the high precision of scoping. >> > snip;) > --- > Someone might misinterpret my words "under breakout" > here.I have just noticed this. > It could be wrongly understood as "during obvious > breakout" or "in breakout". > I was certainly refering to the energy shot below or > prior to visible breakout of secondary. > Words below and under have quite a similar meaning to > me but when put in context can change the point upside > down. > My apologise if I caused any confusion as conserns > this matter. I agree. Part of the problem is the relatively large dynamic range and the statistical character of the phenomena. The currents associated with initial corona will be in the microampere range, and the actual discharge may be only barely visible. However, even these small coronal currents are redistributing space charge around the terminal, thus altering the local environment (unfavorably?) with respect to future breakout events. Peak currents associated with streamers and leaders may be a million times larger, so instrumenting to detect/measure both may be a challenge. Perhaps small corona currents can be indirectly detected via subtle changes in secondary Q combined with secondary base charge changes?? Tough problem... > > regards, > BorisBest regards, -- Bert -- -- Bert Hickman Stoneridge Engineering "Electromagically" (TM) Shrunken Coins! http://www.teslamania.com
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.