Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rpics!yerazuws From: yerazuws@rpics.RPI.EDU (Crah) Newsgroups: sci.electronics Subject: Re: Tesla Coil - broadcast power Message-ID: <556@rpics.RPI.EDU> Date: Mon, 22-Dec-86 11:24:49 EST Article-I.D.: rpics.556 Posted: Mon Dec 22 11:24:49 1986 Date-Received: Mon, 22-Dec-86 22:49:08 EST References: <4815@reed.UUCP> <823@A60.UUCP> <824@A60.UUCP> The multisegment gap doesn't give you any more harmonics - but Organization: RPI CS Dept., Troy NY, USA Lines: 38 Summary: Why some coils use multisegment spark gaps it does have a couple of other advantages: 1) When a disk pits from spark erosion, it can be rotated without having to remove and re-polish it. When the entire periphery is eroded, then you remove it and put it on a lathe for repolishing. 2) Greater thermal mass - helpful in two ways. First reason is that the spark is quenched by cooling- which happens in two ways. First way is by radiative transfer - the bluish light. Second way is by conduction to the electrodes (remember that plasma has a lot of properties we normally associate with metals - and heat conduction is one of them) So, if we have a 1/4 inch spark gap as a single gap, the longest distance from an ion to a cool electrode is 1/8". If we break the 1/4 inch into four gaps, each 1/16" gap will have the same radiative cooling, but now no plasma ion will be more than 1/32" from a nice cool copper disk. Net result is that the spark quenches faster and more dependably. The second advantage of greater thermal mass is that as the electrodes heat up, they lose some of their quenching ability. Spreading the heat load over a number of electrodes helps this (in the short term, at least) Note to people in the Pittsburgh area: Buhl Planetarium had a wonderful twenty-foot or so Tesla coil in operation last time I was there (about 6 years ago). It apparenty was built as an exhibit by some engineers at Westinghouse, materials paid for by Westinghouse. Maybe some CMUer can post a followup article on the coil (is it still there? Still in operation? What are it's vital statistics?). I saw this coil fired up once - the sparks were at least fifteen feet long. Very impressive. -Bill Yerazunis