Re: weird beginner's-thoughts on RF-chokes

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

Original poster: "Paul Marshall by way of Terry Fritz <teslalist-at-qwest-dot-net>" <klugmann-at-hotmail-dot-com>

You need a Safety Gap....



Paul S. Marshall





>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: weird beginner's-thoughts on RF-chokes
>Date: Tue, 28 Jan 2003 12:19:45 -0700
>
>Original poster: "Christoph Bohr by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <cb-at-luebke-lands.de>
>
>   Hi Folks!
>
>I spent some more time optimizing my coil-design with wich I had some
>initial problems last week that were discussed on the list.
>I changed the thin wire for 1/4" copper tubing and got a bunch of OBIT's to
>power the thing up to 1,2KVA
>although I only replaced the xfrmers the results were really astonishing.
>The streamers were actually 4 to 5 feet or even longer, much more than I
>expected.
>In fact I was a little bit frightning as the arcing was much more violent
>than expected, I should have known that something was about to go wrong. at
>this point.
>Nevertheless after some rather short runs I ended up with one xformer less
>than the 6 ones I stared with ;-)
>It just burned out in some way. I can't measure anything wrong but it won't
>deliver any voltage anymore...at least it was the oldest one of the
>xformers.
>
>This might have happened because of RF-kickbacks that should be surpressed
>with RF-chokes if my information is right.
>I had two air-chokes ( 40turns of insulated HV-capable wire on an 2"
>PVC-pipe ) that caused me a lot of trouble as they got the primary circuit
>ringing, causing breakouts even at the most unlikely spots.
>After I removed these chokes everything worked fine at 400VA. During the
>short runs at 1,2KVA I observed another interesting phenomenon:
>sometimes, after switching th coil of ( sorry, no variac at this time, full
>power or no power...) It wouldn't re-ignite ( sorry for the term, I didn't
>find a better one ).
>After some 30 seconds I was able to fire the coil as if nothing had
>happened. This was repeated 2 times and then the xformer was gone. :-(
>Furthermore the sound of my static sparc-gap was really annoing the
>neighbours as this time it wouldn't make cracking sounds at about 200Hz, but
>almost somthing sounding like a whistle and really loud.
>
>Now I tried to build some RF-chokes. Therefore I got 4 ATX-PSU's from our
>dumpster an disambled them to get some ferrite-cores, and thats what I got:
>
>4 torus-shaped ferrite.cores, ca 1 1/8" in diameter
>
>and
>
>2  pole-shaped cores qinch in length and ca 1/4" thick.
>
>On all of the cores I applied 2 layers of very-high quality electrical tape
>and put about 40 turns on each of the toroid cores and about 30 turns on the
>pole-shaped cores.
>The idea was to make up two chains, each consiting of 2 toroid and one
>pole.shaped cores in it with the pole-shaped core in the middle like in this
>asci-drawing: O-O.
>But while holding th single parts in my hand some questions came in my
>mind..:
>
> > I'm not quite the mathematician and I don't own a meter for inductances,
>so can the inductance of this combined chokes be high enough for my
>purposes? What should it be?
>
>( just to get an impression on what I use: 6 or 6OBITS, 10KVrms/15KVpeak /
>20mA each, making up a 1,2KVA power-source, for an 11nF tank-cap. )
>
> >  is it bad if some of the cores are wound clockwise while the other ones
>are wound counterclockwise ind one row... or will it cause any kind of
>erasement....?
>
>I'd really like to power the thing back up, but I'm very afraid that I will
>loose all my OBITS which were really hard to find. ( Almost only gas-heaters
>in my region )
>
>So I'd be glad for any suggestions.
>
>Sincerely
>
>
>Christoph Bohr