[TCML] DIY Tank Capacitor - Plate configuration confusion
Gary.Lau at hp.com
Wed Sep 24 18:37:45 MDT 2008
It's not obvious, but I believe that there is a difference between:
Case 1 t-m-d-m-d-m-d-m-d-m-t and
Case 2 t-m-dddd-m-t.
They would both result in the same theoretical voltage rating and capacitance, but I suspect that given that dielectric materials are not completely uniform, case 1 may result in a more uniform voltage gradient across the dielectric layers.
Additionally, there is a maximum voltage that may be applied to a given dielectric, called the corona inception voltage, above which corona will form and degrade the dielectric. It doesn't matter how thick the dielectric is; that's just the physics. It is for this reason that one can't build or buy a single layer cap with an arbitrarily high voltage rating. It it's built to last, the cap must be constructed as multiple seriesed units, each sustaining no greater than the corona inception voltage. Even the 2000V rated CD MMC caps that we use, are actually cleverly constructed as two seriesed units.
Regards, Gary Lau
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of William Noble
> Sent: Wednesday, September 24, 2008 6:15 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] DIY Tank Capacitor - Plate configuration confusion
> without reviewing the diagrams, the following thought experiment might be helpful
> let's imagine a series stacked plate capacitor - where T indicateds the terminal, D
> means Dielectric, and M neans a metal foil conductor. It would look like this:
> t-m-d-m-d-m-d-m-d-m-t right?
> ok, now think about the foil (m) layers in the middle - they don't actually do anything
> - they aren't connected to anything - all they do is lie between two dielectric plates
> (d). So, when you think about htat capacitor, it really is the same as:
> So, what you are doing by putting capacitors in series is really the same as what
> you get by increasing the gap between the plates/thickening hte dielectric. So, if
> you were using 1/8 inch glass, for example, you couild go to 1 inch glass, keeping
> hte metal foil plates the same size, and you would get the same effect as putting 8
> of the 1/8 glass capacitors in series.
> does this help a little?
> > Date: Wed, 24 Sep 2008 17:11:02 -0400
> > From: ka1bbg at verizon.net
> > Subject: Re: [TCML] DIY Tank Capacitor - Plate configuration confusion
> > To: tesla at pupman.com
> > CC:
> > HI, Grant, first there are no idiots on this list.....some have much less
> > knowlege of coils, some have extensive physics, electrical, engineering
> > backgrounds, math background who often give regularly of the
> > knowledge....write programs, and might even be a ham radio operator as i
> > am.....so skip the idiots...Jeff Behary who runs
> > www.eletrotherapymuseum.com/
> > has a huge stack of older information, and i bet he would be able to point
> > you to some information, despite how busy he is..
> > for stacked capacitors.......cul brian f.
> > www.genapro.com
> > ----- Original Message -----
> > From: "Grant Visser"
> > To:
> > Sent: Wednesday, September 24, 2008 1:26 PM
> > Subject: [TCML] DIY Tank Capacitor - Plate configuration confusion
> >> Hi all,
> >> I have held off on asking this question for many many MANY hours because I
> > was :
> >> 1. 98% convinced that my memory of the theory was correct so didn't
> >> want to embaress myself by seeming just plain stupid.
> >> 2. 100% convinced that a few seconds research on the net would not
> >> only confirm my theory but also give me a bunch more ideas to play
> >> with!
> >> Well, following many many MANY hours of searching the net and reading
> >> way too many articles/papers/tutorials/etc. on capacitors, my
> >> conviction regarding my theory has dropped to around 2%, which is low
> >> enough to be extremely depressing but not low enough to allow me to
> >> simply give up, so here I am ..... ready to embaress myself! LOL
> >> I have built a few smaller stacked plate caps in the past, have also
> >> blown a few so no problem there. Am certainly no guru in the field of
> >> amateur electronics but am also no .... idiot .... or at least I
> >> didn't think I was until today!
> >> Capacitors can be wired in parallel to increase capacitance or in
> >> series to decrease capacitance and to spread the voltage load (as in
> >> an MMC array).
> >> When constructing a stacked plate capacitor the cells are hooked up in
> >> parallel thus this type of DIY cap is often referred to as a "Parallel
> >> Plate Capacitor" and bunches of these can be strung together in series
> >> to build up a tank capacitor suitable for the intended use.
> >> Don't 'think' I have made any mistakes yet so so far so good!
> >> My theory, which I was convinced was ELEMENTARY, is the source of my
> >> confusion at this stage because I have been completely unable to find
> >> any reference to it in my hours and hours and HOURS of searching!
> >> ALL I wanted to do was to use a SERIES STACKED PLATE configuration in
> >> each of my capacitor modules to increase the Voltage Capacity of each
> >> individual module. I could then wire these modules externally in
> >> parallel or indeed in any configuration required for my application.
> >> I really didn't think that using a series stack configuration would
> >> pose any challenges but now I am not so sure!!!
> >> I have put together a diagram simplifying what I wanted to do for clarity.
> > http://i238.photobucket.com/albums/ff108/FreeekyG/FreakyTesla/FreakyCaps.jpg
> >> PLEASE, I would be most grateful if you would take a moment and let me
> >> know if (D4) and (D5) are workable as I thought or if I am indeed ...
> >> an IDIOT! *grin*
> >> If my concept of the Series Stacked Plate Capacitor doesn't work or
> >> has "issues", PLEASE could you explain why or maybe point me to some
> >> reference material so that I can figure this one out!
> >> Very best regards
> >> Grant
> >> _______________________________________________
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> >> Tesla at www.pupman.com
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