RE: Modeling Secondary Inductance

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

Original poster: "Johnson, Jeffrey D -at- PWC by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jeffrey.d.johnson-at-l-3com-dot-com>

Thanks Terry, I've been reading and learning from you guys, the experts and
the more I learn the more fascinating a subject it becomes.  These things
definitely don't seem to behave like anything I've built before (100mW
microwave amps, etc.)!  Much like quantum physics and Newtonian physics,
these are like two different worlds.  Thanks to all of you dedicated guys
who have put so much work into this great hobby.
Jeff Johnson

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, September 10, 2001 5:27 PM
To: tesla-at-pupman-dot-com
Subject: Re: Modeling Secondary Inductance


Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Jeff,

Well, if your an engineer and really can't help yourself, here is probably a
lot more than you wanted to know :-)))  It has kept me busy for a few years
;-))


Basically, the secondary coil is a complex mess that can be modeled
successfully with a coil capacitance (Medhurst capacitance) and a top load
capacitance.  It has now also been modeled in great detail using computer
analysis.  I could go on for hours but this will get you started on the
subject
Richard Hull warns "will simply make you nuts" :o)

If you really want to know the nasty details (as many of us do :-))), see
the
great work by Paul Nicholson:

http://www.abelian.demon.co.uk/tssp/

Especially:

http://www.abelian.demon.co.uk/tssp/pn2511.pdf.zip

Also a general paper of mine at:

http://hot-streamer-dot-com/TeslaCoils/MyPapers/modact/modact.html

I use MicroSim and have some coil models:

http://hot-streamer-dot-com/TeslaCoils/Programs/91pspstu.exe
(that one is 27mB!)
http://hot-streamer-dot-com/TeslaCoils/Programs/MicroSim/MicroSim.html
http://hot-streamer-dot-com/TeslaCoils/MyCoils/BigCoil/BigCoilSCH.gif
http://hot-streamer-dot-com/TeslaCoils/MyCoils/SmallCoil/SmallCoilSCH.gif

Also:

http://hot-streamer-dot-com/TeslaCoils/Programs/E-Tesla6.zip
http://hot-streamer-dot-com/andrewb/

Is a program that finds the resonant frequency (see the text files...)

More general info at:

http://hot-streamer-dot-com
http://hot-streamer-dot-com/TeslaCoils/TeslaCoils.htm

Cheers,

        Terry


At 05:28 PM 9/9/2001 -0600, you wrote: 
>
> Hi everyone,
> I was using WinTesla to design my coil and started playing with the Spice
> model provided.  A book I have (The Tesla Coil Book by Brent Turner)
> describes the secondary as a series resonant ckt but the Spice model from
> WinTesla shows the self capacitance plus the toroid cap in parallel.  This
> makes sense to me since self-capacitance comes from inter-winding and
planar,
> both of which are in parallel with the coil inductance.  Is the book wrong
or
> am I missing something?  Another point of confusion for me is how the
> secondary is treated both as a quarter-wave resonator and an LC resonator.

> The first is a transmission line concept (i.e. distributed inductance and
> capacitance) while the second is a lumped element concept.  Is this like
> wave/particle duality of light or something?  
> Something else I noticed about the model was that when the spark gap
switch
> closed, the coil output spiked up and rang down.  I thought the secondary
> oscillations built over successive firings until the voltage reached a
> threshold and blasted out sparks.  I read an analogy with lasers
somewhere...
> Anyway, if some of you theoriticians out there wouldn't mind setting me
> straight on the concepts, I would be most grateful.  I am an engineer so I
> can't help having to know exactly how these things work!
> Thanks in advance
>  
> Jeff Johnson
> Salt Lake City