Re: Modular Secondary

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Duncan, all,

On 10 Mar 01, at 18:20, Tesla list wrote:

> Original poster: "Dr. Duncan Cadd by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>
> 
> Bonsoir Monsieur Luc!
> 
> >Original poster: "Luc by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <ludev-at-videotron.ca>
> >
> >Hi all
> >
> >I put this paper on the web at tis address :
> > http://pages.infinit-dot-net/luc2/colapsed_coil.pdf
> >It will be there for 2 weeks.
> >Enjoye it !
> 
> 
> Merci beaucoup, vous etes tres gentil!  And that's about all the
> French I remember, after two years in northern Belgium I can do better
> these days in Flemish ;-)
> 
> Hmmmmmm.  I don't like to carp and criticise, but . . . This paper by
> K.D. Skeldon et al.  Interesting for its concept of portability, a
> major plus point, and also for measurement of discharge current of
> 10-100mA average (though Terry's milage may certainly vary) sad for
> its continued reliance on intermediate frequency transformer theory
> etc.  They do give an expression for the input impedance of the coil
> under cw conditions (or double-tuned intermediate frequency
> transformer, IFT) which I think dates from 1943 and K.R. Sturley's
> "Radio Receiver Design" volume 1, publ. John Wiley, if not earlier.
> Given this paper was published last year, and received for publication
> in October 99, one wonders if academia will ever wake up (says he
> after 20 years in 5 universities in two countries blah blah blah yawn
> snore ;-) to the fact that an impulse-driven TC is *not* an IFT.
> 
> I particularly like the comment (half way down p132, p7 in the .pdf)
> that "a well-designed coil should be able to generate an output spark
> length of 30cm for each kilowatt of input power" which is attributed
> to anonymous www-based resources.  I'm sure that'll bring a wry smile
> to John Freau's lips amongst others (I think you're currently getting
> 42ins/107cm for ca. 500W) as will the hit-and-miss asynch rotary gap
> break rate/primary cap size design.  If you're one of those who has
> built a rotary gap, you ought to read this paper just for
> entertainment's sake.  When it comes to "the distribution of voltage
> along the secondary coil follows the first quadrant of a sine
> function" Paul Nicholson will be in stitches.
> 
> When I think what the authors of this paper might have gained via this
> list I honestly don't know whether to laugh or cry, even given they
> did this say three years ago.  If it had been vetted by some of those
> on this list I can envisage a number of amendments might have been
> recommended prior to publication.  They do manage to end up with 1,5m
> arcs for 1,5kW input, which though not likely to impress anyone here
> is at least something for their pains. FWIW, if you don't want to
> plough through all of it, it's a 10kV 1,5kVA 50c/s trannie and a
> 60nF/40kV Maxwell cap-based system, a decent enough LTR design
> (arrived at semi-empirically) if only they'd used a synch rotary.  The
> topload is tiny though, and they don't give dimensions in the paper;
> it looks a lot less than a 4" x 24".
> 
> Perhaps Richie (being possibly our northernmost correspondent in the
> UK) would like to invite the authors of this paper to see a _really_
> efficient coil.
> 
> Thanks to Antonio and Luc for bringing this to our attention.  One day
> perhaps academia will arrive . . .
> 
> Dunckx

I hadn't planned to comment on that paper on the list but I think 
perhaps what you said should have been said in case anyone takes note 
of it. Some of the things said in there are just plain wrong. I had 
gone through a copy I printed out and annotated it with the intention 
of emailing the authors. It is remarkable that they cite so few 
references and even more remarkable that a lot of what has been said 
on the list has completely escaped them. I wouldn't mind betting that 
the 30cm/kW was dredged up from a piece on "controlled sparks" 
whatever they are. I note the absence of a charging choke from their 
MOSFET coil, the totally erroneous secondary voltages cited on p. 132
(still trying to guestimate output based on sparklength), further 
erroneous "information" on p.133 (a complete misunderstanding of how 
the skin effect affects copper losses and no mention of proximity 
effect), an obvious error in Lp given on p.135 (a 6 turn primary 
giving 3.5mH ???) and some bad advice on taking sparks from coils on 
p.139 (apparently its OK to fry yourself at 4MHz).  That this piece 
should have sprung from university researchers is a parody in my 
opinion.

Regards,
Malcolm