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Bert (et al)-
Yeah, I was thinking that that 0.4 must be unrealistic. However...my
simple simulation incorporates a signal source that is independent of
the secondary's Fr. I think that changing the P:S k is also changing
the Fr of the secondary circuit in the process. Thus there is brought
into play a mismatch between the simulation's input frequency and the
secondary's Fr. In the hardware, I utilize the secondary's
return-current to create the driving-current to the primary (after a 90
deg. phase-shift, amplification and pulse-burst gating, of course). That
ensures a continual match between driving frequency and secondary Fr.
I'm not going to bother simulating that further since I know it works,
from my one successful altho insanely complicated effort a decade and
more ago. We're stuck with the P:S k that we can achieve, of course, so
I'm going to leave off the attempt at simulation of the k question and,
when I get my 2nd driving module built, will just experiment with
varying the P:P k (and the P:S, to a degree) while eyeballing the sparks.
BTW, after the expected frustration (and more) because of Murphy's Law,
I've gotten my one driving module to work just fine, altho not yet with
the secondary feedback activated. In 2T of 12"-diameter primary I
measure >200A p-p, ~125 KHz, in 5 ms bursts at ~10/sec with only
moderate warming of the 2 power transistors--& that's not yet at full
input voltage. Next task is to finish the mounting-base for the primary
& secondary coils, which has yet to include a small central coil-spring
to receive the return-current. All the rest of the l.v. apparatus is
already built & tested(and the secondary--two of them, in fact)
fromprevious efforts. Then I will set the secondary in place, fire up
the whole thing & see what I get from that 200A. The object will be to
ultimately draw just under20A from the ~115V mains doubled & rectified,
at 5ms/10-per-sec maximum spark rate, while at the same time keeping
power-transistor temperature manageable. Happily, I already have enough
of those $28 (!) IXFN60N80P transistors for 3 more modules--and have so
far only smoked/flamed 1 of them, in my mains-doubler, a while back.
All of the above assuming, at 87, that I survive...
Ken
Subject:
Re: [TCML] Question for solid-staters
From:
Bert Hickman <bert@xxxxxxxxxxxxxxxxxxxxx>
Date:
4/24/2015 7:34 PM
To:
Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Hi Ken,
A Primary:Secondary k of 0.4 may be somewhat problematic from an
insulation standpoint. It's comparable to the coupling used in magnifier
driver transformers, and these can be prone to P:S flashovers with air
insulation.
Try loosening the P:S coupling to 0.2 - 0.3 and extending the simulation
time to 2-3 msec to allow the secondary to ring up over a longer time.
You may be able to achieve similar voltage output without the need for
excessively high coupling coefficients (and potentially heroic field
control and insulation techniques).