Re: OLTC update - Coupling figured out :-)

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

Original poster: "jimmy hynes by way of Terry Fritz <twftesla-at-qwest-dot-net>" <chunkyboy86-at-yahoo-dot-com>


the reason kens coil has such a slow ring up is that the switches cant handle
any more power. with most coils and the oltc that is not a problem, because it
is actually less stress on the switch the faster the energy is transferred. in
the oltc the turns are in parralell making it like less than one turn instead
of 3 turns. if you use ten big igbts in a s.s coil it would be possible to get
quick ring ups on even bigger coils. using a switch as a spark gap isnt as
efficient as using it in a s.s. coil 

 Tesla list wrote: 
>
> Original poster: "Terry Fritz" 
>
> Hi Ken,
>
> I am using only about a 75 volt firing voltage right now (starting out real
> slow). But perhaps at these low levels the losses are higher and loosing
> power to the primary coil which just "looks" like very high coupling. From
> the scope trace at:
>
> http://hot-streamer-dot-com/temp/OLTC08-24-01.gif
>
> The secondary losses are fine, but not sure about the primary. I will
> check into this. I may just have to keep cranking it up and the problem
> will go away ;-)
>
> YEP! Your right! I ran MicroSim with more realistic "low power" losses
> and got:
>
> http://hot-streamer-dot-com/temp/OLTC08-25-01.gif
>
> That is indeed what I am seeing. The coupling is fine after all. There is
> NO problem. I just need to keep cranking the power up and the losses will
> reduce naturally.
>
> Thanks for the insig! ht here!! It would have taken "me" a long time to
> figure this one out ;-))
>
> I am surprised your coil has such a long ring up. Unless the coupling is
> very low, which a I doubt, Perhaps the square waves don't couple as well.
> Only the Fo sine component may be doing the coupling while the higher order
> harmonics of the square wave are either not coupling or "fighting" each
> other. An interesting and unknown problem, exciting a two coil system with
> square waves instead of sine waves... Maybe Paul's program could analyze
> such a case since the harmonics in the secondary may easily come into play
> in such a case. Simple MicroSim models may not see the true action there.
>
> I will try to run some models on this and see if I can figure anything out.
>
> BTW - I think I know of a very easy way to measure the primary current.
> Just a loop of wire under the primary (or near it) to a scope probe. The
> voltage on the loop should be proportional to the ! current (or maybe it
> needs a load resistor?). A simple and v! ery useful instrument whose details
> will have to wait for another day...
>
> Cheers,
>
> Terry
>
>
> At 09:31 AM 8/25/2002 -0700, you wrote:
> >Terry (& all)-
> >
> >I've been following the OLTC saga off & on. But it's just occurred to me
> >that you may find yourself up against the situation I've found with my
> >s.s. coil: As you may recall, I apply a ~1200 V pp square-wave burst, of
> >up to ~6 ms duration, to a 3-turn (untuned) primary circuit for each
> >spark. With a 140 KHz secondary Fr and a 6" x 24" smooth (Landergren)
> >toroid, it takes ~30 cycles of constant (not exponentially declining!)
> >excitation to bring the toroid potential up to the spark break-out level.
> >
> >You are applying, I believe, ~680 x 2.8 = ~1900 V pp, initially, to a
> >3-turn primary circuit--incorporating much less resistance, admittedly,
> >than mine--but your excitation must (necessarily) exponentially-decline
> ! >quite rapidly. I'd think you might require more or less those 30 cycles
> >to pump up the voltage & I fear that the decline of your primary voltage
> >may preclude that.
> >
> >Were you able to do any simulations on that?
> >
> >Ken Herrick
> >
> >On Sat, 24 Aug 2002 23:02:13 -0600 "Tesla list" 
> >writes:
> >> Original poster: "Terry Fritz" 
> >> 
> >> Hi All,
> >> 
> >> Today I set up the coil for action:
> >> 
> >> http://hot-streamer-dot-com/temp/OLTC08-24-02.jpg
> >> 
> >> I powered up the coil...
> >
> >[snipped]
> >
> > 
> >



JImmy