Re: OLTC update - Coupling figured out :-)

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

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

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 insight 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 very 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" <tesla-at-pupman-dot-com>
>writes:
>> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>> 
>> 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]
>
> 
>