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Re: Tesla Coil Power Factor

Hi Malcolm,

	Thanks for the "sweet spots".  I knew someone would have them.  I was
trying different couplings this afternoon but it didn't make much
difference in my case.  There is still some considerable charge left on the
primary after quench.  I'll test this more.

	Unfortunately, during the last test, the voltage probe measuring the cap
voltages blew the resistor string to bits (there is a certain visceral
thrill when one is turning up the old variac about to max and suddenly a
loud and sickly, bang!...arc...fizz sound is heard :-)).  An old design
flaw in the thing finally caught up with me.  Of course, the 30 feet of
fiber-optic cable protected the scope and such but the $30 voltage probe is
trashed.  I won't be able to take direct voltage measurements for at least
a week or so :-(.  Perhaps I can continue with my other measuring
instruments in the mean time.  Some times the bleeding edge of technical
research is painful....  But that what makes it so much fun :-))

All the best,

	Terry


At 01:58 PM 9/21/98 +1200, you wrote:
>Hi Terry,
>
SNIP..................>> 
>> In john03.jpg it is apparent that the system is loosing energy before the
>> quench.  However, I believe this is due to the high corona loss between the
>> top terminal and the target.  The actual strike discharges the system
>> instantly but the loss before that point seems due to corona.  Thus I
>> wonder if this is a good test to use.  Of course, a streamer has early
>> losses too so maybe it is valid.
>
>In my case, I took all measurements first without a rod in place, then 
>positioned the rod to get the spark measurement. There was no 
>breakout of any kind during the first part of the test.
>
SNIP................ 
>> I have heard that there are some "sweet spots" for the coupling
>> coefficient.  Perhaps a carefully tuned coupling would reduce the energy
>> loss I am seeing.  I will try to play with it some to see if I can reduce
>> the loss.
>
>Two notes on this: the sweet spots are signalled on the scope by a 
>deep null between beats signalling complete transfer (minus circuit 
>losses). The second is that coupling can be adjusted to take 
>advantage of whatever gap one is using. Loose coupling works well 
>with otherwise poorly quenching gaps as it lengthens the null period.
>Unfortunately the gap has longer to add to the losses as the 
>transfer period also increases.
>
>      The sweet spots in descending order are 0.6, 0.385, 0.28, 0.18, 
>0.15 0.12.......   These are the math values for a lossless system. 
>As Bert pointed out once, the fact that the system is losing energy 
>while effecting transfer means that the practical values are somewhat 
>higher than these and exact values for a particular system are 
>dependent on losses for that system (e.g. a lower Q primary will 
>require higher k than one with a higher surge impedance to hit the 
>sweet spot).
>
>Malcolm
>
>