[Prev][Next][Index][Thread]

Re: Answers to a Puzzle


From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Wednesday, September 03, 1997 2:15 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Answers to a Puzzle

Hello all,
           The scope tells the story clearly and starkly to the 
difference in output conundrum. Man do I love storage scopes! :)

(1) k = 0.085 for the smaller resonator as close as I could couple it 
to the primary in question. That is compared with 0.12 for the larger
one. 5 cycles to ringup for the small resonator vs 3 for the larger 
resonator.

(2) It is _obvious_ that the Q of the larger resonator is a _lot_ 
higher. Whereas the gap went out on just the second ringup with the 
smaller coil, it went out on the fourth for the larger one. This was 
with a very moderate air streamer for the large coil and none for the 
smaller one (single shot).
    Moreover, the linear ringdown of the primary was clearly impressed 
on the output waveform for the larger coil whereas it couldn't be 
discerned on the smaller one. So, the Q of the primary is not all that
bad at Xp=12 Ohms/gap and this was born out by the transfer 
efficiencies I was getting for the minicoils although that was with 
50 Ohms/gap which suggests I could do a lot better with this system. 
I have to test this but need more copper pipe to do so.
    The lower k for the smaller resonator is influencing primary 
losses but not to a huge degree.

More interesting tidbits:
- Even at k = 0.85, the output voltage was such that the small 
resonator flashed over from top to bottom several times! This didn't
happen in repetitive operation as an output streamer was readily 
established, albeit a rather inferior one.
- The single shot attached spark was a vastly higher quality with the 
large coil (flashovers excepted).
- It was also an inch or so longer.

Implications:
- If resonator Q matters this much, the primary can't be all that bad 
once again. You cannot use the log dec formula to calculate primary Q 
because losses there are not linear-resistive. We've known this for a 
year or so now.
- It is clear now that cramming heaps of inductance into a small coil
is not going to produce a good one despite the low Cdistr because the 
small wire losses matter a great deal. Better to use a much larger 
coil with a more modest terminal if primary energy is limited, OR, go 
to a higher frequency and use bigger wire in the small coil. My rule
of 3 skin depths minimum for a spacewind stands