[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Re: Spark gap Resistance
John,
Spark gaps work pretty well at high or low currents. The large coils
mostly
are more efficient because there are smaller losses in the transformer
and in the wiring, I think. There may be some issues with spark growth
too,
I don't know. Various folks have done various tests of various things,
but
yes it's difficult to remember it all sometimes, unless one is thoroughly
organized. Don't let it affect your sleep :^)
I would have thought losses would have been higher with all the wiring, as
current increases resistance losses also increase.. I would expect the spark
gap to gain efficiency with higher currents and overcome even the extra
wiring losses.. This suggests the spark gap have a real gain at higher
currents... I dont know....
Well still awake at 3.30AM here in the UK :P
It seems experimental work has slowed greatly among our
list members. I haven't done any TC work lately either.
My SG coil has been in storage for a while now, Long story for another day
maybe...
I'll be looking forward to hearing about the results of your projects as
you complete and test them.
It could be some time as lack of funds are the main killer... I have 2
systems in mind...
1) a 20KVDC based coil ( just won a 60H 15KV choke off ebay) Will be a
resonate charge circuit from 8KVAc 150mA ( need to find a transformer!) It
will be a spark gap based coil, I plan to build the RSG a large dia (maybe
20" dia) and make it so I can place 4 electrodes across the disc. In effect
it will give me a tappable spark gap just to adjust dwell time. The outer
contacts having a faster break time than the inner ones. I hope that 20KV
will be better for spark gap losses, I will be using 5nF which is really low
current. I think it was about 1Joule of energy. I think my 500W coils was
0.5J so should give me some good power input. Operation will be around 1mhz,
probably the secondary coil 100turns of copper tubing. Primary.. what ever
fits :P
2) the low voltage coil. Variac input runs from 0-100VAC. This also uses a
resonant charge running at 100bps. uses a small inductor (2.5mh) and a
massive tank cap of 1,000uF ( yes thats not a typo) It setups up 100hz
resonance and doubles the input voltage. The max I can get is 250VDC on my
tank cap. took over 200 caps in parallel and used 1 full roll of solder and
a lot of copper sheets! 1,000uF at 25VAC input should work out about 1Joule
also.
The spark gap in this case is a BIG SCR. Can take 1400V at a lot of amps...
The primary is 1uH , single turn, low resistance and inductance, hopefully
0.001ohm! A list member is donating me some copper strap for the primary,
will be about 74" long by about 1.5" wide.. The amps pulse of my tank cap
should be able to take anything I throw at it with 200 caps in parallel. The
tank cap's are flat plate types with "apparently" zero inductance and
resistance. So all my losses will be in pure resistance. ( probably the SCR
will be just as bad as have no idea how good it really is).
The primary has a capacitor of about 10nf ( will be adjustable to tune the
coil) and will resonate at about 2mhz. The secondary is 80turn of coaxial
cable spaced out also... will be about 2 mhz unloaded. The idea being to
transfer 1,000uF into the capacitance of the secondary (maybe 20pf?), in
theory gives 700KV output.
The problem is the 1,000uF goes via the primary coil and capacitor so not
sure how that factors in.. The coupling is 0.05K. wanted a low coupling
factor to prevent the secondary from loading the primary coil. My simulation
shows everything running fine. Without the secondary coil effecting the
primary ( do not seem to be able to simulate the secondary correctly) the
primary resonates at 2mhz and rings down over godknows how many cycles, its
a lot put it that way!
My first tests with real hardware I had problems, I forgot the 10nF cap for
a start but I did measure 2mhz on my scope on the secondary and I could not
measure the voltage very well, probably 1-2kv. I am in the middle of
redesign but it is a very confusing project!
I think my point about frequency was overlooked aswell. I tested a
primary/secondary on 12volts to experiment with coupling and efficiency. I
documented the tests and really I found higher frequency worked a lot
better. For example 12V on the primary would give 2volt on the secondary
coil at 15cm gap ( pretty low K factor). this was at about 1mhz. 100khz and
I only got about 5mV on the secondary coil. I also found that x10 the
frequency would allow me to get 2 volts at 30cm range and back at the 15cm
range would be x4 the voltage...
The idea is here, as the frequency is 1mhz, it works a whole lot better than
100khz which pretty much sux it seems. So even though the coupling is low,
there is hope that the frequency will overcome this problem. I do not want
to increase coupling as it will load the primary more and trying to obtain a
high current pulse at low voltages is hard enough as it is!
Over all, I expect both systems will be interesting to build, I do not think
anyone has tried anything like these designs before, so feel a bit left on
my own with designing these systems.... As you can probably tell, I have a
lot going though my mind at the moment! hence it is 4AM now and I am still
pondering over things! I have been pondering over the high Q designs for
about 8 months now and not really getting anywhere very quick... I do not
know even in my idea is sound so do not even know if the system has any
chance of even working... but I am going to try anyway.... It could take a
while to come back to the list with the results. I have zero funds at the
moment which is not helping progress much either.
Chris
P.S if anyone has a 8Kv transformer capable of 150mA then I will be looking
for one after x-mas.. ( or 3x 50mA 8KV will probably work too)
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla