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secondary affecting spark lenth?

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dmg

Fri Jan 29 2010, 04:08PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
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Posts: 627

I wondered this but never actually tried, given that your drive system is the exact same and always resonantes with the secondary (hypotheticly) and the only variable is the secondary coil, does the size (physical dementions) affect spark lenth to any extent?

radiotech

Fri Jan 29 2010, 07:34PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Apart from Paschens law

the length you can pull an arc, DC fed with a series inductance, seem to be longest in my experience, I would think that the hottest longest arc would be when its impedance is the conjugate of what drives it.

Have you guys tried seeding arcs by adding contaminants at the electrode ends, kinda like what Nernst lamps used to make the thermo conductive ceramic glowers?

Take a look at at 'cratering' of rod ends in commercial arc lights.

Since the temperature of arcs is extremely hot, like fusion temps,
wouldn't it be nice to find a way to get over unity (electrical-thermal)
efficiency by 'burning' some element transmigrating via electrolysis
from one electrode to another?

dmg

Fri Jan 29 2010, 07:50PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
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well there are ways to "cheat" on arc lenth, a very sharpend and salted electrode will give longer streamers, but if I wanted to cheat I think its best with a hollow electrode and an Argon injection system, when I draw arcs out of anything, I usually use either a non-contaminated needle sharp electrode gives a few extra inches, but if the electrode is coated with a metalic powder, paint, rust or salted the arcs are generally bigger, considering that It probably vaporized the electrode faster, allowing more conductive particle in the air, I noticed that those type of arcs have a rather strong scent rather then ozone alone, and are a pain in the ass to clean once the coating got melted into the electrode, however, I think the arc lenth (streching it) is inherent on the amperage rather then voltage (look at NSTs and MOTs) you need some sufficiant voltage to "strike the arc" like in a xenon lamp, but then you dont need too much voltage to sustain the arc, you just need amperage. the more amps you can push into that arc, it would make significant arc lenth.

so that was my theory regarding the TC, that even if your driver was the same, the fatter bigger secondary, could perhaps get a higher amperage and voltage output without the use of an extra resonantor (magnifier) to an extent, however since I have not experimented with that style of setup, I dont really know how it will behave when applied to an actual application, or if there will be any actual improved arc lenth.

Edit: I probably should have mentioned that the capacitive terminal on the output doesnt count, this question is purely on the raw output of a secondary coil inherent to its dimentions. (diameter, lenth...).

radiotech

Fri Jan 29 2010, 11:25PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Is t possible to superimpose an AC current of wavelength at least twice arc length on a DC ars and see if nodes show.

Its a bitch trying to communicate with the Shuttle with its nose
glowing redder than Rudolf. Can we find an arc solution?

Steve Conner

Sat Jan 30 2010, 10:07AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The bigger the spark is compared to the secondary coil, the less efficient it is. For instance, one of my coils once produced an arc 4.4 times the length of the secondary, and took 3.3kW to do it.

If the secondary coil had been twice the size, it could have made the same 5 foot spark with less power.

Also, too much power into a small coil can make it arc over and burn up.

dmg

Sat Jan 30 2010, 01:49PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

well that helps,
now im gonna build a powerfull TC driver and wind a 2 inch long 1 inch wire secondary with 40awg wire just to see it burn!
how come the smilly faces dont work for me...

I am building an SSTC and I wondered if the bigger secondary would give bigger arcs without having to push higher power into the mosfet bridge.

Phillip Slawinski

Tue Feb 02 2010, 04:32PM

Registered Member #1732 Joined: Thu Oct 02 2008, 02:34PM
Location: Huntsville, AL
Posts: 112

Steve McConner wrote ...

The bigger the spark is compared to the secondary coil, the less efficient it is. For instance, one of my coils once produced an arc 4.4 times the length of the secondary, and took 3.3kW to do it.

If the secondary coil had been twice the size, it could have made the same 5 foot spark with less power.

Also, too much power into a small coil can make it arc over and burn up.

There is some truth to what you speak of regarding efficiency vs secondary length, but I don't think the effect is that extreme.

My secondary coil of 3.5" X 12" (which seems comparable in size to the secondary on "Mjollnir"). Makes nearly five foot sparks with less than half the power. I'm quite confident it could already be making five foot sparks if I had a better location to run the coil.

There are ways to combat secondary flash over. You need to ensure that the top voltage does not rise too quickly. I run a rather large topload (18" x 4.5") compared to the secondary, this helps bring top volts down, while also allowing for more spark growth. I currently have a .2ÂµF capacitor installed, but I will be downsizing to a .15ÂµF capacitor to slow down ring up.

4.6X Secondary Length

Result of using too large of a tank capacitance, then lifting the toroids up too high. (it survived)

Steve Conner

Tue Feb 02 2010, 04:38PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Not bad! So what break rate and burst length did you use for these results? How did you measure the power?

Phillip Slawinski

Tue Feb 02 2010, 04:44PM

Registered Member #1732 Joined: Thu Oct 02 2008, 02:34PM
Location: Huntsville, AL
Posts: 112

Steve McConner wrote ...

Not bad! So what break rate and burst length did you use for these results? How did you measure the power?

The 4.6X shot was at reduced voltage, because I was having flash over problems at full volts.

Vbus = ~200VDC (60% of Maximum)
On time 70ÂµS - 100ÂµS
Breakrate ~300bps
Power ~1300W (Measured with Kill-a-watt)

It could have used more a little power, I'm not entirely sure, but that 1300W is very close. Until recently strikes to the right wall would arc to neutral

(Arcs went from the wall to a metal strip on the floor which my power cord ran over). Of course, when the arcs went to neutral, the kill-a-watt would crash.

I designed a new primary and strike rail that should allow me to push this coil even harder without flash over. Hoping for the parts to get here this weekend.

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