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SGTC Secondary Question

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Swany

Mon Feb 19 2007, 12:35AM

Registered Member #261 Joined: Mon Feb 27 2006, 12:34AM
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Posts: 22

I have mostly assembled my first telsa coil, which is to be powered by a 9kV 30mA NST. This is fairly low-powered at 270 watts. So, along comes secondary winding time and a friend donated 800ft of 24awg magnet wire. However, this seems a largish diameter to use for a smaller TC. I was considering winding 815 turns of this on a 3 inch form. This would give 3x18 inches of coil with 815 turns. Does this seem unreasonable for a coil of this size?

Like said, I am quite new to Tesla coils, and fairly inexperienced with HV. I understand that the ratio of primary/secondary turns is not as critical as is the oscillating/resonating part. So, should I go along with the 24awg wire, or get something smaller, like 28-30awg?

In short, what would you recommend for a secondary with a TC this size. Any input will be greatly appreciated!

Thanks!

Tom540

Mon Feb 19 2007, 01:11AM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
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Posts: 617

I would go with smaller wire and try to get around 1200 turns, 28 awg would be good.

Part Scavenger

Mon Feb 19 2007, 01:36AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Hey man, welcome to the forum!
EDIT> Dog! Tom beat me to it, serves me right for writing a novel.

With your power plant, you should expect between 16-30" arcs. If you're DC Cox. More realistically, 18-20", if you can get more, great. It will depend on the type of capacitor bank, your layout, total resistance, etc. BTW, the resonance thing is kind of overrated.

Personally, I would go with something smaller, like 28-30awg if at all possible like you said. Reason? You will get more transfomer action, better coupling, better turn density, etc. Plus your streamers will *look* bigger. You'll want your secondary length (in this case) to be around 14-20" So I'd say about 3x15" wound with #28 to make about 1200 turns. #28's a good generic size anyway.

That's what I would suggest... However, if you've already got the wire, go ahead! It'll do something I guarantee, you'll learn a bunch of stuff, probably ruin it a some point, and then you can make a better one!

If you get any results, this won't be your last coil! I went through two or three secondaries before I thought I knew what I was doing.

Like said, I am quite new to Tesla coils, and fairly inexperienced with HV.

If you don't mind, I'd like give you some pointers as a noobie I wish I'd picked up:

1. Be careful with your NST. Everbody knows you shouldn't touch them while they're on or they could kill you, so I won't go there. NSTs are pretty fragile, especially if you don't know much about them. They're designed to run pretty much short circuit all the time, so they're lacking on the internal insulation (because the voltage isn't expected to run anywhere near above 12kV.) They like to short out inside and die if you aren't nice to them. So, make sure to use a safety gap, and go ahead and put in a strike rail if your streamers get anywhere near the primary. DO NOT run your spark gap too wide, this is what kills most of them. To set the SG, hook up only the NST across the spark gap and set so that it just jumps across. Never go wider than this, ever. If you introduce a fan or something, reset the gap. You can make the gap smaller if you want, but generally this is not necessary as the gap should be set at maximum voltage.

2. Don't touch the streamers. Despite what you might have read, they do not travel on the outside of the skin and will use your nerves, vessels, other internals to conduct the electricity. Long-term effects are not known if they exist, but I wouldn't want to push it. Secondly, the streamers will not kill you or even hurt much under normal circumstances, but certain possibilities exist in which the HV component of the streamer mixes with the high amperage of the line or primary circuit resulting in lethal streamers. This can happen from ineffective grounding, primary strikes (another reason for a strike rail), and a couple of other things. Oh, and don't touch anything in the primary circuit unless you're sure it's discharged, but you'd know that.

You can check out my website for other coiling stuff, I've written several articles about coil construction, and I like to plug the site anytime I can.

It's the green arrow in my signature, goto the articles section.

Good luck!
-Part Scavenger

Sulaiman

Mon Feb 19 2007, 11:31AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

800ft of 24awg is a good start!
If you use it all (you should) then I would look for a larger diameter former,
since a 3" former results in a Height/Diameter over 6, which will work
but a 4" would give better results with a H/D of about 4 and better Pri-Sec coupling.
The result will look more impressive too in terms of spark-length to coil height ratio.
You should aim for an operating frequency not more than 300 kHz.

BUT don't let the lack of a larger diameter former stop you...a 3" diameter will work fine.

For good results you will need a fan blowing air through the spark gap.

my 2c worth.

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