Tesla Coil Build Thread

[Sigurthr]

A little tip.
I would personally stay away from wire gauges any higher than 26ga as they become too easy to snap when winding. 26ga or lower should be fine. Lower Ga = larger diameter of wire.

Yeah you're right about that... winding 30ga was an experiment to see how much I could bear without going insane.

Speedy, keep in mind a 12x3 won't fit directly over a 6.5" dia cap, you'll need a standoff, and ideally, a larger toroid would be best for a 6/6.5" coil, but 12x3 is the MINIMUM you can successfully use.

Based on theoretical limitations this NST/MMC combo should be able to make 26" arcs under ideal (unrealistic) situations.

If you want a strong E-field you'll LOVE my SSTC, heh. The e-field from my CW coils are insane. Just remember the more energy you put into e-field the less visual output you get. Nikola's coils has NO visible output.

SG coils are just noise fountains. "Such noise, so static, wow." Pretty much sums it up.

edit: I think you'll be fine with 28ga on an approx. 6" dia coil aiming for ~150KHz with a 12x3 or 100KHz with a larger toroid. The nice thing about a 7.5kV NST is the primary winding interturn distance can be shorter as less risk of primary arc overs. Simplifies things greatly compared to using a 12k NST or a pole pig (14.4k).

 

[Speedy78]

Well if they are unrealistic then I doubt I could achieve that kind of output. If I can get 20 inches or so that would be fantastic. I will have to experiment. May just make a toroid out of dryer ducting. Would fit better size wise on a 6 inch coil. Would just have to work out the bugs in javatc. I think 25 guage will be too large. Though I would love 3 and half feet of winding! Will that mmc be attatched to that plexi or will I just get a box of caps? And will it have bleed resistors with it?

 

[Sigurthr]

Yeah, MMC comes with the plexi base and mounting studs/high current bus rods. No bleeders as I generally don't use them (when I was using the MMC I would go in with welding gloves and a clip lead and manually discharge every cap), but they're cheap and easy for you to add. The problem with bleeders is most resistors can't hold up to more than 600V or so but at full charge there's 1325V across each cap.

 

[Speedy78]

I cant discharge the whole thing at once? Lol. What about the choke you had on the NST. I assume I would need one as well?

 

[Sigurthr]

Nah seriesed (what is the correct word for that? lol) capacitors don't discharge fully by simply discharging the to ends of the array. That would make life simple and physics doesn't like simple.

I don't remember ever using a choke... I first tried a series choke on each NST rail... for like ten minutes, LOL. It was pointless. Terry filters aren't even needed if you follow the correct capacitor-in-series-not-in-parallel topology.

 

[The Lightning Stalker]

The last secondary I did was wound with 32AWG wire. It is difficult getting the turns close together
without overlapping. The coil ended up being like 8" tall and is a poor performer as you can imagine.
Waay too many turns and way too tall. The wire only broke once. It can be done if you are careful.
Having a lathe that will turn at low speeds really helps.

 

[Seoul_lasers]

Yeah you're right about that... winding 30ga was an experiment to see how much I could bear without going insane.

Speedy, keep in mind a 12x3 won't fit directly over a 6.5" dia cap, you'll need a standoff, and ideally, a larger toroid would be best for a 6/6.5" coil, but 12x3 is the MINIMUM you can successfully use.

Based on theoretical limitations this NST/MMC combo should be able to make 26" arcs under ideal (unrealistic) situations.

If you want a strong E-field you'll LOVE my SSTC, heh. The e-field from my CW coils are insane. Just remember the more energy you put into e-field the less visual output you get. Nikola's coils has NO visible output.

SG coils are just noise fountains. "Such noise, so static, wow." Pretty much sums it up.

edit: I think you'll be fine with 28ga on an approx. 6" dia coil aiming for ~150KHz with a 12x3 or 100KHz with a larger toroid. The nice thing about a 7.5kV NST is the primary winding interturn distance can be shorter as less risk of primary arc overs. Simplifies things greatly compared to using a 12k NST or a pole pig (14.4k).

---> was going to add that on an SSTC there is little waste energy switching
(no sparkgap) and as such you can get truly massive magnetic fields on the primary, so much so that some larger coils need their primaries liquid cooled as they get so hot.
I have yet to see a large SGTC need that kind of treatment.
:beer:

My next project will definitely be a large H bridge SSTC.:evil:

I was just going to say that I hand wind my secondaries. No lathe. Just winding jig.

 

[Sigurthr]

I still haven't gotten around to doing a full bridge, but you hit the nail on the head about primary heating, which is why. I've got forced air cooling on my 3kW coil's primary and I can barely run it over 1.5 kW if the runtime is over 30sec. Water cooling a mains powered primary with no isolation is where I draw the line.

 

[DashApple]

I still need to wind my 70Khz secondary for my large SSTC .

You can bump the voltage up to lower the primary current for the same power . I thought about adding a few more primary turns on my SSTC and running from 400V AC .

 

[Speedy78]

What about using a high volume computer fan and just pumping air through the primary? Probably similar to blow air accross it.

 

[DashApple]

What about using a high volume computer fan and just pumping air through the primary? Probably similar to blow air accross it.

That works as well , I did the same thing on my VTTCs I made ,

 

[Speedy78]

Would just have to find something that doesn't conduct electricity to go from the fan to the primary. Not really sure what does and doesn't conduct electricity with these.

 

[Sigurthr]

100% duty cycle at 3kW is going to put out serious heat no matter how you look at it. I've got two 90CFM AC powered fans 90deg off axis of each other to keep the pri and section of sec where pri is wrapped cool. Haven't warped the PVC yet but the poly insulators are a little warped.

In a primary there are factors to balance; conductor size, geometry, price, workability, and in a SSTC impedance (turns). I can't increase voltage without using a doubler, and doublers can't source 10-20Amps of current without ridiculous capacitances. If I increase the turns without increasing voltage then current falls but so does output power. Also this would alter the coupling coefficient. If I increase conductor size it can handle the power better, but that gets expensive and unwieldy. The next step up would be braided welding cable, lol.

So you have to pick a happy medium. Since this secondary is already botched due to aspect ratio I figured I'd just vary power with my variac instead of playing with the primary impedance. It's a lot less hassle and allows a larger dynamic range. Besides I usually just enjoy the efield which is too intense for comfort over about 600W. The diathermy heating is intense at these RF power levels.

Btw, liquid cooling with mineral oil would probably be ok.

 

[Speedy78]

What size copper tubing should I use for the primary? Java is saying about 15 turns to be within resonance but im going to shoot for a little extra. Also what is the minimum sppace between turns that would be safe?

 

[DashApple]

Id use a 230V to 400V transformer for stepping voltages up , may be bulky compared to a doubler but it can supply current no problem

My 5" SSTC had a warped secondary , where as the primary was fine with no fans for short runs .

 

[Sigurthr]

What size copper tubing should I use for the primary? Java is saying about 15 turns to be within resonance but im going to shoot for a little extra. Also what is the minimum sppace between turns that would be safe?

For use with the NST and mmc? Even 1/8" tubing will do fine, there's little waste heat in a sgtc away from the spark gap. As for inter turn spacing I got away with 3/16" without issue. Yup always go two to three turns extra.

@Twirly yep trafo would work, but I can't afford a 3.5KVA step up trafo, haha. I'm not worried about upgrading or improving until I decide to make a new secondary. Then, and only then will I devote myself to going all out. I'm thinking full bridge of CM600s @ 75KHz, aiming for 5kW CW fixed frequency oscillator driven with audio modulation. Will be years before I can afford to do that though.