QCW coil / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

QCW coil

first previous 6 7 8 9 next

Move Thread

LAN_403

Adam Munich

Mon Nov 21 2011, 10:44PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Well, found me a pipe. How the hell this thing ended up 5 miles off a seasonal road in the middle of nowheresville

,-79.115081&hl=en&ll=42.315813,- 79.124823&spn=0.009092,0.01929&sll=42.298192,- 79.115593&sspn=0.009094,0.01929&vpsrc=6&gl=us&t=h& z=16 is beond me, but it's schedule 80 4", perfect for the coil.

And here's a 14 inch piece sanded to 250 grit and cut square on a bandsaw.

Now I need to do some winding. I have 24awg, 25awg, 26awg and 28awg. What do you think would be best if I was going for 350khz?

Dr. Dark Current

Fri Nov 25 2011, 11:24PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Guys, what peak powers are we talking about here? From what I've read, it seems we need around 10-20 kW peak for some 40" QCW sparks, does this sound about right?

Goodchild

Sat Nov 26 2011, 07:24AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Dr. Kilovolt wrote ...

Guys, what peak powers are we talking about here? From what I've read, it seems we need around 10-20 kW peak for some 40" QCW sparks, does this sound about right?

Peak power for what the tank circuit or wall draw?

The peak power for each burst can be rather high, but draw from the wall can be considerably lower. I can get 40" with 800W if I only run 1 or 2 pps

Dr. Dark Current

Sat Nov 26 2011, 08:55AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I meant for the bridge supply, what is the peak output power at the end of the burst.

Goodchild

Sat Nov 26 2011, 04:44PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Well that is the same as the tank current which is usually <100Apk. But this is why you use a large bucket cap on the modulator, so that it can supply those large currents for short periods of time.

All this info is on my QCW page

teravolt

Sat Nov 26 2011, 06:05PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

knowing how much power is being transferred from your energy storage electrolytic to the spark its self is a complex equation. I cant imagine that a Tesla is more than 30% efficient with out mesuring. Goodchild have you ever used a person transformers to mesure the secondary current during a arc.

Steve Conner

Sat Nov 26 2011, 09:29PM

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

No it's not that hard. To a first approximation, take your DC bus voltage, multiply by 4/pi, divide by the square root of 2, multiply by your peak tank current (as measured by fiddling with the OCD, etc) then divide by root 2 again.

Or hook your digital scope up to the coil, multiply voltage and current together, integrate, divide by burst length.

Either way I get about 50kW burst power for my Mjollnir coil. (In its old configuration. I had to lower it for the QCW conversion to avoid overheating, it is now nearer 20kW.)

And from other measurements I know it is at least 65% efficient, not 30.

Dr. Dark Current

Sat Nov 26 2011, 10:50PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Thanks, just wanted to try this with a tube so I can design the tank circuit for the desired kW peak output. I think I'll go for some 12-15 kW and see if it's enough.

teravolt

Sun Nov 27 2011, 02:50AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Hi Steve, is that for a coupling of about .2? the shape of your primary may have less or more transfer of energy depending on its shape and aproximation to the secondary. Steve Wards QCW's primary probly has a coupling of .4 or more. would it be pausible to use a signal generator, scope, and load to figure out the energy transfer for a specific coil?

Goodchild

Sun Nov 27 2011, 08:08AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

I find that a great way to approximate energy transfer is to simulate the coil. The tricky part is the spark loading, I have yet to come up with a decent spark loading model for the QCW. I have used the Terry spark model for DRSSTC in the past with good results, but I remembering Steve Ward saying something about having to modify the model to get accurate results for the QCW.

As for coupling, .4K is about as high as I go with my QCW. I usually run about 0.35k or 0.36k. I find that this coupling is rather important, really important actually to achieve straight sparks. If the coupling is to low you get sparks that look a lot like what you get out of a regular DR with long PW and if to high the system will flash over. Tuning also seems to have a heavy influence on this.

first previous 6 7 8 9 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob