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Building a first-ZVS, inductor feedback!

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LAN_403

Xplorer

Tue Sept 21 2010, 07:01AM

Registered Member #2416 Joined: Sun Oct 04 2009, 04:23AM
Location: Oceanside, CA
Posts: 91

When you supply it with 30v it draws 9 amps peak? Did you measure that voltage as it draws 9 amps? Try a better power supply before you go messing with the circuit. My guess is that the voltage is dropping considerably as the flyback pulls all that current from your transformer.

You should be able to get far more that 1.5in arcs if that's the case. I run mine off 40v max from my variac and i suspect that it draws over 10 amps at that voltage. I can get almost 8in fiery arcs at that voltage.
Here is a video at 40v if you're interested.

-Tony

Proud Mary

Tue Sept 21 2010, 09:20AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Killa-X wrote ...

Well, I talked to someone and i guess i didnt know the core didnt have to be so picky. I even heard people using iron cores. I took a Choke from a TV circuit, that was 1" diameter, and twisted 24awg together (2 pieces) 20 turns.

Good man! It's as well to remember that from an historical point of view, toroidal cores have only come into widespread use relatively recently - perhaps because of the sophisticated machinery needed to wind them.

Before that, chokes were wound either on laminated cores like transformers at low frequencies, or wound on simple cylindrical formers with or without cores according to need.

Toroidal chokes and transformers are generally more efficient, compact, and self-contained field-wise than those wound on simple cylindrical formers, but there's no need to think that just because you haven't got a toroidal core you can't wind a choke, or bifilar transformer. You may just have to wind more turns, and keep the device further away from other components with which its magnetic field might interfere.

Killa-X

Tue Sept 21 2010, 02:52PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Ya, my variac is under reconstruction right now. The 9A peak was using a clamp meter on the 30VAC side of the transformer, with peak pressed down. Ran an average of 5A. When I'm home tonight I'll post/edit and let you guys know the voltage drop of my transformer. Before draw, and during draw. I probably have to play with winding the cores differently too. 70v got a 3" pull with thin (yet white) arcs..

EDIT

So as promised, heres the results.

When drawing an arc, it was around 24V, and dropped as low as 18V, being the farthest pulled. The no-load voltage is 36V.

Xplorer

Wed Sept 22 2010, 09:33AM

Registered Member #2416 Joined: Sun Oct 04 2009, 04:23AM
Location: Oceanside, CA
Posts: 91

Yup, that's why your arc is weak. Mine does no better than 1.5 inches at 18v too.

-Tony

Killa-X

Wed Sept 22 2010, 02:43PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
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So it's amps? I've seen a computer power supply do 6" but I know those are rated like 12v 40A...

I tried a variac, 40v gave about 4" but the white glow around the arc was maybe 3mm. Was a thin one. Would this be an inductor/capacitor problem? Else I figured maybe because my rectifier has only 2 1000uF capacitors in parallel, as a filter.

Xplorer

Thu Sept 23 2010, 06:51AM

Registered Member #2416 Joined: Sun Oct 04 2009, 04:23AM
Location: Oceanside, CA
Posts: 91

If I'm interpreting the schematic right I think the inductor acts like an inductive ballast for the primary windings, so perhaps if you use a smaller inductor the circuit will draw more current at a lower voltage. I've never seen a ZVS with impressive arcs from just 12v, but I suppose it's possible.

I think that experimenting with the number of primary windings will have a similar effect as changing the capacitor value. That LC circuit has to resonate. So try 4 or 6 turns and see what happens. Otherwise try a different capacitor. See if you can find any MKP X2 from an old power supply. That's what I'm using with good results.

When you gave it 40v what was the voltage? How far was the gap when the spark jumps. 1cm is about 10kv. If it was any more that 2cm you can try removing a few turns from your inductor. That should give you more current and a fatter spark, as well as be able to draw out the arc longer.

Yes, use a larger filter cap too. I've got about 5000uf. I tried even larger than that but the result was the same.

-Tony

Killa-X

Mon Sept 27 2010, 03:42AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

I'll have to get back to you on some of your questions, but this video I made should explain most things!

My YouTube video of me testing my ZVS up to 50v. I had a 12v power supply, and fed the inductor variac power...sadly I didn't watch the voltage drop..

Killa-X

Thu Sept 30 2010, 02:07AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Have an interesting idea/question. First, I thought it would be fun to put 2 flybacks on a ZVS. I did so, using the same turns on each flyback, and connected it directly in parallel. The output HV I tried in parallel and series. I actually noticed a REDUCTION in output compared to 1. Why is this? I used a single ballast... Flybacks (DC) in parallel. Yet my output wasnt larger.

You see, I have a box of 24 flybacks that are exactly the same model. Same production date, same brand, etc. So, i thought it would be fun to hook a lot in parallel/series to give me some nasty arcs. I know saturation plays a role, and I had 5+5 on each flyback. I did 5 in parallel long ago on a 555, and I got some thin 8" arcs, and it wasn't even a ZVS.

So...Am I doing something wrong? Also...How can i push more than 50V in? I put a 12V transformer to the board, and variac rectified to the inductor. After 50V it starts to get cruddy, due to saturation...

Xplorer

Fri Oct 01 2010, 02:12AM

Registered Member #2416 Joined: Sun Oct 04 2009, 04:23AM
Location: Oceanside, CA
Posts: 91

I'm not sure how, or even if it's possible, to run two flybacks off one ZVS circuit. I'm not surprised it didn't work. My guess is by adding another inductor (the extra flyback) you're disrupting the LC circuit from properly oscillating. Perhaps both flybacks would need their own capacitor? I'm really not sure.

Anyways, when you start to surpass 40v you should change the circuit a bit. Change the 470ohm resistors to 1k resistors, the 12v zeners to 15v zeners, more turns on primary, larger inductor. Also you'll want to use thicker wire on all the high current connections. That will help minimize the voltage drop under high current.

However, these modern style flybacks wont survive if you try and push anymore power through them. You're driving a ton of wattage through the thin secondary windings. So at some point they'll start burning out, so it's a good thing you've got a box full of them. :p

If you can, try adjusting the air gap on the cores and see if that helps avoid saturation.

Cool video though! Nice job!

-Tony

Killa-X

Fri Oct 01 2010, 03:30AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

I'll try more things when I etch a board out. Right now my flybacks never even got warm. The only warm part was the primary I coiled...once I get my parts I'll experiment more! I just thought it be cool to do more than one seeing I got 24 of the same :)

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