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Finished up ZVS need advice.

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brtaman

Sun Jun 21 2009, 10:34PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Hey,

Will try out your suggestion Henry. I just noticed after a good 15 minutes of running (entire driver luke warm...wow), that the toroid was burning hot. In fact, I almost scorched my finger when testing the driver with my highly accurate implanted thermometer.

I am going to go up in wire size on the torroid which means it will have less turns (now its 75), wonder if that will help out the 3 wind mode.

Thanks
brtaman

Dr. Dark Current

Mon Jun 22 2009, 08:01AM

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

brtaman wrote ...

I am going to go up in wire size on the torroid which means it will have less turns (now its 75), wonder if that will help out the 3 wind mode.

I don't know what's the size of your toroid, but 75 turns sounds way too much for 12 volts. You should be better with something like 15-20.

Proud Mary

Mon Jun 22 2009, 09:25AM

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

The choke shouldn't be cooking off like that. What AWG have got on it, lad?

brtaman

Mon Jun 22 2009, 09:37AM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Dr. Kilovolt, I will make a new toroid with much thicker wire. It is the white/yellow powdered type, so I went for more turns rather than less it doesn't saturate as easily as ferrite so it is good for this driver?

I will go for some really thick wire I got of another torroid 25 turns just to be on the safe side.

Harry, I am really not good at eye gauging the AWG of the wire, I is a bit sbove 20 though...20-23?

Dr. Dark Current

Mon Jun 22 2009, 10:10AM

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

brtaman wrote ...

Dr. Kilovolt, I will make a new toroid with much thicker wire. It is the white/yellow powdered type, so I went for more turns rather than less it doesn't saturate as easily as ferrite so it is good for this driver?

I will go for some really thick wire I got of another torroid 25 turns just to be on the safe side.

From my experience, any core works for this driver, but in theory, powdered iron should work best.

FYI, the core is more likely to saturate with MORE turns than with less turns from the DC current.

Proud Mary

Mon Jun 22 2009, 10:15AM

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

A few words on toroids that may be helpful:

1. The colour schemes are rather abitary, unless you know the manufacturer.

2. Always take care to sand off any rough edges on the toroid. They do conduct electricity and rough edges can scratch the enamel off your winding wire, causing a short. Insulate your core with thin plumber's PTFE tape if you have nimble fingers.

3. There is no sure way without instruments of telling apart iron powder cores from ferrite cores.

4. Remember that ferrite toroids are a fairly recent invention, and that a linear inductor wound on a piece of ferrite rod (for example only) of the same inductance will do just as well in nearly all cases. Toroids have advantages - they are self-shielding, occupy less space, have fewer turns per Henry, and so on, but rarely is it necessary for a small inductor to be toroidal rather than linear.

In this particular case, a linear wound choke will work just as well, and maybe even better, because it is easier to make a more accurate winding along a piece of rod, than it is to wind round a small torus, especially as the wire gets thicker.

brtaman

Mon Jun 22 2009, 02:36PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Thanks for the info, learning more and more.

I will either take another yellow-white torroid or use a ferrite rod left over from a broken flyback, wnd around 20 maybe 25 and see what happens.

Thanks
brtaman

plazmatron

Mon Jun 22 2009, 03:14PM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

Excellent work, I see you dont waste time!

Normally with my ZVS drivers, I use a 5+5 primary, and solder my caps, as close to the flyback as possible, it is also a good idea to keep all connections short too.
Try and get good quality caps for your circuit, instead of those resin dipped things, polypropylene caps are the caps of choice for this.

For the inductors, I was using some I found in old PC power supplies. There is normally at least one in there, sometimes more, and they are generally high current.

The amount of power you can reasonable extract from the circuit is ultimately governed by voltage. The circuit is very robust however, and it is possible to run it off around 40V, at several amps! The question is whether of not your flyback will survive the abuse!

brtaman

Mon Jun 22 2009, 03:39PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Thanks plazmatron!

Yes, I really would like some good poly caps for the circuit, but the place I ordered my ZVS parts from ran out and decided it was a good idea to call me up and ask what they should replace the caps with right while I was in a meeting. I told them to forget it and send the stuff out...I regret it now a bit, but oh well. -.-

Good news, I rewound a new toroid (took it out of a PC PSU ;)) with 21 turns and much thicker enamel wire, my eyeball says 16 gauge at least. Result? 10.2 amps at 12v and at least 20kV (arc forms at 24-26mm) I can draw the arc out for at least 15-20cm (eyeball ruller don't like to get to close to the action). I don't think I can get much more out of the driver @ 12v...but I am very happy getting up to 120ish W, thanks to everyone who helped!

Myke

Tue Jun 23 2009, 02:22AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Hi. I would try to keep the caps as close to the MOSFETs as possible instead of as close to the flyback as possible. It's just what I have heard and I would think so because you don't really want much inductance between the MOSFETs and the tank. The extra inductance between the caps and the flyback would be negligible compared to the inductance of the primary. Does anyone know which configuration would give the best performance? (I should probably rewind my core on a yellow/white core instead of this blue-green one)

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