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Flyback Arc Contest

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Kolas

Sat Feb 11 2006, 03:17AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

Well, Now that the new forum is up, lets get back to buisiness.

I don't really think of this display of flyback punishment as a contest. More like documentation of our accomplishments.
So the flyback can do extreamly high voltage, sstc-like arcs. (i'm up to 10 inches)

Also flybacks can putt off extreme currents...
Anyway too much talking and not enough arcs.
I would say, it doesnt matter how well it holds up to other's results, we wana see them

Dr. Shark

Sat Feb 11 2006, 11:34AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

OK, let me make the first submission to this, even if it's not going to win any prizes. The arc is about 1" long, and in the background you can just make out the halfbridge of IRG4pc50 IGBTs running of 220V mains that is driving it. It's current limited by a 100W lightbulb, so the picture is actually quite a long exposure, about 1 second.

I tried it without the current limiting, but it instantly blew the main fuse and killed IGBTs, so it needs some more work.

Steve Conner

Sat Feb 11 2006, 08:19PM

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

Kolas, can you post a picture of the apparatus you used to get the 10 inch arc?

Kolas

Sun Feb 12 2006, 07:06AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

sure
this is a flyback out of some old TV
it was DC but im quite sure that it's no longer as such.

kolas

here it is
vv

Dr. Shark

Sun Feb 12 2006, 10:21PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

What kind of driver did you use for that? I keep hearing that the ZVS/Royer flyback driver does not work above 50V input, so probably not that. I would have thought that a halfbridge at 200V would be the ultimate flyback driver, but my experiments have been quite disappointing so far. I'm just not good at this stuff...

...

Mon Feb 13 2006, 02:06AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

you cannot use classic the zvs driver at high input voltages because the resistors/zeners on the gates of the mosfets will get too hot. But there is a solution, just use a separate 12v supply (like a dc wall adapter) attached to the 2 470ohm resistors, and leave the inductor attached to your high current supply.

Also, if you try to put 200v into a flyback it is not going to live for very long... You need to use more primary turns/less primary capacitance/greater series inductance...

But the last one to a line powered zvs driver is a weakling

Kolas

Mon Feb 13 2006, 02:44AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

that particular run was using a half bridge, half wave recitfied.
7 turns on the primary, all under oil
input was about 60v 1900w
heh horribly ineficaint
but quite impressive
though the death of my flyback came soon after, ground pin arced to core then to the inside primaries.

kolas

skmetal7

Tue Feb 14 2006, 04:37AM

Registered Member #101 Joined: Thu Feb 09 2006, 08:12PM
Location: Wisconsin
Posts: 41

having killed one flyback, i tried to take some pics of my ac flyback doing its thing, before its ultimate demise:

Dr. Shark

Tue Feb 14 2006, 11:46AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Kolas, did you use a resonant cap in the halfbridge, or was a square wave force feed arangement? Did you find the driving frequency critical, or is anthing in the range 20-50kHz ok?
..., I'll try the line powered ZVS, it would make a nice PSU for my Marx gen. Of course we europeans have an advantage, as we have 220V mains, but then I think by adjusting the impedance matching choke you can work over a range of input voltages. For the flyback, its a current source, it doesn't see the voltage.

ragnar

Tue Feb 14 2006, 01:02PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Joe Doe, for an off-line royer circuit, your MOSFETs should be rated at least pi times the input voltage. (and I hope I'm not spreading a wrong old wives tale. :P)

Here in Australia, our mains voltage is 240V. Depending on where you live, it might be 250V (I do my calculations pessimistically, because I like having overhead).

250 * 1.41 (sqrt[2]) = 353V

353 * pi = 1108V.

For even a tiny (8.5%, not much!!!) amount of overhead, you'd definitely need 1200V mosfets. They DO exist, but not from IRF. Then again, nobody actually gets 353V out of their bridge rectifiers...

If you go to DigiKey, do a search for "MOSFET", and refine your search by the drain-source voltage category - 1200V. I think you'll come up with three suitable FETs, of the order of USD$4.77ea (IIRC) if you're buying < 10.

good luck, take care =)

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