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Berni

Mon Apr 28 2008, 07:05PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

I thrown together a half bridge from STGW30NC60 IGBTs(600V 30A) and hooked it up to a common ignition coil and rectefied mains.
Also a isolation transformer in there to make things safer. The pour thing had to drive a half wave rectifier.Thats because this was first a voltage doubler ran off only 50VAC. But if i send 230V in that i would get about 600V on the output and fry my IGBTs since they are 600V.So i simply left out half of the doubler.

The IGBTs are driven by a GDT driven by a H bridge IC, and the IGBTs driven the coil trough a 470nF DC blocking cap

I didnt meshure the current consumption cause the multimeter dosent like the half rectified current.So i put it on DC and stuck it right behind the filtering caps and it showed about 10A.I think thats a bit too much that it acualy is.Meh il stick on a full wave rectifier later and meshure the curent there.

Then did one stupid try by putting on a 10 thurn coil and try induction heating.Okey so i stick a screw in there and power it up. Worked fine for about 2 seconds until i noticed the pin on the DC blocking cap has thurned in to a light bulb and so quickly cut the power.The screw was very hot, licked my finger and toched it and it made a hising shound and so it did like 20 seconds later too then it finaly cooled down. As for the IGBTs they ware cold. So this would make a great induction heater if we used meaby like a output transformer or something.

Youtube video

br]

Spedy

Mon Apr 28 2008, 10:54PM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

WOW! thats amazing man. Great results. =)

quicksilver

Tue Apr 29 2008, 03:11PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Ignition coils are so readily available, I think folks are doing a great thing by working out new and potent ways of getting them to preform. Thanks again for your efforts!

You touched on a couple of points and I'd love to see a schematic (even hand drawn) of what you'd suggest as a way to stripping down the circuit. I get the feeling that those sized arcs are only the beginning!

Berni

Tue Apr 29 2008, 04:02PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

Well there are a lot more from where the 2 IGBTs came from.(i have about 7 of then left) Also you can see there are a few unconected terminals on the white cirucitboard. Thats a nother 2 IGBT/MOSFET drive signals that can be used to drive a full H bridge.

Unluckuly i dont have a variac to run this thing at 500V. But i have to watch out because the whole top section of the coil is glowing blue/violet.The electrical tape prevented arcovers a bit but dont think it will for long

The main problem i have to solve is the coil going out of resonance when drawing a arc.

Also something i had in mind was a homemade transformer desgined to handle the power Im talking more power as current not voltage since stuff above 10kV would be hard to insulate.(I think someone from these forums made one and used a simalar IGBT driver and that thing got masive output)

Oh and a lot of peapole think a ignition coil only works pulsed so it makes inductive kickback.Well that is not true at all if you run over 100V in to it it works very nicely like a high freqency trasnformer.

EDIT:

And here is the schematic:

Tinfoil_Cat

Tue Apr 29 2008, 10:58PM

Registered Member #1450 Joined: Sun Apr 20 2008, 09:59PM
Location:
Posts: 10

Great fat arcs FTW! good lad.

Typically what sort of frequency input would an ignition coil prefer to act as a simple HV transformer?

Berni

Wed Apr 30 2008, 06:54AM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

By ear i would say around 10Khz, but this depends on the coil it self and also depends on the capacitor used in front of it. Since that forms a series LC resonant cirucit.

For this design hitting the resonance boosts the output a lot and also drasticly increses the power cosumption.

Oh and soon im makeing other other half of the bridge to make a full H bridge.That means double the voltage to the coil and should increse the output power drasticly.Im also thinking about introducing some more inductance in to the LC resonant cirucit

Berni

Thu May 01 2008, 04:43PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

Full bridge is now working.There ware quie a few "hickups" along the way of geting this to work.

Bug no. 1:
The B side of the IGBT driver is not working properly.Found out the ferite ring was of the wrong material.First used a dark green and light green ring because i had them of the same size.The light green one seamd to be working like crap.So i replaced it with a slightly smaller dark green ring. The B side of the driver works perfectly

Bug no. 2:
I connect up the driver and toght it would be smart to first test the other half of the bridge alone.Stupidly i left the drive signals and power to the other half but no load.Also had the suply at 300V.Instantly that bridge exploded in a loud boom.I guess the dv/dt thing made it somehow latch up and short the suply over it self.

Bug no. 3:
Replaced the IGBTs and now i get nothing out of them.Thurned out that A side of the driver is dead now.Traced it down to 2 busted zener diodes that ware propetcing the gate.Luckuly i still had a few of those 15V zeners around and slaped new ones in

And then finaly sucsses!
This time i didnt let any side run with no load and for testing used a 60V supply voltage.The full H bridge had more than double the performance over the half H bridge.Tomorow full supply voltage to the H bridge and some photos.

And the semicoductors that went to silicon heaven today:

Berni

Fri May 02 2008, 12:02PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

Finaly the full H bridge design has ran on 300V.And the output was great...for 5 seconds that is, then the coil sudenly caught on fire.

Aperantly the electrical tape that was keeping the thing just barely from arcing over in the half bridge deisgn didnt stand the slightest chanse now and arced over catching on fire.

So now i decided its varnish time.So far i have painted the screw terminals entierly in varnish since thats where it arcs over to.But i still dont know how to inprove insulation on the HV output in the midle. I was thinking of useing some plastic tube of some sort and glueing it on the top and then painting it with more varnish.

Anyone has sugestions on how to do this?

YOUTUBE VIDEO:

Dr. Dark Current

Fri May 02 2008, 12:36PM

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

Berni wrote ...

And then finaly sucsses!
This time i didnt let any side run with no load and for testing used a 60V supply voltage.The full H bridge had more than double the performance over the half H bridge.Tomorow full supply voltage to the H bridge and some photos.

It should be roughly 4x more power with fullbridge.

Berni wrote ...

Finaly the full H bridge design has ran on 300V.And the output was great...for 5 seconds that is, then the coil sudenly caught on fire.

Aperantly the electrical tape that was keeping the thing just barely from arcing over in the half bridge deisgn didnt stand the slightest chanse now and arced over catching on fire.
...
Anyone has sugestions on how to do this?

You should get a flyback transformer, these make bigger arcs than ignition coil (10cm arc can be considered "safe power" for nearly all flybacks).

BTW your transistors look like samples from ST

Just one warning, the antiparallel diode included in these devices is just a 15A one, so if you plan on running high powers, it is advised to put another one of at least 15A rating in parallel.

Berni

Fri May 02 2008, 03:35PM

Registered Member #1132 Joined: Mon Nov 19 2007, 06:15PM
Location: Slovenia
Posts: 84

Had a flyback some time back but burned it out by arcover.I want to try how faw i can push this ignition coil.Il proabpbly destroy it at some point.

Also was thinking of winding my own transofrmer for about 10kV.Rather go for current since stuff above 10kV may be very hard to insulate unles its under oil or something.

Oh you got me with the IGBTs they are samples, but they work so well

I also toght about giving induction heating a try(Well already did that but posibly without thuring the capacitor in to a lightbulb)

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