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SISG Flyback's, Ignition coils

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LAN_403

Tesladownunder

Fri Jul 21 2006, 09:38AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I built one stage of Terry Fritz's Sidac IGBT Spark Gap (SISG) driver today to see how they run. I have previously driven flybacks and ignition coils with SIDAC's alone for which they work well. However SIDAC's alone don't drive Tesla coils due to the faster turn on and off requirements, however at low current they happily trigger an IGBT to conduct very efficiently.

Here is my driver. No I don't have a PCB and yes some of those components are vertical. I have built it on part of a multikV strip of SIDAC's that I have cut off.
Nevertheless the fast components have very short paths and should have low inductance and reasonable current rating. The IGBT fits nicely into a terminal block to allow changing IGBT's as I want to try some big IGBT's later. The heatsink was chosen for it's extra holes rather than need for size. An extra aluminium plate allows the IGBT to be secured.
The black wire allows selection of the number of SIDAC's to use.

Here is the unit. More pics of it in action after a reply.

Peter

ragnar

Fri Jul 21 2006, 09:57AM

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

Your protoboard work is always very neat, Peter -- makes me wonder why i bother making my own PCBs sometimes heheh =P

Got first light yet?

Tesladownunder

Fri Jul 21 2006, 10:32AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Ignition coil shown running on output from a voltage multiplied MOT and using a 4uF capacitor. Runs well with no heat from the IGBT. Break rate depends on power input.
The IGBT has been tolerant of reverse polarity which I inadvertently gave it. Presumably the 50A reverse diode wont be blown by the current from a MOT secondary.

The flyback is driven from the same setup from about 10 turns around the ferrite core and puts out a spark over 1 inch easily. Since the break rate is low and less than 50 Hz the total power is still low and sparks are a bit thready. A bigger capacitor would give bigger sparks but I don't know the current drawn and don't want to push this at present.

Peter

1153477935 10 FT13347 Hvsisg1stageignitcoil

1153477935 10 FT13347 Hvsisg1stageflyback

Terry Fritz

Sat Jul 22 2006, 01:51AM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi Peter,

Adding the IGBT to the SIDACs seems to "help" :0)))

Mark is getting like 4 foot sparks now and I have reached the 30 inch limit of my little lab. My new MOT charging circuit is full of great promise to for powering it!

Layout is not critical other than giving the high current IGBT CE section lots of high current copper! Most of the loss is now in the primary "copper" instead of the gap!!

MOTs do about 1.5 to 2 amps into a dead short and the reverse diode is rate at say 50 amps

) You are not gonna break it. The "only" SISG that has ever broken was used in trying that ball lighting thing with a 800 Joule cap >:-)) Opps!! Shoulda thought about that one first :D But the SISG is "tough"!!! You ain't gonna break it...

It has never been done yet, but one problem with the GMHEICSLR was gap loss at low voltage:

Just get an epoxy ignition coil and cut off that iron to make a "real" Tesla coil >:))))

The SISG would LOVE that application!!!!!!!! I was firing at about 1200V with a spark gap made from nails (yuck!!). That was the level that fried the ignition coils. Others also have stopped there since the epoxy secondary of the ignition coils just cant take 14 inch arcs... But at say 900V, with a well controlled spark gap, like the SISG

)) It might be very cool!!!! I see no reason to use a ferrite flyback over a epoxy ignition coil with the iron cut off...

Thanks for "starting" this "SIDAC gap" thing too

))

Cheers,

Terry

Steve Conner

Sat Jul 22 2006, 09:53AM

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

Wow, this SISG thing seems to be a real success!

I want one now!

Does anyone fancy organising a bulk buy of the same IGBTs and SIDACs that Terry uses? I can design PCBs for stackable gap sections and get a big batch of them made cheap in China, and we could have a 4hv.org Silicon Spark Gap Party

Dave47

Sat Jul 22 2006, 01:59PM

Registered Member #84 Joined: Thu Feb 09 2006, 01:06PM
Location: Dallas, TX
Posts: 47

I'm in for a bulk buy of everything!

I have parts for a 12KV 60mA coil, but haven't been motivated to put it together. This seems like much more fun. I even already have the MOT ready to go.

David

Terry Fritz

Sat Jul 22 2006, 08:17PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Does anyone fancy organising a bulk buy of the same IGBTs and SIDACs that Terry uses?

I have been thinking about this. I have found that the lead version of the IRGPS60B120KD is consistantly about half the price of the lead free version. Even DigiKey sells them if you know where to look:

But Rell.com is still cheaper and you have them in the UK too. But everyone has a minimum order of 50 or the price is double, so a bulk buy could save serious cash. There are also the SIDACS which are hard for some to get and maybe the 1N5819 diodes. Then there is the &*^%^ little clip to hold the SUPER-TO-247 down to the heat sink (not a simple task!) I ended up just special ordering them after finding that making my own was "painful". Not sure if it is best to have a specific heatsink (another odd pricey part)...

So I was thinking of like selling each part separately and maybe little complete kits too of all the parts for a section. Once you get the IGBTs, SIDACs, diodes... Might as well just throw in the other trivial parts too. I have been using ExpressBPC boards which are sort of pricy but easy to change the design:

Mark Dunn has nice boards too:

He has boards and IGBTs and has been bulk ordering both. I am not sure he wants to be a long term seller of them but he is just basically selling them for experimentation. Basically selling extra to cover his costs.

I was thinking of waiting till I get the next coil going. I do have this small coil:

But it is not a big dramatic sparker. Cute, but I think most folks want bigger sparks rather than a true experimental machine like this. The new coil will also have the new charging circuit.

So that is what I am thinking... Prolly want to start a new thread in Tesla coils...

Cheers,

Terry

Michael W.

Sun Jul 23 2006, 01:17AM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

I'd go in for bulk on this......

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