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Arcstarter

Sun Jul 05 2009, 11:19PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I have changed my plans. Still $40 budget.

So far what i am planning is using my 4.5 inch by 24 inch secondary. It is 160khz and plenty big, so ISOTOP are perfect for this.I expect some 4-5 feet in the end. I should have a scope coming my way, so hopefully it is not *too* far-fetched.

Onto the electronics. I am receiving a professionally etched drsstc board. It is the drsstc 3 from Steve Ward's site. The bridge will be a fullbridge with ISOTOP IGBT's. Voltage will be doubled with 2x 7,700uf 250vdc capacitors in parallel to make up each of the two capacitors for the doubler. The tank cap will be 4 series .68uf 1600vdc 942C caps, and however many parallel strings i need.

Primary will be 1/4 inch copper tubing. I am still debating on whether to use solenoid or conical. Not sure what material i will use for the supports, most likely wood as usual. The strike ring will likely be either copper tuning or some solid copper wire.

Interrupter will hopefully have variable BPS, pulse width (of course) and burst mode. It will be handheld (though kind of bulky) and connected to the coil via shielded RCA's, unless at some point i get some cheap fiberoptics.

This is all i have figured out as of now.

Arcstarter

Thu Jul 16 2009, 05:48PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I have changed my plans. Main post updated.

hvguy

Sun Jul 19 2009, 05:38AM

Registered Member #289 Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154

I highly recommend skipping the SOT-227 parts and going straight to a half bridge brick. It will likely save you money in the long run and will easily make 4-5' arcs. The minblocs are not much IGBT for the money. Get a CM300 module off eBay.

Go with the fiber right off the bat, it's infinitely better. If you're ever in Houston, EPO has all the fiber stuff you need. Also, 1/4" tubing is too small, IMO, 3/8" is my personal minimum for DRSSTC's.

Arcstarter

Sun Jul 19 2009, 05:55AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

hvguy wrote ...

I highly recommend skipping the SOT-227 parts and going straight to a half bridge brick. It will likely save you money in the long run and will easily make 4-5' arcs. The minblocs are not much IGBT for the money. Get a CM300 module off eBay.

Go with the fiber right off the bat, it's infinitely better. If you're ever in Houston, EPO has all the fiber stuff you need. Also, 1/4" tubing is too small, IMO, 3/8" is my personal minimum for DRSSTC's.

Well, i do have a CM200 200a 1200v and CM400 400a 600v halfbridge modules, but they are much too slow for my 160khz secondary. I do not have the money to wind a new secondary, so i do not have any choice but to make this one work. Winding a 60khz or lower secondary would require alot of fine wire, so i would also need to make a winding jig. Though that is not a problem.

Yea, i would like to use optics, but once again, no money

hvguy

Sun Jul 19 2009, 06:15AM

Registered Member #289 Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154

I have used the CM300, 400, and 600 DU series modules at 200KHz with no problems. You just need to drive them hard (no gate resistors, low impedance drive, etc.) Have you taken your toroid into account when determining that Fo? Also, if you need a few parts PM me, I may be able to help you out.

Steve Conner

Mon Jul 20 2009, 07:26AM

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

What silicon did they have in them? The DU/DY/whatever doesn't tell you that, it's a code for the topology (single switch, halfbridge, whatever) The usual surplus Powerex bricks are H-series or F-series with the current limiter board, but there are faster ones that haven't made it through to the surplus market yet.

Also, how much power did you manage to get at 200kHz?

hvguy

Mon Jul 20 2009, 06:57PM

Registered Member #289 Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154

Believe it or not, I have used the H, F, NF, and NHF suffixes to switch at that frequency, so I say DU just to indicate he should get a half bridge module. Yes, you do have to modify the F series to disable the internal current limiter, but other than that they will work. They do need a robust, low leakage gate driver though. I do not use resistors. Even 1ohm would cause unacceptable delay at 200KHz. The 200KHz tests where done at about 1.5KW. I have also switched 20KW at 70KHz with CM1000DU-34NF units

, but next time I do it I will be using Finn's pedikter concept

Hey, look! It's my 100th post in three years! Oh, wait, you managed 30X more in the same time frame

Arcstarter

Mon Jul 20 2009, 07:56PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well, 200khz sounds a bit far-fetched to me

.

160khz is with my topload. The secondary is 250khz. I have nothing but half bridge bricks :P. Perhaps some of these much smaller ones are a bit more capable of high speed switching? They would definitely have lower gate capacitance, which would make gate drive significantly more simple. I even have a pair of half bridge modules, so i could have a full bridge of 150 amp 1200 volt IGBT's.

A big thanks to TheBoozer, for many parts and alot of help!

hvguy

Tue Jul 21 2009, 06:00AM

Registered Member #289 Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154

Haha, it's not as far-fetched as it sounds, especially with the smaller bricks. Steve's new driver, the one that uses a P/N-ch full bridge, should be able to drive a quality brick at 200KHz easily. You should definitely try it, but if your not after more than 4' you'll only need a half bridge. If you want 6'+ go for the full bridge.

Arcstarter

Wed Jul 22 2009, 05:51PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

If what you say is true, i will simply go with a brick IGBT. I will use this semikron halfbridge module to start with. These are super-fast and mine is 100 amps at 600 volts. I will likely try to buy two 10,000uf capacitors for the doubler if that is what i decide on.

Wow, i sure can't make up my mind -_-.

Edit: I forgot to include the link to the datasheet:

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