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Large DRSSTC plan

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Danielle

Mon Sept 24 2007, 12:43AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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Posts: 267

I am now a proud owner of a 60Khz 1200V 400A MitsubishiCM400DU-24NFH dual IGBT brick. I need to build an H-bridge and need a second. If any one has one and would be willing to sell it to me for a reasonable amount I will buy. I really need a second one its for my next DRSSTC and I am constructing the best fault protection systems for them possible. I will take good cair of them.

Steve Ward

Mon Sept 24 2007, 12:54AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

You dont need a full bridge for your coil, that single half-bridge is far more powerful than you might think. While i do have those IGBTs (2 of them), i cant say that i'm willing to give them up, they are just too cool.

Danielle

Mon Sept 24 2007, 01:14AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
Location:
Posts: 267

oh I know how nice that is, I just would much rather use a H-bridge... I am building a huge PSU that I can use for any tesla coil (under 60Khz) and as a base for pretty much any high power use I want, induction heating ect. I am trying to get it past 20KW system... this is my project for the next 2 years. I also purchased a 106A 1200V doubler diode module so that will power the DC bus and the 900V 2400uf capacitance should be enough. I plan to switch 800VDC... or should 240VAC doubled 678VDC at probably max of 60A on my homes special 240VAC 200A line (we had it specially installed separate from the homes line)

Steve Ward

Mon Sept 24 2007, 03:20AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

That sounds like a pretty decent idea. I think your filter cap should be far larger if you ever want to get more than 1-2kW out. Im using 6000uF at 700VDC on my coil which gets up to around 8kW. Typically, to handle the ripple current you will need rather large capacitors, probably up to 10,000uF across your supply.

Danielle

Mon Sept 24 2007, 07:15AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
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Posts: 267

so you really would think I need a 6.6kJ cap bank for this, if so I may be able to get (24) 2400uf 450V capacitors for $60 that will give me 900V 14,400uf....That is rather large for a tank capacitor is it necessary or is that only can crusher stuff?

Steve Conner

Mon Sept 24 2007, 10:07AM

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

That single brick would give you something like 8-9 foot arcs in a DRSSTC. It should also easily handle 20kW of CW power, if you want to do induction heating experiments and the like. With a 600V DC bus, you can get nearly 10kW CW from a bunch of TO-247s anyway.

If you want to make a DRSSTC with 20kW average power, well, that is another story, as it implies a peak pulse power of several megawatts

If I were doing that, I think I'd want a H-bridge of the next IGBT size up (the CM600 type) at least, maybe even two H-bridges with their outputs combined in some way, and I'd be looking for sparks around 16-20ft long from a 7ft x 18" secondary tuned to 25kHz. So I wouldn't start constructing such a thing unless I knew I had access to a 40ft x 40ft workshop with a 27ft high ceiling

This thread should perhaps be moved to another board if you want to discuss the design of your proposed system.

FWIW, I'd sell you one if I had one but I don't :(

Danielle

Mon Sept 24 2007, 04:01PM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
Location:
Posts: 267

I see what the litmitations are and I still would rather use a H-Brige of CM400s this will be pleanty for what I will do. I do plan to only use 12 of the 2400uf 450V caps and rate the supply for 20KW. I do not think I am ready to spend the money on 4 CM600s and I think 9ft arcs are large enough for me. I just would like this thred here untill I find someone who would sell me one of them!

thanks everyone for the help.

Daniel Costantino.

Dago

Mon Sept 24 2007, 06:06PM

Registered Member #538 Joined: Sun Feb 18 2007, 08:33PM
Location: Finland
Posts: 181

I'd say you need quite a few more bricks than two if you're inexperienced with DRSSTCs/SSTCs because you will most certainly kill a few. They die very easily when stressed over the maximum ratings in DRSSTC duty.

Steve Ward

Mon Sept 24 2007, 11:17PM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

Yep, even with all the safety features you can think of, they dont mean a thing unless they are implemented properly and are proven to work. This stuff is very sensitive and id say its pretty hard to get it all right the first time around especially being somewhat new to electronics... and given your age you are new.

Im not trying to discredit you in any way, but its pretty foolish to base a whole design on a part that you have trouble finding more than 1 of. Ive only seen a few of these IGBTs on ebay in the past... on the other hand, CM300s and CM600s are very common, and can often be had for about 20 bucks each.

Also, wanting 20kW at a high-ish frequency is what i would consider wanting too much. Either design something for power at low frequency (where you would actually use that much power), or go for less power and more frequency. Its just a trade off you have to make, unless you have the money to buy the best parts on the market (and even still, a 20kW DRSSTC at 60khz is pretty unrealistic).

Danielle

Tue Sept 25 2007, 12:52AM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
Location:
Posts: 267

I understand I plan to get this working with a half and H-bridge of CM300s and then put this in after I have it running consistently without faliuars. I did understand though I was asking for alot and first plan to have my Drive scurcite witch contain everything but the IGBTs and caps.

I think that a more realistic plan will be for a 10-60Khz 10KW system.

Thanks Steve for the hint on ebay I got my first one for $30 so it wasnt too bad for something much faster and powerful than the CM400.

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