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Linas

Sat Aug 23 2008, 06:33PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

i can't buy (ebay sell them) so i found similar,

Is it same good for drsstc ??

Steve Conner

Sun Aug 24 2008, 11:48AM

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

I've used those FGH50N6S2D (you need the D, it means "with onboard diode") in an induction heater running about 1kW at 250kHz, and they seemed to work fine, well, until I trashed them by disabling the current limiter. I've also seen people use them in untuned primary SSTCs. Not sure about DRSSTCs, though.

I also tried the TO-247 "40N60" years ago, and I got about 1m of sparks from a H-bridge of them, until they exploded. I think the explosion was due to a poorly designed coil that needed too much current, along with a driver that didn't have current limiting.

Ceramic insulators have to be used with thermal grease on both sides to make them "conform". Some of them may be made of beryllium oxide, so handle with care. (if they are they should be labelled, but don't count on it)

Apparently the best thing to do is use one heatsink for each device, with no insulators. Any sort of insulator makes the heat transfer worse. The SOT-227 "miniblocks" have a ceramic insulator inside, so a TO-247 bolted straight to a live heatsink with graphite foil could potentially beat them.

Linas

Sun Aug 24 2008, 01:22PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

how lot dollars need, to get 44N60 miniblocks??
Have you seen it in ebay, or who have and want to sell it for me ??

and does it good idea, to make DRSSTC by using ATTINY2313 ?? (as all logic, yes, just for CT I will use (74HC14) )
and does need osi start ?? ( with uC is very simple)

Marko

Sun Aug 24 2008, 03:02PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hm, when hearing of ceramic insulators I thought you guys mean it for mica insulators (very bad)... are there really BeO insulators, where can they be bought?

Sil pads are rather poor too, I wouldn't use them. They add like 3K/W while direct mounted greased TO247 may have thermal resistance no more than like 0.2K/W so do the math!

Indeed, some TO247 packages may have even lower thermal resistances for direct mounting than SOT227 counterparts simply because they lack internal insulator which adds a lot of thermal resistance to SOT227. Still some newer SOT1227 devices are actually surpassing this problem with more and more advanced internal insulators.

Care must be taken though for mounting TO247's, they must not be mounted the typical way using a single screw because high pressure on top of the package actually lifts up the bottom part where the silicon die actually is.

Look here for this mounting method:

Pressure must be applied *externally* right over the die to assure maximum thermal performance.

When mounting packages directly just a thin and even layer of thermal grease should be used. Conductive metal based greases are even better in this use and usually easier to spread, but also more expensive.

how lot dollars need, to get 44N60 miniblocks??
Have you seen it in ebay, or who have and want to sell it for me ??

Generally any device in SOT227 package is very difficult to get today unfortunately, 40N60's seem to be mostly obsolete now and the only decent replacement (IXYS 60N60) is available with very long lead times and only in larger quantities.

You may be able to find something on ebay, but even there they are rare, and all I've seen now shipped only to us.
Some forum members may have stashes they are willing to sell, ask on sale and trade board for that.

It is ironic that you can actually get large bricks like cm300's much more easily and cheap compared to SOT227 devices.

Marko

HV Enthusiast

Mon Aug 25 2008, 01:39AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

wrote ...

It is ironic that you can actually get large bricks like cm300's much more easily and cheap compared to SOT227 devices.

Marko

Thats because those IGBTs are used in practically everything nowadays - industrial motor control, etc... i mean. There are millions of them out there.

On the otherhand, the 40N60 IGBTs had barely a chance during production and only a few ever got out there. Whether they never caught on, or they had production problems, who knows.

Linas

Mon Aug 25 2008, 11:00AM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

hey,i found cheap, ,and powerful IGBT, he quite fast

i think my coil will be 150-180KHz resonant frequency

Marko

Mon Aug 25 2008, 05:11PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Linas wrote ...

hey,i found cheap, ,and powerful IGBT, he quite fast

i think my coil will be 150-180KHz resonant frequency

Hm, most people would not run CM bricks at frequencies higher than about 100kHz.

From other side, the max frequency thing might just be way overblown. I've never seen any credible research on this and lots of people may just blame the frequency when they don't know why is their coil blowing up.

Marko

Linas

Mon Aug 25 2008, 06:59PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

i seen DRSSTC test, was up to 100KHz, and use very powerful IGBT,without falls (, all electronic created and designed very smart people )
here is 100KHz test

and here is normal 8KW test with 50KHz Fr

Linas

Wed Aug 27 2008, 03:15PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

I Have to get IXGN60N60C2D1, because i know head of Distributor.
So, does it possible to make DRSSTC and don't have blow in bridge ?
What i have to know, to make good working DRSSTC ??
I have pipe 61,5cm tall and 11cm diameter , so what diameter use of wire ( i think between 0,12mm-0,2mm)
Also have lot wima FKP 1600Vdc 68nF cap

Marko

Wed Aug 27 2008, 05:05PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

So, does it possible to make DRSSTC and don't have blow in bridge ?

Yes, some people happened to succeed, which is why drsstc exists in first place! :P

And yeah, IXGN60N60C2D1 looks like a very good igbt and was apparently widely used by Dan McCauley with sucess.

What i have to know, to make good working DRSSTC ??

Ok, these are what I could call 'tips for success' for your first coil:

1. Don't be creative nor inventive even a bit. More accurately you copy some of known working designs, larger chance you have to get them working. Copy all the parts and specs as precisely as you can. Also, be complete in the process - don't for example build Steve Ward's circuit and leave out OCD, or similar.

2. Buy someone's working circuit boards rather than building your own, or at least make a good copy of them.

3. Don't do anything for looks, best don't build any chassis at all for beginning and focus purely on functionality. Coil components will work OK sitting on garage floor, just watch not to create wire mess and short something or electrocute yourself!

4. Underrate your IGBT's.. ok this may sometimes be going against the rule no. 1. since this may mean decrease in coil size as well, but I guess that's allowable to some point. Steve Ward used to punish minibrick IGBTs rather badly, and if you don't know what are you doing this may easily kill them.

It is mostly my errors and frustrations that led me to this conclusion, and I wouldn't like newcomers to fall into a same trap.

Marko

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