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Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
Hi,
I would like to know what will be the considering factors about IGBT in the current rating sections, IS the current continuous of IGBT are the one should we look for higher ratings? or IS the current pulsed of the IGBT we should be looking at?
What if it has low pulsed rating like (150 A) and high continuous @25 degree = 100A & @100 degree = 75A ? is this a good IGBT?
Or high pulsed rating like (300 A) and low continuous @25 = 60A & @100 =35A
Also, are the physical packaging(body) of the IGBT are another factor to consider? I've seen some more powerful IGBT in TO-220 than in TO-247.. and powerful TO-247 than in SOT-77B bricks.
all of this if I want to run my drsstc 800 amps reliably.. Thanks..
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
The pulsed rating matters more. However, keep in mind that different ratings from different manufacturers/different product lines are not comparable. For reliable 800A operation, I'd use CM300 bricks - 800A is only a little over their pulsed rating.
EDIT: Random thoughts: I've been fiddling with this thing for the past couple days, and finally experienced my first real (non-human-error) bridge failure. It seems like the FGH40N60SMDF does not like running past 300A. This is a far cry from the legendary HGT1N40N60A4D, which could run 1000A without failing (this failure was at 60uS on time, 340V bus, during continuous ground strikes). Perhaps this is the price to be paid for the improved switching times of field-stop IGBT's? or perhaps manufacturers are getting cheap and not putting as much silicon into the die as they did in the good ol' days.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Remember that the number different manufactures put before the "N" letter always means a different rating... With the xxN60A4D types, it is the actual output current they can swich in CW operation including switching losses, but often it is just the DC current rating and the actual operating current is lower.
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
Dr. Dark Current wrote ...
Remember that the number different manufactures put before the "N" letter always means a different rating... With the xxN60A4D types, it is the actual output current they can swich in CW operation including switching losses, but often it is just the DC current rating and the actual operating current is lower.
Coiler go by the absolute ``how far can i push it before it goes boom?'' rating though which sadly doesn't appear on the datasheet.
Registered Member #2288
Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179
bwang wrote ...
Dr. Dark Current wrote ...
Remember that the number different manufactures put before the "N" letter always means a different rating... With the xxN60A4D types, it is the actual output current they can swich in CW operation including switching losses, but often it is just the DC current rating and the actual operating current is lower.
Coiler go by the absolute ``how far can i push it before it goes boom?'' rating though which sadly doesn't appear on the datasheet.
Has anyone done the I^2T calculation for their coils as they go boom? It's quite possible that's actually a decent explosion limit to go by for coiling.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Ok I'm going to try and clear something up that I didn't understand for a long time about IGBT and power transistor ratings in general. The pulsed and continuous rating of power transistors is dictated by one thing, heat...
For continuous and pulsed operation the die has to be able to constantly transfer and dissipate the power that is dropped across it. For IGBTs this is dictated by the foreword voltage drop from collector to emitter (also called the saturation voltage) much like a diode. Usually on the order of ~2.5v for a lot of larger IGBTs but it also can be as high as 5V or more. Most hobbyist overlook this value in the datasheet when selecting a device. For example the CM600HA-24H has a Vce of 2.5V if I remember correctly so if you are pushing say 1000A the device is going to dissipate 1000A * 2.5V = 2.5Kw of heat. For a DR this is usually not to bad because at DR duty this averages to maybe 300W at the most. The voltage drop is fixed and doesn't change much with current making IGBTs ideal for pulsing with larger currents.
The observant viewer of the datasheet will also note a thermal resistance from die to case rating usually in C/W. This rating tells you how well your particular package can transfer heat from the die to the outside of the package. They will usually also give you a nice graph plotting out thermal impedance over some key operating values of the IGBT in question. A lot of datasheet will even do the hard work for you and give you continuous dissipation rating of the device. This is usually the largest Vce * rated current. For the CM600HA-24H example this is 4.2Kw.
Knowing these values you can get a good idea of how well your device will perform under pulsed or continuous operation. Obviously the IGBT can handle higher pulsed currents because you can give the IGBT more time to get the heat out of the die. Also the dissipation of the the diode and switching losses with also add to the total heat, but that is another hole can of worms.
Bottom line is if you heat the die up to much it fails and you are left with a hunk of useless silicon.
There are also a bunch of good papers on this if you do a quick search on google.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
I think the pulsed rating may have something to do with other things as well such as bonding wire cross section, current distribution in the die, possibly thermal shocks and "temperature ripple" at the interrupter frequency, and turn off SOA.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Dr. Dark Current wrote ...
I think the pulsed rating may have something to do with other things as well such as bonding wire cross section, current distribution in the die, possibly thermal shocks and "temperature ripple" at the interrupter frequency, and turn off SOA.
But all of those thing are about heat in the device and getting it out That's the only point I'm trying to make. You can get a great idea of what your IGBT will do before you run it. Untimely you will know how well it works by testing in the real circuit.
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
Goodchild wrote ...
Ok I'm going to try and clear something up that I didn't understand for a long time about IGBT and power transistor ratings in general. The pulsed and continuous rating of power transistors is dictated by one thing, heat...
For continuous and pulsed operation the die has to be able to constantly transfer and dissipate the power that is dropped across it. For IGBTs this is dictated by the foreword voltage drop from collector to emitter (also called the saturation voltage) much like a diode. Usually on the order of ~2.5v for a lot of larger IGBTs but it also can be as high as 5V or more. Most hobbyist overlook this value in the datasheet when selecting a device. For example the CM600HA-24H has a Vce of 2.5V if I remember correctly so if you are pushing say 1000A the device is going to dissipate 1000A * 2.5V = 2.5Kw of heat. For a DR this is usually not to bad because at DR duty this averages to maybe 300W at the most. The voltage drop is fixed and doesn't change much with current making IGBTs ideal for pulsing with larger currents.
The observant viewer of the datasheet will also note a thermal resistance from die to case rating usually in C/W. This rating tells you how well your particular package can transfer heat from the die to the outside of the package. They will usually also give you a nice graph plotting out thermal impedance over some key operating values of the IGBT in question. A lot of datasheet will even do the hard work for you and give you continuous dissipation rating of the device. This is usually the largest Vce * rated current. For the CM600HA-24H example this is 4.2Kw.
Knowing these values you can get a good idea of how well your device will perform under pulsed or continuous operation. Obviously the IGBT can handle higher pulsed currents because you can give the IGBT more time to get the heat out of the die. Also the dissipation of the the diode and switching losses with also add to the total heat, but that is another hole can of worms.
Bottom line is if you heat the die up to much it fails and you are left with a hunk of useless silicon.
There are also a bunch of good papers on this if you do a quick search on google.
Hope this clears it up a bit.
While I agree that heating has a great deal to do with how long a transistor lasts, aren't there also pure device-physics limitations on how much current a given die can carry? I don't really know enough semiconductor physics to say for certain though...
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Well stop and think about it for a sec. What actually kills the die? The answer is once again our old friend heat. I know it seems like there should be more to it than that but there really isn't. Thing about it in simple terms like a wire. The only way you are going to get that wire to fail is to push enough power through it to get it to melt and fail. If you are able to remove the heat from the wire as quick as you put it in then the wire will never heat up and never fail simple physics.
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IGBT current ratings
which sadly doesn't appear on the datasheet.
