# IGBT and free wheeling diode



## major (Apr 4, 2008)

Georgia Tech said:


> If there is a Diode already in the IGBT module accross the Collector Emitter. The is there a need to have one as well accross the motor as a free wheeling diode?


Depends on the module. Almost all have an antiparallel diode. Some have an extra diode for a chopper or a brake. Go to powerex dot com and nose around.

And yeah, there is a need for the free wheeling diode across the motor.


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## Georgia Tech (Dec 5, 2008)

major said:


> Depends on the module. Almost all have an antiparallel diode. Some have an extra diode for a chopper or a brake. Go to powerex dot com and nose around.
> 
> And yeah, there is a need for the free wheeling diode across the motor.


 Antiparallel diode? What is that for ?? Doese that mean I con NOT parallel Moduels? I was thinking of putting two 1200 amp modules together...


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## major (Apr 4, 2008)

Georgia Tech said:


> Antiparallel diode? What is that for ?? Doese that mean I con NOT parallel Moduels? I was thinking of putting two 1200 amp modules together...


Do a little background on these. powerex dot com. Data sheets. Application notes. A lot of good stuff there. Maybe antiparallel diode wasn't the most correct terminology. But most have a reverse biased diode collector to emitter. That is what I was speaking about.


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## Tesseract (Sep 27, 2008)

major said:


> ...Maybe antiparallel diode wasn't the most correct terminology. But most have a reverse biased diode collector to emitter. That is what I was speaking about.


As far as I know that is correct and current terminology, but I'm 37 so maybe I'm out of date too?  




Georgia Tech said:


> Antiparallel diode? What is that for ?? Doese that mean I con NOT parallel Moduels? I was thinking of putting two 1200 amp modules together...


So, uh... what are you planning on doing with these modules, GT? Gonna make yerself a big, bad 2000A motor controller with 'em?


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## jackbauer (Jan 12, 2008)

As far as i'm aware from my crash course on the subject you can parallel non punch through igbts BUT care must be taken that they are thermally coupled (ie on the same heatsink) and are reasonably matched.


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## major (Apr 4, 2008)

Tesseract said:


> As far as I know that is correct and current terminology.....


Thanks for the support, Tesseract.



> but I'm 37


Rub it in why don't ya 



> so maybe I'm out of date too?


I was 37 once, I think, maybe, gosh, I don't remember 

Hey Tess, didn't you have a thread a while back trying to teach us how to design motor controllers? Maybe you could post up that link for Georgia. Or did you erase it to spoil competition ?

Regards,

major


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## Qer (May 7, 2008)

major said:


> Rub it in why don't ya


Well, you know. Kids today, no manners at all and no respect for the elder. Back in MY days...


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## Tesseract (Sep 27, 2008)

jackbauer said:


> As far as i'm aware from my crash course on the subject you can parallel non punch through igbts BUT care must be taken that they are thermally coupled (ie on the same heatsink) and are reasonably matched.



Oh, you can parallel any of them, but yeah, thermal coupling usually helps make them behave. Same with the FWDs (which, arguably, are a worse problem because they basically switch current without allowing you any control over the process).





major said:


> ...I was 37 once, I think, maybe, gosh, I don't remember


Senility, huh? Happens to the best of us 




major said:


> Hey Tess, didn't you have a thread a while back trying to teach us how to design motor controllers? Maybe you could post up that link for Georgia. Or did you erase it to spoil competition ?


Well, I'd go ahead and dig it up for GT here but it seems only your 500 most recent posts rolleyes are stored and that was one of the first ones I did. In fact, IIRC, that was the one where you gave me a bunch of grief for calling a diode/igbt module with the igbt in the lower position a "boost module" (even though a motor controller is 99.999% of the time a buck converter).


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## Qer (May 7, 2008)

Tesseract said:


> Well, I'd go ahead and dig it up for GT here but it seems only your 500 most recent posts rolleyes are stored and that was one of the first ones I did.


http://www.diyelectriccar.com/forums/showthread.php?t=22398


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## Georgia Tech (Dec 5, 2008)

Tesseract said:


> As far as I know that is correct and current terminology, but I'm 37 so maybe I'm out of date too?
> 
> 
> 
> ...


Hmmmm uh.... don't know was thinking in the neigbor hood of 1200A to 1500A controller....There are 4 of these things on EBAY said to work for under 200 bucks....


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## Qer (May 7, 2008)

Georgia Tech said:


> Hmmmm uh.... don't know was thinking in the neigbor hood of 1200A to 1500A controller....There are 4 of these things on EBAY said to work for under 200 bucks....


You might want a few more because you WILL blow a few while experimenting. You can read about when we blew our first IGBT here:

http://www.diyelectriccar.com/forums/showthread.php?p=116684#post116684

It was the first IGBT we blew but definitely not the last. In fact I've lost count on how many we managed to kill, maybe Tesseract remembers...?


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## Georgia Tech (Dec 5, 2008)

Now that I look back this was a DUMB topic that I started...Why didn't I see that energy is stored in the Inductance of the motor and when the drive switch is open (MOSFET or IGBT) then where does that energy go?? You have to "catch it in either a Diode or a free wheel MOSFET. That's why at times you can have more "Motor Current" and less "Battery current".


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