# We're going to need a bigger heatsink



## jackbauer (Jan 12, 2008)

Part 1 : drilling and taping.


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## zwmaster (Nov 23, 2009)

Congrats on a new design.
It's looking very good.
Keep it small and add simple water cooling.

Just one question.
Why don't you rather use film caps with high ripple current capability?
They are not cheep, but so are IGBT's and having a week spot in a good design is not so good …
What modules do you use?

Anyway thumbs up.
I wish you happy Easter.


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## Guest (Apr 3, 2010)

I agree. Use a thick block and make a nice water cooled heatsink block. Without water or air cooling the aluminum block is not going dissipate the heat fast enough. I did testing on an old controller thinking that a real thick block would dissipate the heat fast enough before it went into shut down mode. The thick block helped but did not stop the problem. When I went to a finned heat sink the problem went away. I was going to make a water cooled sink but decided that I did not have the time so I went with air cooled. The block you have is fine as long as you mount another water cooled block or a finned heat sink to that with a nice fan. Otherwise your going to over heat it. Period. 

Looking good. 

Pete 

What is the power rating going to be?


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## jackbauer (Jan 12, 2008)

Busbars finished. I will be looking at film caps for sure. For testing i'll be using electrolytics. I have some nice large finned heatsinks for the bottom. I would like to do something like what Jack Rikard did with the curtis ac controller. Each igbt is a Powerex CM400DU-12F rated at 400amps , 600v. I'll be derating to 50%.

http://www.pwrx.com/pwrx/docs/cm400du-12f.pdf


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## jackbauer (Jan 12, 2008)

the saga continues :


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## jackbauer (Jan 12, 2008)

Up and running! I'm a bit concerned if the dc dc and drive circuit can handle the load of 4 devices. the top of the wave looks a little "bumpy" ........... Mabey the igbts have been reading too many peak oil books


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## Olaf-Lampe (Feb 24, 2010)

I knew one could parallel MosFets, but does that also work with IGBTs? Do they need to be balanced somehow? The pic with resitors is most probably the gate resistor? On which end of the diode is the gate?

BTW, I don't like the bus connections too much. They don't share current equaly between the IGBTs.
Only my 2Cent
Olaf


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## Weisheimer (May 11, 2009)

jackbauer said:


> Up and running! I'm a bit concerned if the dc dc and drive circuit can handle the load of 4 devices. the top of the wave looks a little "bumpy" ........... Mabey the igbts have been reading too many peak oil books


A couple of thoughts on the gate drive, you could add another gate driver IC. Perhaps glue it upside down to the original and connect it with breadboard wire. Don't forget to add a new pair of 4.7uf/16v caps to the VDD supply very near pins 1 and 8. That is where the "power" is pulled from, and the 6W average output from the DC/DC might be enough to keep all of the caps "well charged".
Olaf is suggesting a review of the bus bars, and he may be meaning that if you connect the batteries to one end of the controller, and take the power to the motor from the other end, then the modules will more evenly split the load amongst themselves. In other words, the M- bar comes out the left side, and the B- comes out the right side.
And remind me, what are the values that you are using for the gate drive resistors and which direction is it connected between the driver and the gates?

Cheers
Mark


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## jackbauer (Jan 12, 2008)

Yeh i only realized the bus bar thing after i had them cut but i'll make the suggested change. Resistors are 10r and another 10r and a uf diode in inverse parallel to aid turn off. I'll be upping the dc dc to a 15v output. At the minute the decoupling caps on the driver are wrong. .1uf instead of 4.7uf. I've ordered the correct part.


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## Weisheimer (May 11, 2009)

jackbauer said:


> At the minute the decoupling caps on the driver are wrong. .1uf instead of 4.7uf. I've ordered the correct part.


 I suspect you will see a nice improvement when they are installed. That may be all that is needed.
All in All, it is looking very good!

Cheers
Mark


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## amesmich (Nov 17, 2009)

Where did you get the driver? Did you make that or just take a generic driver and use it to run the 4 gates?


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## jackbauer (Jan 12, 2008)

Do you mean the control pcb? Thats an open revolt controller board from Paul Holmes with a few simple mods.


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## Amberwolf (May 29, 2009)

Sorry I never saw this when you started it.

Couple of points you might already know but just in case: 

--the bumpiness you see is ringing, meaning there is probably a significant amount of inductance somewhere in the supply circuitry or signal path. Are those tests running the main power from battery or from a lab supply? And is it under a high current load when you see the ringing? Also, is that looking at the gate or the motor output line?

Guessing by voltages that it's the gate, and that the lab supply in the pic is running the whole thing. 

Not sure what wiring you have leading to the gates from the control, but do everything you can to keep it super short and straight, as well as as wide a path as you can manage. 



--for the heatsink paste, put it on as thin as you can get, like by using a credit card or similar to smear it on both surfaces so that only the scratches in the surfaces are filled. 

Otherwise later on when the paste dries out, you'll have airgaps between the devices that make great insulators, and stuff will be a lot hotter than you'll be expecting.  

If you can, lap the heatsink at the contact patches, as well as the back of the IGBTs. Then you don't even really need paste, though you can still use it (again just to fill the scratches).


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## amesmich (Nov 17, 2009)

jackbauer said:


> Do you mean the control pcb? Thats an open revolt controller board from Paul Holmes with a few simple mods.


 
yea thanks.


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## jackbauer (Jan 12, 2008)

Thanks Amber i got it sorted in the end. Running well on the bench now. Might put it in my elmo van!


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