Hi,
I have an issue regarding the positioning of the heatsink and fan on Odrive pro, it seems one can only attach the heatsink and fan to the bottom of the Odrive . But my project demands that I use the motor connected behind the odrive, utilizing the absolute encoder present in the odrive .Any suggestions on where to position the heatsink and fan to get everything working properly??
Hi!
If you need to use the ODrive’s onboard encoder, then you can’t use the heatsink+fan, you’d be limited to the heatspreader plate. I think your best bet in that case would be to use a fan blowing on the Pro from the top, or to machine a custom heatspreader plate or motor mounting plate that can bring heat out the sides to a heatsink.
That being said, maybe this isn’t fully necessary – how much continuous and peak current do you need?
For the record, you could alternatively use an OA1 encoder, which uses the same magnetic angle sensor as the ODrive Pro uses – so this could be mounted to the motor, and the ODrive Pro could be elsewhere, with the full heatspreader+heatsink+fan stackup.
Thanks for your help.
I must add that 100A of continuous current is necessary for working of my application.
Is there anything else you’d like to suggest based on this information?
In that case, you definitely need as much cooling as you can get. I would at a minimum use the heatsink+fan+heatspreader, and use an OA1 instead as the encoder. That will get you at least 80A continuous current, should get you 100A.
A few notes:
- When operating at high current, you should make sure the capacitors on top of the ODrive board also has some airflow. I would maybe recommend adding a second fan on top, pointing down, to cool the capacitors
- You can increase the thermal performance (and thus maximum current) by replacing the stock heatspreader thermal pads (the green ones) with higher performance ones – these are about 1.5x the thermal conductivity, but will have to be cut to size. You can also replace the stock fan on the heatsink with something like this, which is about 2x the airflow, but will require longer bolts for mounting (and is much louder
). However, I’d give the setup a shot just with the parts from our store (and maybe with a second fan for the capacitors, or just a desk fan blowing at it), and only put in the work (and the money) to make these modifications if you can’t reach your desired continuous current.
Would it be okay if I used Thermoelectric Peltier Refrigeration Cooling System instead of the fan which you recommended???
It really depends on the peltier itself. Generally, they’re very inefficient, and can’t move much heat. An ODrive Pro will dissipate about 60W with a 100A output current. FET junction temperature needs to be kept under 125°C, so your peltier needs to maintain under about ~100°C at a continuous 60W dissipation – about a 75° rise over ambient. This will take a pretty beefy peltier – maybe something like this, which is pretty expensive and will draw 135W just to keep the Pro cooled. Additionally, you’d have to machine a custom mounting solution for the Pro and make sure to compress the thermal pads to the correct amount – it’s a lot of work. I’ve also seen people try to use Peltier systems, and they’re rarely better than just a heatsink+fan. If you have the ability to do custom machining, then I’d probably just recommend making a more thermally optimized heatsink than the ones we sell, or consider making a coldplate for a water cooling loop. All that being said, that’s all a lot of work, and I think your best bet is to just start with all the stock components from our shop and see what sort of performance you’re able to get, before considering doing anything expensive/time consuming/fancy.
I see, thanks for your insight.
I also wanted to ask if I can use a thermal paste instead of thermal pads,of higher (higher than 16.6) or similar conductivity
I think thermal paste won’t be a good idea, that usually relies on a direct-contact coldplate, which won’t work for the ODrive, as the FET tops are conductive, so you’d be relying on thermal paste for gap filling, which it isn’t designed for. I’m also very curious as to the thermal paste you’re finding that’s over 16.6 W/m-k, most is around 12-13 W/m-k at the highest.
What if we build a custom plate which has slots on it so as to fit the FET tops and we fill the slots with this thermal paste along with it?
That’s a liquid metal paste, which won’t work, as it’s conductive.
You’d have to use a different thermal paste, since the liquid metal paste is conductive. And at that point, you should use thermal pads, since once again thermal paste won’t work for this application, as there cannot be direct heatsink contact to the FETs (which is required for thermal paste). There’s nothing wrong with a custom heatsink, but you do need to use thermal pads with a heatsink geometry to ensure the correct pressure / squished thickness once the heatsink is assembled.
@Yash_Dale I honestly think you’re doing a lot of unnecessary work, my recommendation would be to just get the stock heatspreader+heatsink+fan as well as a secondary fan to cool the top side of the ODrive board, and see how that works. If that doesn’t have the performance you need, then you can evaluate other options, but this feels like prematurely optimizing without knowing how well a more basic solution will work