We have kraken motors and our chasis is cloges air holes and we had a talk about the cooling but we werent able to get anywhere any help?
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I don’t think the kraken x60 needs cooling? I am not too sure but our team doesn’t cool them.
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For 99.9% of teams cooling would be unnecessary. Just let the bot cool for an extra 2-3 minutes between battery changes during practice at home.
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it can be good if you are really sending it for long periods of time, but generally you dont need to
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How Important
It depends!
I can take the next step for you though.
Motor windings are primarily made of copper. Copper experiences a 0.4% increase in resistance for every 1 deg C of temperature rise.
If you heat your motors up by 30C (a reasonable guess from a hard match… you can gather data from your bot if you want more precision), you can expect ~12% increase in winding resistance.
At stall, this means you only have 89% of the torque available (as compared to fully-cooled-to-room-temperature). Top speed will be a bit lower too.
So, transforming your question - How important is that reduced performance to your end goals?
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Just because I’m curious, how far would this work in the opposite direction? If I could cool my motors to -10 C, would I experience 12% less resistance and thus a performance increase?
If this is how it works, how far could you take it? At some point it gets so cold something breaks, right?
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Maaaaaybe.
My source - there is a caveat that the model works well “near room temperature”.
I’m also neglecting current limits, either software induced, or hardware limits.
If the whole motor gets cold, grease in bearings will start to get thicker which also cuts back on some of these gains.
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Note: I have not done this.
There are teams that rely on precise characterization of their motors to improve response. Starting each match with motors at similar temperatures to your testing will result in them acting more like your characterization.
Some teams cool their motors to improve their performance. (I’m looking at you 2767) @Mark_Wasserman . They would be the ones to ask what material gains they make from this.
Jared Russel @Jared_Russell also recently commented on certain motors being easier to model than others for specific reasons. They may have insight on the hot vs. room temp argument as well - my gut says they’ve looked at it at some point since they’ve eeked every ounce of performance out of everything else.
1293 has done this the last three or four years. Nothing exotic, just a battery-powered fan blowing steadily on motors.
We’ve been a NEO 1.0/1.1 shop, so we don’t have the same deathproofing that Falcon/Kraken motors do and the NEO’s temperature probe is known to be in a spot that’s slower to change. And, uh, we have a reputation for driving hard.
This is what we’ve used since 2022. It’s just right for what we’re trying to do, with easy recharging and good battery life. Amazon.com (Get the warehouse deal ones. No reason to pay retail.)
You can see them in action here; we had a replay at PCH Charleston that created back-to-back matches, naturally on different alliances. So during the bumper swap, we set them to work blowing on the motors.
We’ve also loaned them to other teams at events when their own drivetrains were getting toasty, and I think we made new friends by having them running while the cart was parked during our matches in Houston in 2022. We’d just point them at the stands arbitrarily.
And teams that use CIMs, looking at y’all too. They lose a ton of power as matches go on and the heat soaks in. https://motors.vex.com/media/wysiwyg/PeakPower_1.PNG
Far as I’m concerned, room temperature is best temperature. And fans (whether the ones I linked or even just the 120mm ones in FIRST Choice for the last decade) are valuable for achieving that quickly.
We have started cooling our motors with cold air but not for performance reasons. We cool them to buy a margin of time before they thermal limit especially if the time between matches is short. I assume most teams don’t have this problem. It’s easy to check since the Krakens temperature can be monitored all the time. They will shut off at 110C (citation needed).
As far as performance, If the motor is against a controller regulated current limit (lets say 50 Amps), it will make the same torque regardless of the copper temperature. It will require more voltage to get to said current but if that voltage is less than the battery voltage, same torque. If the battery voltage is less then what is needed to get to the current limit then yes performance will suffer. Some thing that could be noticed is, if it’s a drive motor, the driver would have to push the stick farther to get to the limit. Our driver would complain that the robot feels “spongy”.
For us, the battery voltage sagging is a bigger concern, next it’s the motors shutting off from thermal limit. Motor performance due to heat is not on the RADAR.
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Main breaker performance however…
Agreed on this order of priority. OP, update your firmware check your current limit and don’t worry about it after that.
For an anecdata point, we don’t cool the motors, but we do run ~50A drive motor current limits to try to control battery sag… Have not seen thermal limit shutoffs in hour+ practice sessions.
To know to look for it - monitor motor temps through Phoenix Tuner.
(Before the early season firmware update and before adding a drive current limit, we did kill the drive krakens, and RMA’d them. Latest firmware is not vulnerable to this, and the CTRE swerve template now ships with an 80A drive motor current limit - a good starting point.)
IIRC 1323 does run cooling for their drive practice chassis, 1678 does not?
I suppose that means motor performance due to heat isn’t on the radar, as long as motor performance is greater than zero.
Do agree that all the brushless data I’ve seen avoids a CIM-like falloff of power under peak power or constant current testing. It’s all about ensuring you can go rounds (and, ideally, not burn any fingertips).
We had a lot of folks on other teams advocating for icing down the main breaker in 2022 at our peak “35 pounds of dumbbell, six NEOs on drive, push other colored bumpers at every opportunity” phase. I don’t recall actively cooling it down in Houston, but I do recall we put on a fresh main breaker for the occasion and that is a wear item. So it’s not total bunk, just something a little further down the metaphorical iceberg.
I forgot… Main breaker is also important.
The good news is that with 120A stator current limits on even the most powerful controller, you’re always going to be under 60% of the stall current of a NEO (30% for a Kraken). So a bit of extra winding resistance won’t kill your performance. Once your stator hits 120C+, however, your magnets are going to start suffering, and that will definitely reduce your torque.
You will heat up even faster due to the higher resistance, but the motor will also dissipate it a little faster, so it evens out more or less.
That said, cooling motors can be very useful between elims matches or during practice at home. They can definitely get hot enough to start risking their lives, even with current limits in place. A 5V or 12V fan with a battery bank can work fine for this, or you can use the integrated cooling port (though personally I find that a little overkill). The fan will stay on for longer and encourage heat dissipation over a period of minutes without needing a lot of compressed air.
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In this case i think it was active monitoring with a thermocouple so the robot could enter “limp mode” and not totally die.