What does cooling a brushless motor do?

[RC MAN]

Hi everyone!

How and why do you get more power when you cool your motor?

The efficiency of your motor doesn't change because it depends mostly of the max amp draw and IR of your motor.

If you give the motor the same load , same voltage and same application the power that it makes in theory should not change.

I understand why you would cool a motor and be able to get more power from it because you can increase the load to get draw more amps without exceeding the brushless motor’s thermal limitations which otherwise would have been done without some form of cooling, and in term more HP and torque. But if you were to just cool a motor that was lets say at 60 degrees and you managed to cool it to 40 degrees why would it preform better with the same load, same voltage and same application ?

So i guess what i am trying to say is why do electric brushless motors produce more power when they are cooled and are under the same load, same voltage and same application?

 

[nino]

Some leftover highschool knowledge and a minute of googling:

Resistance increases with temperature and magnetism decreases with temperature.

 

[Jimbobjr]

I don’t cool them for more power. When they get too hot the magnets come unglued and/or lose magnetism. It’s probably better practice to gear(<180f) down and not run a fan at all but who wants to gear down...

 

[WickedFog]

It’s probably better practice to gear(<180f) down and not run a fan at all but who wants to gear down...

This is very true. You gotta figure, if you are reaching a high enough temp at the can to need a fan, the actual internal temps are a lot higher. With a fan, this would be a more drastic difference. But as you said, running a fan helps run taller gears. But this temp difference between the core of the motor and can itself is why I tend to err on the side of caution with my gearing.

 

[nino]

Personally I don't run fans on motors in my Slash 4x4 and Kraton 6s, I'll rather gear down if I find the motors are cooking. Or go for a bigger/better motor if that's what's needed. I'm having enough trouble with ESC fans dying on me and I hate additional wiring and stuff just waiting to fail

 

[RC MAN]

Some leftover highschool knowledge and a minute of googling:

Resistance increases with temperature and magnetism decreases with temperature.

That cleared it up
Thanks!

I don’t cool them for more power. When they get too hot the magnets come unglued and/or lose magnetism. It’s probably better practice to gear(<180f) down and not run a fan at all but who wants to gear down...

True, who does want to gear down

but anyway thanks for the response!

This is very true. You gotta figure, if you are reaching a high enough temp at the can to need a fan, the actual internal temps are a lot higher. With a fan, this would be a more drastic difference. But as you said, running a fan helps run taller gears. But this temp difference between the core of the motor and can itself is why I tend to err on the side of caution with my gearing.

Yep, Thanks!

always a good idea to err on the side of caution so you have some head room

Personally I don't run fans on motors in my Slash 4x4 and Kraton 6s, I'll rather gear down if I find the motors are cooking. Or go for a bigger/better motor if that's what's needed. I'm having enough trouble with ESC fans dying on me and I hate additional wiring and stuff just waiting to fail

Yep, sound like if fans are a pain in your rig and you are only going to get a little more power out of them, why bother
So in short yes, having a cooler motor increases power but only by a little bit?

 

[Doom!]

The important part is cooling the motor increases the lifespan of the motor .

 

[RC MAN]

The important part is cooling the motor increases the lifespan of the motor .

So it doesn't increase the power a bit?

And yes, probably is also a very good to have cool motor to increase the lifespan of it

 

[nino]

Let's say in 99.99% of cases the point is keeping the motor in a safe range of operating temperature. You're not going to notice any performance difference unless chasing that one or two MPH more. So just forget cooling for performance. For most of us, it's cooling so the motor doesn't die of heat stroke.

 

[RC MAN]

Let's say in 99.99% of cases the point is keeping the motor in a safe range of operating temperature. You're not going to notice any performance difference unless chasing that one or two MPH more. So just forget cooling for performance. For most of us, it's cooling so the motor doesn't die of heat stroke.

Ok, Thanks

 

[Jerold]

In general extreme heat is bad (an extreme cold) for electronics. You are correct the resistance curve changes, but I don't think it will matter "that" much given that the current is very high. If your nominal resistance increases by 1%, it's not going to matter that much.

But there is other stuff. Sensored motors do have some electronics in them and typical IC temps range of something like 0-125C. That's junction temp, meaning the temperature of the die inside the package, under the cover, surrounded by really hot stuff. I wouldn't be surprised if a180F (82C) at the case results in >125C on the die of the IC. Running out of spec isn't guaranteed to behave as designed and can lead to premature failure. There is a bunch of math to calculate this, based on statistical models.

There are mechanical issues also like bearings. The lubricant breaks down and the bearing wears. Also everything expands and mechanical tolerances might go out of spec, which is an unknown.

 

[ground_zero298]

Good cooling let’s you run it harder.

 

[RC MAN]

In general extreme heat is bad (an extreme cold) for electronics. You are correct the resistance curve changes, but I don't think it will matter "that" much given that the current is very high. If your nominal resistance increases by 1%, it's not going to matter that much.

But there is other stuff. Sensored motors do have some electronics in them and typical IC temps range of something like 0-125C. That's junction temp, meaning the temperature of the die inside the package, under the cover, surrounded by really hot stuff. I wouldn't be surprised if a180F (82C) at the case results in >125C on the die of the IC. Running out of spec isn't guaranteed to behave as designed and can lead to premature failure. There is a bunch of math to calculate this, based on statistical models.

There are mechanical issues also like bearings. The lubricant breaks down and the bearing wears. Also everything expands and mechanical tolerances might go out of spec, which is an unknown.

Thanks for the info!