Maximum motor temperature

Hello,

I was wondering if anyone knowns what the maximum operating temperature for a 15470 outrunner would be? I believe it is the magnets that are the issue in this case and I expect as its a Chinese motor they are probably nothing fancy.

Cheers
Danny

Not finding what grade magnet is in them. some ref material. https://www.stanfordmagnets.com/neodymium-magnet-grades.html

Most magnets can take at least 80C.

Has anybody written a reference with the multiple relevant temperature limits for motors with sources? Could be useful for responsible limit-pushing...

- Magnet coercivity vs temperature (80C?)
- Magnet curie point (300C?)
- Hall sensor failure temperature (120C?)
- Motor wire enamel (???)
- Any others?

I haven't seen one, but you hit on most of the points. I've seen magnets get toasted and lose their magnetism and also windings burn out. The bigger problem is measuring the temperature. Thermistor stuck to the windings is probably the best, since the windings will be the hottest part. Measuring the temp anywhere outside won't always correspond to what's happening inside.

I have noticed that the magnets get warm quickly when the motor is running, is this due to them being in close proximity to the stator? or do they generate some heat from the changing stator field? I have my motor inside an enclosure with a fan on the motor shaft circulating the air. I am measuring the air temperature, could it be considered that the magnets might be hotter than the air temperature?

What would a typical symptom be for toasted magnets? reduced power output? less cogging? If the motor had reduced power output, would you see less current for a given duty cycle, or just more power wastage?

The magnets don't change polarity, and only respond to the changing field so they should not heat in the same ways as the stator iron. When they get weaker, you would see a KV shift and have lower max torque and higher no load RPM.