Motor internal temp?

I think it was buried in the hub motor thread but looking for results comparing sensors within the windings revealing the wire’s true temp as apposed to just the case

Hummina Shadeeba said:

I think it was buried in the hub motor thread but looking for results comparing sensors within the windings revealing the wire’s true temp as apposed to just the case

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Hi,
I suspect any general or "of thumb" rule will be inaccurate for your specific application. Of course, I don't know the tolerance you seek. But from experience with rating motors, I suggest you test for yourself using the change in copper resistance to indicate the change in temperature of the winding as a whole versus the thermometer reading on the motor case. With the larger motors, we allowed for a 15°C hot spot. You can easily find the copper resistance coefficient for temperature and derive a simple formula to use. You do need an accurate way to measure resistance. We used a Wheatstone bridge. That was back in the old days. I suspect there are nice digital ohmmeters today.

Regards,

major

Of course. Du. Wonder how accurate the vesc ohm meter is and will have to test based on wire length and gauge. Hard to get a good ohm meter.

What of comparing the increased inductance from increased heat?
Speaking of increased inductance with increased heat..seems a surprising benefit. I imagine the esc is already programmed to the baseline temp and inductance and increasing heat would make for a waveform less matched to esc but if that weren’t the case..increasing inductance is a good thing in a motor, like gaining extra turns. With the motor km being produced by the resistance and inductance...how much does the inductance increase in relation to the increased resistance w change in temp? Thinking out loud
Thermal inductance!:
https://en.m.wikipedia.org/wiki/Thermal_inductance


I’m guessing if I create a baseline at room temp can go from there. And maybe the core will still keep the relation of temp and inductance linear. Inductance meters are accurate n cheap

I can't speak for inductance, but the magnetic strength of the magnets decreases at higher temperature. No idea if it's a temporary issue or a permanent issue that only happens above a certain temperature treshold.

The magnets max operating temp, before any decrease in their strength, is pretty high:
https://www.kjmagnetics.com/blog.asp?p=temperature-and-neodymium-magnets

But remembering can’t measure inductance without the rotor off n magnets not involved. Although the vesc tool can, but it’s said to not be accurate. But maybe consistently inaccurate

Thermal inductance is just an analog to electrical inductance. Electrical inductance has no influence on thermal behavior of electric motors to my knowledge. Forget about it.

major