Getting motor winding temp without sensors

How accurate is the ohm meter on the vesc tool? Could get an overall winding temp by doing the bldc test and figuring the temp from increased resistance. Is that possible easily these days from a phone app?
And said the wire could have roughly 15c hotter hot spots on a typical winding
With increased heat it’s increased inefficiency and the eventual enamel failure

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Vesc is inaccurate in both its resistance and inductance measurements.

Maybe consistently inaccurate though?


Yet accurate enough to detect the position of the motor without sensors


So even better control and less cogging while unsensored. I missed does it use current during the positioning? I imagine a bit
Can u run foc and position control together? Sounds not. And says he was getting saturation even with only 50 amps and would lose synch.

If I’m not mistaken Vedder tried that in the past and wasn’t anywhere accurate

But maybe things changed, if that worked, together with the new sensorless positioning, it would mean that just the phase wires would be needed for a safe operation

@hummieee deodand explained why it loses sync in the Vesc tool thread, take a look

And it’s just at speeds that the HFI is active, after that it works as normal

The sensor less positioning may be great but seems loud and more so a problem in being incapable of high current.

Updated my reply above

Would be nice if while the HFI is active you have a secondary current limit that prevents it from losing sync

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You can run FOC sensorless though. This HFI feature would allow you to detect the motor’s position when you’re at a stop, so you could get smooth startup, basically making sensors for positioning pointless I think.

Not sure if what’s shown in the video is still an experimental feature though, or if we can safely enable it and it will turn itself off at higher speed/current when it stops working.

This seems to have better control than standard sensor less foc, but with noise and I’m guessing a bit of current needed, but the current limit at 50 amps seems a shame and for sure with a board people are going to want higher at start up. 50 amps vedder was saturating (don’t know the exact motor). Interesting in itself and wonder what size motor n kv it was that was saturated at only 50 amps. Trampa touts them with magical specs like 100% copper fill.

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Ah, true, I guess it’s useful then only when you first turn your board on :laughing:

Can’t find it, link?

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Is it more than saturation causing it to lose synch? That’s all I heard

Mine and his right bellow

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If going for max efficiency worth finding at what magnetic field strength causing saturation as current is largely wasted beyond that point. Worth setting the max motor amps to it. I’d like a test! Maybe this position sensor is the best test.

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This is why is in my dreams to build a inertia dynamometer for our small motor, it’s quite simple, possibly cheap with the right parts and VESC tool and an excel spreadsheet is all you need to extract all performance data, except maybe continuous rating, but that can be done with open loop and slow speeds and extrapolated from there

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Build it! We can send u all our motors to compare. If u need parts sent to build it I’d help a bit. Think ur out of the country. Others here have said they had made one or were in the process but they’ve either disappeared or something came up n we still don’t have decent comparisons. With the next motors I’m doing lrk n hallbach as well as extended magnets n smaller inner diameter on the stator and want to compare. I feel like the km of the motor gotten with just the kv and resistance is pretty revealing but doesn’t include the load and efficiency at different speeds and saturation.

Looking forward to see it

An easy way would be just to get an used induction motor and use the rotor as flywheel, with the added benefit of a built in explosion shield in case things go wrong. New bearings, probably without grease to lower friction, just a bit of oil at each run

Clearly not accurate enough considering torque generation below 40% duty cycle is very lacking.

I checked measurements using VESC tool, RCL meter in the lab, and with my own power stage.

VESC thinks a motor that has a line to line inductance of 70uH instead has 16uH.
The resistance measurement is closer, but still off by as much as 20%. I got down to consistently better than 5% accuracy on my power stage.

Yep, 20% off, VESC says 15.88mOhms on maytech 6374, power supply and multimeter, separate RCL meter, and my own power stage say 19.25mOhm.


probably off by more since it only measures one phase… ps wouldn’t the vesc measurement also include part of the vesc?