vesc field weakening

anyone using the program this guy made?

GitHub - district9prawn/bldc at field_weakening

doesnt seem official vesc software yet
Field Weakening | VESC Project (


What does it do?

get speed beyond what your motor kv and battery voltage would normally limit you to


you’ll need different rotors for it to work… ones made of a significant fraction of iron which are designed for reluctance torque. switching to these other rotors means you’ll
lose overall torque density.

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U can use field weakening with permanent magnet brushless motors.

The rotor would loom more like this… still brushless and with permanent magents, but you can still generate reluctance torque with the magnets removed (from the shape of the iron).


You can do field weakening with a common magnet motor such as we use

can you explain what @Gamer43 meant in this post:


Dont know but there are many escs that do field weakening with common magnet motor rotors.


what about this post?

If you want more interesting torque curve arent you better off using inrunners instead of risking blowing up esc with field weakening?

You need rotor iron for field weakening to be of any practical use.

Field weakening is meant to provide a constant power region up to 200 to 300% the motors rated operating speed.

Turns out you can get like maybe 10% extra speed with utterly no torque generation with the motors we use, so it’s basically not worth pissing away the current.

That and vesc sensorless observer, on top of the issues with its implementation, is not compatible with flux linkage modulation.

Phase advance on trapezoidal control is NOT field weakening


Not ready for peeps and has big risks. 40% more speed though

Will never be ready without a complete firmware rewrite.

40% with what kind of motor? They were using an EV IPMSM with rotor iron and a precision external sensor.

The best I could get was 20% after driving full load current into the direct axis (no torque generation) on a 6374 with significant position error on the sensorless observer.

Most industrial and ev applications design their IPMSM to get to 200 to 300% rated operating speed so that there is a meaningful constant power region.


Available in new firmware:

“Use at own risk”

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Did you ever try it?

Will be soon but it’s been awhile and I think it’s pretty reliable now.

Why isn’t there a lot more info on this I wonder

cause most don’t have a need to run field weakening
and most likely wouldn’t be smart enough to set it up properly