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).
2 Likes
You can do field weakening with a common magnet motor such as we use
Dont know but there are many escs that do field weakening with common magnet motor rotors.
3 Likes
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
2 Likes
Not ready for peeps and has big risks. 40% more speed though
1 Like
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.
7 Likes
1 Like
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
4 Likes
Who here doesn’t want to go a bit faster lol
2 Likes
Most here hold reliability in high regard.
Field weakening is still too mysterious/risky
1 Like
The onewheel guys who do vesc conversions run field weakening and don’t seem to have any issues with it.
I’ve run it quite a bit too
Functionally the biggest drawback is heat and less range. If you are locked into a hub motor it can make sense, otherwise you are better off changing gear ratios, tire sizes, kv or battery voltage to get additional top speed.
One thing to consider is that if the vesc faults or loses power while in field weakening, the voltage at the motor goes back to RPM/kv which may exceed the mosfet rating. Probably best to use a 20s esc for 12s for example, or use erpm limits to make sure it cannot exceed the 60v mosfets most 12s controllers have
6 Likes
Not a single mention in this thread or the older one on the same topic, on any hardware requirements for Field weakening.
One could assume that a vesc 6 with 3 phase shunts would be safer running FW than like a Focbox 1.7 but no guidelines seem to be around.
1 Like