vesc field weakening

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

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

Available in new firmware:
https://vesc-project.com/node/2859

“Use at own risk”

4 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

1 Like

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

5 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

I went from 72t to 66t and didn’t gain any top speed at all, any idea why that happened? I thought it would pick it a bit of top speed, not much but none at all?

How are you measuring your speed?

GPS app on my phone. I was doing it with my remote at first but I couldn’t belive I was going the same top speed with the 66t as before with the 72t so I downloaded the GPS app on my phone and that confirmed that the speedometer on the remote is pretty accurate.

What speed do u get to? Maybe you need to increase ur battery amps to overcome the increased wind resistance

Probably not enough torque to go that speed, need more amps, like @hummieee said

I can feel it stop pulling when it get to top speed, if i back off the throttle a bit I can feel it pull again. Why is that?