Field weakening is awesome- testers needed

If you’re not sure what field awakening is the long story short is that it makes your motor spin faster without having a higher voltage battery. Benjamin(the creator of the vesc stuffs) just released a firmware that includes this and needs help testing. If you have a vesc that doesn’t throw lots of fault codes I encourage you to check out the link below and try it out. Also, I noticed that when someone donated $200 he got right to work on field weakening so if you REALLY want this feel free to donate what you can and mention field weakening as part of your donation :wink:


This is fucking huge, I can’t tell you how long I’ve been waiting for this.


Up to 2x the speed on outrunners, but it wants a lot of energy at that speed. Test with care, this is BETA FW!


So kv of a motor really doesnt matter as long as your battery can dump more amps?


Is there any proof it works on esk8 motors?

I thought you needed an IPM rotor (magnets embedded in iron) for the reluctance torque…

Interior Permanent Magnet (IPM) Motors have a mechanically robust rotor structure that is effective in flux-weakening operation because it has low effective air gap. So, IPMSM can be operated not only in the constant torque region under the base speed but also in the constant power region over the base speed, and its the architecture most commonly used by OEMs in Electric Vehicles.


IPM rotors have less torque density than esk8 motors, but have an appealing cost per kilowatt of power output.

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Well, Field weakening is not an efficient way to gain speed. It consumes energy to go beyond the motor limits of max RPM.

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Hmmm group buy on some new features anyone? Only partially joking :joy:


According to Vedder you can get up to 2x the speed on esk8 Outrunners. But it would waste a lot of energy at that speed.



“ *So back to our example of 10000 rpm base speed at 50V battery, which is typical for a small e-bike VESC, and you get a fault at 14000 rpm that halts your pwm. If your fault current is high enough to blow the fuse, you will have 140% of your battery voltage, that’s 70V. *

The problem is, those small VESC have an absolute maximum rating of 60V, so you will instantly blow your drive with big fireworks fueled by the vehicle inertia.


Can you elaborate on this?

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the esc has to run twice as fast! very tiring :tired_face:


In general field weakening is not an efficient way to gain speed. A faster motor would be the better choice. However, if you only need more speed from time to time, it is acceptable to waste some energy by fireing additonal coils up, weakening the field.


Variable position stators achieve the same effect as field weakening without producing back emf voltages that exceed the ratings of a typical vesc in the event of a fault that stops the pwm.


So you can gear for torque and have the ability to go over 30mph if needed… if the battery can dump more amps and the motors can handle the heat

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Just so everyone reading is aware, there are some serious safety issues with field weakening.

If the motor is powered into a faster spin than its normal no-load speed, then any ESC failure would feel like an immediate full-brake, likely to pose significant danger to the rider. A lot more danger than a regular ESC failure at top speed, which would likely just put the board in “neutral” or “coast” mode.

Only do this at your own risk. :metal:


Seems like it may be safer (if the speed control can handle it) as we approach 100% duty cyle there will be no pause or cutback- the battery will dump more amps and you can keep going alittle or alot mo faster


A much better way to test this would be to gear a rig so it has an 8mph (12.9km/h) top speed or some shit. Then push it to 16mph (25.7km/h) …

and test the fuck out of that mug at speeds you can run off


One of the few times I wish I had a remote control car with vesc for testing this lol


I dropped one into my sons RC Car, great test bed…