Hello,
As the title says, I am trying to get my VESC 6 MK4 to work for a quite high RPM motor. According to this document https://vesc-project.com/node/183 the VESC 6 should be able to achieve 150K ERPM at maximum. The problem is that as soon as I try to go beyond the default value of 100000 ERPM, even if only by small amount, the motor desyncs when I surpass this value and the ESC starts acting weird until I cycle power on the VESC.
To give some insight, the motor I am trying to drive is a 3658-1857KV to drive an 80mm EDF motor for an rc plane. I wanted to try FOC to mimic the noise of bigger turbines as much as possible. The motor is a sensorless one, has 4 poles, I am using 6s (22.2V battery) and it draws about 100A at max throtle. The theoretical ERPM for this motor on my setup should be arround 22.2V * 1857rpm/v * 4 poles/turn = 164.900 ERPM . If I can reach 150K ERPM that will be more than enough on my part, but on 100K the thrust is just not enough.
I actually don't mind about most of the extra functions, like regenerative braking, cruise control, limits, canbus, etc. but disabling them or even trying BLDC standard driving seems to have no effect on this behavior. Is there anything I can try? I was not able to find motors adequate for my usage which are suitable to be driven at significantly lower ERPM. I am aware too high ERPM can damage the motor/ESC, but I am willing to take the risks in this case. Maybe I am asking for too much?
Thanks for reading to this point, best regards!
Hi,
I have similar problems at high erpm-s, but FYI erpm is counted with pole pairs, not with poles, so the true erpm is only half of what you have counted. Strange is though, I have this problem at rougly 80k erpm too. What I have found out which helps, is setting FOC/advanced/ observer type to iterative, and switching frequency to 30kHz, and "sample a v0 and v7" to enabled. Probably some tweaking with PID could help to completely get rid of the problem.
Set switching frequency to 60khz with v0 and v7 off.
Hello,
Thank you very much velolac and TechAUmNu for your responses. I will try both approaches and see if I can squeeze a tiny bit more out of the vesc. I think I was wrong about the motor specs, and as you say it is 4 pole pairs (8 magnets), because otherwise the data I see make no sense (with 80K ERPM vesc tool says it is arround 50% duty cycle at max throttle). Sadly for me the manufacturer provides close to no information about that matter (this is the motor, if you had curiosity: https://www.motionrc.eu/products/reewing-6s-3658-1857kv-brushless-inrunn... )
Best regards.
Hello,
Thank you very much again for your help. I finally was able to do some tests. For me the setup that worked best was 60Khz, sampling at v0 and v7 disabled, and observer type to iterative. I was able to reach around 140K ERPM with this settings, but still the motor starts failing randomly at high rpm (can be due to heat maybe?). I will try tinkering a bit more with other settings.
Measuring the true RPM at the axis and ERPM value I concluded my motor has 5 pole pairs. Strange setup for an outrunner, but seems fairly common in ducted fan motors. That puts me sadly a bit further away from my goal of running the motor at close to full power with foc. I am still happy to surpass the 100K ERPM barrier, that seemed impossible to me only 2 weeks ago.
Best Regards