Hi guys
Could anyone tell me what the constant high pitched sound is when you put any current into the motors under load? It's kind of line the sound of lots of cicadas in the bush...
It stops in neutral trigger. Even a slight trigger or brake produces the full sound. The sound doesn't increase with extra current or braking. But is quite loud when riding along on the skateboard.
Dual 100kv 6365s.
Thanks Regards
Paul
Please give more infos on your set-up, which VESC version, which firmware, and settings used, if you want efficient help.
Have a Nice Day.
Thierry
The switching (in FOC Mode) produces harmonics at 10kHz. You can hear those,
This is mostly due to your motors acting as a speaker. It depends on the motor how pronounced that is. My bike for instance is almost inaudible, while a friend has the same (not-)VESC but much more sound.... Different motor.
Hi Roger and thanks
Do you know how the motor acts as speaker? and what characteristics make it better and worse when ordering a motor?
Regards
Paul
I think most of the noise is attributed to resonance of the bell (in the case of an out runner motor). If you hit the outer can with something, it rings, especially on the larger ones. Now thinking about it, hub motors are near silent due to the urethane damping the rotor can. Most of the lower pitch noise you are hearing is from various sources of vibration resonating in the rotor. Some from bearings, loose windings, road bumps, and the switching of the phases. The high pitch sound is due to the switching frequency. If you change it in the VESC tool by a few kHz, you can head a noticeable difference. However, the other noises remain almost identical. if you are trying to make a motor run near silent, try to introduce damping on the rotor without sacrificing too much heat dissipation. It might be a fun experiment to put a bunch of rubber bands on the outside of an out runner and record the results.
Cheers!
Hi Josh
Thanks alot for your answer.
It is definitely the high pitch sound that I am talking about, so its set at 20hz at the moment in the vesctool. We are using Vecc6 so I assume it has phase shunts and we have the Sample in V0 and V7 option TRUE.
Should I change the frequency to say 18 or 22 and see?
Thanks
"The switching frequency. The controllers and estimators will run at half of this frequency. If the option Sample in V0 and V7 is active the controllers and estimators will run at the full switching frequency, but this option is only available on hardware with phase shunts."
Yes the VESC 6 has three phase shunts. They are flat copper components on the top of the PCB if you look under the cover PCB. You can change the frequency to 22kHz and you should be able to hear a difference. Note that the higher frequency you go, the less noticeable the sound becomes. However, since the FET's are working harder, they will run slightly warmer. In my experience, bumping up by a few thousand does not effect the heat too much, but jumping up to say 40kHz would have a notable impact. I believe my setup is running at 23kHz. It is something to play around with if you want ot eliminate that high pitch sound.
Cheers!
Hi Josh
24,000 worked an absolute treat. The sound is completely gone. If I could buy you a beer I would.
The fets were only getting to 47 degrees C yesterday after a 20 minute ride.
Thanks heaps
Now to work out why the motors are desyncing at startup on grass with full throttle....
Awesome! I am glad you were able to get that sorted out! The temps should remain almost identical to the previous configuration.
Cheers!
I have a similar issue when running a Hacker Q80 13XS motor at a certain speed/throttle window setting. The noise is constant at some RPMs, but then off and on at others, and off for most of the range. The noise also corresponds with spikes in ERPM, current, and duty cycle (going from about 8-10A). Any other ideas what could cause high pitch screeching noises like this, or what I could adjust in the ESC to test? Acknowledged that it could be the motor and not the ESC, but it would be good to know which one it is.
Update: My noise happens around 22000 even without a load. It is similar to the noise made in BLDC mode, but BLDC noise is throughout the range, whereas the FOC noise is only around 22000ERPM.
Some motors also make noises due to poor manufacturing. A loose magnet can vibrate and cause a noise.