Motor buzz, what causes it?

[Asuckaphish]

So i've been wondering what causes the motor buzz when you first start to apply power with the throttle? My setup has done it with mutliple motors (dynamite 35T, Hackmoto 35T, and Crawlmaster 16T) all with the stock dynamite ESC that comes with the Ascender. I've heard that the Holmes ESCs have a mode that eliminates that buzz but curious as to how it is eliminating the sound.

[Awesome-Sauce RC]

i think its partly to do with the pwm frequency thats being applied when power is given, lower frequency gives more noticable hum/buzz and higher is quieter but other things come into play as well that can change that.


tony

[Hydrocarbon92]

Yep, it's the relatively low PWM frequency. Most are in the audible range, but it depends on the ESC (sub-400Hz or 20kHz+). Most electronics favor silence for power, but not in RC.

Brushed motors actually emit sparks as the brushes touch another part of the communicator, that's why they're fairly loud. Both vibrate from any slight imbalance and/or bearing imperfections. Both will also emit noise from iron/silicon parts slightly changing dimensions - strong magnetic fields will do this to iron and silicon amplifies it. Essentially the can becomes an electric bell...

Good read for geeks: http://www.jimhendershot.com/Jim_Hen...c%20motors.pdf