MMM drive frequency

[MetalMan]

Excellent question. I'm not CC, but I can throw in some speculation. Have you noticed how the CC car ESCs use two different drive frequencies, one to start the motor and the other to keep it going? My guess is CC doesn't have drive frequency as an option because they cater to the masses - and the large majority of the masses would have no idea what this "frequency" is - so CC left it out and stuck with a drive frequency which will suit most motors.

[brushlessboy16]

Originally Posted by MetalMan

Excellent question. I'm not CC, but I can throw in some speculation. Have you noticed how the CC car ESCs use two different drive frequencies, one to start the motor and the other to keep it going? My guess is CC doesn't have drive frequency as an option because they cater to the masses - and the large majority of the masses would have no idea what this "frequency" is - so CC left it out and stuck with a drive frequency which will suit most motors.

can you distinguish the frequency? that screeching/whining sound?

its always higher pitched at the hit of the throttle and then deepens

http://www.youtube.com/watch?v=NXQkS-BigRo

the first trigger pull you can hear it...

What exactly does the frequency do?

[SpEEdyBL]

Originally Posted by brushlessboy16

What exactly does the frequency do?

I a no engineer (at least not yet!), but I will do my best to try to explain. If patrick could chip in and correct me if im wrong that would be great.

First think of an esc as a very fast on/off switch. The drive frequency is the rate per second at which the esc turns the motor on and off. So if the drive freqency is 10,000 hertz and you are applying 50% throttle, the esc will turn on/off 10,000 times every second and stay on 50% of the time. Likewise, if 70% thottle were used, the esc would stay on for 70% of the time and stay off 30% of the time. The result of this is that the current will average some fraction of what the current would be as if full throttle were used. If you picture the graph of the current over time (assuming you maintain a certain level of partial throttle), it will look like a sine wave. The higher the frequency, the smaller and tighter the ripples, the lower the frequency, the larger and broader the ripples will be. As you might be able to imagine, higher frequency = smoother operation, but is not always better. Here is where my limited knowledge comes into play. I'm guessing that different materials including iron, which is commonly used as a stator core, have limits to the rate at which they can change their induced magnetic field. So if the drive frequency is too high, the magnetic field of an iron core will not be able to "keep up" to the changes in the magnetic field created by the surrounding wire, thus creating heat and poor efficienty. Of course at full throttle, drive frequency shouldn't matter since the esc sends power to the motor 100% of the time.