Hi Guys,
Oh! That's the question ...
The width of the pulse coming from the RC helicopter receiver or from your timer is uswed to command an RPM.
For example, with the Castle PHX-45 in HI-Governor mode and a 7-pole pair motor like the AXI 2826/10:
Anything between 1000 microseconds and about 1200 microseconds yields Full Stop.
At about 1250 microseconds the motor starts and runs at maybe 3000 RPM.
At something like 1350 microseconds, the RPM is 10,000, whether you have an 11-5.5 three blader or a toothpick on the motor.
At something like 1380 microseconds the RPM is cbout 11,000.
I don't know what the top end would correspond to, but the best the AXI 2826/10 will do on 4 cells and a shaft run is close to 13,000 RPM.
In LOW-Governor mode, the motor starts as before, and 1900 microseconds commands only 9,250 RPM. That's the maximum you can ask for in low mode. It is useful for inrunner motors that have fewer electrical cycles per mechanical rotation.
Now that you have sent a pulse width to the ESC, It knows the RPM you want. The actual "throttle" or voltage drive duty cycle (% of full) is varied by a control loop that compares the actual RPM to the RPM you asked for with the receiver pulse.
I have a graph at home of pulse width versus RPM for the AXI in HI mode. I'll dig it up.