My question arises from interest mainly in Outrunner motors which are used on RC planes/drones.
With that being said, I understand that these motors are controlled by an Electronic Speed Controller (ESC), which is used to switch DC power into two of the three different phases of the motor at a specific time by monitoring the back EMF (for sensorless operation) on the third phase. I also understand that to regulate speed, the ESC will use PWM to "modulate" the average voltage to the motor.
If my understanding is correct, then I am utterly confused why I have read, in multiple places, that Brushless DC (BLDC) motors are speed controlled by frequency.
For example: "BLAC, BLDC (AC stator, DC rotor) These are basically just Synchronous machines but they have permanent magnets on the rotor. Higher the stator frequency the higher the rotor speed. AC & DC just comes from the type of current control that is used."
Also, I know that Brushless Outrunner motors experience slippage, which means they are definitely not synchronous. Correct?
I am left with the thought that there must be different types of BLDC motors, or different forms of control. May I please have a clarification on this subject or even a correction if I am completely wrong?
EDIT: Changed "Engine Speed Controller" to the correct term: "Electronic Speed Controller"