Honestly, I have no idea how the VESC works or what a MOSFET even does… I’m just repeating what I’ve read around the forums and deduced from that. Everything I’ve said is likely extremely simplified.
How I understand it is that there are two circuits (not sure if that is the correct terminology) one for the battery/ESC and one for the ESC/motor. The battery one has a constant voltage, and the VESC pulls amps to get a desired power figure. On the motor circuit the voltage is determined by % of no load RPM (duty cycle) and the amps are equal to the power supplies by the battery divided by the voltage determined from the speed of the motor (RPM/kV).
This is assuming that power is equal on both sides. I have no idea whether that is true not not.
Again, all of this could be complete bullshit and I’d love for someone that actually knows what their talking about to explain in more detail but this is what I’ve gathered so far.