Archived: the OG noob question thread! 😀

[professor_shartsis]

@professor_shartsis

so for example at 50% duty cycle, the battery could be supplying pulses of 60a, half the time, which averages to 30a. the battery side of the circuit has low inductance and so the current can ramp up to 60a and down to 0a very quickly.

on the motor side, the inductance is very high, so when the current from the battery shuts off, the circuit is rewired/switched so that the leads coming from the motor forms a loop, which allows the current to flow inductively (without applied voltage) for a short time.

the time scale of the on-off pulses from the battery are so short in duration that during the off times when there is no battery current, the current continues to flow in the motor entirely from the inductance.

@Krindor

to make things even clearer, I created this animation:

^you can see half the time (50% duty cycle), 60a current @ 50v is flowing from the battery, averaging to 30a @ 50v

the other half the time, the current flows inductively, and the motor “sees” 60a @ 25v the whole time. but in reality, during the “on times” the current in the motor might be increasing from 59.9a to 60.1a, and during the off times, the current is dropping from 60.1a back to 59.9a, which averages to 60a.