4 ms·

great question! I work on servo controllers, so I can talk a little bit about it. The short answer is most controllers regulate current. They do these by dri

great question! I work on servo controllers, so I can talk a little bit about it. The short answer is most controllers regulate current. They do these by driving at varying levels of voltage, measuring the resulting current, and using that measurement to adjust the voltage until the desired current is attained. So the relative resistance of the motor doesn't matter much with respect to how much current will flow through it. In this case, I would assume the upgraded controller is able to drive a higher voltage in order to attained the increased current. The smaller controller likely has smaller, cheaper power transistors and related components, so it must limit itself to the maximum current (and power and heat) those transistors can handle. BTW, the resistance of motors these days is relatively low... They can likely not handle the full amperage from the battery for very long. They simply must use controllers to switch the current.

margalabargala 4y ago
Got it, thanks. The reason I ask is, I'm working on an ebike that had a cheap undersized controller installed such that if I drive it at full throttle long enough, the controller overheats and shuts off. My plan was to simply upgrade to a controller with a much higher amperage rating, removing that as a concern. But it sounds like doing this could just burn out the motor? I think I can change the software of the controller to limit maximum power output, I'll have to do that I guess. I would not have expected a controller capable of 60A to attempt to actually force 60A through a 48V, 1000W motor if the throttle was held down; I would have expected it to apply battery-level voltage to the motor (or do an internal step up/down to a constant 48V) and simply permit the motor to draw whatever amperage it pleased at that in-spec voltage.

margalabargala 4y ago

Got it, thanks. The reason I ask is, I'm working on an ebike that had a cheap undersized controller installed such that if I drive it at full throttle long enough, the controller overheats and shuts off. My plan was to simply upgrade to a controller with a much higher amperage rating, removing that as a concern. But it sounds like doing this could just burn out the motor? I think I can change the software of the controller to limit maximum power output, I'll have to do that I guess. I would not have expected a controller capable of 60A to attempt to actually force 60A through a 48V, 1000W motor if the throttle was held down; I would have expected it to apply battery-level voltage to the motor (or do an internal step up/down to a constant 48V) and simply permit the motor to draw whatever amperage it pleased at that in-spec voltage.