What do the 3 spd PAS settings on a controller actually do?

[chas58]

What do the 3 speed PAS settings on a controller actually do?

Basic controllers (i.e. KU65 from BMS battery) have a 3 speed switch for the PAS, that offers slow, medium, and high speed.

How do they do this? Are they limiting the voltage to limit the speed?
For instance, at 36 volts, do I get 12 volts, 24 volts, and 36 volts?
This would mean reduced power at the lower speed settings (and reduced power consumption)

Or are they more like a throttle that once a motor reaches a certain speed, the controller just cuts the power (actually allowing it to taper off).

And part 2: I assume the “torque sensing controllers” (bms battery S06) moderate the current and keep full voltage? Thus, I would be getting 36 volts, but might get 5, 10, and 15 amps at different settings?

 

[docw009]

You can google for a KU63 schematic. It shows that a phase wire gets switched between Battery and Ground. Two mosfets per phase. One pulls up to battery voltages. The other pull it down to ground. Volts don't change.

What changes the motor speed is the frequency of the pulse widths used to drive the mosfets.

I don't know the algorithms, nor do I have a storage scope to watch them. If I did. I might. I surmise that the PAS level tells the controller what max pulse frequency to use, which sets max motor speed for that level. There might be some minor tuning on the pulses too, for a given PAS level. Actually, probably some major tuning, to control the current.

 

[chas58]

interesting, thanks.

I'm wondering if at the lower settings, it lowers the power or just lowers the top speed...