Brushless motor phase reversal

Other Hardware General Electronics
1

Hi,

I have an 2000w 60v sensored brushless motor and controller setup such as would be found in an electric bike etc, that I would like to get to run in both directions. (Single direction controllers).

This unit is for an electric boat that previously had a lower powered brushed motor. On that setup I achieved throttle using potentiometers (0-5v) and reverse using a DPDT switch that swapped final polarity to the motor.

Using the new motor, I plan to control forward and reverse all from a single rotary pot feeding an Arduino.

A have my head around everything except the best way to swap 2 of the 3 phase wires (60v 30+A) and 2 of the three sensor wires from the controller to the motor digitally.

Because the phases are in constant fluctuation as the motor turns and I assume polarities are also swapping from the controller, as well as potential latency issues I don't think a H bridge would suffice. (Am I right)?

Also because of the high current involved, it seems standard relays aren't up to the task. Could I run high power transistors or relays in a parallel arrangement to achieve this?

Any ideas are much appreciated.

Cheers.
Pete

2

Does this brushless motor have the control electronics integrated? Then it's going to be really tough as you have to replace that part.

Otherwise you may be able to replace the existing control electronics by something of your own that can operate it in two directions. One controller in the ATtiny range is designed specifically for dealing with brushless motors, it features timers that run at a multiple of the normal clock speed for more accurate timing sequences. That could be a good one to base your controls upon. Of course you would also need a bunch of high speed high current MOSFETs or similar switches, but you shouldn't need an H-bridge.

3

You can't easily commutate two windings when a motor controller is driving them, its best just to get a
bidirectional controller in the first place.

For instance with a sensored motor you'd have to reconfigure the sensor signals at the moment the
windings are swapped, otherwise you've just created a misconfigured setup.