Before doing this we adjusted the rotor such that the rotor flux angle matched (by moving the magnets on the axle of one of the motors until we saw that the output phase / output pattern matched):
As long as the mechanical coupling stays intact (magnet assembly not moving on the axle) the whole assembly should still act like a normal motor but with half the inductance and halve the resistance. We are going to build a 1.5kW load setup to evaluate the performance over time. Lets hope for the best !
I have done this in the past with pump (without the rotors locked together). I had 2 BLDC pumps and was able to run them off one VESC. We only used them on our test bench for an few hours so i cant confirm the life of the VESC.
There was no need to sync the rotors since it was a pump applications. The two motors “found” the same rotor position during startup and since the load on both pumps was the same they stayed in sync.
I was a bit surprised it worked. I image it would not work if the motors have a high start up load like in ground vehicle.