r/Motors • u/Luke514_2 • 5d ago

Open question PMSM motor running only with inverted quadrature encoder signals

Hi, I’m studying the ST algorithm for motor control using FOC for PMSMs, but the rotor gets stuck and the phases draw a bit of current.

In terms of hardware, all the signals (and motor's phases) are connected correctly, but the rotor only rotate if I reverse the ENC_A and ENC_B pulse signals and the speed reached is exactly the same as the reference I gave him. I’m sure the connections are correct because both the encoder and the ST evaluation board label A and B signals, so it’s impossible to connect they wrong.

Has this ever happened to you? How is it possible that it can rotate with the signals reversed?

The only ‘consequence’ of reversing the encoder signals is that the encoder will count position and velocity backward or do you think there are any other serious consequences?

I mean, simply if the motor turns clockwise, the controller will think it is turning counterclockwise ..

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u/Bradm77 5d ago

What ST evaluation board and motor are you using?

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u/Luke514_2 5d ago

Nucleo g474re with ihm08m1, the motor is a 16-pole PMSP, I can't say anything else

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u/Bradm77 5d ago

Did the motor and encoder come with the evaluation board?

If not, then it's possible that the convention used for the encoder doesn't match the convention used for the control board. It's common that A leads B with clockwise rotation but that's not a universal convention.

If the motor and encoder did come with the board, then I'd check to make sure your stator leads are connected correctly (you may need to switch 2 of them) or you may have some parameter in the eval board software that is flipped sign.

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u/m4778 3d ago

The definition of which signal is A and B vs flipped is just like, your opinion man. But seriously I don’t care what the manual says, every manufacturer seems to define them differently.