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Why I_Q_MEAS is zero when motor is locked and I_Q_REF goes up to the maximum value?


I'm using ST workbench 6.2.0 and motor Pilot V1.2.4. NUCLEO+ IHM08M1, three shunt sensor and brushless motor with encoder. 

When the motor is blocked, using TORQUE control-->Torque Ramp in Motor Pilot, the actual drive current I_Q_MEAS is almost zero, although the Torque_Reference and I_Q_REF is shown to reach the expected value.

Once the motor is unblocked, everything seems to be fine.

It seems to me that since the actual Iq is almost zero, the drive isn't capable of delivering maximum starting torque.

What am I missing here?

Gael A
ST Employee

Hello PQ,

Please correct me if I am wrong : you are trying to start your motor with a resistive torque applied.

In that case, it looks like an alignment issue. As you may know, an encoder needs to be aligned correctly before start-up, if you don't or if you can't (for example because your rotor is locked) then your encoder is incorrectly initialized and you will have trouble starting your motor. You may solve your issue by increasing the Final Current Ramp Value (Speed Sensing Config tab in the MC WorkBench) of your start-up parameters to force alignement and then ensure a proper start-up.

If you agree with my answer, please consider accepting it by clicking on 'Accept as solution'.

Hope this will help,
Gaël A.