Stator current operation compensation (SCOC): A novel preprocessing method for deep learning-based fault diagnosis of permanent magnet synchronous motors under variable operating conditions

•PMSM fault diagnosis method under variable operating conditions is proposed.•The method effectively diagnoses PMSM faults with signal units of small length.•The method alleviates frequency changes of stator current caused by speed change.•It eases amplitude changes of stator current by load torque and acceleration change.•It highlights small fault-related residual components of the stator current.