For open-circuit fault diagnosis of the multiphase permanent magnet synchronous linear motors ( PMSLM)

the traditional phase current averaging method is simple in principle but slow in fault diagno-sis

while the single harmonic space current trajectory method offers high accuracy and speed but can on-ly diagnose single-phase open-circuit faults. To address this

an open-circuit fault diagnosis method was proposed based on a combined harmonic space phase current trajectory. By performing a spatial decou-pling transformation on the mathematical model of a six-phase open-winding PMSLM in the natural coordi-nate system

harmonic currents in the 3rd and 5th harmonic subspaces were obtained. Then the combined harmonic space current trajectories for each phase were derived with the corresponding phase currents of the 3rd and 5th harmonic subspaces as the vertical and horizontal axes respectively. Based on the trajec-tory characteristics under different open-circuit fault conditions

fault judgment factors were constructed to achieve accurate and rapid diagnosis of open-circuit faults. Simulation and experimental results show that the proposed method can accurately judge all 21 types of single-phase and two-phase open-circuit faults with a fast speed

requiring only 0. 15-0. 25 electrical cycles for diagnosis.