Objective In the permanent magnet synchronous traction system of rail transit vehicles, when a two-phase short-circuit fault occurs in the permanent magnet motor, the electromagnetic torque may experience large positive and negative fluctuations, leading to severe motor vibration and noise. During vehicle operation, this often results in damage or destruction to the mechanical transmission mechanism, aggravating wheel-rail wear and impact, and even seriously threatening traffic safety during long-term operation. Therefore, it is necessary to study the short-circuit fault mode conversion for permanent magnet synchronous traction systems.

Method To address the aforementioned problems, through theoretical calculation and simulation analysis of the two-phase short-circuit fault of permanent magnet synchronous motors, the change characteristics of electrical quantities during the short-circuit fault are summarized, and a new control method based on fault mode conversion is proposed.

Result & Conclusion  When a two-phase short-circuit fault occurs in the permanent magnet motor during vehicle operation, by simultaneously conducting either three upper-arm or three lower-arm switches of the traction inverter through controlling the converter with the control system, the motor can be converted actively from a two-phase short-circuit state to a three-phase short-circuit state, thus effectively suppressing electromagnetic torque ripples, eliminating abnormal motor vibration, and preventing further fault escalation. The proposed new control method can provide new perspectives for the fault safety-oriented design of short-circuit faults in permanent magnet synchronous traction systems.