An Interturn Short-Circuit Fault Diagnosis Method for Toroidal Winding PM Machines Based on Circular Judgment Curve

Toroidal winding permanent magnet machine (TWPMM) has received widespread attention in the ultra-high reliability field. However, it is difficult to suppress the short-circuit current within the rated value of TWPMM by relying on the impedance change of the machine itself when encountering such severe short-circuit conditions as fewer turns. Timely and accurate fault diagnosis is essential to safeguard the system. Due to the special structure and fault tolerance mechanism of TWPMM, the conventional fault diagnosis methods are hard to detect its subtle changes in terminal voltage/current and air gap magnetic field. This paper is devoted to proposing a fault diagnosis method based on circular judgment curve with yoke-wound search coil for TWPMM, which only requires two yoke-wound search coils to achieve high accuracy fault location with enhanced sensitivity and minimal invasiveness. Firstly, the TWPMM topology, fault tolerance mechanism and fault characteristics are presented. Then, a yoke-wound search coil structure is designed based on the special yoke-annular-leakage flux. The circular trajectory relationship shown by the search coil voltage magnitude and phase is discovered. Furthermore, the localization accuracy and less invasiveness of the proposed method are verified by comparing with conventional tooth-wound and yoke-wound search coil methods. Finally, the prototype is built and tested where experimental results match well with the theoretical analysis.