Research on Interturn Short-Circuit Characteristic of the High-Speed Permanent-Magnet Machine With Gramme-Ring Windings

The conventional lap-winding high-speed permanent-magnet synchronous machine (HSPMSM) usually has a large interturn short-circuit (ITSC) current, seriously threatening the reliability. This article founds that the SC coil of the gramme-ring-winding HSPMSM is wound around the stator yoke, so the inductance of SC coil is considerable large and thus will cause a great reduction of ITSC current. The types of ITSC faults were first analyzed for a multistrand-gramme-ring-winding HSPMSM, and then, the ITSC characteristics and influencing factors were investigated based on finite-element (FE) method. The distribution of flux density is quite different from normal state, the SC current is far lower than that of the lap-winding HSPMSM, and the inductance of SC coil is fluctuant with rotation of rotor. By theoretical analysis of the inductance, the methods of increasing the height of stator yoke and using high-permeability CoFe alloy were proposed to further reduce the SC current. In addition, decreasing the strands number is beneficial to reduce the SC current density.