Finite element analysis of interior composite-rotor controllable flux permanent magnet synchronous machine

A new structure is set forth for the interior composite-rotor controllable-flux permanent magnet synchronous machine (PMSM). NdFeB permanent magnet(PM), which has high remanent flux density as well as high coercive force, and AlNiCo PM, which has high remanent flux density but low high coercive force, are used in this structure. The magnetization intensity and direction of AlNiCo PM can be controlled by stator d-axis current pulse. Consequently, the flux generated by NdFeB is either repelled to stator so that the air-gap PM-flux can be intensified, or partially bypassed by AlNiCo in the rotor so that the air-gap PM-flux can be weakened, and the air-gap PM-flux is kept at a desired value because of the memory capability of PM. Principles of the motors are interpreted. Finite element analysis on magnetic field is done. The size of PMs and the principles of magnetic circuit design are demonstrated, and the conclusion is drawn that effect of flux-weakening is better when the q-axis magnetic resistance is large and the inductance is small.