Variable Flux Memory Motor(VFMM) is able to vary its magnetic field intensity of the permanent magnet(PM). Thus, VFMM has advantage for high speed operation with higher efficiency, when field intensity of PM is reduced. However, shape of the motor and arrangement of PM are important factors within restricted geometry of VFMM, because large d-axis current pulse is requisite to achieve high demagnetization and remagnetization ratio of PM. Moreover, the variable magnetized PM(VMPM) with low coercive force(Hc) is selected in general, for smooth remagnetization and demagnetization. For this reason, undesired demagnetization occurs on PM in load condition, since the magnetic field generated by stator reduces the magnetic field at rear edge of PM, which leads to output performance reduction of VFMM. Thus, it is necessary to design motor considering easily demagnetized part of the PM. This paper proposes a novel design method of surface mounted PM(SPM) type hybrid VFMM(HVFMM). The rotor pole of proposed structure is composed of two different PM materials in each pole. The rotor PM placed in front of the rotational direction is ferrite VMPM, which is selected to vary main flux field by varying its magnetic field intensity. The PM placed at rear of the rotational direction is constant magnetized PM(CMPM), which uses NdFeB, to produce the main flux of the rotor. The arrangement of these PMs is determined to prevent demagnetization of the PM in load condition, and to take advantage of the combined PM pole, which are increase in thrust of the magnetic system and torque density of the motor. To verify the validity of the proposed structure, nonlinear 2-dimentional finite element method and magnetic equivalent circuit are adopted to analyze operation characteristics of VFMM. Finally, we propose novel design configuration and parameters of SPM type HVFMM for 30kW traction motor.
|Submitters Country||Republic of Korea|