基於行車曲線能耗之軸向磁通電動車馬達最佳設計分析

Abstract

本研究針對用於電動車的軸向磁通同步永磁馬達規劃了一套系統性的多目標設計方法，在最佳化的設計過程中，為了達到所有的行車需求，以特定的轉矩轉速曲線做為設計目標，在特定的驅動控制條件下計算出其曲線所對應的反電動勢常數目標以及電阻、電感值限制，並以此條件計算馬達各部位之尺寸大小。在馬達磁場的分析中，利用分環法(Quasi-3D)將馬達磁場建立成磁路模型進行分析，在每個環狀平面裡，利用一維的無槽型馬達氣隙磁通解析解搭配等效磁路模型以及有效氣隙分布函數修正槽效應與徑向漏磁等現象，求得馬達的氣隙磁通密度分布函數，並進一步得到馬達的各參數值。在最佳尺寸尋找的過程中，利用妥協規劃法(Compromise Programming)來評鑑各尺寸組合在綜合了重量以及行車曲線能耗表現上優劣與否的指標，在眾多尺寸組合中權衡出一組馬達尺寸組合在各目標上最為符合需求的最佳解。 最後利用三維的有限元素分析比較模型準確性與設計可靠性，確保馬達可達成最初的設計需求，驗證了利用本研究所規劃的系統性設計方法，可設計出一電動車馬達，其滿足行車所需的條件，並且在重量、行車曲線能耗上有最佳的綜合表現。此操作區域效率最佳化方法，相較於額定點效率最佳化，可降低15%以上行車曲線能耗。

This thesis proposes a systematic process of a multi-objective optimal design of an axial-flux permanent-magnet synchronous motor (AFPMSM) for electric vehicle. The optimal design process uses a Quasi-3D analytical model of the magnetic field in an AFPMSM to calculate motor sizes under back-EMF factor target and phase resistance, inductance limit to achieve the specific motor torque-speed curve requirement. This model is derived from a one-dimensional analytical solution of the slotless air-gap flux density distribution and equivalent magnetic circuit model with an effective air-gap permeance distribution function to correct the flux distribution with the slot effect and flux leakage. In the search of the optimum motor sizes, the Compromise Programming is used to assess the set of motor parameters and make the performance indices, such as mass and energy loss during driving cycle, closest to all its best valuation on aggregate. The 3-dimensioanl finite element method verifies the final design, demonstrating that the proposed design process develops an axial-flux permanent-magnet motor with a high performance and reliability for electric vehicle. The optimized design can reduce over 15% energy loss during driving cycle compared to optimize the efficiency at the rated operating point.