軸向和徑向磁通混合開關磁阻馬達之設計與分析

Abstract

近年來，電動車和混合動力車用輪內馬達之設計已成為一個重要的課題。應用於電動車及混合動力車之馬達選擇上，通常由重量、效率、成本三個方向去考量。因此具備最輕重量級最大效率的永磁無刷馬達為現今電動車驅動系統的主流。鑒於考量未來永磁材料稀土金屬的成本，不需要稀土金屬的磁阻馬達成為值得探討的裝置。 開關磁阻馬達因為其簡單的結構、強健性及容錯能力、極高速運轉、高功率密度和低製造成本等優點逐漸在電動車及混合動力車應用上獲得關注。然而對於車輛應用上，開關磁阻馬達的缺點為噪音、振動及轉矩漣波的產生。根據相關文獻，噪音及振動主要來源為徑向馬達運轉時所產生之徑向力及軸向馬達運轉時所產生之軸向力。定子和轉子特殊的凸極結構及非線性電感曲線導致轉矩漣波過大。本研究建立馬達電腦輔助設計流程。藉由推導馬達輸出方程式及可行性三角法決定馬達尺寸大小，再以開關磁阻馬達中對正與不對正位置下的氣隙磁導之解析解，搭配等效磁路分析求解對正與不動置位置下的磁交鏈曲線，再者以最大磁共能變化率得到最佳激磁電流與繞阻匝數之乘積，最後以有限元素法驗證馬達其他相關性能。 本研究亦提出一新型混合開關磁阻馬達同時具備軸向和徑向氣隙，使其磁通方向達成軸向和徑向兩種方向，目的是為了增加輸出轉矩及減少振動和噪音問題。其新型開關磁阻馬達轉子同時具備軸向和徑向轉子磁極，使其徑向力及軸向力降低，進而抑制振動及噪音產生。而其新型開關磁阻馬達定子是由數個C型獨立鐵芯所組成，使其具有繞線簡易，製作成本低，槽空間大及散熱佳等特點。本研究運用所建立的設計流程，設計並實作，最後與傳統開關磁阻馬達做比較。

Designing in-wheel motors for electric vehicles and hybrid electric vehicles has already attracted attention in recent years. The choice of motors for both electric vehicles and hybrids is generally determined by three factors: weight, efficiency and cost. Hence, the permanent magnet brushless motors that have the lightest weight and maximum efficiency are becoming the mainstream of electric vehicle drive systems nowadays. However, based on the cost of rare earth metals of the permanent magnet consideration in the future, reluctance motors without using rare earth metals have become interesting research topics. Switched reluctance motor (SRM) is gaining widespread interest as a candidate for electric and hybrid electric vehicle due to its simple structure, ruggedness, ability of fault-tolerance, extremely high-speed operation, high power density and low manufacturing cost. However, for vehicle applications, the disadvantages of SRM are the generation of acoustic, vibration and torque ripple. According to the literatures, the dominant source of acoustic noise and vibration are radial force produced by radial motor and axial force produced by axial motor. The unique salient pole structure of stator and rotor and nonlinear inductance contributes the higher torque ripple. This study establishes the computer-aided design process of SRM. By deriving the motor output equation and feasible triangle method, the size of SRM can be roughly decided. Then according to the analytical results of air gap permeance at aligned and unaligned position with equivalent magnetic analysis where the flux linkage curves at aligned and unaligned position can be obtained from. Furthermore, by finding out the product of current and turns which produces the maximum variation of co-energy determine the optimum current and turns. Finally, use the finite element method to verify the performance of motors. This study also proposed a novel SRM with axial and radial air gap to make the flux flow have both radial and axial directions. The motor is hence called hybrid flux SRM. The purpose is to increase the output torque and reduced acoustic and vibration problem. The rotor of HSRM is composed of radial and axial rotor pole to lower the radial and axial force for reducing acoustic noise and vibration. The stator of HSRM is constructed by several independent C-core stators. The features of this C-cores are wound individually and automatically without complex and expensive winding equipment, low production cost, more space of motor slot and better thermal dissipation. Based on the design process which has been already established, the HSRM is designed and implemented in this study. Finally, the performance of HSRM is compared with the traditional SRM and other motors.