25kW磁鐵輔助式磁阻電機設計研究

Abstract

近年永磁同步電機因使用高性能的稀土磁石，而有高功率密度高效率等優點。然而稀土材料有三大不確定性，一則是近年環保意識抬頭，稀土磁石的開採提煉所造成的環境破壞受到世界各地環保團體的諸多反對；另一方面，佔世界稀土材料出口量90%以上的中國大陸，自2010年起逐年加重對稀土材料的出口總量限制，造成稀土磁石的單位價格不斷飊升，讓稀土磁石電機的整體成本大幅上升；最後是稀土磁石受到科技快速發展的刺激下，應用層面愈加廣泛，甚至在許多國家成為軍用管制輸出材料，使得取得稀土材料的取得越來越困難，不利高性能電機的發展。 本研究的目的在於設計避免使用稀土磁石材料的永磁同步電機，用以避免前述稀土材料的三大不確定性。鐵氧磁石是最普遍便宜的磁石材料，然而僅改變原稀土電機的磁石材料會讓原電機的性能低弱，為了改善這個情形，本研究採用多層磁極式的轉子材料，增加轉子的凸極比以增加磁阻力矩，同時增加磁極軸的磁阻以減緩對磁石抗退磁能力的需求。迴異於傳統多層磁極式電機，本研究轉子磁極使用雙平板V形磁極形狀，磁石使用平板的形狀能夠降低磁石加工成本，V形磁極為聚磁設計的表現，透過聚磁增加氣隙磁通進而增加磁鐵扭力。 另一方面，本研究在設計初期即對有限元素分析模型進行驗證，透過既有H公司之電機建模及分析比對實驗及分析結果，確認有限元素分析模型建立流程的正確性。 最後，由分析結果顯示，本研究之磁鐵輔助式磁阻電機能與原同功率稀土電機具有相近輸出性能，而無稀土材料的衍生問題，若能持續發展，相信將為取代稀土永磁電機的主要方案。

The objective of this work is to design a rare earth free permanent magnet machine for 25kW ferrite magnet machine. An important challenge of rare earth free machine is to overcome the defects of ferrite magnets, such as low coercive force and low residual flux density. As a result, the multi-layer rotor configuration with ferrite magnet was adopted to permanent magnet synchronous machine. Moreover, considering the output torque is predominantly the reluctance torque, the multi-layer rotor configuration with ferrite magnet PMSM is also called permanent magnet assisted synchronous reluctance machine (PMASynRM). Due to there are many finite element analysis (FEA) models use in development process, the FEA model verification was performed before the design process begin. The FEA model verification was performed by examine and analysis a well-known ISG which was constructed by H-company. Therefore by comparing the results data difference between test and analysis, we can ascertain the validity of FEA model creating process. This report presents a systematic exploration of the PMASynRM in FEA for the influence of rotor geometric design on the torque, speed, power stress, demagnetization, losses and efficiency properties. To be specific, this thesis proposed a design with permanent magnet being embedded in the double layer V-shape flux barrier compared to the original PMSM, which is a rare earth permanent magnet machine with same outer diameter and same electric power. The comparisons of the torque composition, terminal voltage at rated output, no-load back EMF, no load air gap flux density are given. The results of the machine performance comparisons are based on comprehensive use of finite element analysis tools (JMAG-Designer). From the FEA results, it shows that the PMASynRM with double layer V-shape configuration can have similar mechanical output performances. Although the overall volume and weight of PMASynRM is larger than original PMSM, it will still be a better candidate if the defects of rare earth material weighed.