本文旨在研製小型電動載具用之六相永磁式同步電動機設計及控制。配合直驅式的輪內電動機選用外轉型36槽38極的結構，針對磁路分析做電動機的幾何結構及尺寸最佳化設計，可減少感應電動勢的諧波失真及提高運轉效率。本文以有限元素分析軟體(Ansoft Maxwell_2D)之分析結果，作為實作之依據，其實測與分析結果相符合。在額定轉速為250 rpm、額定功率為500 W下，感應電動勢相電壓峰值為41.3 V，總諧波失真率為2.09 %，每相之電阻值為0.797 Ω，交軸電感為4.9 mH，直軸電感為3.5 mH。
六相永磁式同步電動機之控制，首先依據兩組霍爾磁極偵測元件判斷出感應電動勢之磁極角位置狀態，再依各個狀態切換功率電晶體驅動電動機。六相控制策略可視為兩組三相系統獨立控制，電動機其中一組系統故障，可由另一組載獨立運轉，提升了小型電動載具之驅動系統可靠度。本文以微控制器為核心，完成實體製作，實測結果驗證控制策略。電動機實際轉速於250 rpm，負載為300 W，六相正常驅動下其相電流峰值為3.1 A；若電動機一組故障由另一組獨立運轉，相電流則為6.1 A，驗證了單組系統獨立運作之可行性。最後負載為500 W，六相正常驅動下其相電流響應峰值為5.6 A，完成本文500 W六相永磁式同步電動機驅動。

This paper focuses on developing the design and control of a six-phase permanent-magnet synchronous motor which can be applied to small electric vehicles. An optimal design of the geometric structure and size of the motor, which is a direct-drive in-wheel motor with an out-runner structure of thirty-six slots and thirty-eight poles, has been accomplished by analyzing the magnetic circuit. By doing so, not only harmonic distortion of the induced electromotive force can be reduced, but also the efficiency can be increased. The simulation is done with Ansoft Maxwell_2D and the experiment is conducted based on the simulation results obtained. Clearly, the experimental results match with the analysis. The rated rotational speed is 250rpm and the rated power is 500 W. The peak value of the induced electromotive force is 41.3 V and the total harmonic distortion is 2.09 %. The resistance of each phase is 0.797 Ω. The quadrature-axis inductance is 4.9 mH. The direct-axis inductance is 3.5 mH.
The control strategy of the six-phase permanent-magnet synchronous motor is as follows: The status of angular positions of the induced electromotive force is detected by two Hall effect sensors. IGBTs are switched on and off according to corresponding statuses to drive the motor. The six-phase control strategy can be considered as two three-phase systems controlled independently. If one of the systems fails, the other one will be able to operate independently. This control strategy increases the reliability of drive systems of small electric vehicles. A microprocessor is used as a primary device to help accomplish the performance of the motor. Moreover, the experimental results have validated the feasibility of this control strategy. The peak value of the phase current of the two three-phase motor is 3.1 A when the actual rotational speed of the motor is at 250 rpm, with the load of 500 W, and six-phase motor drive is operating normally. Assuming one of the two three-phase motor systems fails, the phase current of the normal system is 6.1 A. The results above have proved the feasibility of a single three- phase system which can be operated independently. In addition, with a load of 500 W, the phase currents of the two three-phase motor are both 5.6 A while the six-phase motor driver is operating normally. Therefore, the 500 W six-phase permanent-magnet synchronous motor presented in this thesis is completed and driven successfully.

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