一般三相感應馬達是利用切換式電力轉換器驅動，故電力轉換器之切換模態可直接影響感應馬達的轉動效能，包含：轉矩漣波(脈動轉矩)、功率損失、峰值電流與噪音等。因此，如何調整切換模態使得感應馬達的轉動效能達到最佳化，是一個重要的研究主題。
本論文係利用理想旋轉變壓器元件(IRTF: Ideal Rotating TransFormer)，建立新的感應馬達等效電路，並與傳統等效電路相比較後，得知兩電路相互等價。
本論文利用魚形法探討電力轉換器之切換模態，其中切換模態乃架構在簡單的感應馬達等效電路(AFM: Analytic Flux Model)上，將等效電路之定子交鏈磁通軌跡經由旋轉座標轉換後，可得到磁通魚，此“磁通魚”唯一對應“一組切換模態”。當磁通魚形框面積愈小時，感應馬達之轉矩漣波就愈小。
根據魚形法可設計新式切換模態：包含離線式同步切換模態與線上式非同步切換模態，以改善電流漣波與轉矩漣波，使感應馬達轉動達到最佳化。由於離線式同步切換模態為開迴路控制；然而線上式非同步切換模態為閉迴路控制，可以應付DC電壓 之變動，故比離線式同步切換模態優越。
本論文以軟體Simulink模擬新式切換模態，並與傳統SPWM切換模態相比較。在實作方面則擬以DSP微處理器設計控制器，實現上述兩種不同的新式切換模態，進而改善感應馬達的電流漣波與轉矩漣波，並與傳統SPWM切換模態實作比較。最後，根據模擬結果得以驗証理論的正確性。

In general, a three-phase induction motor (IM) is driven by a switching power converter. Then the performances of IM, including torque ripple, power loss, peak current and acoustic noise etc. are related directly to the switching pattern. Therefore, how to optimize the rotating performances of an IM by adjusting the switching pattern becomes an important issues.
In this thesis, a novel equivalent circuit of IM using the ideal rotating transformer (IRTF) is proposed. It is interesting to note that the novel equivalent circuit is identical to the traditional one after detailed analysis..
It is aimed to study the switching pattern of power converter by the fish method in this paper. On the basis of the analytic flux model (AMF), the switching pattern of the inverter is investigated. Then the flux fish, related to a unique switching pattern, can be obtained after a coordinate transformation of the stator flux. It is worthy to note that lower torque ripple of IM is concerned with a smaller, rectangular looking flux fish.
Based on the fish method, the novel switching patterns, including the off-line synchronous switching pattern and the on-line asynchronous switching pattern, are designed to reduce the current ripple and torque ripple. Then the optimal performances of IM can be obtained. Among them, the off-line synchronous switching pattern is related to the open-loop control. On the other hand, the on-line asynchronous switching pattern, regarding of the varying DC-link voltage , is related to closed-loop control.
The novel switching patterns and the traditional SPWM switching patterns are both simulated by Simulink. Some comparison results are shown for comparisons in the thesis. Moreover, it is desired to implement two types of the novel switching patterns to reduce the current ripple and torque ripple by a DSP microprocessor controller in the near future. In addition, the traditional SPWM switching patterns will also be implemented for comparison. Finally, the validation of the fish method will be successfully verified by simulation results.

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