應用修正愛普斯坦方框法測試之感應電動機鐵損研究

STUDY OF CORE LOSSES OF INDUCTION MACHINES BASED ON REVISED EPSTEIN FRAME TEST METHOD

蘇韋銘(Wei-Ming Su)

指導教授 ： 王培仁

國立清華大學/工學院/動力機械工程學系/博士(2019年)

摘要

隨著能源效率規範提升與電腦輔助工程分析技術的進步，準確估算電機運轉時損失已成為學術研究的重要方向。現今電磁鋼片的損失量測方法已無法針對電機之旋轉磁化特性，提供更精確得損失物理模式，造成電機設計時估算鐵芯損失誤差過大，必須仰賴經驗公式來修正設計之基本參數。本論文的研究目的在於根據愛普斯坦方框測試法研究提升感應電機鐵損計算準確度，先對量測方法之誤差來源進行分析，輔以電腦輔助工程分析軟體之分析結果，更新鐵芯樣品之設計尺寸。論文中採用商用有限元素電磁場分析軟進行電磁場的靜與動態分析，分離出標準樣品之角落雜散損失，修正量測之各種規格電磁鋼之鐵損數據。
對於感應電機而言，磁路複雜之定子轉子鐵損不易計算。本論文以一標準四極5馬力感應馬達為參考樣本，進行三種規格電磁鋼之實驗雛型製作，再進行損失效率量測。實驗數據證明經過修正後之數據建立之鐵損模式，於電腦輔助工程分析後預測之鐵損值無差減低至2%。證明若根據修正方框樣品量測之鐵損將更準確預測感應馬達之運轉時鐵損。
根據電腦輔助電磁場暫態分析結果觀察，感應馬達的定子齒部及齒根部均工作於近磁飽和狀態，因交變和旋轉磁通向量間之互擾產生高階雜散損，若以磁通密度描繪之橢圓度判斷高階雜散損，佐以實驗數據可進行雜散損驗證。經實驗驗證後，本論文提出以氣隙磁阻置入磁路方式進行修正定子齒根處磁通飽和度，先以電腦輔助工程分析結果證明確可減低高階雜散損，更因電裝載之效率提升導致感應馬達之整體能效提高，達成不改變電磁鋼規格而提高馬達能效之設計目的，實驗結果證明雛型馬達於改善後整體效率可提升1.8 %。

關鍵字

愛普斯坦方框量測法 ； 鐵芯損失 ； 雜散損失 ； 感應電機

並列摘要

With the development of frequency conversion technology and computer-aided computing software, accurate prediction of motor losses has become the focus of academic research in electrical engineering. Today, the standard test of electrical steel in core losses cannot fulfill the design requirements due to the rotational magnetization in electrical machines. The uncertainty in design calculations has driven the design methodology to rely on empirical design rules. The objective of this dissertation is based on improved Epstein frame test method so that the accuracy of core losses calculations in induction machines can be increased. Hereby, both computational and experimental methods have been adopted for correlating core losses in terms of various sources. According to the simulation results, excess losses of the Epstein Frame has been observed at the four frame corners. The excess losses could be deducted from the main losses by comparing the electromagnetic field density maps between the standard Epstein frame and the revised Epstein frame. By utilizing the methodology on various grades of electrical steel, systematic model parameters can be obtained.
In induction machines, magnetization characteristics of magnetic cores are different from the standard frame test. To confirm the accuracy of the core losses via experiments, three prototypes of 5HP-4poles induction machines made of three grades of electrical steel have been built. With the core losses parameters given by revised Epstein frame, a commercial CAE program predicts the core losses of the machines for experimental verifications. The simulation results agree to the experimental ones in 2 % to conclude that the revised Epstein frame is more accurate than the standard Epstein frame in the prediction of core losses of induction machines.
Furthermore, the CAE transient simulation results have shown that it is often for tooth and tooth root in stator to operate at magnetic saturation condition. Whereas, the coupling interferences between alternating and rotating flux generate high-order extra losses. It would be heuristically to examine the degree of ellipticity in flux density loci on the points of interest to determine if the core area exhibits high-order excess losses. In practical consideration, the adding of an air-gap reluctance in the outside edge of stator would reduce the degree of saturation at the tooth root to reduce the high-order extra losses of the machine. To be more precise in conclusion, the simulation results show the remedy not only reduce the high order excess losses but also lower the input power to the machine with contribution in enhancing energy efficiency. The air-gap reluctance insertion would account 1.8 % of energy efficiency in improvement of the original machine without upgrading grade of the electrical steel.

並列關鍵字

Epstein test method ； iron core loss ； High-order excess loss ； Induction machines

參考文獻

BIBLIOGRAPHY

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