NUMERICAL MAGNETIC FIELD ANALYSIS AND CHARACTERISTICS OF AN INDUCTION MOTOR

• Main Authors: HONG, CHAIN-GEE, 洪振基
• Other Authors: HUANG, GUANG-JYH
• Format: Others
• Language: zh-TW
• Published: 1990
• Online Access: http://ndltd.ncl.edu.tw/handle/51197214575229970504

博士 === 國立清華大學 === 動力機械研究所 === 79 === This dissertation gives numerical analyses of magnetic field distributions (1) in air gaps with the effects of slot depth, slot width,air gap curvature and armature reaction, and (2) in a squirrel cage induction motor. In the first part of this dissertation, the Carter coefficient and average reluctance with the effect of armature reaction are studied on a simplified model, and a dimensionless parametric approach is utilized to cover wide ranges of parameters that frequently appear in electric machine design. A nonlinear dimensionless Maxwell equation is solved by using a finite-difference successive relaxation technique. In the region of study, various constant fluxes and load currents are applied. The Carter coefficient in a straight or a curved air gap and the coefficient of average reluctance with the effect of armature reaction are calculated and compared with the data in the existing literature. In the second part, the application of the finite-element method for predicting the performance of a squirrel cage induction motor is described. The field region is discretized into triangular elements and the Galerkin approach is employed to solve a nonlinear Maxwell equation. In teh analysis, core saturation and the induced rotor bar currents are considered. Based on the obtained field solution, the induced back voltage and inner impedance in the equivalent circuit are obtained, the stator current is then determined iterately by using a fixed phase voltage and an external and an inner impedances. The characteristics studied are (1) the magnetizing inductances, the slot leakage inductances, the iron core losses and power factors in the wide ranges of magnetizing currents and the four rotor positions (2) slip performance of stator current, sorque and power factor with various applied voltages. Finally, a 1 hp squirrel-cage motor is tested to verify the calculated results. 本文利用數值法來分析⑴氣隙中具有槽深、槽寬、氣隙曲率與電樞效應的及⑵一鼠籠 式感應馬達內的磁場分佈。在第一部份中採用無因次參數法並以涵蓋常見於電機設計 之廣泛無因次之參數範圍來探討。文中以有限差分連續鬆弛法來解非線性之馬克斯威 爾方程式。在研究區域中加入不同之定磁通密度、槽電流密及變化槽曲率半徑或槽數 來計算氣隙之平均磁阻並與現存文獻之卡特係數相比，結果尚屬合理。 第二部份中，吾人採用有限單元法（Galerkin approach） 來預測感應馬達的性能。 在分析中，鐵心的飽和及轉子棒的感應電流都必須考慮，根據所得的磁場分佈，吾人 可計算等效電路中的內感應電壓及內阻抗，而定子上的電流便可由固定的外加相電壓 與總阻抗重複計算求得。所探討的性能有⑴在無轉子棒情況下，磁飽和度及不同轉子 位置對磁化電感、槽漏電感、鐵損及功因的影，⑵不同外加電壓下，馬達的定子電流 、轉矩及功因的轉差特性。最後吾人用一具20KVA 的變壓器來測試一大同的1hp 感應 馬達，以證實上述⑴⑵所得之計算值。