【作者】 范国栋；

【导师】 朱常青；

【作者基本信息】 山东大学 ， 电机与电器， 2013， 硕士

【摘要】 稀土永磁电机由于其效率高、转矩质量比高、功率密度大、控制性能好,且结构简单、运行可靠,因此获得了越来越广泛的应用。但是永磁体磁场波动和退磁与电机内电流、温升以及功角相互影响,导致电机发热和转矩性能变差,严重情况下电机可能报废,限制了永磁电机的应用范围。这也使得永磁体退磁分析正逐步成为人们所关注的科研方向及研究课题。本文围绕永磁电机的异步起动及稳态运行两种工况,对永磁体的退磁分析方法、退磁风险预估以及局部退磁现象展开研究,主要内容有以下几个方面：(1)从永磁材料退磁机理出发,对永磁材料的特性与性质做了较为详尽的描述。结合电流、温升、损耗与永磁体退磁的相互影响关系,分析了电机内永磁体的退磁方式与主要退磁原因。(2)基于电机气隙内磁动势的基波分布,分析了定、转子合成磁动势对于永磁磁场的增磁以及去磁作用。使用路与场两种方法搭建了自起动永磁同步电动机模型,通过综合对比两者的仿真计算结果,分析了转子鼠笼导条磁动势对于定子绕组磁动势的互补屏蔽作用,同时分析了不同负载条件下定转子合成磁场与永磁磁场的夹角和夹角余弦变化情况。(3)常温时,通过施加不同负载以及参数化设置不同转子起动位置,对白起动永磁同步电动机在起动过程中的退磁规律进行了归纳、分析与总结。(4)在额定工作温度时,通过电磁转矩-功角特性以及突加不同重载,对永磁同步电机稳态运行以及稳态运行失步时的退磁情况进行了分析。(5)基于本文中起动与稳态运行中的两个最恶劣工况,结合电机内温升所导致钕铁硼永磁材料的退磁拐点的改变情况,建立了在产生局部退磁后的永磁体模型。根据该模型,对比分析了退磁前后电机内电磁参量值以及电机性能的变化情况,进一步分析了退磁恶化的趋势。更多还原

【Abstract】 Rare earth permanent magnet electrical machines are widely used because of the high efficiency, big torque-quality ratio, large power density and good control performance; moreover, they also have outstanding advantages of simple structure and reliable operation. However, motor heating and bad torque property are caused by filed fluctuation and demagnetization of the permanent magnet and the mutual interaction of current, temperature rise and power angle, motors could be scrapped under serious circumstances, which significantly restrict further application of permanent magnet machines. Therefore, the demagnetization analysis of permanent magnet machine becomes a widespread concern of scientific study area and research subjects.This thesis is primarily concerned the method of demagnetization analysis, risk estimation and partial phenomenon of demagnetization, under asynchronous starting operation and steady-state operation these two working condition, the main contents are as follows:(1) From the demagnetization principle of permanent magnet material, the properties and characteristics are thoroughly described. Combining with the mutual interaction of current, temperature rise, losses and demagnetization, the methods and main reasons of demagnetization of permanent magnet in the machine are discussed.(2) Based on the fundamental harmonic distribution of MMF in the air gap, the increasing magnetization effect and demagnetization effect on permanent magnet field produced by the synthesis MMF of stator and rotor. The model of self-starting synchronous motors are modeled by the methods of circus and filed. By comparing two simulating calculation results, complementary and shielded effects on the stator winding MMF caused by the MMF in squirrel-cage conductor of the rotor are analyzed, at the same time, the changes of the angle between the stator and rotor synthesis field and the permanent magnet field and its cosine value under different loading circumstances are discussed, too.(3) Under normal temperature, by exerting different loadings and giving parameterized different rotor starting positions, the demagnetization principles of the self-starting synchronous permanent magnet machine in the starting operation are generalized, analyzed and summarized.(4) Under rated operation temperature, by the electromagnetic torque and power factor angle characteristic and giving different sudden overloads, the demagnetization conditions in steady state operation and out-of-step operation are analyzed.(5) Based on the two most serious working conditions in starting and steady state operations, combing with the changes of demagnetization inflection point of the NdFeB permanent magnet material caused by temperature rises in the motor, the magnet model, which under the situation that the partial demagnetization area has been produced, is created. According to this model, by comparing the conditions before and after demagnetization, the changes of electromagnetic parameters and properties of the machine are analyzed; tendency of the demagnetization deterioration is under further investigation.更多还原