复合转子异步起动永磁同步电动机永磁体退磁研究

发布时间：2018-03-31 18:53

本文选题：复合转子异步起动永磁同步电动机　切入点：退磁　出处：《山东大学》2017年硕士论文

【摘要】：复合转子异步起动永磁同步电动机兼有实心转子永磁同步电动机和笼型转子永磁同步电动机的优点,既有良好的起动性能,又有较高功率因数和效率。但作为永磁电机的一种,永磁材料的退磁问题也制约着它的应用,因此有必要研究其永磁体在各种工况下的退磁情况。本文以一台355kW、10kV、6极复合转子异步起动永磁同步电动机为例,建立了计及涡流、饱和等因素的有限元模型,分析电机在起动过程中、三相突然短路及突加负载时的退磁规律及原因,并分析了转子结构对起动过程中退磁的影响。简要介绍复合转子异步起动永磁同步电动机的基本结构与工作原理,并对此电机的磁动势进行求解,同时介绍了一种永磁体工作点的判断方法,定义了最小工作点、平均工作点、最大去磁工作点及最大去磁平均工作点等相关概念。对电机起动过程的分析,综合考虑转子初始位置、初始负载转矩与转动惯量的影响,发现永磁体的最小工作点与定转子合成磁动势位置有关。当永磁体磁场与定转子合成磁场的夹角为110°、240°左右时,永磁体局部退磁风险大;最大去磁工作点出现在低速,而非普通起动永磁同步电动机那样出现在接近同步速;永磁体靠近气隙侧的边角处局部退磁最严重。合成磁动势直轴分量能反映永磁体退磁磁场的强弱,负载越大,永磁体的最大去磁平均工作点越低,其对应的转速越接近同步速,整体出现退磁的概率越大。分析转子槽楔的材质、尺寸以及有无导条对永磁体工作点的影响,发现铜槽楔及铜导条的存在对永磁体起动了屏蔽保护作用,没有铜槽楔和铜导条时,永磁体的去磁点值减小,使可能局部退磁的时刻更加靠前。并且铜槽楔的尺寸越小,去磁点值越高,有利于降低永磁体退磁的风险,而铜导条还能提高电机的起动性能,减小退磁发生的概率。分析电机三相突然短路发现,永磁体的最小工作点与电枢磁动势轴直轴分量有关,平均工作点受合成磁动势直轴分量的影响。同时分析了短路时刻、初始负载转矩及初始转动惯量对永磁体工作点的影响,并研究了三相突然短路时永磁体去磁点的规律。经分析发现,三相突然短路时,但是不论是局部退磁还是整体退磁,退磁情况远没有起动过程中的严重。分析电机突加负载发现,突加负载造成电机失步时,永磁体工作点变化较大,易发生退磁。并分析了突加负载大小、突加负载时刻、初始负载转矩及初始转动惯量对永磁体工作点的影响,并研究了失步时永磁体去磁点的规律。分析发现,不论是局部退磁还是整体退磁,失步时的退磁情况远没有起动过程中的严重。
[Abstract]:The composite rotor asynchronous starting permanent magnet synchronous motor has the advantages of both solid rotor permanent magnet synchronous motor and cage rotor permanent magnet synchronous motor. It has good starting performance, high power factor and high efficiency. The demagnetization of permanent magnet material also restricts its application, so it is necessary to study the demagnetization of permanent magnet under various working conditions. Based on the finite element model of saturation and other factors, the demagnetization law and reason of three-phase sudden short circuit and sudden load are analyzed. The influence of rotor structure on demagnetization during starting is analyzed. The basic structure and working principle of permanent magnet synchronous motor (PMSM) with complex rotor asynchronous starting are briefly introduced, and the magnetodynamic potential of the motor is solved. At the same time, a method to judge the working point of permanent magnet is introduced, and the concepts of minimum working point, average working point, maximum demagnetization point and maximum demagnetizing average working point are defined, and the starting process of the motor is analyzed. Considering the influence of rotor initial position, initial load torque and moment of inertia, it is found that the minimum working point of permanent magnet is related to the position of stator / rotor synthetic magnetic force. When the angle between permanent magnet and stator / rotor magnetic field is about 110 掳or 240 掳, The local demagnetization risk of permanent magnet is high, the maximum demagnetization working point appears at low speed, but not in close to synchronous speed as the common starting permanent magnet synchronous motor. The local demagnetization is the most serious at the edge corner of the permanent magnet near the air gap side. The direct axis component of the synthetic magnetoEMF can reflect the demagnetization magnetic field of the permanent magnet. The larger the load, the lower the maximum demagnetization average working point of the permanent magnet, and the closer the corresponding rotational speed is to the synchronous speed. The larger the probability of demagnetization, the greater the probability of demagnetization. By analyzing the influence of the material and size of rotor wedge and the influence of guide bar on the working point of permanent magnet, it is found that the existence of copper slot wedge and copper guide bar can shield and protect the permanent magnet. When there is no copper wedge and copper guide bar, the demagnetization point value of the permanent magnet decreases, which makes the possible local demagnetization time more forward. And the smaller the size of the copper slot wedge, the higher the demagnetization point value, which is conducive to reducing the risk of demagnetization of the permanent magnet. The copper guide bar can also improve the starting performance of the motor and reduce the probability of demagnetization. By analyzing the three phase short circuit of the motor, it is found that the minimum operating point of the permanent magnet is related to the axial component of the axis of the armature magnetic motive force. The average operating point is affected by the direct axis component of the synthetic magnetic EMF, and the influence of the short-circuit moment, the initial load torque and the initial moment of inertia on the working point of the permanent magnet is analyzed. The law of demagnetization point of permanent magnet with three phase short circuit is studied. It is found that the demagnetization is not only local demagnetization but also global demagnetization when three phase short circuit occurs. The demagnetization situation is far less serious than in the starting process. It is found by analyzing the sudden adding load of the motor that the working point of the permanent magnet changes greatly and it is easy to demagnetize when the motor is out of step caused by the sudden addition of the load, and the size of the sudden addition load and the time of the sudden loading are analyzed. The influence of the initial load torque and the initial moment of inertia on the working point of the permanent magnet is studied. The law of demagnetizing point of the permanent magnet when it is out of step is studied. It is found that both local demagnetization and global demagnetization are obtained. The demagnetization situation is far less serious than that in the starting process.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM341

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