本文選題：復合轉子異步起動永磁同步電動機　切入點：退磁　出處：《山東大學》2017年碩士論文

【摘要】：復合轉子異步起動永磁同步電動機兼有實心轉子永磁同步電動機和籠型轉子永磁同步電動機的優(yōu)點,既有良好的起動性能,又有較高功率因數和效率。但作為永磁電機的一種,永磁材料的退磁問題也制約著它的應用,因此有必要研究其永磁體在各種工況下的退磁情況。本文以一臺355kW、10kV、6極復合轉子異步起動永磁同步電動機為例,建立了計及渦流、飽和等因素的有限元模型,分析電機在起動過程中、三相突然短路及突加負載時的退磁規(guī)律及原因,并分析了轉子結構對起動過程中退磁的影響。簡要介紹復合轉子異步起動永磁同步電動機的基本結構與工作原理,并對此電機的磁動勢進行求解,同時介紹了一種永磁體工作點的判斷方法,定義了最小工作點、平均工作點、最大去磁工作點及最大去磁平均工作點等相關概念。對電機起動過程的分析,綜合考慮轉子初始位置、初始負載轉矩與轉動慣量的影響,發(fā)現永磁體的最小工作點與定轉子合成磁動勢位置有關。當永磁體磁場與定轉子合成磁場的夾角為110°、240°左右時,永磁體局部退磁風險大;最大去磁工作點出現在低速,而非普通起動永磁同步電動機那樣出現在接近同步速;永磁體靠近氣隙側的邊角處局部退磁最嚴重。合成磁動勢直軸分量能反映永磁體退磁磁場的強弱,負載越大,永磁體的最大去磁平均工作點越低,其對應的轉速越接近同步速,整體出現退磁的概率越大。分析轉子槽楔的材質、尺寸以及有無導條對永磁體工作點的影響,發(fā)現銅槽楔及銅導條的存在對永磁體起動了屏蔽保護作用,沒有銅槽楔和銅導條時,永磁體的去磁點值減小,使可能局部退磁的時刻更加靠前。并且銅槽楔的尺寸越小,去磁點值越高,有利于降低永磁體退磁的風險,而銅導條還能提高電機的起動性能,減小退磁發(fā)生的概率。分析電機三相突然短路發(fā)現,永磁體的最小工作點與電樞磁動勢軸直軸分量有關,平均工作點受合成磁動勢直軸分量的影響。同時分析了短路時刻、初始負載轉矩及初始轉動慣量對永磁體工作點的影響,并研究了三相突然短路時永磁體去磁點的規(guī)律。經分析發(fā)現,三相突然短路時,但是不論是局部退磁還是整體退磁,退磁情況遠沒有起動過程中的嚴重。分析電機突加負載發(fā)現,突加負載造成電機失步時,永磁體工作點變化較大,易發(fā)生退磁。并分析了突加負載大小、突加負載時刻、初始負載轉矩及初始轉動慣量對永磁體工作點的影響,并研究了失步時永磁體去磁點的規(guī)律。分析發(fā)現,不論是局部退磁還是整體退磁,失步時的退磁情況遠沒有起動過程中的嚴重。
[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 擄or 240 擄, 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.
【學位授予單位】：山東大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM341

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