【作者】 陈益广；

【导师】 唐任远；

【作者基本信息】 沈阳工业大学 ， 电机与电器， 2008， 博士

【摘要】 论文对永磁同步电机各种弱磁调速方法进行了深入分析研究,认识到V.Ostovic所提出的三明治式转子结构可控磁通电机——记忆电机的不足之处,提出了3种适用于不同极数的内置混合式转子结构可控磁通永磁同步电机。新结构电机充分利用钕铁硼永磁体剩磁密度B_r和矫顽力H_c都很高,而铝镍钴永磁体B_r很高而H_c很低的特点,在转子内同时放置两种永磁体,科学分配两者的尺寸,使两者在磁性能上合理配合,在保障电机各项基本性能的前提下,实现宽范围弱磁调速。电机运行时,通过闭环工作的调速控制系统在定子绕组上施加方向和幅值均受控的直轴电流矢量i_d脉冲,改变铝镍钴磁化方向和剩磁强弱。正向强磁化后,两种永磁体磁化方向一致,虽然铝镍钴对气隙永磁磁通贡献不大,却将钕铁硼贡献的磁通推向定子,气隙永磁磁通最强;两者磁化方向相反时,铝镍钴将钕铁硼产生的磁通在转子内部分旁路,气隙永磁磁通被削弱,被削弱的大小是可以控制的。每次重新磁化后永磁磁场能够保持住,而称为记忆电机。研制了模拟内置混合式转子结构可控磁通永磁同步电机工作机理的静止磁路装置。经过试验分析,认知了该电机磁通可控的原理,从而了解在控制转子永磁磁通的过程中钕铁硼和铝镍钴两种永磁体的磁化过程和磁化后工作点的变化规律;为了进一步加深分析和理解,同时给出了相应的等效磁路图。利用有限元法对3种电机进行了磁场分析和计算,给出在不同工况下电机内部磁场分布情况和气隙磁场波形,并对负载电流产生的交轴电枢反应磁动势对直轴永磁磁场的影响做了分析。计算结果表明,增大交轴磁路磁阻,既能减小交轴电感,降低交轴电抗压降,提高逆变器电压利用率,还能减小负载电流对直轴永磁磁通量的影响,有效提高电机弱磁及调速范围。给出了转子内永磁体尺寸选取一般原则。合理选择钕铁硼的宽度,使其尽可能多地贡献磁通量,气隙永磁主磁通主要由其产生;选择其厚度,除主要防止在极端情况下定子绕组产生的去磁磁动势造成不可逆的去磁外,还应该顾及永磁体成本、材料利用率和加工工艺性。合理选择铝镍钴宽度,可有效地调整可控磁通量大小,以调整弱磁倍数,其宽度为钕铁硼的0.5～0.7倍时,弱磁倍数就可以达3倍以上;选择其厚度,保证其与钕铁硼被i_d脉冲同向强磁化后,不应被钕铁硼再反向去磁而重新反向磁化,其总磁动势源比它为外部一对磁极磁路提供的磁动势高20～30%即可。编制出4极内置混合式转子磁路可控磁通永磁同步电机电磁计算设计程序,给出了算例,制做了样机,实验结果基本满足要求。更多还原

【Abstract】 In this dissertation,diverse field-weakening methods are researched and analyzed in detail.Based on the deficiencies of composite-rotor controllable-flux PMSMs with sandwich structure proposed by Vlado Ostovic,three types of magnetic circuit structure of interior composite-rotor controllable-flux with different poles are proposed.Two kinds of PMs,NdFeB and AlNiCo,are fully used in the new structure motor.Their features,that NbFeB PM has high remanent flux density B_r as well as high coercive force H_c,and AlNiCo PM has high B_r but low H_c,are especially taken into account.These PMs are fitly placed in the rotor spaces,and their sizes are decided appropriately to make them work well together.With the proposed structure,the speed of PMSMs can be controlled by a field-weakening regime in significantly wide range without losing any basic performance of the motor.In the operating mode,if the controllable direct axis current vector pulses on stator windings are changed by the speed regulation driving system with close-loop structure,the magnetization direction and the retentiveness intensity of AlNiCo PMs are changed consequently.As the magnetization directions of both PMs are uniform,AlNiCo PMs will push the magnetic flux of NdFeB PMs to stator side,and the air-gap magnetic flux becomes strongest although AlNiCo PMs contributes little to it.As the magnetization directions of PMs are opposite,the air-gap magnetic flux is weakened because part flux of NdFeB PMs is bypassed by AlNiCo PMs.The proposed motor structures are named memory motors for their ability to preserve the controllable flux in rotor magnets.A static magnetic circuit device was designed to simulate the mechanism of controllable-flux PMSM.Related experiments revealed the principle of the interior composite-rotor controllable-flux PMSM.Consequently,the law of two kinds of PMs’ action spot change during and after magnetization were cognized in the process of controlling rotor-flux.For more awareness and understanding of the magnetization,the equivalent magnetic circuits of different action spots were present. Finite-element method was adopted to analyze and calculate the magnetic field of 3 kinds of interior composite-rotor controllable-flux PMSM,and the internal magnetic field distribution and air-gap magnetic field waveforms in different work conditions are shown, and the impact on the d-axis PM-flux created by load current was analyzed.The increment of q-axis magnetic reluctance in interior composite-rotor controllable-flux PMSM can not only reduce the q-axis induction,decrease the quadrature axis inductive drop,raise the utilization ratio of input voltage from inverter,but also reduce the impact of q-axis armature-reaction magneto-motive potential generated by load current on d-axis PM flux, expend PM-flux weakening range and speed scope.The general principle of the rotor PM size selection was given.Reasonable choosing the NdFeB PM width make the NdFeB PMs contribute to PMs main air-gap flux as much as possible.In order to avoid the extreme cases that the NdFeB PMs is irreversibly degaussed by the demagnetizing magnetomotive force generated by the stator windings armature reaction,the NdFeB PM thickness should be decided reasonably.In addition,the cost of NdFeB PM,the utilization ratio of material and the processing technology also should be taken into account.By selecting AlNiCo PM reasonable width,the size of the controllable flux can be effectively adjusted,and then the field-weakening multiples are regulated.For example,when the AlNiCo PM length is equal to 0.5～0.7 times of NdFeB length,the field-weakening multiples can reach more than three times.Selecting magnetization direction length of AlNiCo PMs could follow two principles.One is that after the AlNiCo and NdFeB magnetized by the i_d pulse,the AlNiCo must not be demagnetized or remagnetized reversely by the NdFeB;the other one is that the total magnetomotive force source of AlNiCo is higher from 20%to 30%than the magnetomotive force for the external magnetic circuit.As an example,electromagnetic computing program for 4-pole interior composite-rotor controllable-flux PMSM was developed and a prototype was made.The experimental results coincide with expectation.更多还原