【作者】 王骞；

【导师】 邹继斌；

【作者基本信息】 哈尔滨工业大学 ， 电机与电器， 2011， 博士

【摘要】 与旋转电机构成的直线驱动装置相比,直线电机具有结构简单、控制精度高、不受离心力作用等优点,但输出力密度低的不足限制了它在直线伺服系统中的应用。将横向磁场结构应用于直线电机构成横向磁场直线电机,能够提高电机的力能指标,对促进直线伺服系统的发展具有重要意义。本文以一种圆筒型横向磁场永磁直线电机(Permanent Magnet Linear Machine, PMLM)为研究对象,对该电机的电磁场计算、电感计算与相间磁耦合分析、电磁力计算与分析等问题进行了研究。针对传统结构的横向磁场电机,分析了其磁路结构和特点,基于永磁体面电流模型对电磁力产生机理进行了分析。分析结果表明,如果将定子绕组电流产生的磁场定义为气隙磁场、永磁体用等效面电流来表示,则仍可采用洛伦兹力定律对横向磁场电机的电磁力进行分析。在此基础上,提出了一种新型结构的圆筒型横向磁场PMLM,该电机的定子可采用叠片铁心结构,从而解决了传统横向磁场电机结构复杂、机械强度差等问题。根据电机的结构特点,在对电磁场计算模型进行简化的基础上,采用三维有限元法对圆筒型横向磁场PMLM内的电磁场进行了计算。研究了永磁体磁化方向长度和定子叠片单元轴向长度对电机相空载磁链的影响,指出电机相空载磁链随这两个尺寸的变化规律与传统永磁电机不同,并非是单调递增的,从而为电机结构参数的选择提供了参考。针对电机漏磁大的问题,对圆筒型横向磁场PMLM永磁体之间的漏磁进行了分析,通过在定子叠片单元之间嵌入辅助铁心,有效地抑制了轴向相邻永磁体之间的漏磁,并在此基础上分析了电机相空载磁链随辅助铁心轴向长度的变化规律。研究了边端效应对圆筒型横向磁场PMLM性能的影响,指出边端效应使圆筒型横向磁场PMLM的各相不对称,影响电机的平稳运行。针对电机行程短、运行速度不平稳导致反电势难以准确测量的问题,通过实时检测电机的速度和反电势信号并进行处理,实现了电机变速下的反电势的测量。针对圆筒型横向磁场PMLM样机绕组电感计算量大的问题,通过计算单元电机的绕组的总电感、端部漏感和定子叠片单元间的绕组漏感,并将它们进行合成,得到了圆筒型横向磁场PMLM样机的绕组电感,其结果与实验结果基本一致,从而验证了上述计算方法的正确性。在电感计算的基础上,对圆筒型横向磁场PMLM各相之间的磁耦合问题进行了分析,得出了“圆筒型横向磁场PMLM各相基本解耦”的结论,为简化电机的特性分析提供了依据。计算和分析了电枢电流对绕组电感的影响规律。计算结果表明,电枢电流对圆筒型横向磁场PMLM绕组电感的影响较大,它不仅影响电感的大小,而且对电感的波形也有较大的影响,主要表现为当电枢电流较小时,绕组电感随动子位移在一个电周期内呈现二次波动,而当电枢电流较大时,绕组电感在一个电周期内呈现一次波动。采用虚位移法对圆筒型横向磁场PMLM的定位力特性和基本电磁力特性进行了分析。针对三维有限元计算量大的缺点,提出了二维等效模型来计算电机的定位力,有效节约了计算时间,其结果与三维有限元计算结果的一致性验证了等效的有效性。在此基础上,对定位力的影响因素及抑制措施进行了研究,通过对电机结构参数进行合理地选取,有效地减小了电机的定位力。计算和分析了电机在不同通电方式下的基本电磁力特性,并研究了电机结构参数对基本电磁力的影响,为提高圆筒型横向磁场PMLM的电磁性能提供了指导。针对直线电机的特殊问题,研究了边端效应对电机电磁力的影响,指出边端效应使圆筒型横向磁场PMLM的电磁力发生较大的波动,影响电磁力的平稳性。样机定位力和基本电磁力的实验结果验证了上述计算和分析的正确性。更多还原

【Abstract】 Compared with linear drive systems constructed by rotating electrical machines, linear electrical machines have many favorable features, like simple structure, high control precision, no centrifugal forces, et al. However, the drawback of low force densities has limited their applications in high-performance linear servo systems. By applying the transverse flux configuration to linear machines, high force density can be achieved, which is of great significance to the development of linear systems. In this thesis, a novel tubular transverse flux Permanent Magnet Linear Machine (PMLM) is put into focus, and the problems of electromagnetic field computation, inductance computation, and electromagnetic force analysis have been studied.Aimed at traditional transverse flux machines, the magnetic circuit and its features are analyzed, and the operating principle is brought forward according to PM’s surface current model. The results show that if the field generated by armature currents is regarded as the air-gap magnetic field and the PM is represented by surface current, the electromagnetic force can also be analyzed with Lorentz Law. Based on them, a novel tubular transverse flux PMLM is proposed. By taking steel laminations, the proposed tubular transverse flux PMLM is easy to manufacture and thus can overcome the shortcomings of traditional transverse flux machines, like complex structure, weak construction, et al.According to the features of the machine structure, the computation model is simplified, and the electromagnetic field of the tubular transverse flux PMLM is computed by 3-D Finite Element Method (FEM). The influences of PM magnetization length and axial length of stator segment on no-load main flux linkage are then studied. The results show that the no-load main flux linkage does not increase all along with the increase of the two parameters. Aimed at the problem of large leakage flux, auxiliary cores are inserted between stator segments to eliminate the leakage flux between PM, and the influence of axial length of the auxiliary core on no-load main flux linkage is also computed. And then the edge effect is analyzed, and the result shows that the edge effect makes the three phases asymmetric and would have an impact on the steady operation of the machine. The back-EMF of the tubular transverse flux PMLM at variational speed is tested by detecting the real-time speed signal.Aimed at complex computation of the inductance of the prototype, by computing the total inductance of one element machine, end-winding inductance and the leakage inductance between stator segments and then combining them, the inductance of the prototype is obtained. The comparison of the experimental result and FEM result has confirmed the correctness of this method. Based on it, the problem of magnetic coupling between phases is analyzed, and the result shows that the three phases of the tubular transverse flux PMLM are basically decoupled, which provides formula for simplification of performance analysis. And then the influence of armature current to the winding inductance is studied. The results show that the armature current not only influences the numerical value of the inductance, but also the waveform, mainly embodying that the inductance varies two periods within an electrical cycle when the current is small and it varies one period when the current is large.With virtual work method, the cogging force and mutual force are theoretically analyzed. An equivalent 2-D model is proposed to compute the cogging force, and the comparison of the obtained results, via 2-D and 3-D FEM analysis, has proved the validity of the equivalence. Based on it, the influence factors of the cogging force are analyzed and the cogging force is reduced effectively. The mutual force characteristics are computed and analyzed at different operating modes, and the influences of parameters on the mutual forces are also studied. And then the influence of edge effect on the electromagnetic forces is analyzed. The results show that the edge effect causes the pulsation of the thrust force and thus make an impact on the calmness of the thrust force. The experimental results of cogging force and mutual force have proved the correctness of the computation and analysis above.更多还原