【作者】 杨通；

【导师】 周理兵；

【作者基本信息】 华中科技大学 ， 电机与电器， 2010， 博士

【摘要】 直线电机是一种将电能直接转换为直线运动形式机械能的电力传动装置,其中,直线感应电机具有结构简单、运行可靠等优点,因而在伺服系统、轨道交通车辆牵引、工业自动化设备、传送与搬运装置中应用前景广阔。由于短初级直线感应电机制造成本和运行费用低、能量消耗少,因此在目前的研究和应用中,绝大部分以该结构为主,而在长初级结构中,次级重量轻,并且在供电时无需移动电缆或集电装置,供电可靠性高,因而在数控机床、电磁弹射系统、冲撞试验平台等短时间歇运行场合具有更大的优势。本文以高速、大推力长初级双边直线感应电机为研究对象,通过电磁场分析,对其磁场分布、性能计算、电磁设计和控制方法进行理论研究与仿真计算,主要工作包括以下几个方面：建立并求解长初级直线感应电机考虑纵向动态端部效应时的一维电磁场方程,计算电机在恒流源供电时的气隙磁密和各种性能(如电磁推力、功率和次级涡流等),分析电机设计参数对端部效应特征参数、推力和推力因数的影响,通过气隙磁密相量图,重点研究纵向动态端部效应对推力特性的影响,并提出增加推力的措施。根据二维电磁场理论,计算不计纵向动态端部效应时次级和气隙中的磁场分布以及施加于次级的推力。根据一维电磁场求出的复功率与等效电路求出的复功率相等的关系,建立长初级直线感应电机的等效电路,其中,纵向和横向端部效应的影响通过对励磁电抗和次级电阻进行修正加以考虑,无次级覆盖的初级无效部分的影响(如绕组和铁心)也体现在等效电路中。对长初级直线感应电机的电磁设计方法进行研究,包括主要尺寸、电磁负荷、次级导电板的尺寸和气隙长度等主要设计参数的选取,初级绕组型式和槽形的确定,磁路、等效电路参数、损耗及性能的计算方法。根据设计流程,使用MATLAB软件编写电磁设计核算程序,程序可根据计及端部效应的等效电路,计算在电压源或电流源供电时电机在任何速度下的各项特性,并设计出应用于电磁弹射系统的两台额定推力分别为4kN和1.345MN的样机。建立计及端部效应影响时,长初级直线感应电机在任意转速q-d-0坐标系下的动态数学模型,根据弹射系统中对加速度、速度和位移的要求,分别对电机在全压起动、速度开环和闭环恒压频比控制、次级磁场定向控制时的各项机械特性和电气特性进行仿真研究。通过研究表明,端部效应使长初级直线感应电机的推力特性变软,额定运行时的速度和电机的最大推力减小,电机效率有所降低,但其影响要远小于对短初级结构的影响,在电机设计时可通过合理选取设计参数抑制端部效应,在应用时没有必要增设补偿装置。更多还原

【Abstract】 Linear motors (LMs) are the transmission devices that can convert electric power to mechanical work in the form of translational motion. Of the various types of LMs, the linear induction motors (LIMs) take the advantages of simple constructure and reliable operation, therefore, they are widely applied in servo drives, propulsion systems for ground transportation, industrial automation equipments and conveying and handling equipments, etc. To date, the extensive investigations and applications on the LIM have been mainly focused on the short primary LIM (SP-LIM) for its lower manufacturing and operating cost, as well as for the reduced energy consumption. However, although long primary LIM (LP-LIM) seems to be a costly choice as the primary windings need to be installed along the entire track, the weight of the conductive secondary can be significantly reduced, no sliding electric brushes or moving cables are required for power delivery and consequently, system reliability is greatly improved. These features make LP-LIM a prefer option in the applications with short-time or intermittent duty operation, such as numerical control machines, electromagnetic launching systems, impact extrusion test units, etc.The theoretical investigation and simulation analysis for the prediction of magnetic field distribution, performance calculation, electromagnetic design and control strategy of high-speed and high-thrust double-sided LP-LIM have been carried out by using the electromagnetic field technical theory. The research reported in this dissertation can be summarized as follows:The 1-d analytical governing field equations in the airgap region of LP-LIM, taking account of longitudinal dynamic end effect, are established and solved. Both the airgap magnetic flux density and the performances, such as thrust, active/reactive power, secondary eddy current, etc., under constant current excitation are formulated and validated against finite element calculations. The variations of motor design parameters on the end effect characteristic parameters as well as on the thrust and thrust ratio are analyzed. The influence of longitudinal dynamic end effect on the thrust-vs.-speed characteristics, with particular reference to the measures to improve the performances, based on the phasor diagram, is also investigated. The magnetic field distribution and thrust are also calculated in terms of quasi-2-d models, in which the short secondary is extended to infinity in the longitudinal direction.Since the complex power derived based on 1-d electromagnetic field is identical to that from the circuit, the influence of both longitudinal and transverse end effect can be explicitly taken into account in the equivalent circuit of LP-LIM as being the modified coefficients of the magnetizing reactance and the secondary resistance. In addition, the primary winding and iron core uncovered by the secondary are also represented in the equivalent circuit.The electromagnetic design procedure for LP-LIM is described. It involves selection of main dimensions, electromagnetic load, secondary specification and the airgap length, determination the primary windings and slots, arid calculation of magnetic circuit, equivalent circuit parameters, copper losses as well as associated performances. According to the flow chart, a design procedure, based on the MATLAB platform, is programmed to predict the overall characteristics of LP-LIM under either constant voltage excitation or constant current excitation. A 4kN and a 1.345MN prototype were designed specifically for electromagnetic launching applications, respectively.The dynamic model of LP-LIM, accounting for the end effect, is developed in arbitrary q-d-0 reference frame and validated by line starting simulation. To evaluate the dynamic response of variable-speed LP-LIM drive systems, the dynamic simulation with several types of control strategies, such as open-and close-loop constant volts/Hz control, secondary flux-oriented vector control, on the basis of the requirements to the fast tracking to the commanded acceleration, velocity and displacement, are implemented on the MATLAB/Simulink environment.The thrust-vs.-speed characteristics of LP-LIM show that the end effect will lead to wider statically stable speed range of operation and slightly lower breakdown thrust, the rated operating speed could be far away from the synchronous speed, thereby resulting in the higher secondary copper losses and hence lower efficiency compared to LIM with negligible end effect. In general, however, the influence of end effect on LP-LIM is much less than that on SP-LIM, therefore, to alleviate the end effect, it is preferable to select the proper motor design parameters rather than equip with additional compensation units.更多还原