“电机学”课程实践环节教学改革的探索

“电机学”是电气工程类专业的一门主要技术基础课,具有理论性强,与工程实际联系紧密的特点.以往,学生由于缺乏对电机结构的感生认识,工程意识差,在理论学习中颇感困难.为使电机学课程教学做到理论联系实际,除在课堂教学中运用电化教学手段和电机模型加强直观教学外,还应加强电机生产实习和电机教学实验等实践性环节教学,这对学生动手能力的培养,加深对电机理论的理解,增强工程意识均有着十分重要的作用.近几年来,我们在电机学课程实践环节教学中,对电机生产实习和电机学教学实验课进行了改革,培养了学生的工程能力,收到良好效果.现介绍如下.     

以学生为主的控制电机课程教学方法

针对控制电机课程综合性强、内容复杂、理论抽象、学生难懂的问题,开展了基于以学生为主的课堂和实验相结合的教学方法研究。在以学生为主的课堂教学方面采用以学生为主、教师为辅的教学形式,结合北航工科的特点,在强调基础理论教学的同时,突出各种控制电机在实际工程中的作用,增强学生对各种控制电机基本原理的理解;在实验教学方面,设计了基本类-综合类-创新类三个层次的课程实验,培养学生的动手能力、应用能力和创新能力。经研究和教学实践表明,基于以学生为主的课堂和实验相结合的教学方法可以有效地调动学生的学习积极性,增加学生对课程内容的理解,提高学生分析问题和解决问题的能力,取得了较好的教学效果。     

弯振模态板状直线超声电机的研究

通过改进直线超声电机的驱动足、夹持等结构形式,提高了电机的输出特性。设计了一款新型直线电机,电机由对称分布的板状振子和具有柔性的驱动足组成。通过ANSYS软件建立了电机有限元模型并分析电机工作模态,根据模态一致性原则设计电机尺寸;利用板状结构的弯振模态,降低了驱动频率,提高了输出效率;电机驱动足具有一定的柔性,在夹持组件作用下实现预压力的施加。最后对样机开展实验研究,结果表明,电机定子模态测试数据与仿真分析结论吻合,工作频率为27.5kHz,附近无干扰模态,相位差为90°,工作时发热较少;最大输出力为44N;双向驱动速度一致性良好,其中最大输出速度为267mm/s。     

电机模型的对称美学解读

针对“电机学”课程中涉及到的相关电机模型,本文尝试从对称美学的视角加以解读和阐述,以期丰富“电机学”课程的教学内容,为电机基础理论赋予美感,同时帮助学生进一步深刻地理解复杂难懂的电磁学知识。通过分析电机的物理模型、微分方程、结构框图和dq轴等效电路,论文指明了电机模型的物理意义,讨论了电机模型的对称美学特征,增添了电机模型的艺术气息。从对称美学视角的解读,通过不同层次的思考,同时给予学生科学理性的教导和人文素养的熏陶,能够激发学生在感性中接受电机模型、理解电机模型、掌握电机模型,提高“电机学”课程的教学质量。     

基于MAXWELL2D静磁场分析的特种电机教学

特种电机应用越来越广泛,已成为“电机学”教学的重要内容,其结构和磁场分布不同于传统同步电机,是“电机学”教学的难点之一。本文以永磁电机为例,探讨了MAXWELL2D建模实现电机旋转结构动画显示的方法,并利用MAXWELL2D对永磁电机进行静磁场有限元分析,直观呈现电机内磁场分布特点,便于学生理解和接受特种电机的结构和原理。本文方法对于其他特种电机的教学具有参考价值。     

永磁电机的研究现状与发展趋势

本文通过介绍永磁电机结构特点、工作原理及其优越性,讨论了其应用领域和应用前景,最后又给出了永磁电机推广所面临的问题,希望对未来永磁电机的发展有所帮助。     

Ansoft软件在电机教学中的应用

本文借助Ansoft软件工具对开关磁阻电机进行优化设计、静态矩角特性分析和电动运行分析,并在后处理中制作了瞬态磁场分布动画。通过使用静态分析和动态分析图形教学,便于学生理解电机的结构原理以及运行特性,提高学生的形象思维能力,从而提高教学效果。本文方法对于其他电机的教学具有很好的参考价值。     

关于讲解"无轴承电机径向悬浮力"

本文在回顾电机中的洛伦兹力和麦克斯韦力基础上,通过介绍无轴承电机基本结构,径向悬浮力产生机理和悬浮力系统的运动方程等来讲解无轴承电机的径向悬浮力,并且介绍了教学过程中的实践经验。通过采用本文的讲解方法,学生易于理解和掌握无轴承电机的结构和径向悬浮力产生原理。     

电机理论教学的探索与实践

分析了“电机学”课程的课堂教学现状,针对教学过程中存在的若干问题——电机理论内在联系不够紧密、结构淡化导致学生对理论理解下降、电机内部磁场描述过于抽象以及与后续相关专业课程缺乏联系等,阐述了抓住电机基本理论的内在联系、强化电机结构的理解、突出工程的分析方法、深刻理解磁动势的平衡以及注重与后续课程的联系等一系列想法和做法。通过近三年的教学实践,取得了良好的教学效粜。     

电机结构及故障演示软件系统研究

笔者结合电机学课程的特点,开发了一个电机结构及故障演示软件系统。该系统完成了动态图制作,对电机内部结构、大型发电机氢、油和水系统及电机常见典型故障用动态图进行演示,并结合仿真进行分析,使该教学软件具有理论与实践有机结合的特点。该系统实现了理论和实践结合,有助于提高学生工程实践能力,收到了较好的效果。     

Guest Editorial

The 51 papers in this special section on electrical machines have been divided into seven subtopics: theory, modeling, and simulation; design; losses, efficiency, mechanical and thermal analysis; diagnosis, fault detection, and monitoring; high-speed machines; linear machines; and electrical drives and control techniques. Most of the papers published in this special section come from the 2008 International Conference on Electrical Machines (ICEM), held in Vilamoura, Portugal.     

基于VB的电机旋转磁场模拟实现

旋转磁场是电机理论教学中的重要教学内容。通过分析三相交流电机内部磁场的实际运动情况,采用功能强、效率高的编程工具VisualBasic,结合多媒体技术,制作了一套完整的旋转磁场动态演示系统。文中介绍了演示系统的设计思路、软件结构以及实现方法。演示系统具有很好的交互性和生动性,能够形象直观地描述三相对称交流电流与三相交流电机内部旋转磁场的关系,展示出三相交流电机内部磁场的实际运动情况。     

Barking up the wrong (electric motor) tree

Even the best electrical engineers can make a mistake, and some of our Victorian forefathers wasted much time and energy in pursuing lines of research that ultimately came to a dead end. It was like that with some of the early attempts to make an electric motor based on magnetic machines rather than "electromagnetic" machines. The origin of the electric motor is usually traced back to the discovery by Oersted of the deflection of a compass by an electric current. Following that, Faraday produced continuous motion by electromagnetism in 1821. Probably Faraday never dreamed of producing power by electrical means, but other 19th-century researchers were trying to develop "electromagnetic engines" as a source of useful power. The American Joseph Henry (1797-1878) appreciated that electromagnetism might provide mechanical power. The article looks at Henry's engine and other early electric motor designs. In a commercial sense, all these machines were failures. Machine theory tells us that magnetic machines get better as they get smaller, while electromagnetic machines get better as they get larger. The future of electric power lay with electromagnetic machines.     

Technology trends in microcomputer control of electrical machines

A comprehensive review of technology trends in microcomputer control of electrical machines is presented. Although microcomputer control and computer-aided design techniques are the main themes of discussion, motion control as multidisciplinary technology has been reviewed in the broad perspective of electrical machines, power semiconductor devices, converter technology, microcomputers, and VLSI circuits. The concepts discussed are valid not only for small machines, but for large machines as well     

Electrical engineering education and certification, validation, and licensing

Evidence is accumulating that legislative actions will result in new requirements for practicing electrical engineers and electrical engineering educators. These requirements will include registraction and licensing as professional engineers for both groups as well as proof of up-to-date competence before relicensing. Such requirements will provide problems as well as opportunities for electrical engineering educators. The problems are associated with responding to the new require ments while retaining some degree of control over and responsibility for the educational programs. The opportunities are available because continuing education will play an important role in the relicensing of practitioners as well as their career development. This paper will dis cuss the many ramifications of the interface between government, the public, practicing electrical engineers and electrical engineering educators.     

Controlled AC Electrical Drives

The use of AC electrical machines in controlled electrical drive applications is reviewed. The major types of electrical machines are briefly summarized to set the context and establish the physical basis for the control techniques used. Machine properties, which are the key to successful control, can be obscured by the necessary mathematics required for machine analysis and control scheme derivations. The main focus of this paper is on control techniques which are being applied to make AC drives a rapidly growing area. Development of the control is discussed, with concentration on recent trends suitable for practical applications in the industry with good dynamic behavior. A particular feature is the increasing importance of speed or position sensorless techniques.     

“误差理论与数据处理”课程研究型教学探索

本文针对“误差理论与数据处理”课程的特点,开展研究型教学模式的探索。在教学过程中优化课程结构,采用专题授课的理论教学模式、课内与课外相结合的实践授课模式和优化整合等教学手段,帮助学生建立完善的课程知识体系,引导学生通过实践,提升主动探索能力。     

"电机现代控制技术"课程教学方式探索

为提高电机现代控制技术研究生课程的教学效果,本文探索了该课程的教学方式。针对教学中发现的问题,我们采取了理论教学与实验教学相结合的方法,提出了适合研究生教学的电机控制系统实验平台建设方案,注重了平台的通用性、开放性和先进性。而且还探讨了如何基于该实验平台改进教学方式,包括采用渐进式教学和引入教师科研项目等方法。从学生的反馈情况看,上述工作取得了积极效果。     

Axial flux machines drives: a new viable solution for electric cars

For electric car propulsion systems, the wheel motor is an application that requires the electrical machine has shape flexibility, compactness, robustness, high efficiency, and high torque. Axial flux machines are an interesting solution, where the motor is directly coupled to, or inside, the drive wheels. In this paper, axial flux induction and synchronous machines as wheel motor applications are presented and some considerations for each motor type are drawn by the authors. The structure with two rotors seems to be a very promising solution for both induction and synchronous machines. In the induction motor case, the two rotors can rotate at different speeds, thus the motor can act as a mechanical differential. The axial flux permanent magnet motor with two rotors is very compact and can be integrated inside the wheel     

"电力系统分析(暂态)"中同步发电机部分教案

“电力系统(暂态)分析”历来是电气专业比较难教难学的课程，其中同步发电机基本理论与三相短路分析部分则是该难课中的难关。加之目前专业课程学分课时缩减，如何在有限的课时内把重点、难点讲清，更增加了难度。这里将笔者教案要点和盘托出，以期抛砖引玉。由于篇幅限制，省略了许多解释、图表以及大家熟悉的公式等。