Optimal Design of Coreless Axial Flux Permanent Magnet Synchronous Generator with Reduced Cost Considering Improved PM Leakage Flux Model

This paper presents an optimal design of coreless axial flux permanent magnet (AFPM) synchronous generator using particle swarm optimization method based on sizing equations of the machine. The design optimization is performed in order to reduce the active material cost of the generator. General practical and mechanical limitations are considered as optimization constraints. A magnetic circuit model based on quasi three-dimensional (3-D) model of the coreless AFPM machine is taken into account to calculate the permanent magnet leakage flux (PMLF) accuracy. A computer-aided program is evaluated according to the proposed optimized design procedure that is used to design a 2-kW, 16-pole AFPM generator with two rotors and one coreless stator. Finally, the 3-D finite-element model (FEM) of the machine is prepared to confirm the validity of the proposed PMLF model and proposed optimized design algorithm.     

12/3相双绕组异步发电机定子谐波漏感的计算

为计算12/3相双绕组异步发电机多达上百的相间谐波漏感，在两线圈间谐波电感的求取和绕组与线圈连接关系确定方面采用了新的分析方法。以单一线圈而不以一相绕组为基础，通过总电感减去基波电感的方法计算两线圈间的谐波电感，并在区分控制绕组和功率绕组情况下给出了异步发电机任意2个定子槽中线圈间谐波电感值。仿照图论结合回路电流法分析电路网络的过程，列写了表示线圈支路电流与一相绕组回路电流间的关联矩阵，用规范统一的编程方法计算各相绕组间的谐波漏感，并对其中几个电感值进行了定性分析。所用分析方法通用性强，对绕组连接复杂多相异步电机定子谐波漏感参数计算优势明显。     

定子无铁心轴向磁场永磁轮毂电机损耗分析及效率优化

减速装置的引入使得轮毂电机分布式驱动系统对电机本体的效率提出了更高的要求。为了实现定子无铁心轴向磁场永磁轮毂电机在其常用工况下的高效率,该文分析了利兹线和扁线对定子槽满率的影响规律,建立了不同线型绕组的交流损耗计算模型,对不同线型绕组电机的交直流铜损进行了计算与对比分析,并基于损耗产生机理提出扁线绕组分股和换位的交流损耗抑制方法。在此基础上,针对轮毂电机驱动系统的常用工况,对不同线型绕组电机的损耗和效率进行全面对比。结果表明,采用该文提出的效率优化方法可以实现扁线绕组的低损耗及电机的高效率,使用改进型扁线绕组的定子无铁心轴向磁场永磁电机适合作为减速驱动轮毂电机应用,尤其是对转矩需求较高的轮毂电机。试验结果验证了理论和仿真分析方法的正确性。     

Multistage axial-flux PM machine for wheel direct drive

The design of direct-drive wheel motors must comply with diameter restrictions due to housing the motor in a wheel rim and allow the achievement of very high torque density and overload capability. Slotless axial-flux permanent magnet machines (AFPMs) prove to be the best candidate for application in electric vehicles as direct-drive wheel motors, as in comparison with conventional machines they allow designs with higher compactness, lightness and efficiency. The paper presents a newly conceived AFPM which has a multistage structure and a water-cooled ironless stator. In the proposed new topology of the machine, the space formerly occupied by the toroidal core becomes a water duct, which removes heat directly from the interior surface of the stator winding. The high efficiency of the machine cooling arrangement allows long-term 100% overload operation and great reduction of the machine weight. The multistage structure of the machine is suited to overcome the restriction on the machine diameter and meet the torque required at the wheel shaft. The paper gives guidelines for the design of a multistage AFPM with water-cooled ironless stator, and describes characteristics of a two-stage prototype machine rated 215 Nm, 1100 RPM     

Proposal and development of radial air‐gap coreless generator suitable for small wind turbine used in urban area

Independent distributed power generation using small wind turbines is becoming more widespread as wind power generation increases. Installation of small wind turbines in densely populated urban areas is not only useful from the viewpoint of extracting wind power sources in weak‐wind areas but also for making renewable energy easier to access when power supplies are closer to consumers. It is from this point of view that the authors proposed “urban wind power generation” using a collective system with a number of small vertical wind turbines, and have developed a suitable generator for low‐speed vertical wind turbines such as a Savonius windmill. Based on a standard coreless generator, the proposed generator is designed to make the direction of the magnetic flux radial in order to install the magnets and coils on the outer end of the generator. The change of magnet composition and flux direction maximizes the speed of the flux change and output voltage within a limited space. With the above configuration, the power of the proposed generator is independent of the diameter. In this report, the authors describe and evaluate the fundamental performance of a prototype of the proposed generator. Based on the experiments, a maximum output power of 283 W was obtained. The obtained starting torque is small enough to begin rotation under weak wind conditions of no more than 1 m/s. Therefore, it is clear that the proposed “radial” coreless generator is suitable for self‐starting and producing high power at low wind speed. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 26– 34, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20695     

散热匝磁极线圈制造及匝间绝缘结构研究

利用普通扁绕机,通过对设备的功能及运行轨迹的研究,改进模具结构,在普通绕线模上镶嵌镶块,绕制散热匝磁极线圈,匝间绝缘采用新型绝缘结构-Nomex纸结构,减薄电机匝间绝缘,降低温升,提高电机的性能,为同步发电机的开发提供工艺技术保证.     

A new self-excitation scheme for three-phase synchronous generators

A new self-excitation scheme has been developed for three-phase synchronous generators. The generator that uses this scheme behaves as a flat-compound machine without automatic voltage regulators. The stator of the generator is provided with an armature winding that generates the fundamental and 2nd-harmonic mmfs. The rotor is equipped with a field winding and a harmonic winding. The harmonic winding is magnetically coupled to the 2nd-harmonic mmf produced by the armature winding. The current flows in the stator armature winding by way of a three-phase set of capacitors connected across its three-phase terminals and the ac voltage is induced in the rotor harmonic winding due to the armature 2nd-harmonic mmf. By connecting the harmonic winding to the field winding through a rectifier circuit, self-excitation of the generator is obtained. This excitation scheme is both self-excited and brushless, and no exciter is required. Additionally, voltage regulation due to load variation can be improved by connecting suitable capacitors. In this paper the operating principle and circuit configuration of the generator are explained and the experimental results using a 1-kVA prototype machine are shown. The generator characteristics are theoretically clarified by approximate analysis, and appropriateness of the theory and the usefulness of the proposed scheme are experimentally confirmed.     

无槽环形绕组轴向磁通永磁电机空载反电动势解析

无槽环形绕组有两种类型,即扇形绕组和矩形绕组。针对这两种绕组空间分布对空载反电动势的影响,分别对两种绕组轴向磁通永磁电机的空载反电动势进行了解析推导。在气隙磁密解析计算时,提出通过建立虚拟等效直线电机模型用以计算气隙磁场端部效应函数。为了验证解析公式的正确性,以一台电机方案为例,利用推导的解析公式对空载反电动势进行了计算,与有限元计算结果进行了对比,结果表明解析计算结果和有限元计算结果相对误差小于2.1%,满足工程要求。因此,推导的空载反电动势解析公式可以作为电机设计人员参考使用。     

PCB定子无铁心盘式电机绕组结构设计与优化

为改善盘式定子无铁心电机空载反电动势波形的正弦性和降低反电动势的高次谐波,本文提出了一种PCB绕组盘串联叠加的定子结构,且叠加的定子绕组盘之间具有角度差。首先采用理论的方法得到了电机绕组的基波和谐波反电动势有效值的解析式,并建立了电机绕组结构的优化模型以确定叠加绕组盘间角度差的范围。通过三维有限元分析,确定了最佳角度差。最后对样机进行空载反电动势实验,可以发现实验结果与仿真结果基本吻合,证明了本文提出的定子结构对提高电机反电动势正弦性的有效性。     

变速运行的定子双绕组感应发电机电磁优化设计

文中提出了变速运行时通过电机本体参数与励磁电容同时优化来实现双绕组感应发电机控制绕组励磁调节器容量最小的优化设计策略，推导了控制绕组电流与电机参数的关系式，给出了3/3相双绕组结构的dq轴互漏感解耦的选取原则以及变速运行的磁路设计特点，以此建立了具有航空电源特点的优化设计数学模型，并采用动态全域映射收缩算子的复合形法对一种双绕组感应发电机进行了优化设计。样机设计结果表明，该优化设计策略可以有效地降低控制绕组励磁调节器的无功容量、系统成本和体积。     

基于基波电势分布特征的大型发电机定子接地故障定位方法

提出一种基于基波电势分布特征的定子接地故障定位方法,该方法按各相各分支定子线圈的实际连接关系,确定发电机中性点至接地故障点的基波电势,建立了该基波电势、机端三相基波电压、基波零序电压、接地过渡电阻阻值之间的数学关系,准确定位定子接地故障,并对波绕组发电机故障定位中的特殊情况进行了分析。采用基于准分布电容参数的定子接地故障仿真模型验证了所提方法的有效性。最后对现场实际故障案例进行分析,进一步验证了所提方法的准确性,其可大幅缩短现场故障检修的时间。     

盘式无铁心永磁同步发电机的设计

介绍了轴向磁场无铁心盘式永磁电机的结构形式,探讨了这种新电机的设计特点,解决了电机主要尺寸确定和磁路分析计算问题。最后,设计了一台200W盘式永磁无铁心发电机的样机,改进了电枢盘的制作工艺,并对样机进行了实验分析。     

宽变速运行的双绕组感应发电系统优化的研究

宽变速运行的双绕组感应发电系统相对于恒速运行,在电机的设计及系统控制等方面需要有特殊的考虑。介绍了宽变速运行的双绕组感应发电机的优化设计特点,为实现控制绕组励磁变换器容量的最小化,给出了励磁电容和发电机参数同时优化的设计策略,对一台原理样机进行了优化设计。利用控制绕组定子磁场定向控制策略,在dSPACE仿真平台进行了试验研究,结果证明,在1:2的宽变速运行范围内,空载和额定负载运行条件下,控制绕组与功率绕组的容量比可降到1/3左右,这对于降低控制绕组励磁变换器的容量、体积和成本很有意义。     

An Energy-efficient Switching Scheme with Reduced Switching Transients for a Wind-driven Induction Generator

This article presents a scheme for improving the power output of grid-connected induction generator commonly used in wind energy conversion systems. Generally, the stator of the induction generator is connected in a star with a line voltage of √3 times the rated winding voltage to reduce the line current and, hence, conductor size. To extend the generating operation over a wider speed range, delta-star switchable stator windings are also in vogue. In such cases, the stator is star connected in the lower speed range and switched to a delta connection above a threshold speed. In this study, a new switching scheme is proposed wherein the stator coils are always connected in a star, while the stator is connected to different voltages in low- and high-speed conditions. At low wind speeds, nominal winding voltage is applied to the stator, whereas at higher speeds, the stator applied voltage is √3 times higher than the rated winding voltage. The efficacy of the scheme is demonstrated experimentally with a suitable microcontroller-based switching arrangement. Typical results indicate an increase in output with reduced switching transients. A case study on a 3-Φ, 50-kW induction generator is presented to emphasize the performance improvement with the proposed scheme.     

Fundamental characteristics of a brushless and self-excited sinusoidal-wave single-phase synchronous generator having a two-phase field winding excited by a half-wave rectified current

It is desired from the viewpoints of maintenance and construction to make single-phase synchronous generators of brushless and self-excited types. A novel brushless and self-excited single-phase synchronous generator was devised by one of the authors. The stator exciting current is made to flow simultaneously with the load current in the armature winding. Thus, the iron core for the magnetic circuit can be both for the synchronous generator itself and for the exciter. Experimental studies of the brushless and self-excited single-phase synchronous generator of which the rotor winding is used as a rotor exciting winding and a field winding are described in this paper. In the proposed generator, the rotor is provided with a balanced two-phase field winding to improve the voltage wave distortion. The terminal voltage of this generator can be kept constant in spite of the load variation. Therefore, the proposed synchronous generator can be expected to be used widely.     

大型发电机定子线圈绝缘结构试验研究

本文详述了大型发电机定子线圈绝缘结构试验的设备选取原则和试验程序;结合国内外标准,对定子线圈绝缘结构开展电应力、电热应力、环境应力、热机械应力、电机械应力评定试验。严格的诊断与评定为定子绕组的正常运行提供可靠的质量保证。     

Multiple coupled circuit modeling of induction machines

A new multiple coupled circuit model is presented for simulation of induction machines with both arbitrary winding layout and/or unbalanced operating conditions. The model is derived by means of winding functions. No symmetry is assumed. The parameters of the model are calculated directly from the geometry and winding layout of the machine. The behavior of an induction machine during starting is simulated using this model. The results are shown to be in good agreement with the solution obtained by a conventional d-q model for symmetric conditions. The new model is then extended to the solution of a wide variety of fault conditions such as broken bars and end rings and open or short circuited motor coils     

Partial discharge. XXV. Calibration of PD measurements for motorand generator windings-why it can't be done

In most types of high voltage apparatus, a PD acceptance test is required. In contrast, the PD test is very rarely used as an acceptance test for new motor and generator windings. The closest that machine manufacturers come to a PD acceptance test is the power factor tip-up test (IEEE Standard 286), which is an indirect PD test. The tip-up test is sensitive to PD sources when testing individual coils/bars but is relatively insensitive when testing complete windings, due to the presence of stress relief coatings. The lack of a direct PD acceptance test fundamentally results from the inductive nature of a stator winding. This article discusses the reasons for the lack of an absolute PD measurement criteria for stator windings, after a discussion on measurement methods and the quantities used to measure PD activity     

印制板式Rogowski线圈研究

为了增强印制板式Rogowski线圈拾取感应信号的能力,有效提高其信噪比,将具有相同结构的Rogowski线圈顺次串联并分别获得顺串单、双面板Rogowski线圈后,分析了由单面板构造的顺串单面板传感器的计算模型和等效模型,对比研究了顺串单、双面板Rogowski线圈的阻抗、相频、自感系数和内阻等重要电气参数随着被测电流频率的变化特性,推导了顺串单、双面板Rogowski线圈的最佳阻尼电阻的计算模型,提出了用于判断顺串单、双面板Rogowski线圈测量脉冲大电流的结果有效性的方法及其判据。研究表明,取印制板线圈的顺次串联方式有利于提高传感器的信噪比。