Characteristic analysis and trial manufacture of permanent‐magnetic type linear generator

This paper describes the design and trial manufacture of a linear generator which can convert any mechanical vibration of an automobile to electrical energy. A mover, which includes permanent magnets, is linearly driven through a stator by vibrations. The Nd‐Fe‐B magnets in the mover are placed facing the same magnetic poles in order to produce a change of magnetic flux in the coils of the stator. The coils are placed in the stator with the same intervals as the magnets. Successive coils are wound in opposite directions and are connected in series. A magnetic iron core covering the stator makes the magnetic flux extend through the case and reduces flux canceling in the coils of the stator. The distribution of the magnetic field, the electromotive force, and the driven power of the mover were calculated by numerical simulations in order to determine the size of the linear generator. A linear generator and experimental apparatus were built on the basis of the simulation. The performance characteristics were tested in experiments, and the produced linear generator was confirmed to be useful as an onboard auxiliary power supply. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 94– 100, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20751     

Performance and conceptual design of superconducting magnet for disk MHD generator

This paper describes superconducting magnets coupled with two kinds of disk-type MHD generators. One is coupled with a disk generator in the closed-cycle MHD experimental facility FUJI-1. The other is for a full-scale disk MHD generator. These are split-pair magnets. In the magnet for the FUJI-1 facility, a unique structure which supports the coils against the electromagnetic force has been fabricated and the magnet has been operating stably. During MHD power generation experiments, an induced voltage across the terminals of the coil was measured. A magnitude of the Faraday current in the generator was calculated from this induced voltage. A possible construction of magnetics for a full-scale disk MHD generator is indicated. It is suggested that a high performance of the generator (output power density of 0.3-1 GW/m³) can be obtained with high magnetic field up to 10 T.     

中国NdFeB磁体产业近况

过去50年间永磁体的磁能积从40kJ/m3(5MGOe)提升到400kJ/m3(50MGOe).1940年代初到1960年代末商品磁体以铝镍钴为主,70年代以后逐渐转为以铁氧体为主,预计2010年以后将变成以高性能稀土磁体为主.自90年代以来,日本的经济始终未从低谷中走出,而欧洲的经济也不见起色,2000年初美国经济发展放缓,这一切无疑对全球磁体产业的发展影响巨大.首先,由于采购的减缩,发达国家磁体产业的关、停、并购极为频繁,磁体产业结构变化迅速,一些新公司的名字尚未被人们所熟悉,却已经消失了.此外,生产成本的增高,迫使许多厂家,包括一些知名的公司也已停止材料生产,转向下游的器件生产.磁体的生产多转移到包括中国在内的发展中国家.     

Calculation of the Characteristics of Salient‐Pole Synchronous Machines Assisted by Permanent Magnets on the Basis of the Operating Principle

In this study we investigate a method for accurately calculating the characteristics of salient‐pole synchronous machines assisted by permanent magnets. First, the operating principle of the machines is investigated by using both finite element analysis and a simple magnetic circuit. Then, a theoretical representation of the assist effect on the permanent magnets is derived based on the magnetic circuit. Finally, the measured and calculated results are compared in order to confirm the validity of the proposed calculation method. We show that the load characteristics of the proposed machine can be accurately estimated from the no‐load and short‐circuit characteristics of the conventional machine without permanent magnets, and the size and magnetization of the inserted permanent magnets.     

Application of Superconductors-High Tc and Otherwise-to Electric Power Generators

ABSTRACT

Because superconducting magnets are capable of making large magnetic fluxes over large volumes of space with no dissipation and without the need for iron magnetic circuits, they appear to offer distinct advantages for use in electric machinery. In addition to eliminating the field winding losses, superconductors help improve efficiency by increasing flux density, thus shortening the armature conductor length per unit of flux linked. The elimination of iron allows for innovations in generator design and reduces reactance, thus improving dynamic performance. The basic feasibility of using metallic superconductors, operating at liquid helium temperature, has been demonstrated by investigators at several different organizations. While there is not yet agreement on exactly how a superconducting generator would be built, it is generally agreed that machines using liquid helium temperature conductors will be economically viable in at least some range of ratings.The use of higher transition temperature superconductors will make superconducting generators even more attractive if such conductors can provide satisfactory performance, measured by current density and magnetic field. Recent studies point out that even substantial improvements in operating temperature will not justify large reductions in current density.     

圆筒型Halbach永磁直线发电机磁场结构的优化

为了提高永磁发电机的发电功率和永磁体的利用率,提出了一种新型的用于海浪发电的圆筒型Halbach永磁直线发电机。该发电机内的电磁场具有轴对称性,故将其三维电磁场简化为二维场进行分析,建立了二维有限元方程。应用ANSYS软件对使用常规永磁阵列与Halbach永磁阵列时发电机的气隙磁场进行了比较,也对Halbach永磁阵列中相邻永磁体块的磁化角度差δm分别为45°、60°、90°时发电机的气隙磁场进行了比较,得出了结果较优的方案,结果可靠。     

Development of a large‐current high‐precision pulse power supply

JAEA and KEK are jointly constructing a high‐intensity proton accelerator project J‐PARC. Its main accelerator is a 3‐GeV synchrotron. Its injection bump magnets, especially horizontal paint bump magnets, are excited by large pulse currents. Their rated currents are over 10 kA and pulse widths are about 1 ms. Tracking errors are required to be less than 1%. Multiple connected two‐quadrant IGBT choppers are adopted for their power supplies. Their output currents are controlled by feedback control with minor loop voltage control (m‐AVR). When output current of a chopper intermits at small current, its output voltage rises and current control becomes difficult. In this paper, response of m‐AVR and output voltage characteristics at current intermittent region are studied and an improved control scheme is proposed. The performance is confirmed by a test. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 62– 72, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20783     

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     

直驱永磁风力发电机永磁体抗失磁能力分析

稀土永磁电机由于其效率高、转矩密度高、功率密度大、控制性能好等特点被广泛应用于风力发电领域,但是永磁体内的磁场波动与电机内的电流和温度相互影响,有发生不可逆失磁的风险,会影响发电机运行的稳定性。以1.5 MW直驱永磁风力发电机为研究对象,从永磁材料的退磁机理、故障电流对永磁体的影响、涡流损耗、永磁体温升的计算和试验等方面进行分析,为大功率直驱永磁风力发电机的设计提供了参考。     

不同工况下永磁同步风力发电机饱和同步电抗的计算与分析

以一台400W永磁同步风力系统所用发电机为例,给出了不同工况下电机内电磁场的求解方法,计算了永磁体嵌入转子表面结构的永磁同步发电机的饱和同步电抗值,在此基础上进一步分析了不同运行工况下永磁同步风力发电机同步电抗参数的变化规律,并进行了相应的实验验证,可为控制系统的设计及风力发电机运行性能的进一步研究提供参考。     

A mandarin text‐to‐speech technique implemented on a PIC‐based microcontroller platform

In this paper, a Mandarin text‐to‐speech (TTS) technique is employed to achieve the implementation of a voiced E‐book on the PIC‐based embedded platform. A transformation from the text of E‐book to the corresponding speech can help blind users and make the reading more effortless and relaxed. Both the microcontroller with a PIC32 Ethernet Starter Kit (80 MHz, 32‐bit, 128 kB SRAM, 512 kB Flash) and the Multimedia Expansion Board designed by Microchip Technology Inc. are adopted as the embedded platform. Four subsystems, namely text analysis, a recurrent neural network‐based prosodic generator, a synthesis unit generator with 411 Chinese syllabic waveforms, and a pitch‐synchronous overlap‐add‐based speech synthesizer, are made in the Mandarin TTS system and are implemented with C programming language. Experimental results find that a system requirement of 1.66 MB storage memory and less than 25.4 kB runtime memory, as well as 21.3% CPU runtime, is sufficient for real‐time operation such that a natural and fluent speech with a 16‐bit PCM at 8 kHz sampling rate is provided. The performance of the PIC‐based Mandarin TTS system is demonstrated to be good. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Determining electrical efficiency of permanent magnet synchronous machines with different control methods

An algorithm to calculate the electrical efficiency of permanent magnet synchronous machines with four different control methods is presented. The direct- and quadrature-axis stator current components are optimized to find the control method producing the maximum electrical efficiency. The developed computation algorithm was tested with three different permanent magnet synchronous machine applications, i.e., a low-speed high-torque direct-driven wind power generator with rotor surface magnets, a hybrid drive for an energy recovery system and a geared wind power generator with rotor buried magnets. The performance of the developed computation algorithm was verified by comparing the calculated electrical efficiencies with the measurements in the case of the hybrid drive machine.     

Numerical simulation of blow‐down closed‐cycle disk MHD generator

Numerical simulations of the closed‐cycle disk MHD generation experiment with Tokyo Institute of Technology's Fuji‐1 blow‐down facility are performed. In the calculations, the r–z two‐dimensional time‐dependent simulation code developed by the authors that can take the effect of water contamination into account is used, and the experimental conditions of Run A4109 operated by Disk‐F4 generator are selected as the numerical conditions. When the water contamination is the lowest level realized in the experiments, the simulation results coincide with the experimental results reasonably well, though there exist some discrepancies caused by inaccuracy of used basic plasma parameters, limitations of the two‐dimensional approximation, and so on. The voltage–current curve is almost linear, indicating that the MHD interaction is relatively weak and the flow field is mainly determined by the back‐pressure. The increase of the water contamination level results in decreased seed ionization rate at the generator channel inlet, leading to the steep deterioration of the generator performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 46–54, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10335     

Three‐dimensional numerical analysis of a liquid metal MHD generator

Three‐dimensional numerical analysis of a liquid metal MHD generator has been carried out. The three‐dimensional structures of the electromagnetic field and fluid flow in the MHD generator have been clarified, and the effect of the electrode width on the performance has also been examined, taking account of the current flow in the electrode. Structures of the electromagnetic field and fluid flow are complicated owing to the three‐dimensional current flow, induced magnetic field, and Lorentz force. The highest performance is found to be obtained when the width of the electrode is equal to that of the generator. The performance predicted from three‐dimensional analysis is somewhat lower than that from two‐dimensional analysis because of the larger input power. The increase in the input power is attributed to the increase in Lorentz force caused by less reduced magnetic flux density and to the additional friction loss on the insulator walls (x?y plane). © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(3): 19–26, 2007; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20282     

A new electro‐static micro‐generator for energy harvesting from diaphragm muscle

In this paper, we propose a new energy scavenging system for powering bio‐implantable devices. Different available energy sources and micro‐generators are examined. The operation of electrostatic generators will be examined in detail, and their design issues are discussed. The proposed generator is analyzed, and a closed form formula is developed for the capacitor voltages. Also, an equation is obtained for the output power for the proposed circuit. It will be shown that the diaphragm muscle in conjunction with the electrostatic micro‐generator can be used to extract energy from human body. The diaphragm muscle has a continuous movement with a relatively fixed frequency. There is enough space around this muscle to place the micro‐generator. Using the proposed system, it will be shown that it is possible to produce 230 mW power in a 125 mm³ volume from the diaphragm muscle. Copyright © 2017 John Wiley & Sons, Ltd.     

Analysis of a self‐regulated,self‐excited,brushless three‐phase synchronous generator,which includes the effect of core losses

This paper presents a novel analysis of a self‐regulated, self‐excited, brushless three‐phase synchronous generator, which includes the effect of core losses. The core losses are modeled by equivalent core loss resistances connected to additional windings on the generator's magnetic coupling model. A magnetic circuit is drawn from the magnetic coupling model, and an electrical equivalent circuit of the generator is derived by utilizing a duality between the magnetic and electric circuits. Using this equivalent circuit, the generator's steady‐state performance is theoretically predicted, and the results are verified through experiment. In addition, the power losses during power generation are analyzed quantitatively. The proposed analysis takes into account the nonlinearity of the exciting impedances due to magnetic saturation. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 51–60, 2000     

Analytic model for spread‐spectrum clock generator circuit characterization

The spread‐spectrum clock generator (SSCG) is one of the most efficient techniques to reduce the radiated emission of electronic devices. Despite its popularity, there exists no analysis that can be used as the design guidance to accurately project SSCG performance. In this paper, we develop a mathematical model to analyze SSCG EMI reduction and the clock period deviation performance. For model validation, Cadence Spectre simulations are conducted. Copyright © 2010 John Wiley & Sons, Ltd.     

Performance Evaluation of an Axial‐Type Magnetic‐Geared Motor

This paper first proposes an axial‐type magnetic‐geared motor that uses permanent magnets only in the high‐speed rotor. The operating principle of this motor is described and the torque–speed characteristics are computed by using three‐dimensional finite element method analysis. In order to increase the torque density, a novel axial‐type magnetic‐geared motor with permanent magnets on the high‐speed rotor and stator is also proposed. The torque–speed characteristics are compared to the original model with permanent magnets only on the high‐speed rotor. Finally, the computed torque–speed characteristics are verified against measurements on a prototype.     

永磁直驱同步风力发电机电磁设计及仿真分析

介绍了3MW永磁直驱同步风力发电机电磁设计参数要点的选取,尤其是对不同每极每相槽数下发电机的性能进行了对比仿真分析。列举了3MW永磁直驱同步风力发电机的主要技术参数,并通过有限元分析软件对所设计发电机的空载特性、负载特性及短路特性进行了仿真计算分析,并对三相短路状态下永磁体是否会发生不可逆退磁进行了验证。     

Power maximization control of variable‐speed wind generation system using permanent magnet synchronous generator

This paper proposes sensorless output power maximization control of a wind generation system. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed system. The generator torque is suitably controlled according to the generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control method, where the information on wind velocity is not required. Moreover, the maximum available generated power is obtained by the optimum current vector control. The current vector of PMSG is optimally controlled according to the generator speed and the required torque in order to minimize the losses of PMSG considering the voltage and current constraints. The proposed wind power generation system can be achieved without mechanical sensors such as wind velocity detector and a position sensor. Several experimental results show the effectiveness of the proposed control method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 11–19, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20043