Design and implementation of a contact‐less power charger for robot applications

In this paper, a contact‐less power charger for robot applications is studied and developed. Contact‐less charging can be achieved by a separable transformer design. The transformer primary core is in the charger unit, and the secondary core is in the robots. The transformer air‐gap is equal to the distance between these two parts. By theoretical analysis, software simulations, and circuit implementation, the relationship among the transformer's coupling coefficient, the core geometry, and gap are formulated. In addition, a high‐efficiency circuit topology for the studied contact‐less charger is fulfilled. It is anticipated that the research results of this paper can contribute to the development of the contact‐less charging techniques for robot systems. Copyright © 2012 John Wiley & Sons, Ltd.     

开关电源高频功率平面变压器热设计研究

高功率密度要求和高频下涡流损耗(包括磁芯和线圈的涡流损耗)的急剧增大对高频功率平面变压器的热设计带来巨大挑战.通过分析平面变压器热传递特性,提出一种可分别计算线圈和磁芯温升的热模型及其建模方法.此外,根据铁氧体磁芯的损耗温度特性,还提出一种平面变压器温度设计准则.实验证明提出的热模型具有足够高的工程精度,而提出的温度设计准则可使变压器具有良好的热稳定性,从而改善了平面变压器热性能.     

Advanced design methodology for single and dual voltage wound core power transformers based on a particular finite element model

The paper presents an accurate and cost effective three-dimensional finite element model for the analysis and design of wound core, shell type, power transformers, focusing on the short-circuit impedance evaluation. The model efficiency lies on the detailed representation of the transformer geometry along with the adoption of a particular reduced scalar potential formulation enabling three-dimensional magnetostatic problem solution without prior source field calculation. Its accuracy is validated through local field measurements and through comparison of the calculated short-circuit impedance value with the measured one for several commercial wound core, shell type transformers. In such transformers, involving extensive winding parts out of the core window, the detailed representation of the transformer geometry, including the winding cooling ducts, provides accurate results for low densities of the three-dimensional finite element mesh, resulting to reduction of the required calculation time. The model is used in the development of a computational tool, which enables the automated and accurate transformer characteristics prediction, adopted to the manufacturing process. This tool has also been applied in the impedance calculation for different winding connections of dual voltage transformers, thus providing the information needed for the achievement of an accurate design and the enhancement of the manufacturer's ability to reduce design margins. The methodology presented in this paper has been incorporated in the design process of a transformer manufacturing industry.     

新型多功能反激式开关电源设计

以峰值电流型PWM控制芯片UC3842为核心设计了一种新型多功能反激式开关稳压电源,该电源具有6路直流隔离电压输出。介绍了其工作原理和外围电路设计。为了满足电磁兼容性和安全性要求,设计了EMI抑制电路。详细介绍了一种新型变压器绕组缓冲电路的设计方法,着重介绍了反激式变换器的变压器设计过程,包括齐纳箝位电压的计算、实际占空比的计算、电感值的计算、磁芯的选择、各路输出绕组匝数的确定以及气隙的计算。实现了对输出电压的负反馈调节及各种保护机制。实验结果表明,该开关稳压电源具有稳压性能优良,纹波小,电压调整率、负载调整率高,体积小,质量轻,电磁兼容性好等优点。     

平面集成磁件在电源中的应用

在有源钳位正激变换器工作原理基础上,利用磁集成技术,将变压器与滤波电感集成在一个磁芯上,对该集成磁件进行了分析研究。通过电路和磁路推导,提出了该集成磁件的等效模型和设计依据。设计了特殊的磁芯和绕组结构,采用特殊磁性材料制作薄膜磁芯,实现集成磁件的平面化。采用有限元分析工具,对集成磁件进行仿真,得出了磁通密度的分布情况。在集成磁件模型基础上,对变换器进行仿真,得出了变换器的输出结果,实现了变换器的零纹波,验证了设计的正确性。     

电力变压器铁心振动特性分析

作为电力变压器的主要部件,变压器铁心的振动信号主要与铁心紧固状况、绝缘程度密切相关,具有较强的非线性非平稳特性。本文以电力变压器铁心为研究对象,将希尔伯特黄变换(HHT)时频分析方法引入变压器铁心非线性振动信号分析领域,并结合传统频谱分析法对六种不同型号的电力变压器铁心振动信号进行了分析及实验研究,从时域、频域及时-频域等几个角度分析了铁心本体振动特性、油箱表面空载时振动特性及负载时绕组振动对铁心振动的影响。该研究分析结果为电力变压器的状态检测与故障诊断提供了一个良好的基础。     

Autoconnected-electronic-transformer-based multipulse rectifiersfor utility interface of power electronic systems

In this paper, an autoconnected electronic transformer (ACET) for 12- and 24-pulse rectifier systems is proposed. Considerable reduction in size and weight is achieved by operating the transformer core at a higher frequency. The rating of the autotransformer is a fraction of the output power. Utility line currents are multipulse in nature with the cancellation of several lower order harmonic currents. Furthermore, the magnetic components on the rectifier DC side are also exposed to higher frequency and can be reduced in size and weight. With an operating frequency of 990 Hz and utilizing conventional grain-oriented steel, a size reduction of 1/3 is achieved compared to a conventional 60 Hz design. Finer grades of steel or alternatives, such as amorphous material, would increase the performance advantage even further. Another unique feature of the proposed concept is that the switching frequency components are neutralized at the input side of the rectifier system. A second configuration using an open delta ACET is also presented. The proposed concept is suitable for higher power rectifier systems, which demand clean input power characteristics. This paper presents analysis, simulations, design example and experimental results for a 208 V 10 kVA prototype system     

A new approach to power supplies for robots

A cableless power supply system for multiaxis robots is proposed. As key components, it contains rotatable transformers placed in the joints of the robot. It consists of two halves of a ferrite pot core containing the primary and secondary windings, respectively. The energy is transferred to the movable parts of the robot through this transformer at a frequency of 25 kHz. This frequency allows a compact design of the transformer. A schematic representation of the new system is offered. Investigations of the steady-state and the transient behavior were carried out. Experimental results were obtained from an experimental setup with a 20 kVA, 650 V IGBT converter     

运行中电力变压器油箱表面振动特性的研究

电力变压器油箱表面的振动信号与变压器绕组及铁心的压紧状况、位移及变形状态密切相关.因此,振动信号分析法是监测电力变压器绕组和铁心状况的有效方法之一.本文利用组建起的变压器振动测量系统,对现场正在运行中的电力变压器油箱表面的振动信号进行了测量,分析了变压器型号、传感器安装位置对所测得的振动信号的影响,结果表明:同型号变压器油箱表面的振动特性相似;油箱表面上下对称位置处的振动特性相差不大,而其它各个位置处的振动信号都没有可比性.最后,本文研究了传感器的安装位置略有变化时,所测得的振动信号的变化情况,提出了应对传感器安装位置进行标记,在进行下次测量时,传感器安装位置最好在标记点处或偏离不超过5 cm.本文的研究成果对于振动信号分析法的实际应用具有一定的指导意义.     

A novel prototype design for a transformer for high voltage, highfrequency, high power use

A prototype transformer has been designed and built which is novel in its combination of high voltage (50 kV), high frequency (20 kHz) and high power (25 kVA) specifications. The design technique utilized a spreadsheet approach which facilitated an iterative design procedure. The transformer used a ferrite core, nylon insulated secondary bobbins and pressurized sulfur hexafluoride encapsulation. It was designed as part of a high-voltage switched-mode power supply for driving electrostatic precipitators. The transformer was field tested at a large coal-fired power station and was found to have an efficiency of better than 98%     

Simulation of hysteresis and eddy current effects in a power transformer

This paper presents a simulation algorithm to simulate the hysteresis characteristics in the core of a power transformer. The algorithm is based on the Jiles–Atherton phenomenological model of a ferromagnetic material. The new transformer model is capable of producing a close representation of the transformer magnetizing current. Comparisons are made between recorded and simulated waveforms using a single phase distribution transformer. A good agreement is achieved between recorded and simulated data.     

Quasiperiodic (QP) oscillations in electrical power systems

The occurrence of quasiperiodic (QP) oscillations in power systems, a phenomena hitherto unknown, was first experienced in the French grid when attempting to energize an unloaded transformer at the end of a long transmission line. There are no simple analytical tools available to study conditions for the occurrence of QP oscillations. In this paper, the conditions necessary for the occurrence of quasiperiodicity are shown by solving the system equations using the method of harmonic balance. It is shown that QP oscillations will occur due to the severity of magnetizing nonlinearity of the transformer core. It is also shown that if core losses are high, only frequency locked oscillations can occur. The results are confirmed by numerical solution on the original set of differential equations.     

多级磁压缩脉冲电源

阐述用于EUV光刻技术的脉冲功率电源的设计。该脉冲电源由充电电容组,半导体开关(IGBT),脉冲变压器和四级磁压缩回路组成。解释磁开关的工作原理,提供各关键元件的设计参数。根据磁性材料的物理特性参数,利用Pspice仿真软件建立磁芯模型,构建磁开关和仿真电路,对各级电压和电流波形进行分析,进而设计调整各级磁开关的参数。实验结果表明,该脉冲电源输出峰值为30 kV,上升沿为<85 ns,脉冲宽度<100 ns的脉冲信号。     

电力变压器振动信号分离方法研究

以独立成分分析(ICA)为代表的主流盲分离技术对信号独立性要求较高,难以分离具有高度相关性的变压器铁芯与绕组振动信号。为了分离变压器铁芯和绕组振动信号,建立了变压器振动信号混合模型,在该模型基础上提出了一种基于时频比盲源分离算法(TIFORM-BSS)的变压器振动信号分离方法。将该方法分别应用于分离人工混合后的110 k V三相变压器油箱壁信号和实际运行中的500 k V单相变压器油箱壁振动信号,结果表明该方法能够有效分离具有强相关性的变压器绕组和铁芯振动信号。     

Effect of iron core loss nonlinearity on chaotic ferroresonance in power transformers

This paper investigates the effect of iron core loss nonlinearity on the onset of chaotic ferroresonance and duration of transient chaos in a power transformer. The transformer chosen for investigation has a rating of 50 MV A, 635.1 kV, the data for which is given by Dommel et al. (Tutorial Course on Digital Simulation of Transients in Power Systems (Chapter 14), IISc, Bangalore, 1983, pp. 17–38). The magnetisation characteristics of the transformer is modelled by a single-value two-term polynomial. The core loss is modelled by a third order power series in voltage. With nonlinearities in core loss included, three effects are clear: (i) onset of chaos at larger values of open phase voltage, (ii) shorter duration of transient chaos, and (iii) less susceptibility to ‘ jump ’ phenomena.     

基于CAN总线的电力变压器远程在线监控系统

介绍了一种基于CAN总线的电力变压器远程在线监控系统的设计方法,该系统可通过CAN通信使一台主机在线监控多台远程变压器,并通过上位机的软件全面分析变压器运行参数,预测变压器故障。该系统具有数据传送可靠性高、抗干扰能力强、容易扩充新节点等特点。     

模块化电力电子变压器的设计与实现

基于级联H桥拓扑的模块化电力电子变压器(Power Electronic Transformer,PET)具有最优的灵活性和功能扩展性,是PET中研究最为广泛的一种拓扑结构,但是其高压工程样机的实现具有一定的难度。本文研究了10k V/400V模块化电力电子变压器的设计与实现方法,考虑PET内部高低压隔离因素重新进行了三级结构划分,高压级联模块利用无锁相环控制消除电网电压波动引起的输入电流相位误差,研究了模块化的控制系统设计方法。研制的工程样机接入10k V配网进行了实验,各工况下的实验波形和数据分析验证了所提设计方法的正确性与有效性。     

Characteristics analysis of superconducting power transformer without iron core

With the progress of superconducting wires for ac power use, research on superconducting power transformers is increasing. These transformers can be divided into two types: the iron-core type [1, 2]; and the air-core type [3–9]. The latter type has such advantages as absence of iron losses and magnetic saturation, and greater possibility of reduction of size and weight. However, the air-core transformer has a large magnetizing current due to the absence of iron core. Hence, research has been carried out on the possibility of using the air-core transformer also as a shunt reactor in a power transmission system. However, the operating characteristics of the air-core transformer, such as voltage regulation and reactance voltage, are not clear at present. In this paper, the equivalent circuit without losses is proposed first. Since this equivalent circuit is expressed by means of the magnetic coupling factor and self-inductances of windings, the effect of these parameters on the transformer characteristics can easily be investigated. Then, based on this equivalent circuit, the per-unit expressions for the air-core transformer characteristics are derived and the characteristics are analyzed in detail. The validity of the theoretical results are confirmed by experimental results obtained by the use of an experimental superconducting transformer.