Sliding Transformer With Long Magnetic Circuit for Contactless Electrical Energy Delivery to Mobile Receivers

A new type of sliding transformer with long magnetic core and movable secondary winding is presented. The basic transformer configurations and wiring are described. The magnetic flux distribution along the magnetic circuit and its influence on transformer parameters are discussed and examined. Also, the leakage inductance of the transformer primary winding, as the main cause of voltage drop and energy losses, has been discussed. The main experimental results of transformer model investigation are presented in this paper     

短波宽带高功率传输线变压器设计

针对高功率短波通信系统中天线与馈线之间的宽带阻抗匹配及平衡转换问题,对于传输线变压器的设计进行了理论分析,重点分析了高功率应用时,如何正确选择磁芯材料技术参数从而确保特定传输线变压器指标的实现。根据理论分析结果,设计并制作了一只传输线变压器,在2～30MHz的带宽内,驻波系数小于1.4,应用于1.6kW高功率短波通信系统中得到了满意的结果。     

A novel principle of magnetic flux compensation and its application in power systems

A novel principle of magnetic flux compensation of a linear transformer is proposed. The current of the primary winding is detected and multiplied by a compensation coefficient to get a reference current, which is tracked by a voltage source inverter to produce a compensation current. This compensation current is injected inversely in phase into the secondary winding. According to the law of superposition and the transformer's voltage equations, the main magnetic flux in the transformer and the equivalent impedance of the primary winding correlate linearly with the current compensation coefficient, and this equivalent impedance varies linearly with the current compensation coefficient. This new principle can be widely applied in power systems, such as series hybrid active power filter, fault current limiter, continuously controllable reactor, arc suppression coil and power system load flow control, and many FACTS devices can be implemented in terms of the new principle. A current control scheme is analysed. The theory is validated by experimental results, and some new devices based on the principle are discussed.     

Voltage equaliser for Li–Fe battery

In this article, a voltage equaliser is proposed for a battery string with four Li–Fe batteries. The proposed voltage equaliser is developed from a flyback converter, which comprises a transformer, a power electronic switch and a resonant clamped circuit. The transformer contains a primary winding and four secondary windings with the same number of turns connected to each battery. The resonant clamped circuit is for recycling the energy of leakage inductance of the transformer and for performing zero-voltage switching (ZVS) of the power electronic switch. When the power electronic switch is switched on, the energy is stored in the transformer; and when the power electronic switch is switched off, the energy stored in the transformer will automatically charge the battery whose voltage is the lowest. In this way, the voltage of individual batteries in the battery string is balanced. The salient features of the proposed voltage equaliser are that only one switch is used, the energy stored in the leakage inductance of the transformer can be recycled and ZVS is obtained. A prototype is developed and tested to verify the performance of the proposed voltage equaliser. The experimental results show that the proposed voltage equaliser achieves the expected performance.     

Design issues for the transformer in a low-voltage power supplywith high efficiency and high power density

Circuit model, design feasibility, and design tradeoffs are investigated for the transformer in 1.5-5 V power supplies with high efficiency and high power density. The transformer is constructed from a single or a matrix of pot cores and from interleaved planar windings. It has been determined theoretically and verified experimentally that such a transformer is realizable as long as the loss constraint is not severe (e.g. less than 0.5 W transformer loss per 100 W output). The primary source of loss is the winding, not the core, in 1.5 V/turn design. Measures to reduce the transformer height tend to increase transformer loss or volume     

Research on the filtering characteristic of single phase series hybrid active power filter based on fundamental magnetic flux compensation

In this article, the PWM inverter works as a controlled fundamental current source in the single phase series hybrid active power filter (APF) based on fundamental magnetic flux compensation (FMFC). The series transformer can exhibit the self-impedance of primary winding to harmonic current, which forces harmonic current to flow into passive power filter. With the influence of harmonic current, the voltage of primary winding of transformer is a harmonic voltage, which makes the inverter output currents have a certain harmonic component, and it degrades the filtering characteristics. On the basis of PWM inverter, the mathematical model of series hybrid APF is established, and the filtering characteristics of single phase APF are analysed in detail. Three methods are gained to improve filtering characteristics: reasonably designing the inverter output filter inductance, increasing series transformer ratio and adopting voltage feed-forward control. Experimental results show that the proposed APF has greater validity.     

High density interconnect EmbeddedMagnetics for integrated power

We introduce here a new transformer/inductor technology which is suitable for integrated power for multichip modules (MCM), microprocessors and chip sets. The transformer/inductor is embedded within the ceramic substrate, as are the chips and other components. It provides for extremely tight secondary side circuit layouts with very low and fixed leakage inductance. The core is a new multipole structure which can be considered as a number of transformers integrated into one monolithic structure. The core consists of a bottom ferrite plate, and the winding is constructed using high density interconnect techniques (HDI), such as laminating dielectric layers and depositing winding metals using sputtering followed by electroplating. Winding patterns are etched using photo-resist and wet etching techniques. Multiple vias are used to connect different primary and secondary winding layers. A conformal metal mask is used to laser-drill through (large) holes for the posts of the top part of the core. An experimental 50-W, six-pole transformer has been built using these techniques. It operates at 1.0MHz with efficiency approaching 98.7% and has a net height of about 0.09in (/spl sim/2.3mm). It has a power density of 71W/cc (or 1170W/in/sup 3/) and a surface power density of 17W/cm/sup 2/.     

传输线变压器相位补偿技术及其应用

传输线变压器是在短波和超短波频段使用广泛的重要器件,根据传输线变压器原理设计制造的器件具有结构紧凑、功率容量大、频带宽、损耗小等优点.该文研究了利用慢波线原理和相位补偿技术克服传输线变压器对于传输线电长度的限制,使其适用频率向s波段以上扩展的方法.文中给出了1:4阻抗变换器电路的传输损耗和高低端输入阻抗理论公式并对其进行了讨论.对所设计的S波段1:4阻抗变换器及功率合成器进行了仿真分析并设计制作了实物.仿真和实测结果表明,利用慢波线原理和相位补偿后的传输线变压器能够适用s波段及以上微波器件.     

Integrated magnetic full wave converter with flexible output inductor

A new integrated magnetic full wave DC/DC power converter that provides flexible transformer design by incorporating an independent output inductor winding is introduced. The transformer is implemented on a traditional three-leg magnetic core. The inductor winding can be separately designed to control the output current ripple. The cross-sectional area of the inductor core leg can be reduced dramatically. The operation and performance of the proposed circuit are verified on a 100 W prototype converter.     

松耦合反激LED电源的分析与设计

在利用松耦合变压器进行电能传输的系统中,系统的工作频率和器件选取跟系统电能传输的大小有紧密联系.本文对松耦合变压器在反激电源中的应用做了分析,并对松耦合变压器的原边和副边的电压和电流波形进行了时域分析.确定了副边导通和关断的时刻,对系统的可行性有了直观的判断,为器件的选取提供了依据.     

A self-compensating lumped element broadband HF directional coupler

A novel design criterion for the lumped element coaxial transmission line directional coupler is discussed for HF band operation (2 to 30 MHz). This technique utilizes the inherent self-compensating low-pass equalizing characteristic of a high reactance secondary transformer winding. Experimental results of a representative coupler design are shown.     

家用电器变压器的设计计算与实践

变压器直接影响着家用电器的使用性能,因此,变压器的设计属于家用电器设计中重要的一个环节。在此提出家用电源变压器的设计方法,系统地叙述了变压器的变压静电路中电流、电动势及绕组每伏匝数的设计计算过程。并以某家用电器公司实际使用的变压器为例做了验证。实践证明该方法切实有效,为从事家用电器设计工作人员、或者售后维修服务人员提供参考材料。     

基于DP-BOTDR的500kV变压器绝缘监测系统设计

针对传统布里渊光时域反射传感系统空间分辨率低的问题,详细分析了基于双脉冲布里渊光时域反射(DP-BOTDR)的传感系统原理,并对DP-BOTDR系统的性能进行了仿真,结果表明DP-BOTDR技术具有高测量精度、高空间分辨率的优点。根据500kV电力变压器绝缘性能在线监测需要和绕组结构,探讨了DP-BOTDR系统在500kV变压器绝缘监测中的应用方案,设计了基于DP-BOTDR光纤传感技术的变压器在线监测系统。     

一种低漏感平面变压器

变压器的漏感是电磁干扰的主要来源之一,这是因为开关管在高速关断时,在变压器的漏感上产生感应电动势,叠加在变压器绕组的关断电压上,形成关断电压尖峰,这些电压尖峰不但造成电磁干扰,还会使开关管的电压应力增大,重者可能击穿开关管,并增大开关损耗,降低开关电源的效率。本文提出一种分布磁路结构的低漏感平面变压器,其原边绕组的匝数降低为一匝,副边绕组的等效匝数降低为小于一匝,因而漏感显著减小,这种分布磁路结构可以用于低压大电流电源的变压器,其有效性通过Maxwell 3D得到验证。     

Calibration Technique for Maximum Power Harvest of Passive Wireless Microsystems

A calibration technique for maximizing radio-frequency power harvest of passive wireless microsystems with a step-up transformer is proposed. We show that both the impedance and resonant frequency of the step-up transformer matching network can be adjusted by varying the capacitance of a shunt varactor placed at the secondary winding of the transformer to maximize power transfer from the antenna to the transformer and the output voltage of the transformer subsequently the power efficiency of the voltage multiplier. A low-power current-mode tuning technique and a maximum peak amplitude detection technique to allocate the optimal tuning capacitance at which the maximum power harvest exists are introduced. The transformer matching network has been designed in IBM CMRF8SF 130-nm 1.2-V CMOS technology, and its performance is validated using both simulation and on-wafer measurement results.     

Analysis of the ferroresonant transformer with a rectified outputin the low-line-voltage minimum-line-frequency full-load condition

Most previous analyses of the ferroresonant transformer address the unrectified-output AC-load case, and do not include some or all of the important loss mechanisms. The analysis reported in this paper addresses the rectified-output DC-load case and includes the stray losses. The low-line-voltage minimum-line-frequency full-load condition is the focus of this analysis because it is the worst-case condition for supplying power to the load. Assumptions about the operation of the transformer in this worst-case condition lead to a simplified equivalent circuit. Given equivalent-circuit element values, a special-purpose time-domain computer simulation analyzes transformer performance in the periodic steady-state condition. This analysis technique is used to find equivalent-circuit element values for which the transformer winding currents are a minimum and the input power factor and conversion efficiency are at a maximum     

浅议变电站PT二次回路中性点安装过电压保护的重要性

近年来,变电站设备因遭受雷击或输电线路雷电侵入波而导致绝缘损坏的事故时有发生,由于雷电冲击传递过电压将对二次绕组绝缘耐受电压造成很大的威胁,因此,在电压互感器二次回路中性点就地安装过电压保护措施具有重要的意义。本文对电压互感器二次中性点安装过电压保护的必要性进行分析研究。     

Design of LCL-T Resonant Converter Including the Effect of Transformer Winding Capacitance

The transformer winding capacitance, which is significant in high-voltage power supplies, is not gainfully utilized in an LCL-T resonant converter (RC). A simplified analysis presented in this paper predicts the severe degradation of output current regulation of an LCL-T RC due to transformer winding capacitance. The presence of winding capacitance, in fact, changes the third-order LCL-T resonant tank into fourth-order LC-LC topology. Using an AC analysis, it is shown that, under the derived design conditions, LC-LC RC also exhibits constant output current and in-phase source voltage and current, simultaneously at all loading conditions. Thus, the transformer leakage inductance and winding capacitance are gainfully utilized as a part of a resonant network, resulting in improved output characteristics. Closed-form expressions for the converter gain and component stresses are derived. The condition for converter design optimized for the minimum size of the resonant network is obtained. Experimental results on a prototype 100-mA 2-kV DC power supply confirm the observations of analysis.     

电子式电流互感器采样电路的计算与测试

电力系统中一个非常重要的高压设备就是电流互感器,在测量电流与继电保护中经常需要使用到电流互感器.传统的电磁式电流互感器虽然具有较高的可靠性、稳定性、丰富的运行经验且原理简单,可是,伴随着电力系统电压等级的不断提高,人们对大容量、远距离互联电网及输电线路也提出了越来越高的要求,电磁式电流互感器已经无法满足人们的需求,此时电子式电流互感器便应运而生了.本文对电子式电流互感器采样电路的计算与测试进行了探讨,可供参考.     

基于UC3844反激式开关电源的设计

设计了一种基于UC3844的反激式多路输出开关电源,采用工业上常用的DC12~18 V输入,输出2路24 V/300 mA。此开关电源充分利用高频变压器原边绕组特性,把反馈绕组与供电绕组合二为一,简化了外围硬件电路,同时充分考虑了其成本和体积大小,除消除高频杂波用的共模电感、功率电阻、输出整流二极管及滤波电解电容外,其余元器件均采用贴片,最后经实验进一步测试并验证了此开关电源稳定且可靠。