磁势自平衡回馈补偿式直流传感器

研究了一种新型磁势自平衡回馈补偿式直流传感器，介绍了这种传感器的工作原理与设计方案，给出了该系统的稳定性分析、误差分析、暂态性能指标。该传感器将开环原理与闭环原理的优点有机地结合起来，使其既具有准确度高(从传统直流传感器0．5％的测量准确度提高到0．1％)、线性度好、抗干扰能力强的优点，也不存在系统振荡及大功率驱动问题的弱点，且电路结构简单、稳定性好、可靠性高、自动跟踪补偿和响应速度快。     

智能配电网电能计量设备的运行状态监测终端研究

针对现阶段智能配电网中电能计量设备在线运行状态评价难的问题,该文分析温度、直流偏磁与二次回路状态对电能计量准确性的影响,提出一种电能计量设备状态监测终端。该设备使用铂热电阻的测温电桥对环境温度进行监测,使用具有交流反馈的自激磁通门对直流偏磁进行监测,通过对二次回路电流测量的方法实现二次回路短路的监测,通过高频信号注入的方向实现二次回路开路监测,并通过窄带物联网实现监测终端与电力云平台间的数据通信。最后,进行温度、直流偏磁和二次回路实验,对所提监测方法进行验证,实验显示温度、直流与二次回路监测结果均可准确反映实际运行状态。     

电抗器饱和对短路电流的影响

并联电容补偿装置中的铁芯电抗器的饱和特性对电力系统短路电流产生影响，此影响体现为在短路初期使短路电流增大，其增大的程度与补偿装置接入点距电源的远近，和补偿回路的参数有关，在某些条件下其增值右达２０％以上，本文给出了在哪些情况下，选择和校验电器设备时应考虑电抗器饱和影响。     

一种抑制直流大电流源纹波的新型方法

提出一种抑制直流大电流源纹波的新型方法,采用双铁芯磁平衡式电流传感器,使得电感铁芯直流磁通近似为0。非晶铁芯由于其高磁导率特性可等效为一个大的电感器,而电感器的交流阻抗对直流大电流源的纹波有较大抑制作用,从而提高直流大电流源的精度。此新型方法使用双铁芯叠加体积小,电路简单,对大电流直流电流源纹波的抑制效果明显,为检定直流电能表提供更高精度大电流直流源。实践证明:该新型方法中的抑制模块可将输入纹波抑制比控制在5%左右,与传统抑制纹波方法相比,具有低损耗、低成本、高效率和易控制等特点。     

CT二次回路开路的故障原因及处理方法

电流互感器（CT）是根据电磁感应原理由闭合铁芯和线圈制成的,其一次绕组的线圈匝数较少,二次绕组的匝数较多。电流互感器的功能是把数值非常大的一次电流转化为二次电流,以此保护电路或者电器等。当电流互感器出现二次回路开路时,一次电流全部通过铁芯,从而产生上千甚至上万伏的电压,对作业人员人身及设备造成极大的威胁,属于电力系统中常见且危害性较大的故障。     

级联H桥SVG控制策略研究

对于H桥级联型SVG,采用基于瞬时无功功率理论的无功电流检测法对SVG的输出电流进行检测,采用ip-iq检测法可以有效地检测电网处于平衡或不平衡条件下的无功电流。该文研究了直流侧电压控制方法,由于三相损耗的影响,SVG的直流侧电压采用分层控制,即直流侧整体电压平衡控制、各相电压平衡控制以及各相模块电压平衡控制。其中,电流内环作用于直流电,起到跟踪、补偿无功的作用,电压外环要维持直流侧的整体有功平衡。     

电流二次回路短接判别试验装置的研制

文章在分析抽头式双变比电流互感器的原理和接线方式的基础上,提出根据电能表计量回路的电流是否随着回路阻抗的变化而变化来判断抽头式双变比电流互感器存在接线错误与否,并研制一台电流二次回路短接判别试验装置。该装置可准确地判断出现场安装的抽头式双变比电流互感器有无错误接线,同时还可判断电流互感器的二次线圈有无匝间短路情况,对现场运行中的电流互感器的接线检查带来极大的方便。     

面向铁氧体裂纹检测的感应加热电源研制

针对常规感应加热电源对铁氧体加热时存在加热均匀性差和负载回路谐振频率漂移的问题,提出了一种全桥逆变拓扑结构的串联谐振式数字感应加热电源.基于负载串联谐振回路换流时电压和电流的相位差特性,通过PSPICE软件分析了阻性、感性和容性三种换流状态,仿真结果表明,串联谐振回路工作于弱感性状态,可以保证电路安全可靠运行;基于电磁耦合原理,对比分析了原边补偿和副边补偿两类负载匹配变压器,通过匹配负载等效电阻实现电源系统最大能效输出;采用Fuzzy-PI频率跟踪技术实现负载谐振频率实时跟踪.最后,将研制的数字感应加热电源成功地应用于铁氧体裂纹检测实验.     

电能表磁路气隙改变的影响

电能表经检修或改绕线圈后，如果重新装配不当，使电压铁芯与电流铁芯之间的工作气隙发生了改变，对满载调整和相位角调整都有影响，尤其对相位角调整的影响更为显著。经常发现有些电能表经检修后，由于工作气隙发生了变化，虽然利用满载调整装置还能将满载时误差调整合格，但依靠相位角调整装置很难将相位角调整好的现象。本文就这种现象作定性分析，仅供参考。由于空气的磁导率比铁芯材料的磁导率小很多，当电压铁芯与电流铁芯间的工作气隙发生了变化．就会使电流磁路的总磁阻有相当大的改变。根据磁路的欧姆定律可知，当通过电流回路的负…     

三电平四桥臂有源电力滤波器的预测电流控制研究

为解决三电平四桥臂结构开关矢量多、计算量大及控制复杂等问题,重点研究适用于三电平四桥臂结构的电流预测控制策略,并通过建立Matlab模型,进行理论分析和仿真研究。仿真和实验结果表明:采用预测电流控制方法的有源电力滤波器对谐波电流和中线电流有较好的补偿效果,并能有效地控制直流侧电压平衡。     

DC sensor based on magnetic potential self-balance and feedback compensation

A new type of DC current sensor for 10 000 A, which integrates the advantages of DC measurement devices based on the open-loop and closed-loop principle, is presented. One magnetic core carrying two windings is designed as a magnetic potential self-balance loop. In order to detect and compensate the remaining ampere-turns except magnetic potential self-balanced, two feedback compensation detection magnetic cores are designed as a feedback compensation loop. Its operation principle and characteristics, including stability, error analysis and dynamic response, are analysed in detail. Finally, its validity is verified by experiment and the results show that the measuring accuracy of the proposed DC sensor can be enhanced up to 0.13% whereas the accuracy of a conventional DC sensor is only 0.5%.     

一种圆鞍形磁屏蔽线圈的设计与性能研究

以毕奥-萨伐尔定律为基础,推导了一种圆鞍形线圈在空间任意点处的磁场分布表达式,优化了一种线圈结构,证明了圆鞍形线圈可以产生一定区域的稳恒磁场,并定量地给出了线圈内部磁场的空间分布情况。所设计线圈产生的磁场中,1%均匀度的磁场均匀区占轴上区域的28%,0.1%均匀度的磁场均匀区占轴上区域的10%;在1 mA的电流下,单圈线圈最大磁场补偿值为15 nT,相对偏差量不超过0.14 nT,验证了所推导表达式的正确性,为多维磁场补偿系统设计与研究提供了理论依据和参考。     

A magnetic sense amplifier

A new mode of operation of a balanced magnetic circuit is described. With this new mode of operation, which utilizes pulsed current excitation, the detection sensitivity of the magnetic modulator circuit is combined with the high-speed amplification of parametric buildup. This combination permits detection of low-level current pulses applied during a specified time interval of the excitation sequence and provides subsequent amplification of the detected signal. Matched square-loop toroids are used. Signal currents which are a small fraction of the coercive MMF have been successfully detected. The limit of detection sensitivity depends upon the matching of the two cores. The parametric buildup has been made to occur for pump cycle times of 30 μs to 120 μs, depending upon the magnetic material used. The signal information is retained when the pulse excitation sequence is interrupted during buildup because the signal information is stored as a flux unbalance in the two cores during the time interval between excitation pulses. The use of this circuit mode as a sense amplifier for the detection and amplification of sense winding currents in magnetic memories is suggested.     

Hardware control of an active magnetic shield

The presented hardware controller controls the current in an active shield consisting of a number of compensation coils at well-chosen positions. In combination with a converter and the active shield, the controller reduces the fundamental component of the magnetic stray field of an induction heater by generating a magnetic counter field in a defined target area. The controller uses two input signals (from two magnetic field sensors) and generates amplitude and phase information for the converter. Based on this information, the latter produces the compensation current wave that is sent to the compensation coils to minimise the magnetic field. The frequency range of the controller is 1-100 kHz. Its dynamic behaviour is explained in theory and validated by experiments     

直流电流比较仪双铁芯磁性能一致性的研究

搭建了由对称方波电压源、直流电流源、示波器、峰差解调电路组成的试验线路,提供了铁芯的具体参数和绕线要求,将10个绕制好的铁芯两两组合依次进行磁性能一致性的试验,测量了灵敏度和10 min内的漂移量。试验结果表明,物理参数相近、制造工艺相同的铁芯两两组合后的磁性能仍然有明显的分散性,灵敏度的最大值为7 mV/（μA·T）、10 min内最小漂移量为3 μA·T。     

The microfluxgate magnetic sensor having closed magnetic path

This paper presents a microfluxgate magnetic sensor in printed circuit board (PCB). In order to observe the effect of the closed magnetic path, the magnetic cores of rectangular ring and two bars were each fabricated. Each fluxgate sensor consists of five PCB stack layers including one layer magnetic core and four layers of excitation and pickup coils. The center layer as a magnetic core is made of a Co-based amorphous magnetic ribbon with extremely high dc permeability of /spl sim/100,000. Four outer layers as excitation and pickup coils have a planar solenoid structure and are made of copper foil. In the case of the fluxgate sensor having the rectangular ring-shaped core, excellent linear response over the range of -100 to +100 /spl mu/T is obtained with 780-V/T sensitivity at an excitation sine wave of 3 V/sub P-P/ and 360 kHz. The chip size of the fabricated sensing element is 7.3/spl times/5.7 mm/sup 2/. The very low power consumption of /spl sim/8 mW was measured.     

Eddy-Current Nondestructive Inspection with Thin Spiral Coils: Long Cracks in Steel

The impedance of a cylindrical coil and a planar circular spiral coil carrying an alternating current above (i) a defect-free conducting magnetic half-space and (ii) a conducting magnetic half-space containing an infinitely long slot with uniform depth and width is examined in detail. Closed-form expressions for the coil impedance in these cases are presented, based on the theories of Dodd and Deeds and Harfield and Bowler. The validity of these expressions is tested by measurements using steel plates over the frequency range 100 Hz-10 MHz. The theoretical predictions are in good agreement with experiment, with the best agreement for the smallest slot width. The results confirm that thin, flexible spiral coils offer some attractive features for eddy-current detection of cracks in metals, particularly in terms of sensitivity and potential for unobtrusive permanent attachment to the material being inspected. Approximate expressions for a spiral coil above a defect-free magnetic half-space are also given to allow easy calculation in limiting cases.     

磁性液体水平传感器的研究

利用磁性液体既具有磁体磁性又具有液体流动性的特性设计出一种新型的一维磁性液体水平传感器.推导了水平传感器输出电压的表达式.对影响传感器灵敏度的各因素(激励信号频率、峰值电流、磁性液体磁化系数)进行了分析,并进行了相应的实验研究.理论计算结果与实验结果相符合.这种传感器具有高灵敏度的特性.     

New hybrid technology for planar fluxgate sensor fabrication

We have adapted a new printed circuit board (PCB) technology to the fabrication of ultraflat and sensitive fluxgate magnetic field sensors. The two outer layers of the PCB stack compose the electrical windings of fluxgates, while the inner layer is made of a micro-patterned amorphous magnetic ribbon with extremely high relative magnetic permeability (μ_r≈100 000). Two basic configurations were considered: one based on a toroidal magnetic core and the other on a rectangular core with and without an air gap. The field response and sensitivity of the fluxgate devices have been studied as a function of the gap length, the excitation current, and excitation frequency. Compared to fluxgate sensors of similar size, a relatively high sensitivity of 60 V/T was found at 30 kHz for a five-winding detection coil wound around a rectangular E-shaped magnetic core. This high performance is primarily attributable to the high-permeability magnetic core. The results clearly show the potential of this fluxgate device for application as a magnetic sensor