一种精密互感测量的新方法

提出了一种精密互感测量的新方法,并且从理论上证明了利用这种方法对互感进行测量,互感的寄生电容、导线电阻、泄漏电导等寄生分布参数对最终的测量结果并不产生影响.初步的测量结果表明,利用这种新方法可以达到3.7×10-6量级的互感测量准确度.这一结果已经接近目前世界互感测量的最好水平2×10-6.     

多回不共端高压输电线路互感参数的带电测试

提出一种用于带电测量输电线路互感参数的新方法。该方法采用全球卫星定位系统（ＧＰＳ）送出的时间同步信号作为各测量点的同步采样基准，解决了不同端线路互感参数带电测量的同时性问题。文中对该方法进行了理论上的分析，对用于带电测量互感的计算机系统的硬件组成进行了介绍。该装置已成功地用于实际之中     

变压器直流电阻测量方法改进方案的探讨

电力变压器绕组具有大电感和小电阻的固有特点,测量直流电阻时充电时间常数很大,长期以来技术人员研究各种方法试图缩短测量时间。本文研究了电力变压器直流电阻快速测量的各种方法,分析了方法的优缺点,简介了变压器直流电阻测量改进方案。     

直流大电流测量电路中电流纹波的研究

介绍了直流大电流测量中纹波对于测量仪器的影响,发现二次仪表的差摸抑制能力对于测量的影响最大.论述了如何从纹波的两个主要来源(电源和同路)治理纹波分量,分析铜排框架的纹波治理效果,并提出一种利用带铁心铜排框架抑制纹波的方案,最后给出一套简易工程设计方法.     

计量测试技术的新动态

介绍了国际单位制(SI)基本单位的量纲方程、新定义,以及中国计量研究院在质量单位研究的最新进展.阐明了"能量天平"方案核心中M/T的量纲是欧姆.建立了互感测量装置,自行研制的低频数字补偿器法.模型试验结果表明:测量不确定度主要来自被测标准互感的不稳定性.其不确定度为1.5×10-3,说明了不确定度主要来源于测量位置准确性,采用激光系统后有可能得到改善.该项研究的重要意义在于研究和验证一些国际上已有计量方案,而不是简单地模仿之.     

直流低电阻表校准方法研究及测量不确定度评定

文章分别介绍了直流数字低电阻表(以下简称低电阻表)的两种校准方法("整体"校准法和"电流表-电压源"模拟电阻校准法)及其适用范围。重点介绍了后者的实现过程和可行性评定。通过对两种方法测量结果的不确定度评估,充分体现了间接校准法的优势,为直流低电阻表提供了一种非常有效的提高测量不确定度的计量方法。     

能量天平研究进展

能量天平法已在中国计量科学研究院开展了几年的研究。研究的目的与功率天平法是一致的,即通过测量普朗克常数来建立质量量子基准,但具体方法不同。2010年以来该项研究取得一定进展。例如对于直流互感量测量这一关键问题,已研究出一种新的方波补偿方法,测量不确定度达到10^-7量级（k=1）。还研发了一种涡流传感器,可更准确地对可动线圈定位。线圈系统的准直问题也得到进展,研制了一种油阻尼器,大大减小了由于天平基础振动和线圈加热上升气流引起的线圈抖动。这些措施改善了线圈位置及互感测量的不确定度。测量普朗克常数h的最新结果为6626104(59)×10^-34J·s,综合的相对不确定度为8.9×10^-6（k=1）。对所遇到的困难和进一步的改进措施也在文中进行了讨论。     

QJ55KZ型直流比较仪电桥测量标准电阻的一种简便方法

<正>QJ55KZ型直流比较仪电桥测量标准电阻的方法属于过渡传递法。现对该方法进行详细介绍,并针对该特定方法介绍一种简便方法。一、QJ55KZ型直流比较仪电桥测量标准电阻的测量原理直流比较仪是一种绕组的回形变压器,由两个不同的电流源分别给标准电阻RS和被检电阻RX供电,当两个电阻上的压降大小相等、方向相反时,测出两个电流之比,由检流计G指示出它们电压相等时的平衡     

标准高压高阻箱精密校验技术的研究

本文对标准高压高阻箱的校验问题进行了详细地分析,提出了一种采用直流分压技术,以精密直流数字电压表和直流标准电阻作为标准,来校验标准高压高阻箱的方案,并介绍了本方案的工作原理和校验方法,同时采用标准不确定度分析的方法论述了所采用方法的可行性。     

2K以上超导转变温度标准的测量装置

本文描述了利用互感法测量超导转变温度的原理、测量装置和测量方法。测量装置包括:低温恒温器、两种超导材料(铅和铟)的超导器件、简单的互感电桥线路及测量系统。测量结果的重复性小于±1mK,综合不确定度为±3mK(置信度为99%)。从而建立了2K以上超导转变温度测量装置。     

Mutual Inductance and Force Calculations Between Coaxial Bitter Coils and Superconducting Coils with Rectangular Cross Section

Mutual inductance and force calculations between coaxial Bitter coils and superconducting coils with rectangular cross section in a hybrid magnet system using derived semi-analytical expressions based on two integrations were performed. The mutual inductance and force calculations are based on the assumption of the uniform current density distribution in superconducting coils. The current density distribution of a Bitter coil in radial direction, however, is inversely proportional to the radius of the Bitter coil. The influence of the current density redistribution caused by a cooling hole and an inhomogeneous temperature distribution of Bitter coil of a water-cooled magnet was not considered. The obtained expressions can be implemented by Simpson’s integration with FORTRAN programming. We confirm the validity of mutual inductance calculation by comparing it with a filament method, and give the accuracy of two methods. The mutual inductance values computed by two methods are in excellent agreement. The derived semi-analytical expressions of mutual inductance allow a low computational time compared with filament method to a specific accuracy. The force is derived by multiplying the currents of the two coils by their mutual inductance gradient.     

Inductance of Bitter Coil with Rectangular Cross-section

The self-inductance of Bitter coil and mutual inductance between coaxial Bitter coils with rectangular cross-section using semi-analytical expressions based on two integrations were introduced. The current density of the Bitter coil in radial direction is inversely proportional to its radius. The obtained expressions can be implemented by Gauss integration method with FORTRAN programming. We confirm the validity of inductance results by comparing them with finite filament method and finite element method. The inductance values computed by three methods are in excellent agreement. The derived expressions of inductance of Bitter coils with rectangular cross-section allow a low computational time compared with finite filament method to a specific accuracy. The derived mutual inductance expressions can be used to accurately calculate the axial force between coaxial Bitter coils with mutual inductance gradient method.     

Mutual inductance critical current measurements in oxygen-deficient YBa2Cu3O7−δ thin films

Comparative studies of a standard four-contact DC method and a contactless mutual inductance setup have been carried out on the temperature dependence of the critical current of YBa₂Cu₃O_7– (YBCO) thin films. The DC measurements are restricted to low currents due to contact heating, whereas the mutual inductance method works well at higher currents. The temperature dependence of the values obtained by the two methods agrees fairly well in the temperature window accessible by both of them. Hence the DC values can be used to calibrate the mutual inductance ones. Thus, the critical current can be determined in a larger temperature range as compared to simple DC measurements. We have applied both techniques to two films with oxygen deficiencies of 0.08 and 0.31. The obtained calibration factor allowed us to determine the critical current density of a third sample with =0.24 inductively. The critical current density drops dramatically with the oxygen content. At T/T_C=0.80, the critical current of the film with =0.08 is more than 40 times larger than that of the film with =0.31.     

能量天平悬挂系统初始位姿识别方法

溯源至普朗克常数的能量天平法由于悬挂系统的初始位姿不理想,电磁力与砝码重力之间很难达到理想的平衡状态,总会不可避免地产生水平力与转矩,进而引起准直误差。立足于能量天平悬挂系统的准直误差的产生机理,结合能量天平悬挂系统的力学和电磁学特性,分析并建立悬挂系统初始位姿与寄生位移之间的数学模型,为准直误差的抑制奠定理论基础。     

基于光伏直驱变频式离心机系统的三元换流控制方法

针对目前市面上缺乏可应用于光伏中央空调系统的DC/DC稳压设备,以及常规光伏空调存在的能量损耗较大、能量不能实时上网等问题,提出一种无DC/DC和DC/AC等传统变流环节的光伏直驱变频式离心机系统;在系统及其3个独立单元之间建立能量平衡关系,采用三元换流控制方法对3个独立单元进行联动控制,实现能量的双向流动及实时切换。通过仿真建模及系统试验,证明该系统方案的可行性以及控制方法的合理性。     

Inductance calculation of twisted conductors by the broken line approximation

The mutual inductance between two skew straight thin conductors is obtained as a function of two vectors corresponding to two current carrying line segments. Based on the obtained analytical expressions for the mutual inductance, the versatile calculation method for the self- and mutual inductances of various twisted conductors is studied by means of the broken line or polygonal curve approximation. In particular, it is confirmed that this numerical calculation is consistent with the analytical calculation of the self- and mutual inductances for coaxial helical conductors for the asymptotic form of the long axial length. Furthermore, for the inductances of general twisted conductors, the similar asymptotic forms of the length dependence are obtained.     

非线性电磁振动能量采集的辨识研究

提出一种单自由度电磁振动能量采集器的系统辨识方法——电压映射方法,该方法基于恢复力曲面法的辨识思想,在系统恢复力函数、电磁机电耦合函数和等效电感函数的具体形式未知的情况下,能准确辨识出具有强非线性的恢复力函数、电磁机电耦合函数和等效电感函数.利用两个典型的非线性模型算例进行验证:一是含有非线性弹性恢复力的电磁振动能量采...     

A Method for Calculating the Mutual Inductance of a Coil System Using a Model of an Axially Magnetized Cylinder

Technical Physics Letters - A method for calculating the mutual inductance of a system of tightly wound coils through the energy of axially magnetized cylinders is proposed. Formulas for...     

基于SQUID的直流电阻电桥指零仪设计

设计了一款基于超导量子干涉仪(SQUID)的直流电阻电桥指零仪电路,该电路可用作高精度电阻电桥中低值电阻(0.1~100Ω)测量的指零仪电路。通过自制SQUID外围电路并优化电路其输入耦合线圈的互感值,实现微弱电桥不平衡电流的精密测量。与传统电阻电桥基于测量不平衡电压的纳伏计指零仪相比,其检测灵敏度在中低值电阻测量范围有数量级的提升。设计的作为指零仪的SQUID磁通锁定环1/f转折频率在2Hz左右,磁通白噪声水平在3.5μΦ₀/左右,并且输入线圈与SQUID互感系数高达10nH,其等效的电流白噪声密度0.7pA/。将其用作电阻电桥指零仪测量100Ω标准电阻(工作电流为10mA)的分辨率可达到10^-11量级。