使用绝缘电阻表测量绝缘电阻时应注意的几点问题

判断电器设备能否安全运行 ,除了测量它的电器特性外 ,在使用前还应测量其绝缘电阻的大小。绝缘电阻表属国家列入强制检定目录的工作计量器具 ,使用前必须送检 ,合格后方可使用。绝缘电阻表的使用 ,主要选择电压级别及其测量范围。一般选择原则是 :５００Ｖ以下的电器设备使用５００Ｖ～１０００Ｖ的绝缘电阻表 ;瓷瓶、母线、刀闸应选用２５００Ｖ以上的绝缘电阻表。绝缘电阻表的接线柱有三个 :一个为“线路”（Ｌ） ,另一个为“接地”（Ｅ） ,还有一个为“屏蔽”（Ｇ）。测量电力线路或照明线路的绝缘电阻时 ,“Ｌ”接在被测线路上 ,“Ｅ”…     

如何正确测量电器设备的绝缘电阻

为了避免因绝缘材料老化而造成电器设备漏电或短路事故的发生，就要求经常测量各种电器设备的绝缘电阻，判断其绝缘性能是否满足设备需要。普通电阻的测量通常有低电压下测量和高电压下测量两种方式。而绝缘电阻由于一般数值较高(一般为兆欧级)，在低电压下的测量值不能反映在高电压条件下工作的真正绝缘电阻值。绝缘电阻表是测量绝缘电阻最常用的仪表，它在测量绝缘电阻时本身就有高电压电源，这是它与其它测量电阻仪表的不同之处。绝缘电阻表用于测量绝缘电阻既方便又可靠，但是如果使用不当，它将给测量带来不必要的误差。绝缘电阻表的工…     

绝缘电阻测试中的合理接线

生产实践中,绝缘电阻表(俗称“兆欧表或摇表”)是测试绝缘电阻应用最为广泛的仪器,由于其结构和原理比较特殊,加之被测电器种类的繁杂和各自的特殊性,使得如何接线成为绝缘电阻测试工作中的重要一环。以下将结合生产实践和笔者长期从事电气安全工作和计量工程技术工作的体会,谈谈绝缘电阻测试中的合理接线问题。     

数字式绝缘电阻表示值误差的检定与不确定度评定

本主要论述了数字式绝缘电阻表示值误差的表达，检定方法，及其测量不确定度的分析与评定。     

电线电缆绝缘电阻的测量

本文论述了影响绝缘电阻的因素及测量电线电缆绝缘电阻的注意事项。     

回路电阻测量结果的不确定度评定

<正>一、测量过程简述1.测量依据JJG837-2003《直流低电阻表检定装置》检定规程。2.环境条件温度:(20±5)℃;相对湿度:25%～75%。3.测量标准回路电阻检定装置(以下简称"检定仪"),测量范围:(10～200000)μΩ;最大允许示值误差:±(0.05%×读数+0.03μΩ)。     

如何正确使用绝缘电阻测量表测量绝缘电阻

本文介绍了如何正确使用绝缘电阻测量表测量绝缘电阻。首先应进行测量范围的选择，然后进行电压范围的选择，侧量前的检查，要接线正确。消除误差，保证人身，设备安全。     

绝缘电阻表检定规程适用性分析

检定规程中所确定的检定项目和检定方法与被检仪表或设备的结构及工作原理密切相关,根据绝缘电阻表结构和工作原理,对绝缘电阻表检定规程适用性进行分析,给出对绝缘电阻表检定规程进行合并,或者对绝缘电阻表进行重新分类的设想。     

低成本实用模拟乘法器设计

本文介绍了利用通常器件构成的一种低成本模拟乘法器。分析了其工作原理和应用条件．最后给出了具体的实现电路。     

A Wide-Band Digitally Controlled Frequency and Phase Multiplier

A method is considered for designing a wide-band digitally controlled frequency and phase multiplier based on nonlinear polynomial transformation of Chebyshev type applied to the initial harmonic signal. The method provides an output signal with a frequency a multiple of the input signal 1. Computer calculations are used to examine the output signal.     

Multiplier methods for engineering optimization

Multiplier methods used to solve the constrained engineering optimization problem are described. These methods solve the problem by minimizing a sequence of unconstrained problems defined using the cost and constraint functions. The methods, proposed in 1969, have been determined to be quite robust, although not as efficient as other algorithms. They can be more effective for some engineering applications, such as optimum design and control of large scale dynamic systems. Since 1969 several modifications and extensions of the methods have been developed. Therefore, it is important to review the theory and computational procedures of these methods so that more efficient and effective ones can be developed for engineering applications. Recent methods that are similar to the multiplier methods are also discussed. These are continuous multiplier update, exact penalty and exponential penalty methods.     

Analysis of the Modified Tomota-Sugiyama-Yamaguchi Multiplier

A numerical analysis of the modified Tomota-Sugiyama-Yamaguchi (TSY) time-division multiplier is compared with an extension of the analysis due to Filipski of the original TSY multiplier. Some errors and inconsistencies in a previous paper by Stabrowski are discussed. It is shown that corrections of less than 100 parts per million up to at least 2 kHz, and for any phase difference, may be achieved.     

A Multi-Tenant Usage Access Model for Cloud Computing

Most cloud services are built with multi-tenancy which enables data and configuration segregation upon shared infrastructures. It offers tremendous advantages for enterprises and service providers. It is anticipated that this situation will evolve to foster cross-tenant collaboration supported by Authorization as a service. To realize access control in a multi-tenant cloud computing environment, this study proposes a multi-tenant cloud computing access control model based on the traditional usage access control model by building trust relations among tenants. The model consists of three submodels, which achieve trust relationships between tenants with different granularities andsatisfy the requirements of different application scenarios. With an established trustrelation in MT-UCON (Multi-tenant Usage Access Control), the trustee can precisely authorize cross-tenant accesses to the trustor’s resources consistent with constraints over the trust relation and other components designated by the trustor. In addition, the security of the model is analyzed by an information flow method. The model adapts to the characteristics of a dynamic and open multi-tenant cloud computing environment and achieves fine-grained access control within and between tenants.     

An Electronic Multiplier for Accurate Power Measurements

The time division multiplier-type wattmeter is based on a new principle of operation. An operational amplifier operates as an integrator of the sum of Ez (one of the two inputs) and either +E8, or -E8, E8 being an internal standardized voltage. A pulse-width modulation in the form of switch reversals is obtained which differs from balance condition by an amount proportional to Ex. Instantaneous multiplication provides a wattmeter with dc accuracy of ± 0.1 percent up to at least 10 kHz. The output voltage is ± 1 volt for a ± 1-volt input from Ex and Ey. To obtain the required flat frequency characteristics, a coupling transformer and an adjustable resistor are provided. A time constant of 6.8 X 10-9 seconds has been achieved. The voltage signal is readily provided by a precision ratiotran. Errors of ± 0.0001 percent in magnitude and 50 microradians in phase angle are reasonable.     

扭矩倍增器计量校准和误差分析方法

介绍扭矩倍增器的原理和计量校准方法,对扭矩倍增器校准结果的表达方式和校准误差做出理论分析.     

利用试验模态参数修正有限元模型的再正交拉哥朗日乘子法

本文给出了一种利用试验模态参数来优化有限元动态模型的再正交拉哥朗日乘子法,即首先利用先验测试信息来优化初始分析模型,然后以优化模型得出的特征向量和测试频率再次作为先验模态信息来优化前次优化的模型。文末将此方法应用开工程结构的实际优化得到了满意的结果。     

A Subterahertz Multiplier Based on a Traveling Wave Tube with a Sheet Electron Beam

Technical Physics Letters - In this paper, we present the results of the study of a multiplier based on a traveling wave tube with a sheet electron beam and slow-wave double-grating structures....