三相电动机单相运行故障分析

电动机单相运行(又称两相运行),是指三相电动机在运行中,由于某相电源线因故断电,电动机却运行的一种情况。此时电动机温升会很高,伴有焦糊味,且发出异常沉闷的"嗡嗡"声。(一)导致三相电机单相运行的原因1.电源故障。由于供电线路负荷过大,在用电高峰期造成变压器低压侧的保险片和配电室内供电总闸刀熔断器熔断,导致三相电源缺相。     

利用无功元件平衡不对称有功负载的研究

对于三相四线制供电的配电系统中的单相负载,由于负荷消耗的随机性,经常会引起三相有功负载不平衡。本文提出了一种有效的方法,利用相量图分析了如何用纯电感和纯电容这两种无功元件平衡三相不平衡的有功负载。     

仿真软件在三相电路性能分析中的应用

三相交流电路是复杂的正弦电路,由三相电源、三相负载及三相传输导线构成,由于三相供电与单相相比,具有成本低,效率高的优点,所以在电能的产生,传输及使用方面得到了广泛应用.本文首先论述了三相电路的概念,在此基础上利用仿真软件辅助教学,验证三相电路的性能.     

三相异步电动机用于单相电源的改接

三相异步电动机由于构造简单、成本低、维修使用方便、运行可靠等优点,被广泛应用于工农业生产。三相电动机的电源应是三相电源,但实际上常会遇到只有单相电源的问题,特别是在家用电器上用的都是单相电动机,坏了以后想用三相电动机代替,就必须做适当的改接,以使三相电动机适应于单相电源而正常工作,下面具体谈其接线方法。改接原理三相异步电机是利用三相互隔120°角度的平衡电流,通过定子绕组时产生一个随时间变化的旋转磁场,以驱使电动机运转工作的。在谈到三相异步电机改单相使用之前,先要说明单相异步电动机旋转磁场建立问题,单相电动机…     

基于Matlab/Simulink的电力变换电路仿真

由于电力变换电路种类较多,在"电力电子"课程教学中,学生难以理解复杂电路.本文应用Matlab/Simulink强大的仿真功能,对各种电力电子变换电路进行建模仿真,并着重介绍了三相半波整流电路、三相桥式整流电路和直流斩波电路的仿真,并对其中的难点进行了详细分析.使学生对课堂上所学的内容有一个直观的认识,对加深学生的理解和后续学习有较大的作用.     

有功负载引起无功功率转移现象分析

在三相四线制供电系统中,当单相有功负载跨接两个单相电源时,就会在两个单相电源内部分别引起多余的感性无功负载和容性无功负载。对此,本文利用简单、直观的相量图及等效原理分析有功负载引起无功功率转移的原因。论述了两种虚拟无功负载存在的机理。     

基于配电系统节电器的谐波抑制研究

模拟配电网用户侧典型负荷组成,搭建了节电器节电行为研究平台.通过电能质量分析仪、三相可编程电源等在线监测与分析仪器,研究了配电系统节电器在阻感负荷运行工况下对负荷侧电网谐波的抑制行为.结果表明,配电系统节电器抑制电力用户侧谐波效果明显,单相电流谐波可降低2％ ～5％,波型稳定,电能质量得到有效提高.     

基于DSP的三相-单相矩阵变换器的设计

本文主要介绍了三相-单相矩阵变换器基本的工作原理,并设计了以DSP为控制器的三相-单相矩阵变换器系统.论文给出了关键的系统电路原理图及程序流程图.结果表明,本系统可以满足电源的变换要求.     

浅析配电台区三相负荷不平衡产生的原因及治理技术

在智能配电台区中会经常三相负荷不平衡问题,因此供电企业必须加强对配电台区的三相负荷不平衡现象分析,并采取有效的措施对问题进行治理.本文分析配电台区三相负荷不平衡原因和解决方案.     

MathCAD在“电力电子技术”教学中的应用

计算机仿真为"电力电子技术"课程的教学提供了一个有效的工具。本文以单相交流调压电路和三相逆变电路为例,对MathCAD在"电力电子技术"教学的应用进行了介绍,并和Matlab及PSpice进行了比较。结合演算过程及结果分析进行教学可以使学生更容易理解、掌握相关的知识,这对提高教学质量和培养创新人才具有重要的意义。     

BST移相器的优化设计算法

近年来,人们在微波应用领域对BST移相器进行了很多研究。本文对BST铁电移相器电路进行了等效分析,就电路中重要部分-BST电容加载的方法进行研究,创新地提出了BST电容非周期性加载的设计思路。用M atlab编程实现并论证这种设计思路。使用这种优化方法设计出的非周期性加载移相器各项指标均优于周期性加载移相器,现已申请专利(专利号:200510028313.9)。     

Impedance Characteristics of Two Coplanar RLTs in Millimeter Wave VCO Waveguide Cavities

Impedance characteristics of two coplanar radial line transformers (RLTs) placed in millimeter wave voltage control oscillators (VCOs) waveguide cavities have been studied in this paper. Mode matching methods are employed to calculate self impedance of the RLT mounted on active device and mutual impedance of the two coplanar RLTs. Some general rules concerning impedance characteristics of two coplanar RLTs configuration influenced by the parameters of the structure have been deduced. In addition, an equivalent network is presented based upon the impedance matrix of the coplanar RLTs; the load impedance looking outward from the active device has been derived in virtue of the equivalent network and the impedance of varactor diode. The equivalent network which describes the relationships between the load impedance and the impedance of varactor diode is helpful for developing millimeter wave varactor-tuned VCO of this structure.     

A controllable resistor and its applications in pole-zero tracking frequency compensation methods for LDOs

unit-gain compensation ceil and pseudo-ESR (equivalent serial resistor of load capacitor) power stage have been realized by this controllable resistor.Their advantages and limitations are discussed and verified by simulation results.     

A two-section dual-band Chebyshev impedance transformer

We derive a two-section dual-band impedance transformer that matches a resistive load at two arbitrary frequencies. The transformer is equivalent to a two-section Chebyshev transformer whose parameters have been adjusted to achieve reflectionless notches at the two desired frequencies.     

无功功率及其相关概念的深度理解

有功功率、无功功率、视在功率和功率因数是电工学中非常重要的基本概念,贯穿电气工程专业课程体系的始终。一些本科教材体系中存在着对这些概念——特别是无功功率概念的模糊引导,导致歧义产生。典型的误解是把电源与负载间存在功率交换视为无功功率产生的必要条件。这种歧义影响了电气工程专业学生及其从业人员对这些概念的理解和应用。本文通过一些典型实例,深入阐释这些概念的内在含义,以期消除歧义,提高教学效果。     

A Theory of the Multimode Resonant Raman Scattering Compared with the Experiment

The dynamics of the Resonant Raman Scattering (RRS) of multimode broadband lasers is described and resolved without neglecting the phase and cavity effects. The multimode pump structure leads to an equivalent Raman structure by mixing interaction. When the stokes and the pump modes have the same phase, the forward multimodal Raman scattering shows a gain equivalent to the gain of a single mode pump with an equivalent mean power, so that in a Raman resonator the Raman modes can be synchronously amplified to the saturated power until the de phasing destroys the Raman conversion. All these effects have been experimentally observed. Besides an incoherent scattering process is always present in competition with the coherent one.     

New insights into board level drop impact

This paper presents new insights into board level drop impact using analytical relations that have been developed. The dominance of bending moment as a failure driver leads naturally to the dynamic–static analysis technique, which together with the dominance of fundamental flexing mode led to a simple relation for interconnection stress. Using this relation, it has been found that miniaturisation of interconnection with accompanying reduction in load bearing area is the most significant source of drop impact vulnerability. Finally, a low cost PCB has been proposed with equivalent dynamic characteristic and near equivalent interconnection stress as the eight-layer microvia board specified in JEDEC Std JESD22-B111.     

Real-time optimization of an active filter's performance

Recent advances in power electronics have meant that many loads now draw a distorted current from the power supply. For the same real power consumed, the apparent power for the distorted load is greater than the equivalent sinusoidal load. A real-time active filter optimization algorithm has been implemented in a TMS320C30 DSP, with the aim of maximizing the monetary saving from active filtering by reducing the apparent power consumed at the point of supply. As the basis for this optimization a savings function which takes into account active filter efficiency, the cost of energy, and the supply and load current distortion before and after filtering, has been derived. A simplex optimization technique, which is able to find the optimum operating point even under varying load conditions, is used to maximize these energy savings     

Broadband phase modulators in integrated fin-line technique for millimeter-wave applications

Three structures of broadband reflection type phase modulators in unilateral fin-line are presented. The circuits have been analysed assuming ideal transmission line equivalent circuits for the fin-line sections, while the switching element, a pin-diode, is represented by a typical equivalent circuit at Ka-band. The insertion loss in all three cases is better than 1.5 dB and the phase error for a 180 degrees phase shift is less than 4 degrees over a 12% bandwidth, while a 16% bandwidth is achieved for a 90 degrees modulator at a phase error of 2 degrees.     

一种适用于锁式铁氧体器件的驱动电路

分析了锁式铁氧体器件的等效负载特性,在此基础上给出了专用驱动电路的设计,并分析了其原理以及应用结果。从中可以看出,该电路能用于驱动所有锁式铁氧体器件,特别适用于驱动锁式铁氧体移相器。