变频压缩机在冷柜上的应用分析

由于变频技术在制冷空调领域的应用逐渐成熟,以及未来节能环保的趋势,很多大型超市、商场等终端用户逐渐采用变频压缩机冷柜取代传统的定频压缩机冷柜,利用变频控制系统调节压缩机的转速并控制柜内环境温度。目前市场上运用最广泛的控制方式是PID控制和Stand Alone控制。本文根据冷柜的应用实验结果,分别对使用两种控制方法的冷柜的制冷能力和耗电量进行比较,并分析未来变频压缩机的应用前景。     

基于风冷冰箱薄壁化需求的节能研究

以一款薄壁化大容积率风冷冰箱为研究载体,分析多种节能技术方案,完成整机能耗的匹配验证.结果表明,采用单循环制冷系统,通过应用高效变频压缩机、变频风机风机、高效风道结构,控制逻辑优化以及VIP板等设计方案,全薄壁大容积风冷冰箱达到了新国标一级能效设计要求,较常规的大容积冰箱用三循环制冷系统性价比更优.     

压缩机低温工况对冰箱耗电量影响

通过对冰箱压缩机实际运行工况与GB/T 9098-2008工况差异计算、对比分析,提出优化压缩机低温工况对冰箱实测耗电量影响;通过实验表明优化冰箱压缩机低温工况,能一定程度降低冰箱耗电量,达到节能降耗目的.本文对压缩机优化设计提供了一定参考依据,对压缩机与冰箱如何实现最优匹配具有指导意义.     

仿真计算指导超节能冷柜系统设计

家用冰箱/冷柜的系统设计过程复杂,需要综合考虑箱体漏热量、压缩机制冷量以及与蒸发器、冷凝器等的匹配,这一过程仅仅依赖经验往往难以快速、准确地达到最佳效果。计算机仿真技术近些年快速发展,已应用到许多领域,但在家用制冷器具中的应用尚刚刚开始。本文率先引入AMEsim模拟对家用冷柜制冷系统进行模拟,通过该模拟得到了系统的最佳灌注量以及能耗数据,并且与实际测得的数据一致。     

变频压缩机在冰箱中的节能技术初探

冰箱应用的压缩机与冰箱的能耗关系密切,变频压缩机可以有效降低冰箱的能耗,实现冰箱的节能。基于此,本文从变频压缩机发展及其工作原理入手,对变频压缩机在冰箱中的节能技术进行了分析,首先介绍了变频压缩机的节能原理,然后阐述了节能技术的应用效果,最后分析了节能技术的应用方式,技术人员可以通过直冷单循环制冷系统、无霜冰箱系统以及风直冷多循环系统实现冰箱的节能。     

HCs冷柜系统最佳充注量的实验研究与理论分析

制冷剂的物性对制冷系统的循环性能有很大影响，在小型制冷装置中使用新型制冷剂时，只有对毛细管和制冷剂充注量进行优化匹配，才能使系统在较好的状态下运行。本文对一台使用R290／R600a(1／1)制冷剂的冷柜系统进行了选择最佳充注量的实验研究，讨论了充注量的多少对蒸发压力、冷凝压力、蒸发器温度分布、压缩机开停机时间等方面的影响，得到了耗电量最少的充注量，并对此条件下的循环特点进行了理论分析。     

新型节能技术在对开门冰箱上的运用研究

在对开门冰箱设计过程中,采用新的节能技术,同时引进先进的实验分析手段,通过优化冰箱保温层材料配方,减小冰箱发泡层的泡孔直径,降低发泡料的导热系数;其次通过改善门封结构设计减小通过门封进入冰箱的负荷量;同时通过提高制冷系统的制冷效率和换热效率以及优化冰箱PCB的控制方法,从原理分析和实验验证进行充分的论证,使对开门冰箱的耗电量降低20％左右。通过以上措施对开门冰箱能效指数比国家1级能耗要求低20％,达到国家超级节能产品的要求。     

风冷冰箱实际工况及该工况下压缩机效率提升的研究与应用

压缩机是冰箱的核心零部件,压缩机性能是影响冰箱能耗的重要因素.按照规定的试验和数据处理方法研究风冷冰箱实际运行情况下的制冷系统工况,研究发现实际工况较标准工况压缩机负载减少.按实际工况指导压缩机性能设计,并测试优化后的压缩机性能:在标况条件下单机性能下降,但在规定的冰箱实际工况条件下单机性能提升0.5％～4％,选定的整机样品能耗可降低2.2％.     

风冷冰箱实际工况及该工况下压缩机效率提升的研究与应用

压缩机是冰箱的核心零部件,压缩机性能是影响冰箱能耗的重要因素.按照规定的试验和数据处理方法研究风冷冰箱实际运行情况下的制冷系统工况,研究发现实际工况较标准工况压缩机负载减少.按实际工况指导压缩机性能设计,并测试优化后的压缩机性能:在标况条件下单机性能下降,但在规定的冰箱实际工况条件下单机性能提升0.5％～4％,选定的整机样品能耗可降低2.2％.     

风冷冰箱实际工况及该工况下压缩机效率提升的研究与应用

压缩机是冰箱的核心零部件,压缩机性能是影响冰箱能耗的重要因素.按照规定的试验和数据处理方法研究风冷冰箱实际运行情况下的制冷系统工况,研究发现实际工况较标准工况压缩机负载减少.按实际工况指导压缩机性能设计,并测试优化后的压缩机性能:在标况条件下单机性能下降,但在规定的冰箱实际工况条件下单机性能提升0.5％～4％,选定的整机样品能耗可降低2.2％.     

感应电机无速度传感器控制自适应速度观测器

理论与实践证明自适应速度观测器是实现高性能的感应电动机无速度传感器控制系统的有效方法之一。由于该系统的非线性性质,在观测器设计以及系统应用中还有许多有待解决的问题。针对此类问题,从理论联系实际的角度,分析现有的电机磁链、速度观测器理论的要点及其成果,如建模的条件、自适应速度估计算法及其物理性质、系统稳定性分析、线性化方法、以及观测器参数的辨识等。同时,给出了实验结果、指出了这些内容中尚存的相关问题。     

High speed power

This paper presents the need for compatibility between European rail networks. This leads to the adoption of dual 25 kV as the power of choice for operators. Dual 25 kV literally doubles the power available to rail networks, helping rail operators to meet some of the demands they are facing. Not surprisingly, this fact, along with the EU directive on 'interoperability of the trans-European high speed rail system', which aims to ease the circulation of high-speed trains through the various train networks of the European Union, will lead it to become the future standard across Europe     

Very low speed and zero speed estimations of sensorless induction motor drives

Recently, speed sensorless control of induction motor drives received great attention to avoid the different problems associated with direct speed sensors. However, low speed operation with robustness against parameter variations remains an area of research for sensorless systems. Stator resistance is of utmost importance for good operation of speed sensorless systems in low speed region. In this paper, a sliding mode current observer for an induction motor is presented. An estimation algorithm based on this observer in conjunction with Popov's hyper-stability theory is proposed to calculate the speed and stator resistance independently. The proposed speed observer with parallel stator resistance identification is first verified by simulation. Experimental results are included as well as to demonstrate the good performance of the proposed observer and estimation algorithms at very low and zero speeds.     

Improving Web application speed

The paper begins by discussing bottlenecks to users accessing Web sites. It goes on to consider database structure, tables and indexes. Also considered are query syntax, the role of application servers and their numbers. The paper concludes with a discussion of network architecture and content quantity     

风速传感器实测风速不确定度评定对比研究

在风速传感器实测风速不确定度的评定中,传统方法是将实测风速测量模型简化后采用GUM(guide to the expression uncertainty in measurement)进行评定。但GUM并不适用于复杂模型,为了研究实测风速不确定度评定的可靠方法,对风速传感器分别采用GUM和MCM(Monte Carlo method)进行不确定度评定,对比分析评定结果,并利用MCM评定结果验证GUM的适用性。结果表明,简化模型下GUM和MCM评定结果差异较小,但只有标准不确定度取一位有效数字时,GUM评定方法通过验证,评定结果一致性好;实测模型下MCM和简化模型下GUM评定结果对比得到,两者包络形状相似,但实测风速最佳估计值明显偏大,GUM评定方法不能通过验证;改变部分输入量分布时,两种方法得到实测风速最佳估计值非常接近,但GUM评定得到包含区间比MCM明显增宽,概率分布相差较大,GUM评定方法不能通过验证。因此,应当根据模型的复杂程度、输入量分布情况以及测量结果准确度的要求选择合适的评定方法,如果输入量分布均服从正态分布且对测量准确度要求不高,可使用GUM进行评定,反之建议使用MC...     

Energy yield of passive stall regulated fixed speed wind turbine with optimal rotor speed

This paper presents a lucid mathematical deduction of optimal rotor speed to maximize the energy yield of wind machines with passively stall regulated Fixed Speed Scheme (FSS). The power captured at a particular wind speed is dictated by the turbine characteristics in conjunction with the type of drive (variable speed or fixed speed). However, the energy yield estimation requires knowledge of wind speed frequency distribution. Studies have revealed that the probability density function could be fairly represented by Weibull distribution with wind velocity being suitably scaled. Considering these facts, the concept of Maxima Energy Indicator (MEI) for FSS has been developed from first principles to obtain optimal rotor speed ($w_{\text{opt}}$) numerically. Alternatively, MEI is further simplified using Incomplete Gamma Function which forms the mathematical solution for $w_{\text{opt}}$. It turns out that $w_{\text{opt}}$ of FSS varies with location owing to changes in Weibull parameters. Therefore, it is deceptive to compare the energy yields of FSS with its counterpart Variable Speed Scheme (VSS) without taking into consideration the optimum rotor speed of FSS. With this motivation, computations have been performed which compare the annual yields of both the alternatives, the rotor speed of the low cost stall regulated FSS being optimized.     

异步机调速原理及转速公式探讨

与直流机相同,异步机转速是由理想空载转速和转速降合成。同步转速与理想空载转速的运动属性不同,两者没有直接、必然的联系。传统电机学导出的异步机转速表达式仍然是定义式,不能视为公式,更不能作为指导交流调速的理论依据。高效率调速的关键在于:在主磁通恒定的条件下,控制定子或转子的感应电势(E1或E2)以改变理想空载转速。异步机可等效于直流并激电动机,调速的关键在于使主磁通不变,相当于将并激电动机改变为它激电动机。串级、内馈、双馈调速和调压变频调速同属于电磁功率控制原理,性能一致,区别是控制对象不同。转差率和效率是完全不同的两个概念,不能用转差率变化与否来评价调速性能。转差率应具体区分为电转差率和静差率,前者影响理想空载转速,后者影响转速降。     

A new speed measurement system

Magnetic contactless speed measurement sensor targets steel industry. Controlling any production line requires the use of many sensors along the line. A basic measurement in steel lines is the determination of the exact linear speed of some portions of the process. This article comments on the complete speed measurement system for steel lines, with a cost lower than US$300, a range up to 800 m/min, and accuracy of about 0.4%. Accuracy is influenced by the position of the sensors.     

Variable speed drives evaluation test

We present a test protocol and results of tests on pulse width modulated (PWM) drives rated at 3 hp and 20 hp and supplied from a 480 V line. The induction motor was turning a 25 hp computer-controlled DC dynamometer. This dynamometer was powered from the same source through a stepdown transformer and a regenerative controlled rectifier. Data (speed, torque, input voltages, currents) were collected and processed in a data acquisition system. The following tests were performed: efficiency and harmonics, voltage sags, and capacitor switching transients. Tests wee also conducted on three nontypical drive configurations     

High speed fiber optics backbones

In late 1995, the data communications networks at the Fletcher Challenge Canada's Crofton pulp and paper mill had reached capacity and were suffering from overload. The large growth in process control information and personal computers over the past few years was straining the abilities of existing coaxial and fiber optic systems to reliably transfer data. In addition, increased network complexity made troubleshooting the networks extremely difficult and time-consuming. This article discusses the design methods used to create a new fiber optic backbone to provide the data carrying capacity and reliability needed for the pulp and paper mill's computers and control systems. High-speed network technologies such as ATM (asynchronous transfer mode), FDDI (fiber distributed data interface) and fast Ethernet were compared for their suitability in industrial environments. The design also incorporated Ethernet switches so that the existing Ethernet networks could attach at minimal cost. These switches subdivided the original single large network into approximately 24 sub-networks. This division greatly increased the network's allowable traffic capacity and prevented problems in any one area from propagating throughout the mill, and thereby reduced network and process downtime