Influence of tyre pressure and vertical load on coefficient of rolling resistance and simulated cycling performance

The coefficient of rolling resistance (C _r) for pneumatic tyres is dependent on hysteresis loss from tyre deformation which is affected by the vertical force applied to the tyres (F _v) and the tyre inflation pressure (P _r). The purpose of this paper was to determine the relative influence of five different levels of P _r and four different levels of F _v on C _r and to examine the relationships of C _r with P _r and F _v during cycling locomotion. F _v was modified through carriage of additional mass by the subject. C _r was determined with the coasting deceleration method from measurements performed in a level hallway. Iterations minimizing the sum of the squared difference between the actual deceleration distance and a predicted deceleration distance were used to determine C _r. This latter distance was computed from a derivation based on Newton's second law applied to the forces opposing motion. C _r was described by a hyperbolic function of P _r (C _r = 0.1071 P _r ^?0.477, r ² = 0.99, p < 0.05), decreasing 62.4% from 150 kPa (C_r= 0.0101) to 1200 kPa (C_r = 0.0038). F _v was related to C _r by a polynomial function (C _r = 1.92.10^?8 F _v ² ?2.86.10^?5 F _v + 0.0142, r ² = 0.99, p = 0.084), with an added mass of 15 kg (C _r = 0.0040) resulting in an 11.4% increase in C _r compared with no added mass (C _r = 0.0035). From this study, it is concluded that the relationships of P _r and F _v with C _r for cycling are non-linear. Furthermore, a simulation model shows that changes in P _r and F _v of the magnitude examined here have an important effect on competitive cycling performance.     

基于联合试验装置的TCR阀高电压试验方式损耗分析

详尽分析了晶闸管控制电抗器(Thyristor Controlled Reactor,TCR)阀高电压试验方式的电路拓扑与工作原理,采用对损耗分类的方法对TCR阀高电压试验方式下各类损耗进行了详细定义,并给出了各类损耗的计算公式.在此基础上,结合高电压试验方式中TCR阀的工作时序分析了试品阀开通1次的总能量损耗及辅助阀开通1次的总能量损耗.针对同一算例的损耗分析结果与EMTDC仿真结果比较表明,在TCR阀高电压试验方式下该损耗分析方法可给出比PSCAD/EMTDC仿真更准确、更全面的结果.     

田湾核电站失去外电源的概率风险评估

对江苏田湾核电站失去外部电源(Loss of offsite power，LOSP)事件进行概率风险评估。考虑了核电站接入华东电力系统后电网与系统间的相互影响．指出导致核电站失去外电源的4个事件：①主网稳定破坏：②计划检修与故障重迭，导致4个回路联络线全部不可用；③飓风导致断线．使4个回路联络线全部不可用；④500kV及220kV主变电站电气设备故障，主变全部停电。使核电站失去外电源。给出这4个事件的计算方法和定量计算结果．并给出了提高可靠性的措施。     

高温超导线材交流特性研究进展

本文简要概述了高温超导线材交流特性的研究进展，并对其实际应用和存在的技术问题进行了探讨。     

干式空心电抗器电流分布与损耗

根据干式空心电抗器的结构特点，阐述了干式空心电抗器的电流分布与损耗。通过对计算程序、制造工艺、原材料使用的分析，指出了干式空心电抗器环流损耗产生的原因，提出了解决环流损耗的途径。     

兔毛纱防掉毛机理研究

解决兔毛织物掉毛是目前世界性难题，本研究在保证兔毛风格前题下，找到了解决掉毛问题的关键，并分析了兔毛掉落的机理和防止掉毛的重要因素，从而提出一种新的防掉毛方法，热熔粘合法，为兔毛生产打通了一条新的途径。     

无功和电压质量

针对电网的特点,浅谈电力系统电压和无功功率的重要作用及几种控制技术的应用。     

前苏联核电站用1000 MW四极汽轮发电机

介绍"电力"工厂20世纪80年代研制的TBB-1000-4型四极汽轮发电机的主要技术数据、结构以及厂内试验结果.图1表3     

A study on the improvement of release application characteristics of pneumatic brakes for freight train

We have performed experimental studies for the improvements of pneumatic brake systems of freight trains. Currently, most of the freight trains operated by the Korean National Railroad have either empty-load or diaphragm type brake systems. In this study, appropriate methods that the air pressure characteristics in both type of brake systems are in accordance with each other have been investigated. We have also performed running tests using a 30 car-train set to design optimum capacity of a quick release valve. The test results show that the quick release valve is considerably effective in shortening the release time of the diaphragm type brake system. In the case of a normal brake application, the diaphragm type brake system with the quick release valve reduces the release time to 34% of that of the system without the quick release valve. This release time is almost equivalent to that of the empty-load type brake system. Accordance of braking performance in different types of brake systems in a train set is expected to prevent wheel flats and to reduce maintenance costs.     

Closed loop torque SVM-DTC based on robust super twisting speed controller for induction motor drive with efficiency optimization

This paper presents a space vector modulation (SVM) based Direct Torque Control strategy (DTC) for induction motor (IM) in order to overcome the drawbacks of the classical DTC. SVM can reduce the high torque and flux ripples by preserving a fixed switching frequency. This technique is known by the closed loop torque SVM-DTC. Moreover, the control scheme performance is improved by inserting a second order sliding mode super twisting controller in the outer loop for speed regulation. This nonlinear technique ensures a good dynamic and high robustness against external disturbance. Furthermore, the IM energy optimization is treated in the second objective of this paper. A proposed model based loss minimization strategy is presented for efficiency optimization. This strategy chooses an optimal flux magnitude for each applied load torque. The proposed optimized SVM-DTC algorithm will be investigated by simulation and real time implementation using Matlab/Simulink with real time interface based on dSpace 1104 signal card.