Applied Mechanics and Materials Vols. 241-244

Abstract: In this paper, the electrical transient mode of synchronous generators is studied, four different simulation model of synchronous generator on sudden short circuit was built, various physical quantities were studied by simulation during the short circuit. By comparing theoretics with simulation, various physical quantities of synchronous generator produced tremendous impact and surge during the sudden circuit and they stabilized in the proceeding state of short circuit. Thoroughly simulation analyzed, the results of simulation are identical with theoretical analysis. The simulation results show that these influence factors should be considered when we design the relay protections.

Abstract: This paper presents a timing extraction algorithm which is based on the near optimum criterion, the near optimum phase appear when the spectrum of sampling signals maximum at f=1/2T.The algorithm has some features, such as fast convergence, the jitter is small, a small amount of computing and so on. This algorithm easily implements on the DSP and has a good application in the all-digital receivers.

Abstract: Due to the features of complicated test environment, variable parameters, and limited conditions in real car experiment, it has proposed a Hardware-in-Loop test platform in this paper for Hydrogen Management System (Short for HMS) based on hardware of NI PXI and software of NI Labview to plug-in fuel cell vehicle. According to HMS’s control strategy, I/O signal map, CAN communication and sensor characteristics, it has designed the hardware configuration, software program, test interface, and rapidly made validation to control logic and fault diagnosis of Hydrogen Management Unit (Short for HMU). The experiment result shows that this test platform is effective for HMU control logic validation, system status monitor, fault injection, fault tracing, and it can shorten the vehicle research and development cycle, reduce the development cost, optimize test environment and promise safety for test engineer. This test platform will make good effect to vehicle electrical system development and supply reference for vehicle test.

Abstract: This paper introduces a monitoring system for electric leakage protection based on AVR Single-Chip Computer, which the terminal monitoring PC communicates with AVR single-chip computer through wireless channel, so as to monitor the operational status of the residual current protective device (RCD) in real time. In addition, taking both amplitude and phase angle of the residual current as leakage protection judgment parameters could increase the accuracy of RCD effectively.

Abstract: At present, about 80 ~ 90% of high-power LED input power is converted into heat, so heat dissipation is a key factor affecting the use of LED. By the theory of thermal resistance, the heat conduction mode of the 4W high power LED light is obtained, and the effective cooling area of the LED radiator is computed. According to the EFD method the natural convection thermal analysis is conducted. Finally the heat experiment is conducted to verify the simulation results. The results show that the LED radiator meet the application requirement, namely the maximum temperature is less than 65°C. Undoubtedly the research will provide design guidance on the heat dissipation of LED lighting

Abstract: Among the modern industry, soft-starter has taken an important role in large-capacity motor systems. But all kinds of using soft-starters have some shortcomings, their application is restricted because of that. This article describes a type of solid-state soft-starter with a novel structure, in which a rectifier bridge structure is used in stead of the traditional antiparallel structure. Its same points and differentia are analyzed comparing with the traditional soft-starters. The new soft-starter overcomes some traditional shortcomings. It can be used for both low voltage and high voltage motor starting. Especially, when applied to a high-voltage motor starting, it has the advantage of simple structure and high reliability. This kind of soft-starters can be used in broad application prospects.

Abstract: The pulse power source; Control system; Sequential control; Trigger control Abstract. In this essay, the working process of Capacitor-Based Pulsed-Power System and the requirement of the sequential control component applied in such system has been discussed. Based on that, further description of the composition and working principle of the sequential control system has been made .The diagram of each block of the sequential control system are displayed to illustrate the working process in engineering application and problems would confront in engineering designing process. Finally, the charging and discharging test and electromagnetic emission experiments have been conducted and prove that such sequential control system can function stably and reliably in strong electromagnetic interference environment and it also has good expansibility.

Abstract: The common information model CIM in IEC61970 standard is an abstract description of existing physical objects and their relationship in power system, which has been widely used in the construction of computer application systems of power system. In order to track the real-time operation state of power system when analyzing the area of vulnerability (AOV) to voltage sags, this paper proposes a novel method to obtain the data required by AOV analysis through parsing source data defined with CIM, and source data are from the SCADA system, equipment management system and management information system of safe production. The design scheme of AOV analysis using CIM is introduced, and method of parsing CIM is also provided. Finally, the method is applied to a regional power system of China, and graphic results of AOV are shown under balanced and unbalanced faults.

Abstract: This paper presents a current comparator based four-terminal impedance bridge for quantity-value dissemination of national AC resistance standard in China. In order to enhance the feedback adjustment ability and simplify the balance process, the bridge applies a frequency selective amplifier instead of feedforward and feedback networks to balance the magnetomotive force of the current comparator. The resistance difference between the measured and standard resistor can be calculated according to their voltage difference indicated by a digital lock-in amplifier. The AC/DC resistance relative differences between Double Helix Resistor and Tinsley standard resistor are measured with the proposed bridge under 1592Hz.

Abstract: According to the transfer impedance getting from distributed parameter model,we analyse the influences of the number of turns ,capacitance to the shield and interturn capacitance on the high frequency characteristic of Rogowski coil through theories and simulations. Simulation shows that there are a series of zeros in high frequency band, but on the whole, the high frequency response does not change with the increase of frequency. The number of turns and capacitance to the shield can influence the frequency at which zero appears, but the high frequency characteristic of Rogowski coil can’t be influenced. Considering the interturn capacitance, the curve of high-frequency response characteristic presents a "V" shape ", and this leads to the reduction of higher cut-off frequency. So we should try to decrease the interturn capacitance to reduce the influence on the high frequency characteristic.