Surge load experiment design and results analysis of relay
Due to the transient overvoltage or overcurrent when relay's contacts switch different loads, the relay's contacts are damaged by transient arc erosion of electrical-over-stress, which influences the reliability of relay seriously. Firstly, according to the life test requirements of one type of electromagnetic relay with permanent magnets, the load circuit and the testing program are designed, which has characteristic of adjustable surge current time. Secondly, the contacts' breaking arc and closing bounce under 2A resistive load, 5A resistive load and surge load are analyzed. The influence of surge load on relay's electrical life is studied with increasing of test cycles. Finally, based on the testing data, the optimal design of relay has been modified and the results have been analyzed, which is helpful for improving the life of the relay.
Research and Design of Three-level Composite Surge Protective Device
In order to solve the problem that the Surge Protective Device design approach is too simplethe protection against overvoltage is ineffective and the operating period is not long,based on the overvoltage protection requirements of signal power distribution system in the ministry of railways,and the request of IEC 61643-21: 2000,it was put forward a design approach of paralleling with a gas discharge tube,Zinc Oxide Varistor and transient suppression diodes to form a three-level composite structure. Through PSpice software simulation analysis and research,combined with the actual impact test,the reliability of the circuit structure is verified. Composite surge protector gives full play to the advantages of three kinds of commonly used surge components,making up the defect of the surge element monomer structure,which has the characteristics of low residual pressure,large currentcapacity,and quick reaction,it has a certain practical engineering exploitation value in over voltage protection of low voltage power supply system.
In-services and empty threats: The roles of organizational practices and workplace experiences in shaping U.S. educators' understandings of students' rights.
This paper applies theoretical frameworks from organizational sociology and sociolegal studies to examine factors associated with educators' conceptions of students' rights to due process in disciplinary actions. We analyze a unique representative data set of 402 teachers and 200 administrators in U.S. high schools to investigate how educators understand the rights to due process articulated in the Supreme Court case of Goss v. Lopez (1975). We then examine whether individual characteristics and participation in organizational processes are associated with educators' understandings of students' due process rights. Findings suggest that educators' understandings of students' entitlements to due process vary with educators' level of education, experience of school-related legal threats, and participation in district or diocese in-service training programs on students' rights. Results point to organizational climate as a key factor in shaping educators' rights conceptions and the role of law in American schools.