Safe Switching Research Articles

Soft-switched matrix converter for high frequency direct AC-to-AC power conversion

Abstract A soft-switched matrix converter is proposed using the zero voltage switching technique in some resonant pole inverters. A high operating frequency with safe and efficient switching improves the dynamic and spectral performances and simplifies the protection logics and snubber networks. Further, it can be implemented using simple analogue circuits, having similar transfer characteristics to those of the modern pulse width modulated matrix converters, such as maximum voltage transfer ratio and unity input displacement factor. Analyses, design and simulation results are presented to verify the operating principle.

Particle Tribology

Progress in wear prevention can be made only when a better understanding of the mechanisms by which wear occurs and of the controlling factors has been achieved. Much of the research on wear has been directed towards the study of surfaces in relative motion and the changes brought about by their interaction and the lubricant or environment present. Little attention has been paid to the particles generated by the interaction of surfaces in relative motion and thus valuable information has been neglected. Each particle present in a lubricant carries with it the history of the conditions under which it was formed, and thus careful examination of particles can yield specific information concerning the condition of the moving surfaces from which they were produced. Techniques of particle examination are reviewed and the various theories of wear are considered in the light of information obtained by the examination of lubricant contaminant particles. The development of a powerful new technique of machinery condition monitoring by particle tribology to allow a prognostic approach to failure prevention and the safe switch from expensive periodic maintenance to failure prevention maintenance is outlined with examples from the work of NEL. The role of particle tribo-analysis in the development of machinery to ensure a maintenance and failure free life of sufficient duration to adequately cover capital expenditure is discussed.