An analysis of pulse transformers
Permanent link to Research Commons versionhttps://hdl.handle.net/10289/15337
This thesis focuses on developing a comprehensive understanding of the behaviour of the output pulse transformer used in an electric fence energiser, a unique application which has received little attention in the literature. Maxwell’s Equations form the starting point for an investigation into the magnetisation of the magnetic core under high current pulse conditions. An equation is derived which describes the time dependent nature of the penetration of the magnetic field into the core material. The concept of a region of high permeability moving into the lamination as a result of rapid saturation is also developed. Quantitative results are obtained for the area of this high permeability region, both from the pulse magnetisation equation and by analytical methods. The analytical approach is also used to derive expressions for the pulse current, output voltage and power, and inductance. The analytical model of the output transformer provides much insight into the transformer’s behaviour, and into the influence upon performance of the various circuit elements. The description of pulse magnetisation is a key factor in the development of both analytical and electrical circuit models of the output transformer. The final part of the thesis considers the output transformer from the perspective of an electrical circuit model, which is developed as a direct representation of the physical transformer. The inductor-reluctance method is used to develop the model, and methods of calculating each parameter are derived, so that the final model may be obtained directly from the transformer’s specification without the need for experimental measurements. The electrical circuit model is implemented using a SPICE simulator, and an analysis of the transformer highlights the major design parameters. The description of pulse magnetisation, the analytical model and the electrical circuit model combine to provide a comprehensive description of the behaviour of the output transformer, and provide the tools required for design and further investigation of this application.
The University of Waikato
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