Induction Heating of Wild Steel Vessels in a Pulsating Field

Abstract

[Master of Philosophy thesis]. This work examines the heating of mild steel vessels in a pulsating field. The vessel heater is a constant voltage mains Pace uanay device which is closely related to a transformer with a short circuited secondary. The development of a design method is the objective of this thesis which is primarily concerned with unshielded heaters. Chapter two discusses. the electrical design problems: the number of heater coil turns required and the prediction of its powerfactor. The chief complication is magnetic saturation and it is worsened by the lack of a highly permeable magnetising flux path. Chapter three outlines the solutions of the latter problem, whilst Chapter four examines the literature and other authors’ approaches to the total problem. It shows the necessity of further experimental work. Chapter five describes the author’s experiments. Simple power index laws relating power input and magnetising flux are demonstrated and compared with the theories We cuenea in Chapter four. The permeances of the major flux paths are found to be unaffected by magnetic saturation. Chapter six’s analysis rests on this work. A new theory of field distribution above a permeable and conductive surface is developed and used to describe the permeances and the loss distribution. This analysis combines with the vector diagram yielding a design method. It is presented in tabular form in Appendix D and is demonstrated in the desien study of Chapter seven. The related problem of flux shielded heaters is discussed in Appendix A. It is felt that the major problems of design have been overcome in this work.