...is the use of magnetic energy storage and transformation techniques as intermediate steps in the process of converting electric energy from one form to another.  When studying the field of Power Electronics, these techniques often receive less attention than the role and performance of semiconductor devices used as power switches and controllers. 

 Nevertheless, there is significant untapped potential available to those engineers who choose to pursue more completely the principles of magnetic theory and design.  Therefore, a primary focus of this book is to offer the reader a fundamental treatment of magnetic principles and a thorough understanding of the coupling of magnetic circuits with complementary electric circuits as a means to manage the flow of energy during the power conversion process.

This work is based on class notes used in senior-graduate level courses taught by Thomas G. Wilson and Harry A. Owen, Jr. in the Department of Electrical Engineering at Duke University, Durham, NC. It assumes that the reader is familiar with general circuit theory and electronics and has a mathematics background that includes differential equations.

​​​​​This book strives to be more than a presentation of procedures and good practices for the design of power electronics equipment.  Rather it seeks to provide the reader with the fundamental understanding upon which an engineer can build a career in power electronics.  Derivations are provided, not just for completeness sake, but in the belief that there is no better way to appreciate the limitations of a particular relationship than to understand the framework of assumptions and hypotheses upon which a particular theorem or proposition is based.

​A distinctive feature of this text is its emphasis on the importance of magnetics in the design of power conversion circuits.  This treatment includes magnetic materials, magnetic circuit analysis, magnetic device design and measurement, including an understanding of the fringing effects of an air gap and transformer leakage inductance. 

​​​​​​​​​​​Because magnetic devices have been so important to the electrical and electronics industry for over a century, numerous models have been developed to assist in understanding their behavior and to provide guidance in their design.  The similarities between models can be confusing and their limitations unclear. To retain a clarity of focus and because the usual conditions of operation of the three most widely used magnetic devices are different, special care is made to distinguish between the following three devices: 

1.  inductors used to store and release energy,
2. transformers used to change ac voltage and current levels with as little loss as possible, and
3. what we call energy-storage transformers that perform both the function of storage and release of energy, and the function of changing voltage and current levels. 
   

​​​​​​​With the different goals kept clearly before the reader, the similarities and differences among the many models presented become more recognizable and thereby more useful.