Inductors and transformers for power electronics

Alex Van den Bossche, Ghent University, Belgium.
Vencislav Valchev, Technical University of Varna, Bulgaria
ISBN: 1574446797, CRC Press number DK4141
Editor CRCPRESS, Boca Raton, Florida
Language (US English) 
Available since March 2005



The second author was during a cumulated period of 3 years also at Ghent University.

The book is mainly intended for designers and users of magnetic components in power electronics where the frequencies are typically between 20kHz en 2MHz. However some parts may also be useful at 50Hz or high frequency communication applications. One observes that the design of magnetic components is still often done by trial and error. This is not strange as the working-in time on the subject is (too) long. The design has many aspects, such as choice of magnetic material and winding, eddy currents, insulation, thermal aspects parasitic effects and measurements.  A lot has already been published on the subject, but the information was spread on many articles and methods. For the considered frequency, the intuition misleads us, indeed a larger wire increases the eddy current losses but decreases. For similar windings, inductors may show 10 times more losses than transformers, especially close to the air gap.  The book is more axed to classical (analytical) calculation methods, although numerical methods are used in the background. Methods are given to obtain good results in the presence of eddy currents. It can be seen as a good complement on books for power electronic circuits.

The chapters are made progressive, from fast and less accurate approaches for non-specialists to more involved, more accurate methods.

Chapter 1 is an introduction about magnetic principles and magnetic materials.

Chapter 2 presents a fast design approach including eddy currents. In the actual designs, the eddy currents are almost never negligible. Simple rules of the thumb like “ the eddy currents are negligible if the diameter is lower than the penetration depth”, are not valid. However it is true that the major part of the eddy current losses is due to transverse fields, like an induction heating. A decision tree leads the designer to a good design. The chapter contains also a number of verified examples. Het hoofdstuk bevat ook een aantal uitgewerkte voorbeelden.
The next chapters show more details about specific aspects, they are quite independent and have own references and appendices.

Chapter 3 describes the use and the losses of magnetic materials such as ferrites, iron powder, amorphous iron and nanocrystalline iron.

Chapter 4 handles on the coil winding aspects, square and hexagonal fitting, filling factor, but also on electrical insulation and insulation distances.

Chapter 5 is quite mathematical and describes the proposed method for eddy current loss calculation, which is used in chapter 2 in a simplified form.
The authors compare the proposed method with existing methods, to know which one can be still applied and where large errors are made.

Chapter 6 describes thermal aspects. It is not obvious to apply general rules of heat transfer on transformer like shapes.

Chapter 7 handles on parasitic capacitances, how to estimate them, influence them and modelling.

Chapter 8 goes into details of inductor design: special shapes, foil winding, planar and litz wire concepts.

Chapter 9 details transformers: such as modelling, interleaving windings and paralleling windings.

Chapter 10 gives an answer to questions as “is 50% copper loss and 50% iron loss always a good solution for minimal loss? What in presence of eddy currents?

Chapter 11 gives an overview of measurement methods like impedance measurements loss measurements with oscilloscopes or with calorimeter.

Appendix A Rms values of waveforms
Appendix B Data of ferrite cores
Appendix C Data of enamelled wire
Appendix D Mathematical functions

The Book contains 480 pages, 247 drawings, 48 tables and more than 700 equations.

It is clear that even more expertise is available, also a number of aspects have been continued after the book in publications.

Relevant publications

  • “Inductors and Transformers for Power Electronics” Alex Van den Bossche, Vencislav Chechov Valchev, , February 23, 2005, CRC-press, Boca Raton USA, ISBN 1574446797, hardcover, 480 pages.
  • A. Van den Bossche, V. Valchev, M. De Wulf,  “Wide frequency complex permeability analytical function for linear magnetic materials”, journal of magnetism and magnetic materials  272-76: pp. 743-744 Part 1 Sp. Iss. SI, MAY 2004  SCI-IF: 0.910 in 2003