# Inductors and transformers for power electronics

Authors:

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