This book is mainly intended for designers and users of magnetic components in power electronics. It can also be used for didactical purposes. Magnetic components such as inductors and transformers constitute together with the control and the semiconductor components, the main parts in the design of power electronic converters. Some experience teaches that the design of the magnetic parts is still often done by trial and error. This can be explained by a (too) long working-in time for designing inductors and transformers. The design has many aspects, such as the magnetic core and winding, eddy currents, insulation, thermal design, parasitic effects, and measurements. A lot of literature exists concerning.