Overview

This course can also be taken for academic credit as ECEA 5703, part of CU Boulder’s Master of Science in Electrical Engineering degree. This course covers the analysis and design of magnetic components, including inductors and transformers, used in power electronic converters. The course starts with an introduction to physical principles behind inductors and transformers, including the concepts of inductance, core material saturation, airgap and energy storage in inductors, reluctance and magnetic circuit modeling, transformer equivalent circuits, magnetizing and leakage inductance. Multi-winding transformer models are also developed, including inductance matrix representation, for series and parallel structures. Modeling of losses in magnetic components covers core and winding losses, including skin and proximity effects. Finally, a complete procedure is developed for design optimization of inductors in switched-mode power converters. After completing this course, you will: - Understand the fundamentals of magnetic components, including inductors and transformers - Be able to analyze and model losses in magnetic components, and understand design trade-offs - Know how to design and optimize inductors and transformers for switched-mode power converters This course assumes prior completion of courses 1 and 2: Introduction to Power Electronics, and Converter Circuits.

Syllabus

Basic Magnetics

Magnetics are an integral part of every switching converter. Often, the design of the magnetic devices cannot be isolated from the converter design. The power electronics engineer must not only model and design the converter, but must model and design the magnetics as well. Modeling and design of magnetics for switching converters is the topic of this course. In this module, basic magnetics theory is reviewed, including magnetic circuits, inductor modeling, and transformer modeling. This provides the technical tools needed in the remainder of the course to understand operation of magnetic devices, model their losses, and design magnetic devices for switching converters.

AC Copper Losses

Eddy currents also cause power losses in winding conductors. This can lead to copper losses significantly in excess of the value predicted by the dc winding resistance. The specific conductor eddy current mechanisms are called the "skin effect" and the "proximity effect". These effects are most pronounced in high-current conductors of multilayer windings, particularly in high-frequency converters. This module explains these physical mechanisms and provides practical methods to compute these losses.

Inductor Design

The goal of this chapter is to design inductors for switching converters. Specifically, magnetic elements such as filter inductors are designed using the Geometric Constant (Kg) method. The maximum flux density Bmax is specified in advance, and the element is designed to attain a given copper loss. Both single-winding inductors and multiple-winding elements such as coupled inductors and flyback transformers are considered.

Transformer Design

In a substantial class of magnetic applications, the operating flux density is limited by core loss rather than saturation. For example, in a conventional high-frequency transformer, usually it is necessary to limit the core loss by operating at a reduced value of the peak ac flux density. Hence, design of core-loss-limited magnetic devices is characterized by finding the ac flux density that minimizes total core plus copper loss.This module considers the design of transformers and ac inductors for switching converters, including minimization of total loss. Design examples include the isolation transformers of a full bridge two-output converter and of an isolated Cuk converter.