Modeling and Python Simulation of Magnetics for Power Electronics Applications

This chapter introduces the book in which is described the motivation for writing this book, the approach used and how it differs from conventional texts. The introduction describes the basic laws of physics which will be used throughout the book. The introduction contains the links from where a reader can access the simulations which will be used in this book. The introduction contains a brief overview of the contents of the book.

This begins with building a simulation model for an inductor. Though it may appear that building a simulation model for an inductor is a silly and useless exercise, the purpose of doing so is to introduce the concept of magnetic circuits and how the magnetic laws can be combined with electrical laws in a simulation model. Since the inductor is the simplest magnetic component imaginable, this will ease us into the process of building a mathematical model using the laws of physics. In this chapter, we build an analogy between electrical circuits and magnetic circuits and describe how knowing the construction of an inductor, we can compute the flux in every part of the core of the inductor. Several simulations are presented with different core constructions. The simulations in this chapter can also be used by a power electronics engineer to verify designs of inductors as, quite often, power electronics engineers need to wind custom inductors especially while designing power supplies.

This extends the mathematical model of an inductor described in Chap. 2 to model more than one inductor wound on the same core and therefore, magnetically coupled to each other. Using the basic laws of physics, we examine several separate scenarios to fully understand the phenomenon of magnetic coupling and also express coupled inductors mathematically. We will introduce the concept of mutual inductance, which will provide us with a manner of expressing the effect of the current flowing in one coil on the flux linking the other coupled coil. The simulation model of an inductor will then be extended to model coupled inductors. Using simulation results, we will verify our theoretical discussions. Since the simulation of magnetically coupled inductors can consist of many inductors wound on the same core, we will convert our simulations models to a flexible and scalable model using matrix equations.

Chapter 4 describes how a transformer is merely a special case of a set of magnetically coupled windings wound on the same core, with the objective being to maximize the transfer of energy from one winding to the others. Since transformers are essentially magnetically coupled coils, the mathematical model of coupled inductors in Chap. 2 will continue to be used. The difference between a transformer and a random set of magnetically coupled coils is that a transformer is an electrical machine that has specifications similar to any other machine like a motor or generator. For example, a transformer will have a rated maximum power and rated maximum voltages that can be applied to each winding. The chapter will describe how using these specifications, an equivalent circuit can be formulated and the parameters of this equivalent circuit can be estimated. Using this equivalent circuit, we will extract the values of inductances that are necessary to use the simulation model of the coupled inductors. We will examine several simulations to understand the working of the transformer. Simulations will examine the magnetizing current and the other components in the no-load current of the transformer. Simulations will also examine the effect of turns ratio in transforming voltages and currents by simulating step-up and step-down transformers.

Chapter 5 describes some of the most common uses of a transformer in electrical engineering while using the simulation models presented in Chap. 4. For a power systems engineer, three-phase transformers are ubiquitous in every system being analysed. Therefore, Chap. 5 describes how the transformer simulation models of Chap. 4 can be extended to simulate three-phase star–star and delta–star transformers. To make the contents relevant for a power electronics engineer, the chapter also presents the simulation model of a flyback converter. The chapter presents the theory behind high frequency transformers and the specific application of high frequency transformers in the specific case of a flyback converter. The purpose of describing the operation of the flyback converter is to describe how even in the context of a non-linear power converter such as a flyback converter, the operation of the transformer can still be interpreted using the basic laws of physics.

Chapter 6 concludes the book. The conclusion describes the highlights of each chapter of the book and what are the significant outcomes from each chapter. The conclusion emphasizes on the non-conventional approach used in the book and a brief glimpse into the overall project of imparting education in electrical engineering. The book provides links and resources that a reader can use to access additional educational content in the domain of learning electrical engineering through open source software and simulations.