Fundamentals of Electrical Drives

Electrical drives consist of a number of components, the electrical machine, converter and controller, all of which are discussed at various levels. A brief r´esum´e of magnetic and electrical circuit principles is given in chapter 1 together with a set of generic building modules which are used throughout this book to represent dynamic models. Chapter 2 is designed to familiarize the reader with the process of building a dynamic model of a coil with the aid of generic modules. This part of the text also contains an introduction on phasors as required for steady state analysis. The approach taken in this and the following chapters is to present a physical model, which is then represented by a symbolic model with the relevant equation set. A generic model is then presented which forms the basis for a set of ‘build and play’ simulations set out in various steps in the tutorial at the end of the chapter. Chapter 3 introduces a single phase ‘ideal transformer’ (ITF) which forms the basis of a generic transformer model with leakage and magnetizing inductance. A phasor analysis is given to familiarize the reader with the steady state model. The ’build and play’ tutorials at the end of the chapter give the reader the opportunity to build and analyse the transformer model under varying conditions. It is emphasized that the use of these ‘build and play’ is an essential component of the learning process throughout this book. Chapter 4 deals with star and delta connected three phase systems and introduces the generic modules required to model such systems. The space vector type representation is also introduced in this part of the text. A set of ‘build and play’ tutorials are given which reinforce the concepts introduced in this chapter. Chapter 5 deals with the concepts of real and reactive power in single as well as three phase systems. Additional generic modules are introduced in this part of text and tutorial examples are given to familiarize the reader with this material. Chapter 6 extends the ITF concept introduced earlier to a space vector type model which is represented in a symbolic and generic form. In addition a phasor based model is also given in this part of the text. The ‘build and play’ tutorials are self-contained step by step simulation exercises which are designed to show the reader the operating principles of the transformer under steady state and dynamic conditions. At this stage of the text the reader should be familiar with building and using simulation tools for space vector type generic models which form the basis for a transition to rotating electrical machines. Chapter 7 introduces a unique concept namely the ‘ideal rotating transformer’ (IRTF), which is the fundamental building block that forms the basis of the dynamic electrical machine models discussed in this book. A generic space vector based IRTF model is given in this part of the text which is instrumental in the process of familiarizing the reader with the torque production mechanism in electrical machines. This chapter also explores the conditions under which the IRTF module is able to produce a constant torque output. It is emphasized that the versatility of the IRTF module extends well beyond the electrical machine models discussed in this book.These advanced IRTF based machine concepts are discussed in a second book ‘Advanced electrical Drives’ currently under development by the authors of this text. The ‘build and play’ tutorials at the end of thischapter serve to reinforce the IRTF concept and allow the reader to ‘play’ with the conditions needed to produce a constant torque output from this module. Chapters 8-10 deal with the implementation of the IRTF module for synchronous, asynchronous and DC machines. In all cases a simplified IRTF based symbolic and generic model is given of the machine in question to demonstrate the operating principles. This model is then extended to a ‘full’ dynamic model as required for modelling standard electrical machines. A steady state analysis of the machines is also given in each chapter. In the sequel of each chapter a series of ‘build and play’ tutorials are introduced which take the reader through a set of simulation examples which steps up from a very basic model designed to show the operating principles, to a full dynamic model which can be used to represent the majority of modern electrical machines in use today. Chapter 11 deals with the converter, modulation and control aspects of the electrical drive at a basic level. The half bridge converter concept is discussed together with the pulse width modulation (PWM) strategies that are in use in modern drives. A predictive dead-beat current control algorithm is presented in combination with a DC machine. The ‘build and play’ tutorials in the sequel of this chapter clearly show the operating principles of PWM based current controlled electrical drives.