The book chapter focuses on localised or microscopic properties of grain oriented (GO) and non-oriented (NO) steels. This ranges from the magnetic domain level to single crystal and grain-to-grain interactions. This is intended to show how the microstructure and controlling intrinsic magnetic properties influence the practical magnetic performance of commercial silicon-iron alloys.

The book chapter considers the performance and applications of electrical steels. In this chaper the authors consider: high silicon steel; cube-oriented electrical steel; ultra-thin and automotive grade electrical steels.

Probably, more than 90% of the GO electrical steel produced each year is used in transformers cores, and this proportion is likely to continue in the foreseeable future. The beginning of this book chapter provides sufficient grounding for non-experts in basic aspects of the principles, terminology, design, operation and characteristics of transformers needed to understand the role of the magnetic core. Next, practical and electromagnetic aspects of strip wound and laminated cores are introduced followed by a description of flux transfer and localised losses in cores. Causes and effects of core faults are described briefly, and the chapter concludes with an introduction to the process of loss capitalisation in evaluating the total ownership cost (TOC) of a transformer.

The book chapter shows that it is rare for soft magnetic materials in a.c. applications to be subject to perfectly sinusoidal flux-density waveforms. The designers and users of electrical machines are placing increasing demands on the magnetic cores. Traditionally, the electrical steels used in these devices are characterised under standard conditions with power frequency sinusoidal magnetisation requiring designers to over-engineer the magnetic components based on previous experience. It is common knowledge that many applications of electrical steels exhibit flux density waveforms which are far removed from the sinusoidal ideal. Even for conventional, sinusoidally excited, devices such as induction motors, the flux density waveforms vary from close to sinusoidal to highly distorted and, behind the teeth, rotational flux conditions.

The main purpose of the book chapter is to show comparisons of the performance of amorphous ribbon in transformer cores with that of equivalent, conventional GO steel cores. It should be noted that where direct comparisons are given, they usually refer to results obtained from a limited numbers of cases which often focus on one or two characteristics. Sometimes, performance characteristics are compared under reference magnetising conditions that suit one material better than another.

The book chapter presents methods for the predictions and measurements of flux density and loss distributions in electrical machine cores. The chapter summarises the background to Maxwell equations on which all the computational electromagnetic solvers are based, and follows with a brief overview of experimental techniques used for measuring flux and loss distributions in cores.

The book chapter summarises the growing use of renewable energy sources for generating electricity and the closely associated changes in power transmission systems in which electrical steel has always had a critical role in transformers and generators. However,It does not include discussion of the relative merits of the various renewable energy sources.

The data presented in the book chapter is designed to illustrate the range of properties available in current commercial electrical steels. Samples were chosen from a large bank of materials supplied by several different manufacturers to be representative of the range of properties of commonly used grades and not the best achievable properties. In a few cases, non-standard materials were chosen to illustrate a particular effect.