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There seems to be a trend in the public perception of engineering and technology that to be able to operate a piece of equipment or a system is to understand how it works.
Nothing could be further from the truth. The gap between the ability to operate and a genuine understanding is, if anything, widening because much of the complexity added to modem electrical equipment has the specific aim of making it operable or 'user-friendly' without special training or knowledge.
The need for a basic explanation of principles, leading to a simple description of how various important and common classes of electrical equipment works, has never been stronger. Perhaps more so than in its predecessor, an attempt is made to address fundamentals in this guide, and the reader is encouraged to follow through any areas of interest using the references at the end of each Section. More comprehensive coverage of all the subjects covered in this guide may be found in a standard Electrical Engineer's Reference Book.
More so now than ever before, the specification and performance of electrical equipment is governed by national and international standards. While it would be inappropriate in a web guide to cover standards in any detail, a summary of key standards is included for reference purposes at the end of each Section.
The structure of the guide is based around three groups of Sections, which address:
--fundamentals and general material
--the design and operation of the main classes of electrical equipment
--special technologies which apply to a range of equipment
The first group comprises three Sections which set out fundamentals and principles running through all aspects of electrical technology.
The opening Section deals with fundamentals of electric and magnetic fields and circuits, with energy and power conversion principles.
This is followed by a review of the materials that are so crucial to the design of electrical equipment, and these are grouped into sections on magnetic, insulating and conducting materials. In each of these areas technology is moving ahead rapidly. The great increases in the strength of permanent magnets in the past ten years has done much to make possible the miniaturization of equipment such as the Sony Walkman, and the introduction of so many small motors and actuators in our homes and motor cars. Developments in insulating materials mean that increased reliability and operation at higher temperatures can now readily be achieved. Under the heading of conductors there are continuing advances in superconductors, which are now able to operate in liquid nitrogen, and of course semiconductor development has transformed the way in which equipment can be controlled and the processing power in computers.
Finally in this opening group there is a Section on measurement and instrumentation.
A classical text book on electrical measurement would in the past have included sections on moving iron and moving coil instruments, but these have been omitted here in favor of the oscilloscope and sensors which now dominate measurements in most areas.
The following group of nine Sections make up the main core of the guide and cover the essential groups of electrical equipment found today in commerce and industry.
The opening five Sections here cover generators, transformers, switchgear, fuses and wire and cables. These are the main technologies for the production and handling of electrical energy, from high power and high voltage levels down to the powers and voltages found in the household. Exciting developments in this area include the advances made in high voltage switchgear using SF6 as an insulating medium, the extension of polymer insulation into high voltage cables and the continuing compaction of miniature and molded-case circuit breakers. A new section in the wire and cables Section addresses the growing technology of optical fiber cables; although the main use for this technology is in telecommunications, which is outside the scope of the guide, a Section on wires and cables would not be complete without it and optical fibers have a growing number of applications in electrical engineering.
The following four Sections describe different groups of equipment that use or srore electrical energy. Probably the most important here is electric motors, since these use almost two-thirds of all electrical energy generated. Static power supplies are also of growing importance in applications such as emergency standby for computers; this technology is now based on power electronics and the opportunity is taken in this Section to explain the fundamentals of power electronic design and technology.
Rotating converters were important for many of the duties now handled by power electronics, but these are now in decline and are not covered here. The range of batteries being developed and appearing in a variety of applications is now very large and this is the subject of a special Section, which also covers the techniques of battery charging and the emerging related technology of fuel cells. If fuel cells fulfill their promise and start to play a greater part in the generation of electricity in the future then we can expect to see coverage of this area grow and perhaps move to the generation section in future editions. Another major electricity consumer is the range of technologies generally known as electroheat. This covers a spectrum of technologies from arc furnaces through microwave heating to ultraviolet drying techniques which are described in a special Section.
The final group of three Sections cover subjects that embrace a range of technologies and equipment. There is a Section on power systems which describes the way in which generators, switchgear, transformers, lines and cables are connected and controlled to transmit and distribute our electrical energy. The privatization of electricity supply in countries across the world has brought great changes in the way in which power systems are operated and these are touched upon here. The second Section in this group concerns electromagnetic compatibility (emc); with the growing amount of electronic and high-frequency equipment in use today it is imperative that precautions are taken to prevent interference and legislation has been introduced to enforce this prevention. The techniques for tackling this are complex and influence a wide range of equipment. Finally there is a Section describing the design and use of equipment for operation in hazardous and explosive environments; this again covers a wide range of equipments and there are a number of different classifications of protection.