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Electric Machinery and Transformers

July 20, 2000

Complete Document

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Active, Most Current

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ISBN: 9780195138900
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Product Details:

  • Revision: July 20, 2000
  • Published Date: July 20, 2000
  • Status: Active, Most Current
  • Document Language: English
  • Published By: Oxford University Press (OUP)
  • Page Count: 722
  • ANSI Approved: No
  • DoD Adopted: No

Description / Abstract:


Without any reservation or exaggeration, we can say that the availability of energy in the electric form has made our lives much more comfortable than ever before in the history of mankind. In fact, we may find it very difficult if not impossible to function if some of the devices that operate on electricity are suddenly taken away from us. Ironically, most of the energy available in the electric form is converted directly or indirectly from some other form of energy. An example of the direct energy conversion process is the conversion of light energy into electric energy by solar cells.

In the indirect energy-conversion process, we may use such resources as oil, natural gas, and coal. By burning these fuels we generate heat, which is then utilized to produce steam in a boiler. The steam propels the blades of a turbine, which in tum rotates the rotor of an electric generator that produces electric power. On the other hand, the potential energy of water is converted into mechanical energy by a turbine in a hydroelectric plant. Therefore, what matters the most in the indirect energy conversion process is the mechanical energy that must be supplied to the rotor of an electric generator. This process may also be referred to as an electromechanical energy conversion process owing to the conversion of mechanical energy into electric energy.

The main objective of this book is to discuss the basic principles of electromechanical energy conversion. Another goal of this text is to highlight the fact that the electromechanical energy conversion process is a reversible process. That is, we can also transform electric energy into mechanical energy by using a device known as an electric motor.

Economically it has been found advantageous to generate electric power at a central location at relatively low-voltage levels, transmit it over a distance via transmission lines at comparatively high-voltage levels, and then distribute it to consumers, again at low-voltage levels. Raising the voltage level at the generating end and lowering it at the consumer's end are done effectively by means of stepup and step-down transformers, respectively. This voltage change is made to reduce the electrical losses along the length of the transmission line. Even though a transformer does not convert mechanical energy into electric energy or vice versa, its study is essential because it plays a major role in the transmission and distribution of electric energy.

The method of treatment adopted for each type of electric machine discussed in this book is as follows:

(a) Discuss the construction of the machine

(b) Explain how the electromagnetic fields interact as a medium in the energy transfer process

(c) Represent the machine by its electric equivalent circuit

(d) Determine its performance using basic laws of electric circuit theory

It is apparent that in order to comprehend electric machines, we must be familiar with electromagnetic fields and be able to analyze electric circuits. The purpose of this chapter is to review some of the basic laws of electric circuits. In Chapter 2 we review the basic laws of electromagnetic field theory and their applications. The discussion in this and the next chapter is intended merely as a review, and the reader is expected to have some prior knowledge of these topics.