Electrical Machines

Abstract

Electric generators are devices that convert energy from a mechanical form to an electrical form. This process, known as electromechanical energy conversion, involves magnetic ?elds that act as an intermediate medium. There are two types of generators: alternating current (ac) and direct current (dc). This section explains how these devices work and how they are modeled in analytical or numerical studies. The input to the machine can be derived from a number of energy sources. For example, in the generation of large-scale electric power, coal can produce steam that drives the shaft of the machine. Typically, for such a thermal process, only about one-third of the raw energy (i.e., from coal) is converted into mechanical energy. The ?nal step of the energy conversion is quite ef?cient, with an ef?ciency close to 100%. The generator's operation is based on Faraday's law of electromagnetic induction. In brief, if a coil (or winding) is linked to a varying magnetic ?eld, then an electromotive force (emf) or voltage is induced across the coil. Thus, generators have two essential parts, one creates a magnetic ?eld and the other is where the emf is induced. The magnetic ?eld is typically generated by electromagnets (thus, the ?eld intensity can be adjusted for control purposes) whose windings are referred to as ?eld windings or ?eld circuits. The coils where the emf is induced are called armature windings or armature circuits. One of these two components is stationary (stator) and the other is a rotational part (rotor) driven by an external torque. Conceptually, it is immaterial which of the two components is to rotate because, in either case, the armature circuits always "see" a varying magnetic ?eld. However, practical considerations lead to the common design that for ac generators the ?eld windings are mounted on the rotor and the armature windings on the stator. In contrast, for dc generators, the ?eld windings are on the stator and armature on the rotor. Electric generators are electromagnetic devices made of electric and magnetic circuits coupled together electri-cally and magnetically, where mechanical energy at the shaft is converted to electric energy at the terminals.

Department(s)

Electrical and Computer Engineering

International Standard Book Number (ISBN)

978-142003704-3;978-084937347-3

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 Taylor and Francis Group; Taylor and Francis, All rights reserved.

Publication Date

01 Jan 2017

Link to Full Text

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