The synchronous electrical generator (also called alternator)
belongs to the family of electric rotating machines. Other members
of the family are the directcurrent (dc) motor or generator, the
induction motor or generator, and a number of derivatives of all
these three. What is common to all the members of this family is
that the basic physical process involved in their operation is the
conversion of electromagnetic energy to mechanical energy, and vice
versa. Therefore, to comprehend the physical principles governing
the operation of electric rotating machines, one has to understand
some rudiments of electrical and mechanical
engineering.
Chapter 1 is written for those who are involved in operating,
maintaining and trouble-shooting electrical generators, and who
want to acquire a better understanding of the principles governing
the machine’s design and operation, but who do not have an
electrical engineering background. The chapter starts by
introducing the rudiments of electricity and magnetism, quickly
building up to a description of the basic laws of physics governing
the operation of the synchronous electric machine, which is the
type of machine all turbogenerators belong to.
Magnets always have two poles: one called north; the other called
south. Two north poles always repel each other, as do two south
poles. However, north and south poles always attract each other. A
magnetic field is defined as a physical field established between
to poles. Its intensity and direction determine the forces of
attraction or repulsion existing between the two magnets.
Figures 1.1 and 1.2 are typical representations of two interacting
magnetic poles, and the magnetic field established between them.
Magnets are found in nature in all sorts of shapes and chemical
constitution. Magnets used in industry are artificially made.
Magnets that sustain their magnetism for long periods of time are
denominated “permanent magnets.” These are widely used in several
types of electric rotating machines, including synchronous
machines. However, due to mechanical, as well as operational
reasons, permanent
magnets in synchronous machines are restricted to those with
ratings much lower than large turbine-driven generators, which is
the subject of this book.
Turbine-driven generators (for short: turbogenerators) take
advantage of the fact that magnetic fields can be created by the
flow of electric currents in conductors. See Figure 1.3.
