Generac Power Systems IM Series - Manual (Page 4)

GENERATOR FUNDAMENTALS
Introduction
It has long been known that a relationship exists between
magnetism and electricity. Revolving fieid a-c generators
depend on this relationship for their operation. The ser­
vice technician must understand that relationship. This
section of your DIAGNOSTIC REPAIR MANUAL will
familiarize you with the basic fundamentals of generator
operation.
Electro-Magnetic Induction
A
Magnetism Creates Electricity: - When a wire or
coii of wire is moved through a magnetic field, an electri­
cal voltage is aeated in that wire. If the ends of the wire
are joined to complete a circuit, electrical current will flow
in the wire. The direction that current flows in the wire
depends on the polarity of the magnetic field.
B
Current Flow Creates a Magnetic Field: - When­
ever electrical current flows through a wire or coil of wire,
a magnetic field is created around that wire. The strength
of the field depends on the amount of current flow and
the number of coils or loops in the wire.
C
A simple a-c generator consists of a spinning mag­
netic field called a ROTOR and stationary coil of wire
called a STATOR. As the Rotor spins, its lines of mag­
netic force cut across the stationary Stator. When the
ends of the Stator winding are connected across a load
(such as a light bulb) to complete the circuit, current will
flow through the circuit. In this simple generator, the
Rotor is a permanent magnet. The amount of voltage and
current flow induced into the Stator windings depends on
(a) the Rotor’s magnetic field strength, (b) Rotor rotational
speed, and (c) the number of turns of wire in the Stator.
A More Sophisticated a-c Generator
D
A more sophisticated generator is equipped with a
Stator a-c power winding and a Stator excitation winding.
Regulated direct current from the excitation winding flows
through carbon brushes which slide on metallic slip rings
and then through the Rotor windings. Regulated current
flow through the Rotor creates a regulated magnetic field
strength. In turn, the regulated magnetic field strength
induces a regulated voltage into the stationary Stator;
winding.
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