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Portable Generator Familiarization & Troubleshooting Guide
Section 1 • Generator Fundamentals
Electromagnetic Induction
In 1831, scientists observed that a conductor moving
through a magnetic field would have a voltage or electro-
motive force (EMF) induced into itself. Electromagnetic
induction may be defined as the action of inducing of a
voltage into a conductor by moving it through a magnetic
field.This principle is illustrated in Figure 1.9.
Figure 1.9 — Electromagnetic Induction
A straight wire conductor is moving through the magnetic
field of a horseshoe magnet. If a sensitive voltmeter were
attached to the ends of the wire conductor, a small voltage
would be indicated as the wire moved through the magnetic
field. However, if the wire conductor were moved parallel to
the lines of magnetic force, no voltage would be indicated.
The greater the strength of the magnetic field through which
the wire conductor is moved, the greater the induced
voltage in the conductor.
Another familiar form of electromagnetic induction is the
automotive engine ignition coil. Current flow through a
primary coil of wires creates a magnetic field around that
coil, which then cuts through a secondary coil of wires.
When the current flow through the primary wire coil is
interrupted, by opening a set of breaker points, the collapse
of the magnetic field induces an electro-motive force (EMF)
in the secondary coil (Figure 1.10)
Figure 1.10 — Typical Automotive Ignition System
Electromagnetism
The previous paragraph explained that magnetic lines of
force, cutting through the stationary windings of the stator
assembly, would induce an EMF into those windings.
Conversely, when a current flows through a wire conductor,
a magnetic field is created around that wire.The number of
lines of magnetic force, or strength of the magnetic field,
increases as the current is increased through the conductor.
When a current-carrying wire is wound into a number of
loops, to form a coil, the magnetic field created is the sum of
all single-loop magnetic fields added together.With lines of
magnetic force entering the coil at one end and leaving at
the other end, a north and south pole are formed at the coil
ends, as in a bar magnet (Figure 1.11).
Figure 1.11 — Magnetic Field Around A Coil Of Wire
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