Generac Power Systems NP-40G - Manual (Page 5)

Section 1.1- GENERATOR FUNDAMENTALS
Magnetism
Magnetism can be used to produce electricity and
electricity can be used to produce magnetism.
Much about magnetism cannot be explained by our
present knowledge. However, there are certain patterns
of behavior that are known. Application of these behavior
patterns has led to the development of generators, mo­
tors and numerous other devices that utilize magnetism
to produce and use electrical energy.
See Figure 1. The space surrounding a magnet Is
permeated by magnetic lines offeree called "flux“. These
lines offeree are concentrated at the magnet’s north and
south poles. They are directed away from the magnet at
Its north pole, travel In a loop and re-enter the magnet at
Its south pole. The lines of force form definite patters
which vary In Intensity depending on the strength of the
magnet The lines of force never cross one another. The
area surrounding a magnet In which Its lines offeree are
effective Is called a "magnetic field".
Like poles of a magnet repel each other, while unlike
poles attract each other.
Electromagnetic Fields
AM conductors through which an electric current Is
flowing have a magnetic field surrounding them. This
field Is always at right angles to the conductor. If a
compass Is placed near the conductor, the compass
needle will move to a right angle with the conductor. The
following rules apply:
□ The greater the current flow through the conductor,
the stronger the magnetic field around the conduc­
tor.
□ The Increase In the number of lines of force Is di­
rectly proportional to the Increase In current flow
and the field Is distributed along the full length of the
conductor.
D The direction of the lines of force around a conduc­
tor can be determined by what Is called the "right
hand rule". To apply this rule, place your right hand
around the conductor with the thumb pointing In the
direction of current flow. The fingers will then be
pointing in the direction of the lines of force.
NOTE: The "right hand rule" Is based on the "current
flow" theory which assumes that current flows from
positive to negative. This Is opposite the "electron"
theory, which states that current flows from negative to
positive.
Electromagnetic induction
An electromotive force (EMF) or voltage can be pro­
duced In a conductor by moving the conductor so that it
cuts across the lines of force of a magnetic field.
Similarly, if the magnetic lines of force are moved so
that they cut across a conductor, an EMF (voltage) will
be produced In the conductor. This Is the basic principal
of the revolving field generator.
Figure 3, below. Illustrates a simple revolving field
generator. The permanent magnet (Rotor) Is rotated so
that its lines of magnetic force cut across a coll of wires
called a Stator. A voltage Is then Induced into the Stator
windings. If the Stator circuit Is completed by connecting
a load (such as a light bulb), current will flow in the circuit
and the bulb will light.
Alternating Current
A simple generator consists of a coil of wires called a
Stator and a magnetic field called a Rotor. As the Rotor’s
magnetic field cuts across the Stator coll, a voltage Is
induced into the Stator windings. The amount of Induced
voltage is equal to the strength of the magnetic field.
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