Generac Power Systems 53187 - Manual (Page 7)

PARTI
THE REVOLVING FIELD AC GENERATOR
1 SECTION 1.2
HOW A GENERATOR WORKS
Section i.2
HOW A GENERATOR WORKS
General
It has long been know n that a relationship exists
betw een m agnetism and electricity. The revolving field
generator (or alternator) depends on this relationship
for its operation. In order to diagnose problem s and
repair a generator, the service technician m ust under­
stand this relationship.
Why Generators Produce Electricity.
Generators produce an electrical current flow be­
cause of the follow ing law s of m agnetic induction:
□ W hen a m agnetic field is m oved so that it cuts across
a conductor, a voltage and current flow are induced
into the conductor.
□ W hen current flow s through a conductor, a m agnetic
field is created around that conductor.
MAGNETIC FIELD CREATES A VOLTAGE;
See Figure 1. W hen a w ire, or coil of w ire, is m oved
through a m agnetic field, an electrom otive force (EMF)
or voltage is induced into the w ire. Conversely, m ove­
m ent of the m agnetic field so that its lines of flux cut
across the w ire w ill induce a voltage into the w ire. If the
ends of the w ire are connected to form a com plete
circuit, current w ill flow in the w ire. The direction in
w hich the current flow s depends on the polarity of the
m agnetic field and the direction in w hich the m agnet is
m oved.
CURRENT FLOW CREATES A MAGNETIC FIELD:
See Rgure 2. Current flow through a w ire or coil of
w ire w ill create a m agnetic field around the w ire. The
strength of the m agnetic field depends on the am ount
of current flow and the num ber of loops or coils in the
w ire. The direction (polarity) of the m agnetic field de­
pends on the direction of current flow through the w ire.
A Simple AC Generator
See Figure 3. In the sim ple generator show n, the
revolving m agnetic field (Rotor) is a perm anent m ag­
net. As the m agnet rotates, its m agnetic lines of flux cut
across a stationary coil of w ire called a STATOR. If the
stator circuit is com pleted (by adding a load such as the
light bulb), current w ill flow through the circuit.
A More Sophisticated Generator
In Figure 4, direct current (DC) is delivered to the
ROTOR coil through CARBON BRUSHES and SLIP
RINGS, to create a m agnetic field around the ROTOR.
The greater the current flow through the ROTOR w ind­
ings, the stronger the m agnetic field around the
ROTOR. The ROTOR’S m agnetic field cuts across the
stationary STATOR w indings, to induce a voltage into
those w indings, w ith the induced voltage proportional
to the strength of the ROTOR’S m agnetic field.
11
11
Z-
oCOIi
K
------
Figure 1. M agnetism Creates Electricity
Figure 2. Current Flow Creates a M agnetic Field
Û.
T
1«V.
ü э ” r ^
< o ¿»V.
STATOR
z
UJ-
a.
oc
u 3
o u
BRUSHES
RINGS
Figure 4. A M ore Sophisticated Generator
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