Guardian Technologies 4451 & 4986 Manual De Usuario
section 1
geneRatoR FunDaMentals
geneRatoR FunDaMentals
A SIMPLE AC gENERATOR
Figure 1-4 shows a very simple AC Generator. The
generator consists of a rotating magnetic field called a
ROTOR and a stationary coil of wire called a STATOR.
The ROTOR is a permanent magnet which consists
of a SOUTH magnetic pole and a NORTH magnetic
pole.
As the MOTOR turns, its magnetic field cuts across
As the MOTOR turns, its magnetic field cuts across
the stationary STATOR. A voltage is induced Into
the STATOR windings. When the magnet's NORTH
pole passes the STATOR, current flows in one direc-
tion. Current flows in the opposite direction when the
magnet's SOUTH pole passes the STATOR. This con-
stant reversal of current flow results in an alternating
current (AC) waveform that can be diagrammed as
shown in Figure 1-5.
The ROTOR may be a 2-pole type having a single
The ROTOR may be a 2-pole type having a single
NORTH and a single SOUTH magnetic pole. Some
ROTORS are 4-pole type with two SOUTH and two
NORTH magnetic poles. The following apply:
1. The 2-pole ROTOR must be turned at 3600 rpm to produce
1. The 2-pole ROTOR must be turned at 3600 rpm to produce
an AC frequency of 60 Hertz, or at 3000 rpm to deliver an AC
frequency of 50 Hertz.
frequency of 50 Hertz.
2. The 4-pole ROTOR must operate at 1800 rpm to deliver a 60
Hertz AC frequency or at 1500 rpm to deliver a 50 Hertz AC
frequency.
frequency.
STATOR
ROTOR
MAGNETIC FIELD
Figure 1-4. – A Simple AC Generator
CURRENT
VOLTAGE
ONE CYCLE
0
180
360
(+)
(-)
Figure 1-5. – Alternating Current Sine Wave
A MORE SOPHISTICATEd AC gENERATOR
Figure 1-6 represents a more sophisticated generator.
A regulated direct current is delivered into the ROTOR
windings via carbon BRUSHES AND SLIP RINGS.
This results in the creation of a regulated magnetic
field around the ROTOR. As a result, a regulated volt-
age is induced into the STATOR. Regulated current
delivered to the ROTOR is called “EXCITATION” cur-
rent.
STATOR
BRUSHES
120 V
120 V
SLIP
RINGS
AC
OU
TP
U
T
DC
CU
RREN
T
STATOR
240 V
Figure 1-6. – A More Sophisticated Generator
See Figure 1-7 (next page). The revolving magnet-
ic field (ROTOR) is driven by the engine at a con-
stant speed. This constant speed is maintained by a
mechanical engine governor. Units with a 2-pole rotor
require an operating speed of 3600 rpm to deliver a
60 Hertz AC output.
Generator operation may be described briefly as fol-
Generator operation may be described briefly as fol-
lows:
1. Some “residual” magnetism is normally present in the Rotor
1. Some “residual” magnetism is normally present in the Rotor
and is sufficient to induce approximately 7 to 12 volts AC Into
the STATOR's AC power windings.
the STATOR's AC power windings.
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