SR 4 GENERATOR
SYSTEMS OPERATION
INTRODUCTION
The SR 4 Generator has no brushes and no
commutator. This gives better performance and longer
service life. It uses a solid-state, automatic voltage
regulator. This regulator has only one moving part in the
voltage build-up system. This part is a completely
sealed relay that is activated only when the generator is
started or stopped.
From the outside, the SR 4 Generator looks very
similar to the SRCR generators.
Here are the design characteristics of the SR 4
Generator:
The windings of the alternator coils are the stator
(L6). The windings of the alternator field coils are the
poles of the rotor, shown in the wiring diagram as
rotating field (L5). The rotating field assembly (RFA)
also has:
1.
Exciter armature (L4).
2.
Rotating rectifiers (CR1 thru CR6).
3.
Surge suppression diodes (CR7 and CR8).
4.
Positive (E1) and negative (E2) heat sinks.
5.
Suppression resistor (R6).
REAR OF GENERATOR
L3 Exciter field
L4 Exciter armature
All of these components are installed on the rotor
shaft. The shaft is connected through a flexible plate-
type coupling to the flywheel of the engine. The rear end
of the rotor shaft uses an anti-friction bearing for support.
The stationary exciter field (L3) has a six-pole
distributive winding on a core that is part of the generator
end housing. Both the field coils of the exciter and the
alternator have their windings on magnetic steel. This
metal keeps a small amount of residual magnetism.
START UP VOLTAGE GENERATION
When the engine starts turning the rotating field
assembly (RFA), the residual magnetism in the exciter
field (L3) causes a small amount of alternating current
(AC) voltage to be generated in the exciter armature
(L4). This voltage causes an AC current to flow which is
changed to direct current (D.C.) by the three-phase full-
wave bridge rectifier circuit (CR1 thru CR6). The DC
current then goes to the rotating field (L5) of the
alternator. Here it adds to the residual magnetism of the
rotating field (L5). With this field turning, an AC voltage
is generated in stator (L6) which causes a current to flow
to the output terminals (T0, T1, T2 and T3). Part of this
AC current is changed to half wave DC and is sent back
to exciter field (L3). As a result, the magnetic field in the
exciter becomes stronger. The flow of current back to
(L3) is explained in more detail on the pages that follow.
INSIDE GENERATOR HOUSING
E1 Positive heat sink
L5
Rotating field
E2 Negative heat sink
L6
Stator
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