Section 8. Generator
GENERATOR/CONTROL COMPONENT
DESCRIPTIONS
The generator and its control components consist
of the following elements (see Figure
8-1
} :
• Control printed circuit board (A
1)
•Brushes
• Rotor
• Stator and housing
• Terminal board (TB1)
• Voltage regulator {VR1)
• Circuit breakers
(CB1
/CB2)
• Wiring harness to load
The ignition module and rotor are mounted inside
the generator; for this reason, their removaVre-
placement are described in this section.
Control Printed
Circuit
Board (A 1)
(Mechanical-governor generator sets)
The starting battery supplies initial excitation volt-
age to the generator rotor. While the engine
cranks, battery
DC
voltage is supplied through the
N.C. contacts of generator relay K2 (on control
board A 1 ), through voltage regulator VR1, to the
brushes and slip rings of the rotor. When the en-
gine starts and generator voltage builds up, gen-
erator relay K2 is energized, opening the N.C. con-
tacts in the battery B+ circuit to the voltage regula-
tor and closing a set of
N.
0.
contacts in the start
disconnect/ run relay K3 circuit of board A
1.
This
circuit keeps relay K3 energized while the set is in
operation. If relay K2 becomes de-energized, the
set shuts down.
Control Printed
Circuit
Board (A 1)
(Electronic-governor generator sets)
Moving the Start/Run/Stop switch to the Start posi-
tion connects battery ground (B-) to relay
K3.
Nor-
mally-open contacts
on
K3
close, connecting B+ to
governor control board A4 (see Section 7), fuel
pump
E2,
ignition coil
E1,
start solenoid
K1,
N.C.
contacts of K2 relay, voltage regulator
VR1
(to
build-up exciter), and relay K2 (through resistors
R1
and R2). The field (rotor) is flashed through the
N.C. contacts
of
K2 . Ignition coil
E1
is energized.
Start solenoid
K1,
solenoid fuel valve
E3
and fuel
pump E2 are activated. After initial start,
K2
on the
control board is activated, opening the exciter cir-
cuit and closing another circuit to the governor con-
trol board, fuel pump and ignition coil after
K3
is de-
energized. Governor control board A4 is ener-
gized, which moves the throttle to an open position.
Brushes
DC
excitation voltage
is
induced through the
brushes and rotor slip rings to the rotor windings.
The brush block assembly consists of a single
brush block with two brushes. The brush block
mounts directly over the rotor slip rings inside the
generator housing, and may be accessed by re-
moving the small plate at the rear of the housing.
Rotor
The 4-pole rotor provides the rotating magnetic
field that is required to generate an AC voltage po-
tential in the stator windings. The
DC
current re-
quired for field excitation is supplied through two
slip rings on the rotor shaft.
The engine end
of
the rotor is connected directly to
the engine crankshaft with a tapered seat/shaft
coupling and through-bolt. The outer end of the ro-
tor is supported by a single bearing that is pressed
onto the rotor shaft. The bearing slip-fits inside the
generator housing.
Cooling airflow for the generator is provided by a
centrifugal fan that mounts on the inner end of the
rotor shaft. The fan also serves as a mount for the
starter ring gear.
Stator and Housing
During genset operation, AC current is produced in
the windings
of
the stator. Stator winding leads are
routed into the set control housing compartment,
for control component connection as follows:
• Leads T1, T2, T3 and T4 to terminal board
TB1.
• (Mechanical-governor sets) Leads
B1
and B2
to control board A 1, to rectifier
CR1
0, to the
electric choke, and for battery charging.
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