4-20 4181383 First Edition
ELECTRICAL
4
Charging Circuit—Theory of
Operation
Power Circuit
Unswitched power is available from the battery positive
terminal to the starting motor battery terminal and then
from the starting motor battery terminal to 50 amp
thermal circuit breaker battery terminal.
Unswitched power is available from 50 amp thermal
circuit breaker battery terminal to key switch terminal A
and control module terminal J3-6.
When the key switch is turned to the run position, voltage
is provided from key switch terminal B to control module
switch power input terminal J3-2, powering up the control
module and energizing the internal switched power relay.
Voltage is also provided from key switch terminal B to
control module select 2 input terminal J4-2, activating the
input. With the select 2 input activated, the control
module selects the software program for this machine.
This allows the control module to be used in more than
one machine.
With the internal switched power relay energized,
switched power is available from switched power relay
terminal 87 to control module terminal J3-3. Switched
power is available from control module terminal J3-3 to
splice 90. From splice 90, switched power is available to
the engine oil pressure light. Switched power is available
from the engine oil pressure light to the hydraulic filter
pressure light and then from the hydraulic filter pressure
light to the glow plug light. From the glow plug light to the
alternator light.
Charging Circuit
With the engine running and the key switch in the run
position, splice 90 provides voltage to the alternator field
terminal, exciting the alternator. With the alternator field
terminal excited, the alternator produces three-phase
alternating current (AC). The AC current is rectified by
internal diodes and direct current (DC) is available to the
internal voltage regulator.
When the battery voltage is low, current flows from the
voltage regulator to the battery, charging the battery.
When the battery is fully charged, the regulator stops
providing current to the battery.
With the engine running, and when the voltage regulator
detects low output voltage from the alternator, the voltage
regulator provides a ground to the alternator light, turning
on the light.
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