TM 9-6115-730-24
0003
DC POWER DISTRIBUTION (FIGURE FO-1, SHEETS 2 AND 3) - Continued
Batteries
Batteries BT1 and BT3 are paralleled as are batteries BT2 and BT4. These two sets of 12 Vdc batteries are
connected in series to supply 24 Vdc for this system. The DC power distribution system operates on 24 Vdc. The
Slave Receptacle (SR) is the NATO connector on the generator set. This is useful for charging the batteries and
jumping the generator set with another if the batteries become discharged. The Battery Disconnect Switch
disconnects the batteries from everything except the slave receptacle. Battery power goes directly to the starter
solenoid (Labeled PS (pinion solenoid) on the schematic) for use when cranking or starting the engine. The
batteries are connected to the alternator through shunt R4 and circuit breaker CB-5. R4 generates a voltage for
the ammeter, which displays the amperage from the alternator when charging the batteries. Battery power is
connected to ECM A8 through circuit breaker CB-4 and relay contacts of slave relay (SRY). SRY is energized any
time power is applied to the GSC. Battery power goes through D1 to the common of the DEAD CRANK SWITCH.
In OFF, battery power is removed from the GSC, DVR, ECM, and Winterization Kit (if supplied). In NORMAL,
battery power is applied to the relay module of the GSC through circuit breaker CB1. Power is distributed to the
other equipment by the ECS. In CRANK, +24 Vdc is applied to the Starter Motor Magnetic Switch (SMMS) relay
coil. SMMS connects battery voltage to the starter solenoid through circuit breaker CB-2, causing the engine to
crank. Since power is not supplied to the electronics, the engine will not start.
Emergency Stop Push Button
The Emergency Stop Push Button (ESPB) (PUSH TO STOP EMERGENCY STOP on EMCP) is there to stop the
generator set in an emergency. When pushed, contacts 3 and 4 ground P7-38, which informs the GSC that the
switch is pressed. Contacts 1A and 2A remove the ground from the output to the engine controller, which enables
the engine to run. This will stop the engine. Contacts 1 and 2 open the circuit between the GSC and relay SMMS
so that the GSC will not be able to attempt to crank the engine.
When the ECS is set to START, starter motor relay (SMR) A1 K4 is energized. +24 Vdc is applied through the
ESPB (if it is not pressed) and D2 to relay SMMS which enables the starter and cranks the engine. D2 prevents
voltage from the DEAD CRANK SWITCH from applying power to Relay Field Flash (KFF) relay.
Field Flash Relay
Relay A1 K4 also applies +24 Vdc to the coil of KFF relay. The contacts of KFF apply the +24 Vdc, which is
across the coil of KFF, to the generator field coil input (see FO-1, sheet 4) through a 15 Ohm, 25W resistor and
diode CRFF (Diode Field Flash). Note that for the acronyms KFF and CRFF, the common reference designators
for a relay (K) and a diode (CR) were used. This excitation voltage starts the generator generating voltage. After
the process is started, it is self sustaining.
Electronic Governor Relay (EGR) Comm Data Links, MPU, CTR, and GFR
The Electronic Governor Relay (EGR) output of the GSC is connected to the engine controller. This output
enables the engine to run. P7-21 and 22 are the Communications Data Link between the GSC and the
Communication Module (CM). P7-1 and 2 are the inputs from the engine Magnetic Pickup Unit (MPU). This
pickup measures speed of rotation of the engine by detecting the starter ring gear teeth. This input is a frequency
proportional to engine speed. P7-19 and 20 are the Communications Data Link between the GSC and the
electronic control module on the engine. (This is also known as the CAT Data Link.) A1 F1 (Labeled F1 GSC on
schematic), and the GSC relay contacts labeled CTR are not used. P7-23 is a low fuel level input from the low fuel
level sensor connected to Alarm Module A2 (FO-1, sheet 3). This input is connected to ground when the fuel tank
is almost empty. The 10A fuse between RM-34 and RM-7 is A1 F5. The Generator Fault Relay (GFR) K2 in the
GSC closes when the GSC detects a generator fault. This energizes the GFR external to the GSC. The contacts
for the GFR are used to de-energize K1 and disconnect the load from Generator G1.
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