ARMY TM 9-6115-672-14
AIR FORCE TO 35C2-3-444-32
MARINE CORPS TM 09244A/09245A-14
The backplane module is an installation point for three DCS modules and for the main electrical connectors
from the AC generator. It connects the front panel switches and these DCS modules with the I/O interface
module. This module simplifies the wiring inside the DCS control box by placing many interconnections onto
one circuit board assembly. This module also includes diagnostic indicators for the DCS. The other DCS
modules are discussed in paragraphs below.
The Fault System (Figure 1-19) protects the generator set and any connected load against the potential faults
described below and provides an indication of any incurred fault. The following summary of the Fault System
will assist in understanding the operation of other generator set systems. Additional details relating to specific
protection devices are provided in the descriptions of the respective systems.
The Fault System consists of the CIM, I/O interface module, fuel level sender, oil pressure sender, coolant
temperature sender, and BATTLE SHORT switch.
Inappropriate signals received from the senders by the I/O interface module will cause the CIM to display the
fault, and a message describing the condition causing the fault, on the CIM display screen. Depending on the
nature of the fault, the generator set will shut down or the operator will be warned that action must be taken to
Activation of the fault system will cause two events to occur. The AC interrupter relay will open and
CONTACTOR POSITION status indicator on CIM display screen will indicate OPEN.
Although it is possible for more than one fault to occur at one time during operation, and for more than one
fault to be displayed on the CIM display screen at a time, only the first fault to occur will cause a message to
appear in the MESSAGES display area of the CIM display screen. Once the condition addressed in that
message has been corrected by the operator, the operator will activate the FAULT RESET switch, and the next
message will be displayed.
After the generator set engine has been started, the BATTLE SHORT switch may be used to override all
potential faults except engine overspeed and short circuit.
Governor Control System.
The governor control system (Figure 1-20) includes the DCS speed control unit, electric actuator, DCS load
sharing synchronizer, magnetic pickup, fuel injection pump, and FREQUENCY SELECT switch.
The electric actuator controls the output of the fuel injection pump in response to the electrical input from the
DCS speed control unit. The DCS provides a signal representing the desired engine speed/generator
frequency to the DCS speed control unit. A signal representative of the actual engine speed/generator
frequency is sent to the DCS speed control unit by the magnetic pickup. Any change in engine speed from that
selected by the operator, as sensed by the magnetic pickup, causes the DCS speed control unit to increase or
decrease fuel injection pump output to maintain the desired speed. Generator set frequency and power output
are indicated on the CIM display screen. The FREQUENCY SELECT switch is used to set the generator for
50 hertz or 60 hertz operating frequencies (MEP-805B only).
Twenty-four VDC power is supplied to the DCS speed control unit through the governor control power relay.
The governor control power relay is controlled by the fault system. The DCS speed control units of two
generator sets operating in parallel are interconnected by the paralleling cable.