TM 9-6115-730-24
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AC POWER DISTRIBUTION (FIGURE FO-1, SHEETS 4 AND 5) - Continued
Dead Bus Low (DBLO) and Dead Bus High (DBHI) Monitoring
Relay DBHI is connected after Load Contactor K1 between L1 and L3 (K1A2 to J31-19 and K1 B2 to J31-8) to
monitor for voltage on the load bus (the output of the generator set). DBLO energizes if 208 Vac is present on the
load bus. DBHI energizes if 416 Vac is detected on the load bus. R3 reduces the voltage seen by the 230 Vac coil
of DBHI so that it will only energize if it sees 416 Vac. DBHI will not energize at 208 Vac. One set of contacts on
DBHI is used to remove the 416 Vac from the coil of DBLO in order to protect the coil from excessive voltage. The
other contacts for DBLO and DBHI are discussed as part of the DC Power Distribution discussion.
Overload and Short Circuit (OL/SC) Module
The OL/SC module gets a current input from current transformers CT-7, CT-8, and CT-9, which are connected
before Reconnection Board TB1. This module monitors the output current and provides two sets of relay contacts
for overload condition and two relay contacts for short circuit condition. Overload condition is defined as an output
current over 130% of the maximum current rating of Generator G1. Short circuit is defined as an output current
over 400% of the maximum current rating of Generator G1. The relay outputs of the module latch after a condition
has been sensed. Setting ENGINE CONTROL to OFF/RESET will reset the latched relays on this module. Also
pressing the LAMP TEST button on Alarm Module A2 will reset the relays on this module. An overload or short
circuit condition causes an alarm on the alarm module and disconnects the load from Generator G1. The overload
condition is disabled in Battle Short mode. The relay contacts and the power input connections for the OL/SC
module are shown in the AC circuit, but the use is discussed as part of the DC Power Distribution discussion. In the
DC schematic, the OL/SC contacts are separate and labeled O/L and S/C respectively.
ELECTRONIC MODULAR CONTROL PANEL (EMCP)
The Electronic Modular Control Panel (EMCP) incorporates Generator Set Control A1 (GSC), Alarm Module A2,
Digital Voltage Regulator (DVR) A3, the Load Sharing Module (LSM) A4, Resistor Assembly A7, a relay module,
panel switches and controls, and various terminal boards.
GENERATOR SET CONTROL (GSC)
GSC Inputs
The GSC (Figure 9) is a microprocessor based control system which accepts programmed values, switch inputs,
data from ECM A8, and data from LSM A4 to control the speed of the engine. A constant engine speed maintains
the desired output frequency. The GSC inputs to the Central Processing Unit (CPU) include signals from panel
controls including touch pad inputs, ENGINE CONTROL switch settings, SYNC MODE switch setting, and the
PUSH TO STOP EMERGENCY STOP switch. External signals are input from engine sensors, generator output
voltage and current samples, load bus voltage samples and the ECM. LSM A4 interacts with the GSC as well.
The touch pad allows inputting parameters into the GSC to determine the desired output voltage and frequency,
and how the GSC reacts to various stimuli. The touch pad also allows the user to display all of the voltages,
currents, and calculated power levels, real and reactive as desired. The generator output voltage, current, and the
load bus voltage are all monitored and can be displayed as desired on the EMCP displays. LSM A4 monitors the
load that the generator powers and allows fine tuning of the load sharing via a speed setting potentiometer. The
LSM sends a speed correction signal to the GSC in order to fine tune the speed based on the load sharing of the
generator. This is utilized primarily when the generator set is in parallel with another generator. Most engine
sensors are connected to the engine control unit and their status transmitted to the GSC via the CAT Data Link.
One engine speed sensor and a low fuel level sensor are directly connected to the GSC. The engine speed
sensor provides positive feedback to the GSC that the engine is operating at the desired speed. The low fuel
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