TM 9-6115-729-24
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AC POWER DISTRIBUTION (FIGURE FO-1, SHEETS 4 AND 5) - Continued
GSC Voltage and Current Monitoring
Three current transformers (CT1, CT2, and CT3) measure the current out of Generator G1 after Reconnection
Board TB1. The outputs of these current transformers are connected to three transformers located on AC
Transformer Box (ATB) A5. The outputs of these transformers go to the GSC for monitoring Generator G1 output
current. Lines G1-1, G1-2, and G1-3 from Generator G1 output after Reconnection Board TB1, are connected to
transformers T1, T2, and T3 on ATB A5 through protection fuses. The GSC monitors the outputs of these
transformers to monitor the output voltage of Generator G1. Two transformers (T1 and T2) on Bus Transformer
Box (BTB) A6 monitor the load bus voltage on the output after Load Contactor K1; and their outputs are
connected to the GSC. The inputs are fused for protection.
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 DC Power Distribution.
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 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 distribution drawing, 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 Woodward 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. Touch pad inputs, ENGINE CONTROL switch settings, SYNC MODE switch setting, and the
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