TM 9-6115-730-24
0003
AC POWER DISTRIBUTION (FIGURE FO-1, SHEETS 4 AND 5) - Continued
Digital Voltage Regulator (DVR) A3
DVR A3 monitors the output of Generator G1 prior to Reconnection Board TB1 and regulates the output of the
generator according to the parameters programmed into it. The voltage from wires G1-7, G1-8, and G1-9 is
connected to the DVR. Also, PT2 measures the voltage between G1-7 and G1-8, divides the voltage in half, and
connects this to the DVR. PT3 is the same as PT2, except measures the voltage between G1-8 and G1-9. Fuses
F1, F2, and F3 protect PT2 and PT3. Whether the generator is connected for 208 or 416 Vac output, the DVR is
monitoring the same voltage. Current transformer CCCT monitors the current in wire G1-8 and G1-2 from the
generator. This total current will not change whether the generator is connected for 208 or 416 Vac output. CCCT
generates a voltage across a 1 ohm resistor A7R2 at a rate of 1.25 Vac per 200A. The voltage across this 1 ohm
resistor is input to the DVR. Rheostat VAR (Voltage Adjust Rheostat) is connected to the DVR to allow the
operator to adjust the voltage approximately 10%. (This control is labeled VOLTAGE on the front panel.) Power
for the DVR comes from the battery (FO-1, sheet 2 and sheet 4 ). The DVR monitors the output voltage from the
generator and applies a voltage to the field coil (F+ and F-) on the generator in order to regulate the output voltage
of the generator. Essentially, the higher the voltage applied to the field, the higher the output voltage of the
generator. The nominal voltage across this coil is 4.6 Vdc at no load and approximately 14 Vdc at full load. The
voltage for the field coil actually comes from the generator output through PT2 and PT3. Because of this, a Field
Flash circuit provides an excitation at the initial startup of the generator set to start this process. The connections J
and K to the field coil circuit come from the Field Flash circuit (FO-1, sheet 2). This circuit provides an initial
voltage excitation to the field in order to get an initial output from the generator. Without this excitation the
generator will not produce power capable of supplying a load.
Load Sharing Module (LSM) A4
Three current transformers CT-7, CT-8, and CT-9, monitor the current from the generator and supply input signals
to LSM A4 and the overload (O/L) and short circuit (S/C) module. The output of each current transformer goes
through a resistance on LSM A4, then through a resistance on the O/L and S/C module. A voltage is generated
across the input of each module for control purposes. LSM A4 is also connected to lines G1-7, G1-8, and G1-9
from the generator and monitors the voltage out of Generator G1 before Reconnection Board TB1. The paralleling
input (pins 10, 11, and 12) is repeated completely in the DC circuits (FO-1, sheet 3) and was discussed there. The
ISOCHRONOUS/DROOP switch is connected to LSM A4 through an auxiliary set of contacts on relay K1.
Ground Fault Circuit Interrupter (GFCI)
The GFCI picks up one phase (G1-9) from Generator G1 before Reconnection Board TB1 and connects 120 Vac
to a standard 2 gang outlet on the rear of the generator set next to the control panel. This is for a trouble light or
other auxiliary components.
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 outputs of these transformers are connected
to the GSC for monitoring the output voltage of Generator G1. There are two transformers (T1 and T2) on Bus
Transformer Box (BTB) A6. These 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.
0003-20
