TM 9-6115-729-24
0003
AC POWER DISTRIBUTION (FIGURE FO-1, SHEETS 4 AND 5)
The output of Reconnection Board TB1 goes through several current transformers, relay K1 (shown as a circuit
breaker) and then to the load connection board. The coil of K1 is shown on the DC circuits (FO-1, Sheet 2 and
Sheet 3 ). There are filters and varisters connected between the outputs and chassis ground. A removable
jumper on the load connection board connects the chassis ground (which will be externally connected to a
grounding rod) and the neutral line out of the generator.
If the PARALLEL/UNIT switch is set to UNIT, setting the AC CIRCUIT INTERRUPTER switch to CLOSED will
apply ground to KR, which will close Load Contactor K1, as long as DBHI and DBLO are closed.
Auxiliary contacts on K1 latches KR on after KR is energized. DBHI and DBLO are relays on the final generator
output (after the load contactor K1) which monitor the output for presence of voltage. If there is no voltage on the
load bus, these relay contacts will be closed. If either 208 or 416 Vac are detected by these relays, one or the
other contacts will be open and closing of the AC CIRCUIT INTERRUPTER switch will not apply ground to KR.
This will inhibit closing the Load Contactor K1. Note that DBHI and DBLO have no affect after KR is latched on.
Digital Voltage Regulator (DVR) A3
DVR A3 monitors the output of the 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. Cross current compensation 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 100A.
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 user 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 A4K1.
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 on the paralleling receptacles panel (WP 0002,
Figure 1, Sheet 3) next to the control panel. This is for a trouble light or other auxiliary components.
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