Woodward 723PLUS Technical Manual page 40

723PLUS Digital Marine Control Manual 26482
An internal load switch selects a multiplier to reduce gain when the engines are
clutched in at a light load. The percentage of gain reduction and load level are
set in service mode, under the header F**DYNAMICS CLUTCHED**, at the
prompt 11 BTH CLTCHED GN FCTR. A setting of 100% disables the light load
reduced gain function.
The control provides an actuator bump feature, which can be set (by the bump
level and duration) to simulate a load transient and test the window width and
gain ratio dynamic settings before actual application of load.
Actuator Output
The actuator output is driven by the fuel demand from the speed control PID. The
dynamic settings determine the amount and rate of change for the actuator output.
The actuator function changes the fuel demand into a signal on Analog Output #3
(TB 19 and TB 20). This function allows for either a direct-acting or reverse-acting
actuator. In a direct-acting fuel system the signal to the actuator increases as the
fuel demand increases. In a reverse-acting fuel system the signal to the actuator
decreases as the fuel demand increases. In either system, the fuel (i.e., diesel oil)
to the engine increases as the fuel demand increases. A reverse-acting system
requires the use of an actuator with a mechanical ballhead back up governor,
which can control the engine should the electronic governor fail.
Standard actuators use effective signals of 20 to 160 mA to travel from minimum
position to maximum position (or 160 to 20 mA on reverse-acting systems). The
fuel demand is scaled from 0 to 100 percent for an output of 0 to 200 mA (or 200
to 0 mA on reverse-acting systems). For either direct-acting or reverse-acting
systems, the result is a fuel demand with a value of ten percent when the
actuator is effectively at minimum and a fuel demand of 80 percent when the
actuator is effectively at maximum.
Actuator type is set in configure mode, under the header B**CONFIG OPTION**,
at the prompt 04 REVERSE ACTING ACT. Set "FALSE" for direct-acting
actuators or "TRUE" for reverse-acting actuators.
For troubleshooting most 723PLUS controls, monitoring actuator voltage is
recommended instead of monitoring actuator current. Take extreme care when
using a current meter in the actuator wiring. An unexpected engine shutdown or
overspeed will occur if a lead falls off. The voltmeter is a safer tool for
troubleshooting since an open lead will not cause an unexpected shutdown or
overspeed. In general, actuator voltage will be between 0–7 Vdc for a Woodward
actuator.
Fuel Limiting Function
The second primary function of this 723PLUS control is to provide fuel rack
limiting to protect the engine. All the fuel limiters and the PID output are applied
to the actuator LSS (low signal select) bus. The lowest LSS input is "in Control"
of the actuator output. All inputs to the LSS bus are scaled from 0% to 100% fuel
demand. The output of the LSS bus goes directly to the actuator driver circuit,
which is also scaled from 0 to 100%. The PERCENT LOAD outputs from these
limiters are re-scaled to actuator output % before applying them to the LSS bus.
30 Woodward