Fault Detection And Annunciation; Shutdown Details - Woodward UG-25+ Installation And Operation Manual

Manual 26580 UG-25+ Actuator
When the desired terminal shaft position is reached, the floating lever provides a mechanical
feedback/restoring signal between the power piston rod and the pilot valve. During this condition, the pilot
valve will be at its "null" position. Therefore, the L-Series control and the hydraulic amplifier are
proportional devices with their positions a direct function of the externally supplied Position Command
signal.
Decrease in Position Command Signal
A decrease in the externally supplied Position Command signal causes the L-Series controller output shaft to
rotate CW. This, in turn, causes the pilot valve to lower allowing the control oil pressure acting on the
underside of the power piston to flow to drain. The pump outlet oil pressure acting on the topside of the power
piston will cause the piston to lower.
As the power piston lowers, the power piston rod moves with it and rotates the terminal shaft towards the
minimum fuel direction. The floating lever then lowers its end coupled to the power piston rod and
provides its position feedback/restoring feedback to the power piston and pilot valve.
Loss of Position Command
Upon loss of the Position Command signal, the actuator terminal shaft goes to minimum fuel, thus
offering a safety feature. With loss of power supply voltage, the L-Series controller loses torque and the
force of the loading or return spring causes the center adjustment to lower. The pilot valve follows,
keeping the control port uncovered. Trapped oil under the power piston escapes to drain, and the servo
power piston moves down until it reaches minimum fuel position.

Fault Detection and Annunciation

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The UG-25 actuator provides complete shutdown fault monitoring. A detected shutdown condition forces
the actuator to go to the minimum fuel (0 %) position. When the shutdown condition no longer exists, the
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UG-25 actuator is returned to a non-shutdown state. Faults are globally set as non-latching. When the
condition no longer exists, the fault is automatically cleared without any reset.

Shutdown Details

Shutdown—Voltage Sense Fail
Indicates an out-of-range signal on the input power. Could indicate input power out of range or a fault in
the supply voltage sense circuitry.
This shutdown causes the Unit Healthy LED to turn off and the External Status output (Terminal 11) to
open-circuit, turning off any External Status device that is connected.
Failure levels: >33 V and <6.25 V
Persistence: 650 ms
Shutdown—Temp Sense Fail
Indicates a failure of the internal on-board Temperature Sensor.
This shutdown causes the Unit Healthy LED to turn off and the External Status output (Terminal 11) to
open-circuit, turning off any External Status device that is connected.
Failure levels: >150 °C and <–45 °C
Persistence: 650 ms
Hysteresis: 5 °C (<145 °C or >–40 °C to clear)
Shutdown—OverTemp
If the on-board temperature sensor reads a temperature above 125 °C, this error will be set. The Current
Limiting based on temperature will effectively make the output "limp" by reducing the drive current to zero
(see Current Limiting Based on Temperature section for details).
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