Woodward 721 - Chapter 7. Major Alarm and Minor Alarm; Major Alarm; Minor Alarm

Manual 26004 721DSC for Marine Propulsion Application
Woodward
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Chapter 7
Major Alarm and Minor Alarm
Major Alarm
If the 721 control detects a major alarm, it will activate the major alarm relay and drive the
actuator output to 0 mA to shut down the engine. If a mechanical reverse-acting actuator is
used with the electronic control, the mechanical governor will take over the engine control.
The condition to cause a major alarm is:
∗ Both speed sensors failed.
CAUTION
The 721 control will not activate a major alarm even on an actuator internal
open-circuit. However, an actuator internal open-circuit will cause engine
shutdown, consequently both speed sensors will fail for engine stalls. This will
then cause the 721 control to activate a major alarm.
Minor Alarm
If the 721 control detects a minor alarm, it will activate the minor alarm relay, but it does not
shut down the engine.
The conditions to cause a minor alarm are:
∗ One speed sensor failed.
∗ KW transducer input signal failed.
∗ Remote Speed Setting input signal failed.