# Parameter Range Notes
11 Inhibit(s) #1 to #32 Varies
Inhibit(s), that if active, can inhibit the alarm from becoming active.
Note that there are only four fields for inhibits in PICUS.
12 Action Varies Action to be taken.
*Note: Trigger level is typically fixed and cannot be changed. However, the set point for Directional over-current determines the
Trigger level. In addition, you can configure I/O alarms with a High or Low Trigger level.
4.2.2 Set point
The Set point is the reference value that is compared by the controller to decide whether the Alarm condition is present in the
system.
When the operating value, that the alarm is based on, reaches the Set point, the controller starts the Time delay (if applicable) for
the alarm. The Set point is often a percentage of the controller's nominal setting.
INFO
Most alarms require a Set point to be configured.
For example, the Set point for the Over-current 1 alarm can be 100 %. This means that the current from the equipment must be 100
% (or more) of the nominal current to activate the alarm.
4.2.3 Reset hysteresis
The Reset hysteresis prevents the operating value from being too close to the alarm Set point when the alarm is reset. The Reset
hysteresis makes the system more stable by imposing hysteresis on the alarm Set point. The Reset hysteresis is a value that is
subtracted from the set point of high alarms (and added to the Set point of low alarms).
A Reset hysteresis can only be used where the alarm is based on an analogue value.
Overspeed example
Consider an Overspeed alarm with a Set point of 110 % of nominal speed and a
Reset hysteresis of 10 %. The overspeed alarm cannot be reset until the operating
value falls below 100 % of nominal speed. The red line in the following figure shows
that the alarm is activated when the value exceeds the Set point. The alarm is only
deactivated when the value drops below the reset value.
Under-speed example
Consider an Under-speed alarm with a Set point of 80 % of the nominal speed and
a Reset hysteresis of 5.0 %. The alarm is only reset when the operating value is
above 85.0 % of the nominal speed.
4.2.4 Action
The alarm Action is the response that you allocate to the Alarm condition. Each alarm can only be assigned one alarm Action. The
controllers are delivered with pre-defined alarm actions. You can change the alarm Action for most alarms.
DESIGNER'S HANDBOOK 4189340911K UK Page 96 of 521
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