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ABB i-bus
KNX
Device technology
46 2CDC 505 056 D0208 | SA/S
It is possible to program two threshold values for each output. With an overshoot or undershoot of the
current threshold value a 1 bit telegram is sent via the bus. Thus for example, the failure of equipment can
be detected and displayed.
With relatively small current values (< 30 mA), natural deviations in the electrical system will be
immediately noticeable, e.g. natural ageing of the equipment, voltage fluctuations through differing load
levels during the day as well as distortions of the sinusoidal load current, e.g. through switching actions or
frequency inverters.
The ideal observation, i.e. where the current consumption of the equipment does not change with
temperature fluctuations, operating voltage deviations and ageing, should always be inspected in the
actual system. The changes of the ambient conditions in practice and the associated changes in current
consumption and the monitored equipment must be considered. As ambient influences cannot be
eliminated in practice, detection via a current threshold model is only viable if a current change caused by
tolerances and ambient influences in normal operation is less than the current change caused by
equipment failure.
Recommended approach when monitoring loads that are close to the detection tolerances of the SA/S
current detection:
•
Connect the complete circuit to the SA/S output.
•
Close the circuit and operate loads in the typical operating range.
•
In ETS, set the data point types of the communication object and start the ETS project group monitor
in order to display the current value.
•
Observe current value I
A
via KNX until a constant current is indicated.
•
Cause equipment failure and observe the current value I
F
again.
•
Determine the difference in current I
D
= I
A
– I
F
.
•
Compare the difference in current I
D
with the current detection tolerances. The current difference must
be significantly larger than the accuracy of the current detection (2 % of I
A
+/-
20 mA).
•
Set the current threshold in SA/S so that it is as near as possible to the determined failure current:
I
A
– ½ I
D
has proven useful.
Содержание i-bus SA/S 12.10.2.1
Страница 1: ...ABB i bus KNX SA S Switch Actuators Product Manual ...
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