24 - ATR144 - User manual
8.8 Loop Break
The function Loop Break allows to detect a failure on the
control loop. During activation of the actuator, the process
is supposed to change towards the setpoint. If this change
is not consistent or fast enough, atr144 will display the
message”loop break alarm”. This message won’t be shown if
parameter 62 or 78 are set to “L.B.A” - in this case the regulator
generates an alarm, enables the corresponding output and
displays the message selected in the parameter 72 (“alarm 1
label”) or 88 (alarm 2 label).
This is only a software control and it only occurs in the output
saturation phase (control percentage 0% or 100%); it should
not be mistaken with a partial or total failure of the load,
which is measured, for example, using a current transformer.
Setting manu. in the parameter 141 L. b . s . (“Loop Break State”),
the controller checks if the process has changed at least by
the value set in the parameter 143 L.b.b. (“Loop Break Band”),
in a maximum time equal to the value of the parameter 142
L.b.t. (“Loop Break Time”).
If you set autom. in the parameter 141 L. b . s (“Loop Break
State”), the values concerning time and change of control
are calculated automatically, but only if the setting action is
made by PID, PI or PD.
The band will assume a value of 0.5*Pb, and the time will be
2*Ti in case of PID or PI setting, or 12*Td in case of PD setting.
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