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• ALARM FUNCTIONS
Alarms can be absolute or deviation, direct or reverse,
symmetrical deviation.
Absolute alarm: limit set with an absolute value compared to 0
(Ex. for 1000: set-point = 400, AL1 = 450, AL2 = 350, AL3 =
500).
Deviation alarm: limit set with an offset compared to setpoint
(Ex. for 1000: set-point = 400, AL1 = +50, AL2 = -50, AL3 =
+100).
Direct alarm: corresponding relay energized with controlled
variable over set limit, in both absolute and deviation mode
(maximum alarm).
For HB alarm, relay energized if current is below set value.
Reverse alarm: corresponding relay energized with controlled
variable under set limit, in both absolute and deviation mode
(minimum alarm).
For HB alarm, relay energized if current is above set value.
With symmetrical deviation alarm : the offset relative to the
setpoint is both added and subtracted, defining an intervention
window.
With absolute alarms, the limits take on at maximum the limits
set in phase CFG2 (Lo.S and Hi.S.
With deviation alarms, the limits have values in range
-199/+999 and the set value is added algebraically to the
setpoint (the deviation alarm limit may extend below the lower
limit or above the upper limit of the set scale) .
• CT (current transformer) INPUT
This input signals changes in load input, indicating the current
value at the ammeter input in the set scale range.
The CT card (signaled by the brd code) lets you read the
current in the CT secondary (5Aa.c) on the auxiliary analog
input (terminals 6 and 7; see connection diagram). You can
define the full scale current value directly referred to the load
circuit with the Hb.S parameter in CFG.1 phase (example:
for a CT 75/5A, set Hb.S = 75.0); by default, scale start is
considered 0. Current reading is available in phase 5 in work
mode (the lower display shows the whole value of current
followed by letter "A;" example: 45.A), or in the setting phase
for the HB alarm limit on the upper display with resolution of a
tenth of an Ampere (ex. 45.8).
Notes:
- The CT card lets you access the ammeter input calibration
procedure (Hb.C).
- The CT input function can be used independently of the HB
alarm to simply display the current at the ammeter input.
HB ALARM (Heater Break Alarm)
This type of alarm is conditioned on use of the current
transformer (CT) input with setting of the brd code in phase
CFG.2. The HB alarm function is independent of alarms AL1,
AL2, AL3.
Enable by setting the Out code in phase CFG.2 to an odd
value (bit1 = 1).
Enabling allows setting of the limit in work mode phase 4, with
display of the ammeter input on the upper display and the limit
with letter A flashing on the lower display (es. 25.A).
Press the Raise and Lower keys instead of letter A to show the
decimal figure of the limit, which remains during the change.
When the keys are released, "A" reappears after one second.
With code A.r.F in phase CFG.2, you can assign the HB alarm
to each of the alarm outputs installed (AL1, AL2, AL3).
10
10 • FUNCTIONAL NOTES
If it is not assigned to an output, the alarm state is still available
in read via serial line (if enabled) at address 10H (see Memory
Map section).
The HB alarm function is selectable from 4 different modes by
means of code Hb.F in phase CFG.2:
0 - alarm trips when load current drops below limit set for ON
time of main output (evaluation time: 30 sec. including ON);
turns off as soon as limit is exceeded.
1 - alarm trips when ammeter full scale (Hb.S) in OFF time is
exceeded by 12%; turns off as soon as value drops below 12%
limit.
2 - alarm trips if one of functions 0 and 1 (described above) is
active (OR logic between functions 0 and 1)
3 - HB alarm for continuous output (PWM control, setting
Ct = -1 or -2); with fixed duty cycle of 100msec.; does not take
account of ON/OFF times and presupposes a special ammeter
card with HW integration of load current.
The alarm trips if current drops below the set limit for 15 sec.
Functions only with power in output greater than 10% (2% for
version 12); otherwise the alarm is deactivated. The alarm
resets automatically if its cause is eliminated.
Deactivate the HB alarm by setting the limit to 0.
Notes:
- ON/OFF times refer to the set cycle time (see CT parameter
in Programming phase 0).
LBA ALARM (Loop Break Alarm):
This alarm identifies interruption of the control loop due to a
possible probe in short circuit, reversed probe, or load break.
If enabled (Lb.t <>0), it causes an alarm in case the variable
value doesn't increase in heating (or doesn't decrease in
cooling) under conditions of maximum power supplied for a set
time (Lb.t) in range 0...240 min.
If the value of the variable is beyond the proportional band,
power is limited to the set value (Lb.P) in range 0-100%.
The active alarm condition is signaled by flashing of the
displays. By means of code A.r.F (in phase CFG.2) the LBA
alarm can be assigned to each of the alarm outputs installed
(AL1, AL2, AL3).
If it is not assigned to an output, the alarm state is still available
in read via serial line (if enabled).
The alarm condition resets if the temperature increases in
heating (decreases in cooling), or by means of the panel keys
by simultaneously pressing the F and Raise keys for 3 seconds
(press F first).
The LBA function is disabled by setting parameter Lb.t to 0.
80343I_MHW_1000_07-2011_ENG
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