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4.4.2.
HB alarm
The HB (Heater Break) alarm identifies load break or
interruption through measurement of the current delivered
obtained by means of a current transformer.
See the diagram in the installation manual.
The following three fault situations may occur:
1.
The current delivered is lower than the rated current.
This is the most common situation and indicates failure
of a load element.
2.
The current delivered is higher than the rated current.
This situation occurs, for example, due to partial short
circuits of load elements.
3.
The current delivered remains significant even during
periods when it should be zero. This situation occurs
when the load control circuits are short-circuited or
relay contacts are welded together. Prompt intervention
in these situations is very important to prevent greater
damage to the load and/or the pilot circuits.
In standard configuration, the power output is associated
with the heating control of a phase, obtained by modulating
electrical power with an ON/OFF control based on the set
cycle time.
The current reading taken during the ON phase makes it
possible to identify an abnormal deviation from its rated
value due to a fault on the load, i.e., the first two fault situa-
tions listed above.
The current reading taken during the OFF phase makes
it possible to detect a possible fault on the control relay,
resulting in an output that is always active (third fault situa-
tion).
The alarm is enabled by means of parameter AL.n.
The type of function desired is selected by means of the
Hb.F parameter:
•
Hb.F = 0: the alarm is activated if the current load value
is below the threshold value set in A.Hbx while the SSR
control output is ON.
•
Hb.F = 1: the alarm is triggered if the current load value
is above the threshold value set in A.Hbx while the SSR
control output is OFF
•
Hb.F = 2: alarm activation is obtained by combining
functions 0 and 1, considering the threshold of function
1 as 12% of the ammeter full scale defined in H.tAx.
•
Hb.F = 3 (continuous alarm): the alarm is activated due
to a load current value below the threshold value set in
A.Hbx; this alarm does not refer to the cycle time and
is disabled if the heating output value is below 3%. The
setting A.Hbx = 0 disables both types of HB alarm by
forcing deactivation of the Alarm status.
The alarm is reset automatically if its cause is eliminated.
An additional configuration parameter for each phase, relat-
ed to the HB alarm, is Hb.t, i.e., the delay time for activation
of the HB alarm, understood as the sum of times for which
the alarm is considered active.
For example, with:
•
Hb.F = 0 (active alarm with current below the threshold
value),
•
Hb.t = 60 sec. and control output cycle time = 10 sec,
•
power delivered at 60%,
the alarm will activated after 100 seconds (output ON for 6
seconds each cycle).
81901A "MSW_GPC-40/600A"_03-2021_ENG_page 139
Under the same conditions, if the power is delivered at
100%, the alarm will activate after 60 seconds. If the alarm
goes off during this interval, the time sum is reset.
The delay time set in Hb.t must exceed the cycle time of
the SSR output.
With a three-phase load, three different activation thresh-
olds can be set for the HB alarm:
•
A.Hb1 = alarm threshold for line L1,
•
A.Hb2 = alarm threshold for line L2,
•
A.Hb3 = alarm threshold for line L3.
4.4.3.
HB alarm threshold teach-in
function
This function allows teach-in of the alarm threshold. To use
this function, it is first necessary to set the Hb.P parameter,
which defines the percentage of current in relation to the
rated load below which the alarm is activated.
The function can be activated by a command from a serial
line, a digital input (see paragraph "3.12.4. Digital input
function") or a key (see paragraph "3.36. Key functions").
When the Teach-in function is activated in ZC, BF and HSC
modes, the RMS current value in conduction ON multiplied
by the Hb.P parameter determines the HB alarm threshold.
When the Teach-in function is activated in PA mode (not in
combination with infrared lamps), the RMS current value is
shown at 100% power, which, when multiplied by the Hb.P
parameter, determines the HB alarm threshold. Before ac-
tivating the function, the module must be switched on with
power, which is recommended to be above 50%.
In the case of HSC or PA mode for infrared lamps (see
parameter hd.5 option +128, paragraph "3.27.1. Enabling
trigger modes") the function activates automatic reading
of the power/current curve useful for determining the HB
alarm threshold.
Automatic reading of the power/current curve takes place in
the following sequence:
•
softstart at maximum power (default 100%), 5 second
delay;
•
reduction of power to 50%, 30%, 20%, 15%, 10%,
5%, 3%, 2%, 1%, with a 5-second delay between
each value;
•
return to normal operation.
Maximum conduction value in this phase can be limited by
means of the parameter PS.Hi.
If required, it MUST only be activated with hd.6 = 0 (the
desired hd.6 value can only be set after calibration).
In HSC mode, the HB alarm threshold teach-in function
does NOT calibrate at 5%, 3%, 2%, 1% to avoid high peak
currents due to low impedance for the low temperature of
the IR lamp filament.
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