JUMO 709061/8-01-020, Руководство по эксплуатации

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V1.04/EN/00561071 [Thyristor Power Switch TYA 201] 77
6 Special device functions
6.1 Detection of load faults
The load monitoring function can detect and signal a load failure, partial load
failure, or a partial load short circuit.
Undercurrent This function is used for one or more heating elements connected in parallel
that are to be monitored for failure.
Overcurrent This function is used for several heating elements connected in series that are
to be monitored for short circuits.
Function This function not only takes the decreasing or increasing load current into con-
sideration but also includes the load voltage in the monitoring process.
The plant's correct load ratios are saved during Teach-In.
Based on this state, the load changes are continuously monitored irrespective
of the required output level. In the event of a failure or short circuit of a heating
element, the load current increases or decreases. This is detected by the load
monitor and a load fault is signaled.
Limit value A limit value must be entered as a % in the configuration or operating level for
load monitoring. This limit value depends upon the number of heating ele-
ments connected in parallel or in series.
For heating elements with a high positive or negative temperature coefficient,
a suitable limit value must be determined independently. The % value shown
below (see arrow) can be used as an aid for this.
This value represents the current deviation from the teach-in value. If the value
is > 0 %, the load has become more high-resistance; if the value is < 0 %, it
has become more low-resistance. This window can be accessed via Operator
level
r
Monitoring
r
Limit value load monit.
For heating elements with a temperature coefficient TC
≈
1, the limit value can
be taken directly from the following tables:
Undercurrent
Number of
heating ele-
ments Single-phase
operation Star connection
with separate star
points without neu-
tral conductor Star connection with
common star points
without neutral con-
ductor Delta connection
5 10 % - -
4 13 % 10 % -
3 17 % 13 % 10 %
2 25 % 20 % 12 %