Special Device Functions; Detection Of Load Faults - JUMO 709061/8-01-032 Operating Manual

6.1 Detection of load faults

Undercurrent
Overcurrent
Function
Limit value
Undercurrent
Number of Single-phase
heating ele- operation
ments
5
4
3
2
V1.04/EN/00561071 [Thyristor Power Switch TYA 201]
The load monitoring function can detect and signal a load failure, partial load
failure, or a partial load short circuit.
This function is used for one or more heating elements connected in parallel
that are to be monitored for failure.
This function is used for several heating elements connected in series that are
to be monitored for short circuits.
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.
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
r r
level Monitoring
For heating elements with a temperature coefficient TC ≈ 1, the limit value can
be taken directly from the following tables:
Star connection
with separate star
points without neu-
tral conductor
10 %
13 %
17 %
25 %

6 Special device functions

Limit value load monit.
Star connection with
common star points
without neutral con-
ductor
Delta connection
-
10 %
13 %
20 %
-
-
10 %
12 %
77