JUMO 709061 TYA 201 - Single-Phase Power Controller Operating Manual - Manual (Page 71)

2012-12-01/00561071 [SCR Power Controller TYA201] 69
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 breakage.
Overcurrent This function is used for several heating elements connected in series that are
to be monitored for short circuits.
Function This function does not only take the decreasing or increasing load current into
consideration but also includes the load voltage in the monitoring process.
The correct load ratios of the system are saved during teach-in.
Based on this status, the load changes are continuously monitored irrespec-
tive of the required output level. In the event of a breakage 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 in the configuration or operator level in % for the
load monitor. This limit value depends upon the number of heating elements
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 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
neutral 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 %