2011-07-01/00561073 [SCR Power Controller TYA202] 65
6 Special device functions
6.1 Detection of load faults
The load monitoring function can detect and signal a load failure, a 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 temperature co-
efficient TC 1 the limit value can be taken directly from the following tables:
Undercurrent
The specifications in % refer to load current changes
Number
of heating
elements
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%
1 50%
50% 21%
Example:
2 heating
elements
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