JUMO 709051, Operating Manual, Page: 63 / 92

V1.00/EN/00741192/2021-03-30 [IPC 300] 63
6 Special device functions
6.1 Subordinate control loop
Subordinate control loops are primarily used to eliminate or compensate for
external disturbances, such as fluctuations in the voltage supply and alter-
ations in resistance that have a negative effect on the control process.
Default setting A subordinate U
2
control loop is set, but U or I or I
2
or P control loops can also
be configured.
k
default setting
6.2 Detection of load faults
The load monitoring detects the percentage change in resistance of the load
following Teach-In (from an input setpoint value
≥
3%). It can detect and signal
a load failure, partial load failure, or a partial load short circuit. Note: With the
IPC 300, there is also the possibility to detect load failures using external cur-
rent sensors.
v
Chapter 6.8 "External current sensors"
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 (resis-
tance measurement).
The system's correct load ratios are saved during Teach-In.
The load changes are monitored based on this state. In the event of a break or
short circuit of a heating element, the load current increases or decreases.
This is detected by the load monitoring 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.
Control
loop Application
U
2 - Positive TC, molybdenum disilicide
- R
≈
constant
- Brightness controls
P - General application, necessary for SiC load and au-
tomatic aging compensation.
I
2
- Negative TC