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2.5.1 LOAD MONITORING
MONITORING OF THE LOAD AND MAINS VOLTAGE
Each power section is fi tted with its own transformer for creating the synchronization voltages. This
also allows monitoring of the phase voltages. In the LBA menu monitoring, the limits may be set for
U
Line min
and U
Line max
. If larger deviations are detected, then a fault indication is generated.
ABSOLUTE OR RELATIVE MONITORING
Relative monitoring for heating elements for R
hot
/R
cold
≈ 1 and absolute monitoring for heating
elements with R
hot
/R
cold
≠ 1 are possible.
ABSOLUTE VALUE MONITORING CURRENT
This function allows monitoring of a freely selectable absolute current limit. The parameters for
the value may be set in ampere.
This absolute value monitoring lends itself to one or more load resistances organized in parallel or
in series. Generally, the effective current value measured is continuously compared with a preset-
table absolute current limit for undercurrent or overcurrent. If these limits are undercut or exceeded
an indication shows. In case of resistor elements organized in parallel, it is therefore possible, using
the lower current limit, to select a partial load interruption. Using the upper current limit, in case of
resistors switched in series, short-circuiting of an element may be detected.
RELATIVE MONITORING
This monitoring is sensible if the resistance value of the load slowly changes. Changes in resistance
may for instance be caused by temperature changes or by ageing. The current (b) of the Power
Controller is regarded as 100% load current (current in fault-free state) after activation of the RESET
or CONTROLLER LOCK. The RESET is automatically activated after each startup, restart or after
mains outage. In case of relatively slow changes of the current, due to characteristics of the above
mentioned heating elements, automatic adjustment of the internal reference value to 100% is
performed (b‘).
i
T
L
I < threshold
indication 16,17 (Chap. 3.4)
t
V
FIG. 4 ABSOLUTE VALUE MONITORING
FIG. 5 RELATIVE MONITORING