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Electrical connection
7-26
2 spots (upper and lower current value) must be selected at which current scaling is per-
formed. Scaling is dependent on the value of the upper current limit (as set in the Elec-
trode Parameter Menu). The lower value should be 40% of the upper current limit and the
upper value should be 80% of the configured upper current limit .
Example: max. current 20 kA, lower current value: 8 kA, upper current value: 16 kA
Consequently, scaling should be performed at 8 kA and 16 kA, if possible. However, at
least 2 test welding operations are to be performed to verify whether the respective elec-
trode is suitable for welding with these desired current values. First, a welding operation
must be performed at the lower current value. On the basis of the required phase angle,
you can now determine whether the upper command current value can actually be
achieved at a phase angle of up to 80%. If this is not the case, the lower command current
value must be lowered until it can be ensured that also the upper command current value
can be reached. Please note that the upper command current value must always be twice
the value of the lower one.
When this has been verified, the actual current scaling process follows. During two weld-
ing operations, each, which must be performed at the upper and the lower command cur-
rent values, the primary and secondary currents are measured. The reference current is
read in through the 24V interface of the external weld current meter.
-
The 24V log is switched back from the weld current meter.
-
Upon correct completion of the scaling operation, the <Current scaling /
check finished> signal becomes high and is held until the <Current scal-
ing> signal is reset.
Current scaling involves the re-determination of 2 values:
1) Toroid sensitivity: Scaling of the primary current to the external weld current meter.
nd
2) 2
toroid sensitivity: Scaling of the secondary current to the external weld current
meter.
These values are shown under Basic Setup - Electrode Setup in the BOS.
You can view the results of the last scaling operation for the respective electrode in the
"Scaling Results" window under the "Electrode Setup" window in the BOS. No <Weld
complete> signal is output during scaling.
If an error occurs:
If an error of any type occurs during scaling, the scaling operation will be aborted, the
<Ready> signal reset and an error message transmitted. The error message transmitted
will always relate to a weld fault. If the abort was caused by some other type of error, also a
welding process error message will be transmitted nevertheless. No <Current scaling/
check finished> signal will be transmitted. What is unusual here is the way in which a
fault is reset. The < Fault reset with WC> signal indicates that the fault is reset. Subse-
quently, however, the signal that is actually output is not the <WC> signal but instead the
<Current scaling/check finished> signal. If the <Fault reset with reweld> signal is
output while the <Current scaling> signal is still high, another current scaling operation
will be started right away. Otherwise, the timer will now be in normal "Weld timer ready"
state.
Typical errors as they may occur during current scaling operations are described under
"Error Messages".
PSI 6XXX.350 L1
1070 080 067-101 (2001.03) GB
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