Monitoring Welding Current - LORCH V Series Service Manual

Monitoring welding current

The welding current is measured via a separate current sensor (VAC or LSW pcb at older machine versions). The
current is monitored by the Microcontroller (Master) and the DSP (Process) at the same time.
Schematic
X2 / 3
X2 / 2
4
3
2
X2 / 1
1
current
sensor
X2 / 3
X2 / 2
4
3
2
X2 / 1
1
current
sensor
The output of the current sensor is a current with a ratio of 1:2000, meaning at a welding current of 300A the sen-
sor output is 150mA. The output current is measured via an internal shunt resistor by the Master and Process.
If the Master measures a current >120% of the maximum value, the machine will stop and displays E03 (second-
ary overcurrent).
If the Master measures a voltage >3.5V at the shunt resistor (that would mean a welding current >988A), the ma-
chine will stop and displays E09 (error v/a measuring).
If the Process is measuring a welding current >20A although the machine is not welding (standby), the machine
will stop and displays E21 (Output voltage/current).
At V40 or V50 (machines with double power units), both power units are working parallel. For example: the ma-
chine is set for 200A welding current, then 100A are generated from power unit 1 and the other 100A are gener-
ated from power unit 2. The outputs of both power units must be the same.
If for some reason one power unit generates less than the other power unit and the difference between the power
units are >40A, then the machine will stop and displays E17 (error current symmetry).
The actual current values of each power unit can be displayed in Menu Extras, Diagnosis, Current module 1/2.
To check which power unit is faulty, it is possible to use the power units independently by converting the V40 into
a V24 (using only one power unit) or converting a V50 into a V30.
This conversion can easily be made by just disconnecting the flat ribbon cables of the second power unit from the
DK-MAPRO (X3 and X5) and changing the DIP switch settings of the DCDRV board.
page 34
DCDRV1
X1 / 16
X1 / 15
X1 / 14
DCDRV2
X1 / 16
X1 / 15
X1 / 14
DK-MAPRO
X2 / 16
-15V
X2 / 15
X2 / 14
+15V
X3 / 16
-15V
X3 / 15
X3 / 14
+15V
+3.3V
DSP
+3.3V
MASTER