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Open Circuit Voltage Generator & VRD
The open circuit voltage of the MicorMIG machines is not produced via the power unit, it is a DC signal voltage
generated by the MAPRO. At machines with active VRD, the VRD voltage is programmed with a lower voltage
(like 24V) instead of 80V.
When the machine is switched on, the MAPRO is activating the open circuit voltage for a short time to check its
function. If no voltage is measurable, the machine stops with
E25-01
“Error voltage generator”
.
Since software version 1.12 the display of the error message is suppressed, when at switching on
the machine. If a short circuit at the output is present (torch is laying on the work table, wire is touch-
ing the ground), the E25-1 is NOT displayed at the front panel. In this situaton (as long as the short
circuit is still present), the wire inching button is not working. As soon as the short circuit is removed
(taking the torch away from the work table), tha machine functions normally.
When switching between to a different welding mode like MMA (stick electrode) or TIG, the open circuit voltage
generator is stopped and started again. If no voltage is measurable after the re-start, the machine stops with the
error code
E25-02
.
Monitoring welding current
The welding current is measured directly via the DSP of the MAPRO using a shunt resistor. Parallel to this, the
FPGA of the MAPRO is also monitoring the voltage across the shunt resistor via an A/D converter.
When the machine is not welding, the voltage across the shunt resistor is 0V. If a voltage is measured anyway
(voltage offset), the machine stops with the error code
E15-01
“current offset FPGA”.
In case of a contact problem between MAPRO and shunt resistor, the machine stops with the error code
E15-00
.
Schematic
R
SHUNT
MAPRO
X5-1
X5-2
DSP
FPGA
A/D
New Shunt resistor
Since May 2020 (from serial number 4xxx-3019-xxxx-x) a new shunt resistor is used where the connecting wires
are now directly soldered to the shunt. Also new spare part kits were generated (including a mounting instruction):
MicorMIG 300/350/400: 666.0012.0
MicorMIG 500:
666.0015.0
old shunt
new shunt
Summary of Contents for MicorMIG 300
Page 1: ...Service Manual MicorMIG 909 2130 1 10 ...
Page 35: ...page 35 ...
