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page 51

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 di󰀨erent 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 o󰀨set), the machine stops with the error code E15-01 “current o󰀨set FPGA”.

In case of a contact problem between MAPRO and shunt resistor, the machine stops with the error code E15-00.

Schematic

RSHUNT

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

LORCH MicorMIG Series User Manual

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