ESAB LKB 400W, Service Manual

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3.1.6 BURNBACK TIME, CONTACTOR, GAS VALVE
• BURNBACK TIME
The burnback time is the time from when motor braking starts until the main contactor opens. The
burnback time can be adjusted from 0 to 0,35 seconds – by the potentiometer R71. (R71 is located in the
drive unit – compartment pos. L).
•
ENERGISING THE CONTACTOR AND GAS VALVE
Contactor is switched - on by relay K1, which is controlled by transistor V28; gas valve Y1 is controlled by
V30 and K2.
3.2 V/A-METER OPTION (STANDARD CONTROL)
COMPONENT POSITIONS, CIRCUIT BOARD VA-MET12 (A2)
V/A-meter for measuring of welding voltage or current (readout is selected by switch S1 on the front of meter)
may be installed as optional accessory. (Assembling details – see section 9.1, connections are also shown in
section 1).
V/A-meter is supplied with 11VAC; input signal for current is delivered from standard 60mV shunt, voltage is
measured directly across welding rectifier output.
Depending on required current range (determined by applied shunt rating) – first the jumpers X3&X4 on the
PCB must be properly arranged, and the reference voltage U-REF must be adjusted by R4 – as indicated in
the diagram herewith (see the table). The final adjusting of U-REF is necessary so as to calibrate accurate
current indication (S1 – in position for current display)
– apply 60mV signal to inputs X1:2 (+) and X1:3 (-) – using reference voltmeter;
– adjust R4 – so as to display value corresponding to shunt rating – 150, 250 or 400A (jumper X4 in correct
position!)
When current calibration is completed change over the S1 to voltage position (locate jumper X3 properly) and
perform voltage calibration.