ESAB LKB 400W User manual

LKB 400W
WELDING RECTIFIER
Service manual
0349 300 020 01-01-24

2
1. CONNECTION DIAGRAM, LKB400W ................................................................................................ 4
2. COMPONENT POSITIONS, CIRCUIT BOARD LA07 (A1) ................................................................ 6
2.1 DESCRIPTION OF BOARD LA07.................................................................................................... 8
3. COMPONENT POSITIONS, CIRCUIT BOARD LKC31 (A2) ............................................................. 9
3.1 CONTROL CIRCUIT FUNCTION LKC31 ........................................................................................ 10
3.1.1 POWER SUPPLY ....... ............................................................................................................... 10
3.1.2 START/STOP ............................................................................................................................. 10
3.1.3 CONTROL MODES-2 STROKE/MOTOR-TEST/4-STROKE ................................................... 10
3.1.4 WIRE FEED SPEED ................................................................................................................... 11
3.1.5 MOTOR CONTROL/DYNAMIC BRAKING .............................................................................. 12
3.1.6 BURNBACK TIME, CONTACTOR, GAS VALVE ...................................................................... 13
3.2 V/A-METER OPTION (STANDARD CONTROL) ........................................................................... 13
4.TECHNICAL DATA ............................................................................................................................... 15
5. LOAD CHARACTERISTIC ................................................................................................................... 15
6. INSTALLATION .................................................................................................................................. 16
7. INSTRUCTION FOR USE .................................................................................................................... 16
8. COOLING CIRCUIT DIAGRAM ........................................................................................................... 17
9. MAINTENANCE ................................................................................................................................... 18
10. ACCESORIES .................................................................................................................................... 18
10.1 V/A METER ALLEMBLY INSTRUCTION .................................................................................... 18
11. SPARE PARTS LIST ...................................................................................................................... 19

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! WARNING !
ARC WELDING AND CUTTING CAN BE INJURIOUS TO YOURSELF AND OTHERS. TAKE
PRECAUTIONS WHEN WELDING. ASK YOUR EMPLOYER FOR SAFETY PRACTICES THAT SHOULD
BE BASED ON MANUFACTURER’S HAZARD DATA.
ELECTRIC SHOCK - Can kill
- Install equipment in accordance with obligatory standards.
- Do not touch live electrical parts or electrodes with bare skin, wet gloves or wet clothes.
- Insulate yourself from earth and workpiece.
- Ensure your work position is safe.
FUMES AND GASES - Can be dangerous to your health
- Keep your head away from fumes.
- Use ventilation and/or extraction to keep fumes and gases away from your breathing zone
and surroundings.
ARC RAYS - Can injure eyes and burn skin
- Protect your eyes and skin. Use correct welding screens, filter lens and wear protective clothes.
- Protect bystanders with suitable screens or curtains.
FIRE HAZARD
- Sparks (spatter) can cause fire. Make therefore sure there are no inflammable materials nearby.
NOISE - Excessive noise can damage your hearing.
- Protect your ears. Use ear defenders or other hearing protection.
- Warn bystanders of the risk.
READ AND UNDERSTAND THE INSTRUCTION MANUAL BEFORE INSTALLING OR OPERATING UNIT
PROTECT YOURSELF AND OTHERS !

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1. CONNECTION DIAGRAM, LKB400W, 400V
Switch positions for switch Q3 Switch positions for switch Q4
COMPONENT DESCRIPTION
A1 Circuit board LA07 M1 Fan
A2 Circuit board LKC31 M2 Pump
A3 V/A - meter M3 Drive unit motor
T1 Transformer V2 Rectifier bridge
V1 Diode bridge B1,B2 Temperature switch
L1 Inductor B3 Flow switch
RI Shunt RV Wire speed reference potentiometer
K1 Contactor R2 Resistor
Q1 Rotary cam switch F1 Fuse 2A slow-blow
Q3 Rotary cam switch F2 Fuse 10A slow-blow
Q4 Rotary cam switch F3 Fuse 4A slow-blow
Q2 Circuit breaker H1 LED (green/yellow)
T2 Control transformer H2 LED (yellow)
C1,C2,C3 Capacitor 2uF 450V H3 LED (green)
C5,C6,C7 Capacitor 0,1uF/275V XGM Terminal block
R1 Resistor 3,3k 1W

5
LKB 400W, 400V

6
2. COMPONENT POSITIONS, CIRCUIT BOARD LA07 (A1)

7
DIAGRAM LA07 (A1)

8
DESCRIPTION OF BOARD LA07 (A1)
Power supply
The board is supplied 20V AC voltage (contacts 8,9 connector X1). Two step voltage regulation (elements
T9, U1) provide voltage 15 V ±5% required for control system power supply.
Inputs
1. Auxiliary contact of main contactor type NO - 11,12 X1,
2. Contact of temperature sensor type NC - 4,3 X1,
3. Contact of liquid pressure sensor type NO - 2,1 X1,
4. Reserved input - 6,7 X1,
5. Reserved input - 5,10 X1.
Outputs
1. Fan switch contact NO, MOV 275V - 1,6 X2, (6- common phase contact)
2. Pump switch contact NO, MOV275V - 3,6 X2, (6- common phased contact)
3. Power supply switch for feeder
type NO , MOV 75V - 1,2 X4,
4. Power supply for LED diode green-yellow (H1) - 1,2,3 X3 (2-common cathode)
5. Power supply for LED diode yellow (H2) - 6,7 X3 (6-cathode)
6. Power supply for LED diode green (H3) - 4,5 X3 (5-cathode)
LED diodes– external
1. H1 – two colours: green - unit on signal,
yellow – unit off signal,
2. H2 - yellow: on when unit overheated,
3. H3 – green: on when cooling liquid flow correct.
Operation
After switching the unit, feeding unit is powered (relay PK1) and fan (relay PK2) and pump (relay PK3) are
switched on. If within 5s the signal from liquid pressure sensor (NO contact ) is not supplied, wire feeding
unit power supply shall be disconnected. Power supply shall be restored on signal from pressure sensor.
Proper pressure (liquid flow) is indicated by green diode placed on the front panel of the unit (H3).
Wire feeder power supply is disconnected as well by means of signal from external thermal NC-type
switches. Overheating is indicated by yellow diode (H2) placed on the front panel of the unit. Wire feeder
power supply shall be restored on absence of overheating.
Oscillator-counter U2 is reset during main contactor operation and during overheating. After 5 minutes from
the last switch-off of contactor and end of overheating period, pump is switched off (relay PK3) and after 10
minutes – fan is switched off (relay PK2). On the fan switch-off unit goes into the idle mode indicated by
yellow lighting of diode H1 placed on the front panel of the unit. Wire feeder remains powered (relay PK1).
In the idle mode, with switched off pump, it is possible to start welding by means of button on torch.
Then, contactor is switched on again, counter U2 is reset, fan and pump are activated. Within 5s signal from
liquid pressure sensor should appear. If not, wire feeder power supply circuit (relay PK1) is disconnected.
Power supply shall be restored on signal from pressure sensor.

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3. COMPONENT POSITIONS, CIRCUIT BOARD LKC31 (A2)

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3.1 CONTROL CIRCUIT FUNCTION LKC31
Sections 3.1.1-3.1.6 below refer to the diagrams in chapter 1.
3.1.1 POWER SUPPLY
The circuit board uses one supply voltage: 42VAC – rectified by the bridge V2 for power supply to the motor
and control circuitry.
•Power supply to the electronic circuitry
-the +26V power supply from V3 through R3 – is regulated to 15V by voltage regulator A1,
-+15V is used for powering of motor control electronic
•+60V power supply is used for motor control,
This voltage may vary (with load/mains voltage deviation) – from –15% to +10%.
•+26V (intermediate voltage for A1) – is also used for powering of relays K1 and K2 (on PCB) and for input
control circuit (“START/STOP”).
3. 1.2 START/STOP
Closing contact S1 on the welding torch starts the welding process – or only motor M3 depending on control
mode selection (see – section 3.1.3)
3. 1.3 CONTROL MODES – 2-STROKE/MOTOR-TEST/4-STROKE
By the switch S3 on the PCB (pos. M) – in the motor compartment – welder may select the following control
modes:
A) 2-STROKE CONTROL
When the trigger switch (welding gun-S1) is depressed – welding process starts (wire feed motor, gas
valve and power unit contactor).
When trigger switch is released – welding process stops (motor and gas valve – immediately, contactor –
when burnback time is elapsed).

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B) MOTOR TEST
When trigger switch is closed – only feed motor starts, gas valve and contactor remain disenergised.
C) 4-STROKE CONTROL
The welding process is controlled by trigger switch S1 (welding gun) – as shown below:
NOTE: On the LKC31 – for selected 2-S/4-S mode – active signals are high!
3.1.4 WIRE FEED SPEED
The wire feed speed setting range is 1,6 to 25 meter/minute, the upper speed may be adjusted by R6A,
minimum speed is adjusted by R15A.
V-REF voltage is reference signal for motor speed control circuit.
Note: By the potentiometer R6A and R15A – there is set the ratio Vmax : Vmin; fine adjusting of the motor
speed (depending on the motor characteristic) – is performed by the R22A (see – section 3.1.5).
As well the motor speed (especially the lower range) – is influenced by the setting of I x R
compensation(R45 – see section 3.1.5).

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3. 1.5 MOTOR CONTROL/DYNAMIC BRAKING
The motor is powered by the smoothed +60 V supply. Pulse width modulation of transistor V6 controls the
motor voltage. The pulse frequency is about 16 kHz, and maximum conduction time of the pulses is about
95% of the pulse cycle time. During the Off parts of the pulse cycle, the motor current freewheels through
diode V8.
•Speed control
The gate pulses to transistor V6 are generated by a PWM circuit, which compares speed reference from
microprocessor electronic with signal proportional to the motor voltage (R22, R22A,R23).
•Current limit
The current limit is set at 12 A. The motor current is measured by resistor R36 which produces a voltage
drop proportional to the current (1A = 33mV). The current limit restricts the conduction time of the gate
pulses to transistor V6.
•Compensation of motor I x R voltage
Potentiometer R45 allows to compensate voltage drop on motor armature resistance so as to improve
wire transportation at low speed settings.
Warning: too high settings may cause drive control instability! Recommended setting is 0,50 – 0,60, if
drive becomes instable – decrease the setting.
Dynamic braking is performed by the loop: R33A,B,C, V7 and R36.

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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.

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Voltage indication is adjusted by potentiometer R1 on the PCB – comparing with reference voltmeter at the
input.
(Note: voltage adjusting is to be made only when jumpers are properly located and U-REF setting is
completed!)
Recommended voltage metering range is: 0V to –40V. (Calibration is performed for –25V).
Recommended current input range is: 0mV to +60mV. (Calibration for 60mV)
(Note: the above described procedure is applied only - when re-calibration of the factory setting is
necessary!)
V/A meter has “HOLD” function – i.e. after stop of welding, there is memorised the last displayed value
(current or voltage – depending on S1 position).
There is also possibility to compensate the voltage drop on current wires – i.e. to get indication of the actual
welding arc voltage.
Compensation is adjusted by potentiometer R28 (on the bottom side of PCB); when utmost CCW position –
there is no compensation, turning CW increases the compensation step.
NOTE: Factory setting is “no compensation”; if necessary – use reference voltmeter and artificial load – so
as to adjust compensation depending on the wire length.

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4.TECHNICAL DATA
Mains voltage 400V-415V 3~ 50Hz
Mains cable cross-section 4x4mm2
Mains fuse 25 A delayed
Rated power consumption 18,8 kVA
Rated primary current @ P35% 26 A
Rated welding current Duty cycle* 35% 400 A
Duty cycle* 100% 237 A
Welding current range 30A÷400A
Open circuit voltage 14÷47V
Dimensions length
width
height
1100
630
845
Weight 215 kg
Working flow of cooling liquid at pressure of 2,5 bar 1 dm3/min (60l/h)
Selection of cooling liquid depending on ambient temperature
-Distilled water
-Solution of 30% Antifreeze Coolant + 70% distilled water
from 0°C to +40°C
from -10°C
Tank capacity 6 dm3
*Duty cycle is based on 10-minute period. Duty cycle 30% means that after 3 minutes of unit operation, 7
minutes break is required. Duty cycle 100% means that unit can operate continuously.
Warning:
The unit is characterised by the following :
-Enclosure class IP 23 indicates that unit is designed for indoor and outdoor use.
-Application class S means that the unit is designed for use in areas of elevated electric hazard.
5. LOAD CHARACTERISTIC
0
5
10
15
20
25
30
35
40
45
50
0 50 100 150 200 250 300 350 400 450 500
I2(A)
U2(V)

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6. INSTALLATION
A competent and authorised person must install the equipment.
Connect the mains cable, and protect it with the appropriate fuses, in accordance with regulations.
Make sure that the power unit is not covered or installed such that cooling is impeded.
PRIMARY CURRENT, MAINS FUSE AND MAINS CABLE
Voltage 400V-415V
3~ 50 Hz
Primary current at:
100% duty cycle 16A
35% duty cycle 26A
Conductor 4x4mm²
Fuse, slow-blow 25A
7. INSTRUCTION FOR USE
The LKB 400W is step-switched welding power unit, intended for welding with solid filler wires of steel,
stainless steel or aluminium, and cored wires with or without shielding gas.
The power units can be fitted with an instrument for display of current and voltage. It incorporates a sample-
and-hold function.
A thermal overload cutout protects against overheating. The cutout resets automatically when the unit has
cooled.
CONTROL PANEL

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A. POWER SWITCH switches unit on when set at „I” position, green LED diode is on (pos. B) which signals
power supply to electric circuits of unit. Cooling fan and pump engine will also be switched on. Green
LED diode on (pos. C) indicates correct liquid circulation in installation. Pump is switched off 5 minutes
after welding process has been stopped. After another 5-minute period cooling fan is switched off and
unit turns into stand-by mode. Yellow LED diode is on at that time (pos. B). After welding process has
been started, fan and pump are activated automatically.
WARNING: If pump emits irregular noises, it signifies presence of air inside. In such a case unit must
be switched off and immediately switched on again.
B. OPERATION INDICATOR - diode indicating that unit is on (green colour) or in stand-by mode (yellow
colour)
C. COOLING INDICATOR - diode indicating correct circulation of cooling liquid (green colour)
D. WELDING VOLTAGE REGULATION is carried out in steps with 5-step switch of coarse regulation and
7-step switch of precise regulation. It means that it is possible to select 35 values of welding voltage.
WARNING: Setting of voltage by means of switches during welding (loaded power source) can cause
damage to unit!
E. OVERHEATING causes automatic switching off of unit, welding is stopped and it is not possible to
activate welding process with trigger switch on torch. Signal LED diode is on (E). It is possible to continue
welding process after temperature has dropped inside the unit.
F. DIGITAL METER indicates actual values of welding current and voltage. Required value is obtained by
setting lever of the switch to a proper position. Semi-automatic welder LKB 400W is manufactured
without meter. Meter is delivered with necessary equipment and assembly instruction KIT (meter has
HOLD function).
G. POTENTIOMETER to set wire feeding speed (in the range of 1,6 ÷25 m/min)
H. CONNECTION (Euro connection) to connect welding torch
I. CURRENT SOCKETS to connect current cable with clamp
J. CONNECTION PIPE for cooling liquid outlet (cold liquid)
K. CONNECTION PIPE for cooling liquid inlet (hot liquid)
L. POTENTIOMETER of burnback time regulation
M. MODE SELECTOR 2-stroke – motor test – 4-stroke
8. COOLING CIRCUIT DIAGRAM

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9. MAINTENANCE
Regular maintenance is important for reliable, safe operation.
•Blow the power until clean with dry compressed air at reduced pressure.
•For problem-free wire feed, clean and replace the wearing parts in the wire feed mechanism regular
intervals.
Note that an excessive pressure setting can cause abnormal wear on the drive roller, feed roller and wire
conduit.
•Blow the wire conduit clean at regular intervals and clean the gas nozzle.
WARNING: If periodical HV tests have to be carried out according to local safety
regulations (in some countries obligatory!) – the following control circuits must be isolated
during the test – by means of disconnecting the connectors X6B(A2), X9(A2), X14(A2).
10. ACCESSORIES
V/A meter kit 0349 302 118
10.1 V/A METER ALLEMBLY INSTRUCTION
1. Take off side panels of unit.
2. Put plastic sleeve on the axle of switch on meter’s board.
3. Fasten meter’s board and sleeve to front panel of unit.
4. Assemble cover of meter to partition of unit.
5. Disconnect current cable (+) from the bridge.
6. Connect shunt with reducing sleeve and bridge, and next connect current cable (+) to free end of shunt.
7. Connect wiring of meter according to schematic diagram of LKB 400W.
1. Meter VA-MET12
2. Shunt
3. Wiring for transformer T2
4. Wiring for board LKC31
5. Wiring for shunt and socket ( )
6. Rectifier bridge
7. Board LKC31
8. Current cable (+)
9. Transformer T2
10. Socket ( )

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11. SPARE PARTS LIST
Ordering No. 0349 302 111 LKB400W 400V-415V 3~ 50/60Hz
0349 302 156 LKB400W 230V 3~ 50Hz
Item no. Qty
400V-415V
Qty
230V
Ordering no. Denomination Notes
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
1
1
1
1
1
-
1
-
1
3
1
1
1
1
1
3
2
1
1
1
1
1
1
1
1
-
1
-
1
1
3
1
1
1
1
1
3
2
1
1
1
1
0349 302 135
0349 302 134
0349 302 137
0349 302 149
0349 302 150
0349 302 190
0349 302 151
0349 302 191
0349 302 133
0457 290 003
0349 302 026
0457 290 004
0457 290 006
0455 172 001
0455 174 001
0349 302 022
0349 302 136
0349 302 092
0349 302 119
0192 859 126
0349 302 173
Front grill
Front panel
Panel
Rotary cam switch
Rotary cam switch
Rotary cam switch
Rotary cam switch
Rotary cam switch
Potentiometer
LED-holder (socket)
LED (green/yellow)
LED (green)
LED (yellow)
Protection glass
Seal
Current connector-socket
Quick connector
Knob
Circuit board VA-MET12
Locking washer
Shaft
Q1
Q4
Q4
Q3
Q3
RV
H1
H3
H2
A3

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Item no. Qty
400V-415V
Qty
230V
Ordering no. Denomination Notes
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
1
1
1
-
1
-
1
1
1
1
1
1
-
1
1
1
1
1
1
1
1
1
-
1
-
1
1
1
1
1
1
-
1
1
1
1
1
1
1
1
0457 290 042
0349 302 048
0349 302 143
0349 302 205
0349 302 206
0349 302 207
0349 302 144
0349 302 145
0349 302 005
0457 290 063
0349 302 146
0349 302 147
0349 302 194
0469 689 002
0469 868 001
0349 302 007
0349 302 175
0349 302 177
0349 302 029
0349 302 196
Temperature switch (90o)
Temperature switch (135o)
Transformer
Transformer
Transformer with switches
Transformer with switches
Inductor
Diode bridge
Circuit board LA07
Fan
Water tank
Mains cable
Mains cable
Lid
Handle
Cooler
Top plate
Side plate
Pump
Pump bracket
B1
B2
T1
T1
T1
T1
L1
V1
A1
M1
M2