LKB 400WS
Service manual
0349 300 040 020322 Valid for serial no. 212-xxx-xxxx
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1. CONNECTION DIAGRAM, LKB400WS, 400V ................................................................................. 4
2. COMPONENT POSITIONS, CIRCUIT BOARDS:
A. CIRCUIT BOARD LA07 (A1) - LAYOUT.......................................................................................
A. CIRCUIT BOARD LKC24 (A2) - LAYOUT....................................................................................
B. CIRCUIT BOARD QSyn-Meter 20 (A3) - LAYOUT......................................................................
7
3. CONTROL CIRCUIT FUNCTION ........................................................................................................ 11
3.1 POWER SUPPLY ....... .................................................................................................................... 11
3. 2 START / STOP ............................................................................................................................... 12
3, 3 WELDING CURRENT DETECTION............................................................................................... 12
3. 4 WIRE FEED SPEED / SOFT START ..............................................................................................12
3. 5 MOTOR CONTROL ...................................................................................................................... 13
3. 6 BURNBACK TIME, CONTACTOR, GAS VALVE .......................................................................... 14
3. 7 CONTROL MODES – 2-STROKE/MOTOR TEST/4-STROKE ..................................................... 14
3.8 MEASURING AND DISPLAYING OF WELDING PARAMETERS
A) U/I – MEASUREMENT INPUTS .....................................................................................................
B) PARAMETERS DISPLAYING AND DISPLAY – MODE SELECTION ..........................................
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3.9 SYNERGY CONTROL PRESETTINGS AND INDICATIONS
A) OFF/ON AND MATERIAL/GAS – SELECTION ............................................................................
B) WIRE DIAMETER PRESETTING ..................................................................................................
C) WELDING VOLTAGE SELECTION ...............................................................................................
D) INDICATION OF SYNERGY CONTROL STATUS ........................................................................
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4.TECHNICAL DATA .............................................................................................................................. 18
5. LOAD CHARACTERISTIC .................................................................................................................. 19
6. INSTALLATION ................................................................................................................................. 19
7. INSTRUCTION FOR USE .................................................................................................................... 19
8. MAINTENANCE ................................................................................................................................... 22
9. SPARE PARTS LIST ......................................................................................................................... 23
INTRODUCTION
This service manual is intended for use by technicians with electrical training. Use it for fault - tracing and
repair.
Use the diagrams in section 1 and the description of operation in section 3 respectively – when fault-tracing.
A brief user guide is included in section 7 to assist understanding how the machine is used.
The manual contains details of design up to and including April 2002.
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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, LKB 400WS,
COMPONENT DESCRIPTION
A1 Auxiliary circuit board K1 Contactor
A2 Control circuit board M1 Fan
A3 Display circuit board M2 Wire drive unit motor
T1 Transformer M3 Pump
T2 Control transformer B1,B2 Temperature switch
L1 Inductor
RI Shunt
R1 Resistor 3,3k 1W RP1 Wire speed reference potentiometer
R2 Resistor H1 LED (green/yellow)
Q1 Rotary cam switch H2 LED (yellow)
Q2 MCB ( 2A ) H3,H5, H6,H7 LED (green)
Q3 Rotary cam switch H4 LED (green/red)
Q4 Rotary cam switch V1 Diode bridge
C1,C2,C3 Capacitor 2,0uF/450V V2 Rectifier bridge
C5,C6,C7 Capacitor 0,1uF/275V XGM Terminal block
F1 Fuse 2,0 A slow-blow
F2 Fuse 8 A slow-blow
F2 Fuse 4 A slow-blow
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LKB400WS
400-415V ~3 50/60Hz
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LKB400WS
230V ~3 50/60Hz
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2. PRINTED CIRCUIT BOARDS
A. CIRCUIT BOARD LA07 (A1) - LAYOUT
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LA 07 - Diagram:
DESCRIPTION OF BOARD LA07 (A1)
Power supply
The board is supplied with 20-24V 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,
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4. Reserved input - 6,7 X1,
5. Reserved input - 5,10 X1.
Outputs
1. Fan switch contact NO, - 1,6 X2, (6- common phase contact)
2. Pump switch contact NO, - 3,6 X2, (6- common phased contact)
3. Power supply switch for feeder
type NO , - 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 (ready) - signal,
yellow – unit off (idle mode) - 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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B. CIRCUIT BOARD LKC24C (A2) - LAYOUT.
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C. CIRCUIT BOARD QSyn-Meter 20 (A3) - LAYOUT.
3. CONTROL CIRCUIT FUNCTION (LKC 24)
LKB 400WS (equipped with control PCBs: LKC24C & QSYN-Meter 20) – may work in 2 control modes:
- standard control (welding parameters set manually)
- “synergetic” control (welding parameters partially stored in microprocessor program)
[For more details – see section 7].
Sections 3.1 – 3.9 below refer to the diagrams in chapter 1.
3.1 POWER SUPPLY
The circuit board uses one supply voltage: 42VAC – rectified by the bridge V2 for power supply to the motor
and control circuitry.
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• Power supply to the electronic circuitry
- the +60VS power supply from diode V1 through R1A, R1 – is regulated to 15V by voltage regulator A1,
- the +60VS from V1 through R3, V3A, R4 is regulated to +5V by voltage regulator A2,
- +15V is used for powering of motor control electronic
- +5V – supplies microprocessor control circuits
• +60V/+60VS power supply
+60V – is used for motor control and indication (LED - on front panel)
+60VS – is used for powering of some input control circuits (see next sections)
These voltages may vary (with load/mains voltage deviation) – from –15% to +10%.
• +26V (intermediate voltage for A2) – is also used for powering of relays K1 and K2 (on PCB)
3. 2 START/STOP
Closing contact on the welding torch starts the welding process – or only motor M3 (motor test) - depending
on control mode selection (see – section 3.7)
3. 3 WELDING CURRENT DETECTION
Signal from current relay is used for detection of welding current presence - after closing of torch triger.
3. 4 WIRE FEED SPEED / SOFT START
The wire feed speed setting range is 1,6 to 25 meter/minute.
The upper speed may be adjusted by trim-pot. R51A ; 4.9V at TP5 (RP1 - max) - correspond to 25m/min.
Current relay
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There is built-in „creep-speed” function in the program (ca 50% of work speed) -i.e. welder starts welding with
reduced wire speed and when the welding current relay picks-up (see 3.4) - the speed rise up automatically
to the value pre-set by RP1.
Note: Apart from the current relay signal - there is additionally implemented time controled (ca.0.5sec.)
changing-over the speed - in case when the current relay fails.
V-REF voltage is reference signal for motor speed control circuit.
In “standard” control mode (-Synergy = OFF by switch “R” – in the motor compartment) – welder may set the
wire speed in full range by the potentiometer RP1. When “synergy” control mode is active – signal from RP1
serves only as corrective value ±10% of the pre-set value of speed - by the microprocessor program.
[Note: This correction is counted from the middle point of RP1].
3.5 MOTOR CONTROL
The motor is powered by the smoothed +60 V supply. Pulse width modulation of transistor V8 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 V10.
At 42V motor supply voltage, the wire feed roller speed is 258 r/min ±5%. At a roller speed of 265r/min, the
wire feed speed is 25 m/min .
• Speed control
The gate pulses to transistor V8 are generated by a PWM circuit, which compares speed reference from
microprocessor electronic with signal proportional to the motor voltage (R10, R24).
• Current limit
The current limit is set at 13 A. The motor current is measured by resistor R32 which produces a voltage
drop proportional to the current (1A = 33mV).
V-REF(max)=4,9V
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The current limit restricts the conduction time of the gate pulses to transistor V8.
• Compensation of motor I x R voltage
Current signal allows to compensate voltage drop on motor armature resistance so as to improve wire
transportation at low speed settings (Compensation is adjusted via trim-pot. R9B, recommended setting
is 60 - 80 % of the pot.).
• Motor speed calibration
On the display ( pos.F / lower row / - on the front panel ) there is shown reference value of motor speed,
the actual motor speed is calibrated with trim-potentiometer R7 (gain of reference signal),with trim-pot.
R53 we may add some speed-offset : 0 - 0.5m/min ( i.e. to shift “vertically” the whole speed range) - so
as to correct the minimum speed.
3. 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 R47 (signal to the
microprocessor electronic). R47 is located in the drive unit – compartment (pos. O).
• ENERGISING THE CONTACTOR AND GAS VALVE
Contactor is switched-on by relay K1, which is controlled by transistor V14; gas valve Y1 is controlled by
V12 and K2.
3. 7 CONTROL MODES – 2-STROKE/MOTOR-TEST/4-STROKE
By the switch S1 on the PCB (pos. N – in the motor compartment – welder may select the following control
modes:
A) 2-STROKE CONTROL
When the trigger switch (welding gun-) 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 (welding gun) – as shown below:
NOTE: On the LKC24 – for selected 2-S or 4-S mode – active signal is low, it means that for “motor - test” –
both signals are high.
3. 8 MEASURING AND DISPLAYING OF WELDING PARAMETERS
A) U/I – MEASURMENT INPUTS
Negative voltage (maximum 60V!) and positive 60mV shunt signal are applied to the LKC24. These signals
are converted into pulse – frequency signals (FU* and FI* respectively) – which are processed by
microprocessor electronic.
FU* - frequency is 6,4 kHz for - 40V input (adj. by R97),
FI* - frequency is 6,4 kHz for +60mV / 400A / input (adj. by R88),
(signals on TP7 and TP8 are referred to TP6!)
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B) PARAMETERS DISPLAYING AND DISPLAY MODE SELECTION
Machine LKB 400WS is equipment with 2-row display – located in the PCB A3 (Qsyn-Meter20), which
includes 2 selectors for choosing of displayed parameters.
By SV1 (upper toggle switch) –U[V] or I[A] display is selected (open contact correspondents to I[A]!).
By SV2 – recommended thickness of welded material [mm] or reference wire speed [m/min] – is selected
for displaying (open contact corresponds to [m/min]!).
Display “QSyn-Meter20” operates in 3 modes:
1) Before start of welding (bright indicators!); there are displayed prospective (expected) values of U or I
(only in “synergy –mode”) – and recommended material thickness or wire speed reference.
2) During welding (bright indicators) – actual values of U or I
3) After stop of welding (dimmed indicators) – memorised values of U and I (“HOLD”- function)
3. 9 SYNERGY CONTROL PRE-SETS AND INDICATIONS
A) OFF/ON AND MATERIAL /GAS SELECTION
10-position selector S2 on the LKC24 (pos. R – in the motor compartment) – serves for selection of control
mode: 1-st position = “SYNERGY-OFF” (i.e. – “STANDARD” control mode), remaining positions
correspond to “SYNERGY” control mode, - for different sets of electrodes – material and shield gases.
(Note: S2 output is BCD-coded)
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B) WIRE DIAMETER PRESETTING
Pre-setting of wire electrode diameter is performed by the potentiometer R61 (pos. L – in the motor
compartment).
C) WELDING VOLTAGE SELECTION
Welder may select required value of welding voltage by Q2 – and Q3 – switches. Each position is identified
by microprocessor so as to determine welding parameter.
NOTE: In the above diagram are shown Q3 and Q4 for 400V machine version, Q4- for 230V machine
version has the following numbers:
43 - 44 ( instead of 29 - 30)
45 - 46 ( instead of 31 - 32)
47 - 48 ( instead of 33 - 34).
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D) INDICATION OF SYNERGY CONTROL STATUS
Depending on the parameter pre-sets made by welder (voltage, material/gas, wire diameter) –
microprocessor determines and displays necessary data and signals.
When the combination of the pre-sets is incorrect – red LED (“SYNERGY”) warns the operator and all
control function are disabled.
When pre-sets are optimal (correct) – green LED (“SYNERGY”) lights continously – i.e. welding is
possible .
When welding functions are enabled – there are displayed prospective welding parameters (see – section
3.8B) and also relevant green LED indicates recommended inductance output (Lmin, Lmed; Lmax) for the
current wire.
4.TECHNICAL DATA
Mains voltage 400V-415V 3~ 50/60Hz 230V 3~ 50Hz
Mains fuse 25 A delayed 35 A delayed
Rated power consumption 18,8 kVA
Rated primary current for P35% 26 A 45 A
Rated welding current Duty cycle* 35% 400 A
Duty cycle* 100% 237 A
Welding current range
30÷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 dm
3
/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 to 0
o
C
Tank capacity 6 dm
3
Warning:
The unit is characterised by the following:
- Enclosure class IP 23 indicates that the unit is designed for indoor and outdoor use.
- Application class S means that the unit is designed for use in areas of increased electric hazard.
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5. LOAD CHARACTERISTIC
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.
4.1 MAINS SUPPLY
Voltage 400V-415V
3~ 50/60 Hz
230V
3~ 50 Hz
Rated primary current:
100% Duty cycle 16A 28A
35% Duty cycle 26A 45A
Mains cable cross-section 4x4mm² 4x10mm²
Fuse, slow-blow 20A 35A
7. INSTRUCTION FOR USE
The LKB 400WS 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.
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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CONTROL PANEL
Fig. 7.1 Front view of the LKB 400WS
A. POWER ON/OFF SWITCH Turning this switch to “I” position applies power to the unit. The green LED
diode (pos. B) will illuminate indicating that power is supplied to the equipment. The cooling fan and
pump engine will also be switched on. The green LED diode (pos. C) illuminates indicating 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. It will be indicated
by illuminating of the yellow LED diode (pos. B). After welding process has been resumed, fan and pump
will be 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 ADJUSTMENT is carried out by means of 5 position switch of coarse control and
a fine control 7 position switch. It is therefor possible to select 35 different welding voltage outputs.
WARNING: Operating these voltage switches during the welding process (loaded power source) can
cause damage to unit!
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