ESAB LKA 150 User manual

0349 300 001 Valid for serial no. 923−xxx−xxxx040928

LKA 150

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Service manual

INTRODUCTION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

RATING PLATE 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

COMPONENT DESCRIPTION, LKA 150 4. . . . . . . . . . . . . . . . . .

CONNECTION DIAGRAM, LKA 150 5. . . . . . . . . . . . . . . . . . . . .

CIRCUIT DIAGRAM, CIRCUIT BOARD AP1 6. . . . . . . . . . . . . .

COMPONENT POSITIONS, CIRCUIT BOARD AP1 7. . . . . . . .

DESCRIPTION OF OPERATION, CIRCUIT BOARD AP1 7. . .

MOTOR DIAGRAMS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LOAD CHARACTERISTIC, LKA 150 11. . . . . . . . . . . . . . . . . . . . .

TECHNICAL DATA 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

INSTALLATION 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OPERATION 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MAINTENANCE 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

WELDING DATA SELECTION 15. . . . . . . . . . . . . . . . . . . . . . . . . .

SPARE PARTS LIST, LKA 150 16. . . . . . . . . . . . . . . . . . . . . . . . . .

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INTRODUCTION

This service manual is intended for use by technicians with electrical training when carrying

out fault tracing and repair of the equipment.

At the end of the manual, there is a brief guide to using the machine in order to assist in

understanding the machine.

The manual contains all design modifications introduced up to and including September

2004.

Use the diagrams in the manual when tracing faults. The machine components are described

in alphabetical order on the pages foregoing the connection diagram.

The LKA 150 is designed and tested in accordance with international standard

EN 60974−1, EN 50199.

On completion of service or repair work, it is the responsibility of the person(s) etc.

performing the work to ensure that the product does not depart from the requirements

of the above standard.

WARNING

READ AND UNDERSTAND THE OPERATING MANUAL BEFORE INSTALLING OR OPERATING.

ARC WELDING AND CUTTING CAN BE INJURIOUS TO YOURSELF AND OTHERS. TAKE PRECAU-

TIONS WHEN WELDING. ASK FOR YOUR EMPLOYER’S SAFETY PRACTICES WHICH SHOULD BE

BASED ON MANUFACTURERS’ HAZARD DATA.

ELECTRIC SHOCK −Can kill

SInstall and earth the welding unit in accordance with applicable standards.

SDo not touch live electrical parts or electrodes with bare skin, wet gloves or wet clothing.

SInsulate yourself from earth and the workpiece.

SEnsure your working stance is safe.

FUMES AND GASES −Can be dangerous to health

SKeep your head out of the fumes.

SUse ventilation, extraction at the arc, or both, to keep fumes and gases from your breathing zone and

the general area.

ARC RAYS −Can injure eyes and burn skin.

SProtect your eyes and body. Use the correct welding screen and filter lens and wear protective

clothing.

SProtect bystanders with suitable screens or curtains.

FIRE HAZARD

SSparks (spatter) can cause fire. Make sure therefore that there are no inflammable materials nearby.

MALFUNCTION −Call for expert assistance in the event of malfunction.

PROTECT YOURSELF AND OTHERS!

Rights reserved to alter specifications without notice.

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RATING PLATE

The rating plate is secured to the back of the machine. The plate is shown below, with an

explanation of how it should be read and interpreted.

1. LKA 150 is the type designation for this power source. The first letter, L, indicates that

the LKA 150 is a rectifier, while K indicates Compact (Kompakt in Swedish) and A indi-

cates the design generation.

The 150 indicates the maximum welding current.

2. These symbols indicate that the LKA 240 incorporates a transformer and rectifier.

3. This section indicates the voltage/current characteristic for MMA welding and a current

range of 20 −100 A.

The voltage values of 15 and 19 V in the heading indicate that we comply with the in-

ternational arc characteristic as defined in IEC 974−1.

X = The duty cycle, indicating for how long a time welding can be carried out at the

specified welding data, expressed as a percentage of a ten−minute period.

I2= The current at the respective duty factors.

U2= The arc line characteristic voltage.

Uo= The open−circuit voltage.

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4. Indicates that the unit is intended for connection to a 230 V single−phase 50 Hz supply.

I1= primary currents at the various load points.

5. IP21 indicates the enclosure class in respect of protection against penetrating objects and

water. Enclosure class IP21 indicates that the equipment is intended for indoor use,

while IP23 equipment is also suitable for outdoor use.

The symbol indicates that the machine is designed for use in areas of elevated electri-

cal risk.

6. The machine’s serial number, in the form of three groups of figures (xxx yyy zzz).

The first group (xxx) indicates the version. The figures represent the year and week of

approval of the version.

The second group (yyy) shows the year and week of final testing of the machine.

The second group (yyy) shows the year and week of final testing of the machine. For

example, 341 indicates Week 41, 1993.

The final group (zzz) consists of three or four figures, and is a serial number in the range

0001 to 9999.

7. Shows that ESAB complies with the international standard, IEC 974−1.

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COMPONENT DESCRIPTION, LKA 150

AP1 Circuit board with control electronics: see the diagram on page 6 and description

on page 7.

C1 Capacitor 0.1µF, 400 VDC, transient protection.

C2 Capacitor 0.1µF, 400 VDC, transient protection.

L1 Inductor.

M1 Wire feeder motor.

QF1 Switch, 8−way, for 7−step and Off (main On/Off switch) adjustment of the welding

current.

For the Australian market the main On/Off part of the switch is 2−pole.

SB1 Welding torch trigger switch.

ST1 Thermal overload cutout, for protection against overload, fitted in the winding of

main transformer TM1.

The switch operates (opens) at a temperature of 130 °C.

ST2 Thermal overload cutout, for protection against overload, fitted on the diode bridge

cooling fins (VC1). It operates (breaks) at 110 °C.

TM1 Main transformer

V1 LED, yellow.

Lights if thermal overload cutouts ST1 or ST2 operate as a result of high

temperature.

VC1 Diode bridge.

XS1 2−pole connector.

XS2 5−pole connector.

XS3 2−pole connector.

XS4 Connector, 2−pole.

XT1 Mains terminal block, 2−pole.

XT2 Terminals, welding current, positive and negative

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CONNECTION DIAGRAM, LKA 150

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CIRCUIT DIAGRAM, CIRCUIT BOARD AP1

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COMPONENT POSITIONS, CIRCUIT BOARD AP1

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DESCRIPTION OF OPERATION, CIRCUIT BOARD AP1

This description relates to the circuit diagram and the component positions diagram.

If the circuit board is faulty, it must be replaced.

1CONTROL CIRCUIT

Pressing trigger switch SB1 on the welding torch energises relay RE1 from control

power transformer TR1. The contacts on the relay connect main transformer TM1 to

the mains power supply.

The power supply to RE1 is half−wave rectified by D1. Resistor R1 is connected in

series with the relay and drops the voltage to it. Capacitor C1 (220µF) smoothes the

voltage. It also delays the drop−off of relay RE1 by about 25 ms, to provide a

back−burn time.

2THERMAL OVERLOAD CUTOUT

In the event of a thermal overload, thermal overload cutouts ST1 or ST2 interrupt the

secondary circuit from TR1, causing relay RE1 to drop off and de−energising the

welding circuit.

When not operated (i.e. with closed contacts), the cutouts short−circuit inputs

B6 and B7.

Operation of either of the cutouts is indicated by LED V1. Interruption of the cutout

circuit energises the LED via D2, R3 and D3. D2 is a half−wave rectifier, R3 limits

the current through the LED and D3 protects it against reverse voltage.

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3RFI SUPPRESSION AND BASE LOAD RESISTORS

Capacitors C4 −C6 protect against RFI. Resistors R12 and R15 provide a minimum

base load for the rectifier bridge: in addition, they act as discharge resistors for the

capacitors.

4MOTOR DRIVE CIRCUIT

The wire feed motor is powered by the rectified secondary voltage from main

transformer TM1.

Pressing the welding torch trigger switch SB1 provides a supply to thyristor TY1 via

contact B4 from the positive side of the main power rectifier VC1.

Resistors R10 and R14 limit the motor starting current: excessive starting current

would demagnetise the motor. D9 is a squelch diode protecting against back−emf

from the motor.

The ignition circuit for TY1 consists of R2, R4, R5, D5 and C2.

When Q1 is not conducting, operation of the circuit is as follows:

If the voltage at B4 exceeds the motor voltage, C2 charges via R2, R4 and R5.

When the voltage on C2 reaches the trigger voltage (0.5 −1.5 V), thyristor TY1 fires.

This means that TY1 conducts each half−cycle when Q1 is not conducting.

D5 protects C2 against negative voltage when Q1 conducts.

MOTOR VOLTAGE CONTROL

C3, R11 and potentiometer R13 form a low−pass filter circuit for the motor supply.

R13 picks off a suitable fraction of the motor voltage for connection to the base of Q1

via diode D6. Q1 starts to conduct at a bases voltage of 0.7 V.

C2 charges more slowly, which means that thyristor TY1 fires later.

Motor voltage is lowest when R13 is in its upper position, the minimum position.

The base voltage is then high and Q1 conducts. The charging time for C2 becomes so

long that thyristor TY1 misses some half cycles, firing only (for example) on every

third cycle.

When R13 is in its lower (= maximum) position, the base voltage on Q1 is low and

Q1 does not conduct. In this state, zener diode D7 determines the maximum motor

voltage.

See on page 10 for the motor voltage and current waveforms.

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