LHN 250
Contents
1. LHN 250 Caddy Professional 250 Service manual 0740 800 114 040427 Valid for serial no 747 xxx xxxx to 417 XXX XXXX LIST OF CONTENTS Page READ THIS FIRST sas uen a dune sees eee ees 2 COMPONENT DESCRIPTION 4 WIRING DIAGRAM 7 APO1 COMPONENT POSITIONS 8 APO1 DESCRIPTION OF OPERATION 10 CHECKING THE GATE PULSES 15 APO2 DESCRIPTION OF OPERATION 16 APO3 DESCRIPTION OF OPERATION 18 MOS TESTER latente Seed ave tes beeen es 20 SOFT STARTING searre ner afe ie ea ame gawd s seen 21 ASSEMBLY DISASSEMBLY 22 TEGHNIGALADATAS kon arab gone toscana at tae ae peni les vi 27 LOAD CHARACTERISTIC 28 MAINTENANCE 28 INSTIRUGTIONS ni eth hits cath tlt ed ts ooh td 29 INTRODUCTION 223 state deimakes safe 29 INSTALLATION os da le na oi Mita cele coe e l fon D are canta 29 OPERATIONS ati ke ane e ee a er kaye 30 FAULT TRACING 22 San ane tipa ko hat 31 SPARE PARTS v ako ekta ao tate ek Ma et atak oi 32 NOTES ice taa nn eet e ave a Re Year ad Dee 32 READ THIS FIRST Maintenance and repair work should be performed by an experienced person and electrical work only by a trained electrician Use only recommended replacement parts This service manual is intended for use by technicians with electrica2. xbxh Weight Duty cycle 472 x 142 x 256 mm Approx 11 kg The duty cycle refers to the time in per cent of a ten minute period that you can weld at a certain load without overloading the welding power source Enclosure class The IP code indicates the enclosure class i e the degree of protection against penetration by solid objects or water Equipment marked IP 23 is designed for indoor and outdoor use Application class The symbol IS indicates that the power source is designed for use in areas where there is an increased electrical hazard clhnidei 27 LOAD CHARACTERISTIC U2 80 Load characteristic war ISO line TIG e ISO line MMA 0 50 100 150 200 250 300 12 cihnip04 MAINTENANCE Clean the air filter in the front panel of LHN 250 regularly and replace it if damaged Remove the filter by inserting a screwdriver in the slit in the grille and prising out the lower part of the grille as shown on the right Remove the entire casing once a year and blow the dust out of the machine with dry compressed air If the machine is used in dusty or dirty areas it should be blown clean and the filter be cleaned more frequently cmha2p23 Removal of filter clhn1de1 28 INSTRUCTIONS INSTRUCTIONS This chapter is an extract from the LHN 250 Instruction Manual INTRODUCTION Note This product is solely intended f
3. 9 Connector XS08 from transformer TCO2 clhnide1 25 FITTING THE MAIN TRANSFORMER TCO2 When replacing the main transformer it is also necessary to replace the transformer core This is because the core is bonded with adhesive and cannot be disassembled Adhesive and tape are required when fitting a new transformer in addition to the coil and core Part numbers for the requisite adhesive and tape are shown as item 301 in the spare parts list e Transfer wire 020 and connector XS08 to the new transformer If the wire needs to be replaced it is important to use the correct type of insulation Teflon 2 turns clhn1p08 Fitting wire 020 e Apply a layer of tape t to each of the three airgaps in the transformer core Use the tape specified in the spare parts list Apply Loctite 649 to the contact faces between the cores and between the core and coil Secure the transformer in position in the machine The adhesive takes about 20 minutes to harden di cmha2p33 Airgap t in the transformer core clhnidei 26 TECHNICAL DATA Load capacity At 35 duty cycle 250 30 V At 60 duty cycle 180 27 V At 100 duty cycle 140 26 V Operating range Stepless 5 250 A Open circuit voltage 50 80 V Mains power supply Voltage 400 V 3 Primary current 12 A Frequency 50 60 Hz Fuse rating 16 A Mains cable cross sectional area 4x1 5mm Application class S Enclosure class IP23 Dimensions
4. APO1 the machine must be soft started as described on page 21 15V e a REA TRES pak po NT max 15 4 V sv See le UT ete Duty 43 5 5V bees ol EEE SR Min 5 112 V 2 5ps 5M5 10M5 clhn1p09 Gate pulses as measured across the dummy gate load on circuit board APO1 between connections FOI and F02 clhn1de1 15 AP02 DESCRIPTION OF OPERATION VO1 VO2 012 RIS FI HEAT SINK oS n a ee y a to APO3 via red A01 4 R20 io e 5 yellow A02 Lan iE II alntp20 to the negative side of C02 2 inus Circuit diagram circuit board APO2 transistor board positive Individual transistors must not be replaced if the circuit board is faulty it must be replaced in its entirety In addition circuit board AP03 must also be replaced Instructions on removing and fitting the circuit board are to be found on page 24 A01 A02 D1 D3 D5 D6 F1 R21 Q1 Q8 clhnidei Connections A01 A02 are for the gate pulses from circuit board APO1 Transient voltage protection Back emf protection diode squelch diode for main transformer TCO2 when the transistors turn off See R21 Fuse for protection of circuit board APO1 if circuit board APO2 fails R21 C3 C4 and D6 are limiting the peak voltage at transistors Q1 O8 MOSFET transistors These require a special instr
5. e Remove connectors XS10 and XS03 from circuit board AP01 clhnidei 22 FITTING THE DIODE MODULES e Clean the contact surface of the heat sink with extremely fine abrasive paper e Apply a thin film of contact oil see item 506 in the spare parts list to the contact surfaces e Fit the diode modules and tighten the screws A M6 to a torque of 6 Nm Tighten the screws B M4 to a torque of 1 Nm The screws C 1 4 20UNC2B are to be tightened to a torque of 6 Nm From serial number 011 xxx xxxx From serial number 011 148 xxxx From serial number 011 148 xxxx a new diode module is used The rated current for the new module SCOMES MKK300 4 is 300 A The rated current for the old module Motorola MURP20040CT is 200 A Because of the higher rating only two modules are needed for the rectifier unit The ordering no for the new module is the same as for the old When replacing the diode modules in machines with serial number prior to 011 148 xxxx it is sufficient to use only two modules if the new type SCOMES MKK300 4 is mounted The busbars with item numbers 333 334 336 434 and 436 see the spare parts list are not more available If they have to be replaced fit the new type of diode modules and the busbars with item no 543 clhnide1 23 REMOVAL OF TRANSISTOR CIRCUIT BOARDS AP02 AND AP03 Remove the rear panel and casing Remove all wires and busbars connected to the board Remove the springs tha
6. or electrodes with bare skin wet gloves or wet clothing Insulate yourself from earth and the workpiece e Ensure your working stance is safe FUMES AND GASES Can be dangerous to health e Keep your head out ofthe fumes e Use 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 e Protect your eyes and body Use the correct welding screen and filter lens and wear protective clothing e Protect bystanders with suitable screens or curtains FIRE HAZARD e Sparks spatter can cause fire Make sure therefore that there are no inflammable materials nearby NOISE Excessive noise can damage hearing Protect your ears Use ear defenders or other hearing protection e Warn bystanders of the risk MALFUNCTION Call for expert assistance in the event of malfunction READ AND UNDERSTAND THE INSTRUCTION MANUAL BEFORE INSTALLING OR OPERATING PROTECT YOURSELF AND OTHERS WARNING STATIC ELECTRICITY can damage circuit boards and electronic components Observe precautions for handling electrostatic sensitive devices Use proper static proof bags and boxes clhnide1 3 COMPONENT DESCRIPTION This component description relates to the wiring diagram on page 7 The LHN 250 rectifier power unit is of primary switched type using parallel connected MOSFET transistors as switching devices Switching frequency is 48 kH
7. sure the mains switch is on SOC Check that the welding and return cables are properly connected Make sure the welding current set is correct The welding current is interrupted in the course Check if the thermal cut out has tripped the of welding orange indicating lamp on the front panel is on Check the mains fuse The thermal cut out trips frequently Check that the filter is not packed with dust Check that the ratings of the welding power source have not been exceeded overload of the power source Poor welding result Check that the welding and return cables are properly connected Make sure the welding current set is correct Check that there is nothing wrong with the electrodes clhn1de1 31 SPARE PARTS The spare parts list for the LHN 250 and Caddy Professional 250 is published in a separate document with filename ordering no 0457 552 990 NOTES notes 32 notes 33 ESAB subsidiaries and representative offices Europe AUSTRIA ESAB Ges m b H Vienna Liesing Tel 43 1 888 25 11 Fax 43 1 888 25 11 85 BELGIUM S A ESAB N V Brussels Tel 32 2 745 11 00 Fax 32 2 726 80 05 THE CZECH REPUBLIC ESAB VAMBERK s r o Prague Tel 420 2 819 40 885 Fax 420 2 819 40 120 DENMARK Aktieselskabet ESAB Copenhagen Valby
8. transformer This pulse is led via D21 D22 and connection E01 to the gate of the MOSFET transistors It returns via the source connection E02 D24 and C46 The peak gate source voltage is 12 15V The presence of the gate pulse between connections E01 and E02 charges capacitor C46 to 5 6 V When Q5 is turned off the voltage from the pulse transformer changes polarity resulting in transistors Q6 and Q7 starting to conduct This results in a negative gate voltage turning off the MOSFET transistors clhnidei 14 CHECKING THE GATE PULSES If circuit board AP02 or APO3 has failed the gate pulses must always be checked Remove connections XS04 and XSO5 gate pulses and connect a gate load to connections E01 and E02 and to F01 and F02 4 7ohm L 33nF En Gate load A set of different gate loads can be ordered from ESAB The part number is 0468 469 003 The gate loads can be used to the following machines LUC LHL 130 160 LHL 250 315 LTL 160 LTL315 LUB 315 LHN LIN LTR LTO MechTig 315 and Protig 315 IMPORTANT never check the gate pulses when AP02 and AP03 are connected always use a dummy gate load The gate pulse minimum level must be 3 5 to 5 5V and the average maximum level 12 to 15V Frequency must be 48 5 kHz 0 5 kHz Check that the maximum pulse time measured at a voltage level of 5 V is 43 1 of the cycle time If the gate pulses are not within these tolerances APO1 must be replaced After replacing
9. 53 4039 Fax 54 11 4 753 6313 BRAZIL ESAB S A Contagem MG Tel 55 31 3369 4333 Fax 55 31 3369 4440 CANADA ESAB Group Canada Inc Missisauga Ontario Tel 1 905 670 02 20 Fax 1 905 670 48 79 MEXICO ESAB Mexico S A Monterrey Tel 52 8 350 5959 Fax 52 8 350 7554 USA ESAB Welding amp Cutting Products Florence SC Tel 1 843 669 44 11 Fax 1 843 664 44 58 Asia Pacific CHINA Shanghai ESAB A P Shanghai Tel 86 21 6539 7124 Fax 86 21 6543 6622 INDIA ESAB India Ltd Calcutta Tel 91 33 478 45 17 Fax 91 33 468 18 80 INDONESIA P T Esabindo Pratama Jakarta Tel 62 21 460 01 88 Fax 62 21 461 29 29 MALAYSIA ESAB Malaysia Snd Bhd Selangor Tel 60 3 703 36 15 Fax 60 3 703 35 52 SINGAPORE ESAB Singapore Pte Ltd Singapore Tel 65 861 43 22 Fax 65 861 31 95 ESAB Asia Pacific Pte Ltd Singapore Tel 65 861 74 42 Fax 65 863 08 39 SOUTH KOREA ESAB SeAH Corporation Kyung Nam Tel 82 551 289 81 11 Fax 82 551 289 88 63 UNITED ARAB EMIRATES ESAB Middle East Dubai Tel 971 4 338 88 29 Fax 971 4 338 87 29 Representative offices BULGARIA ESAB Representative Office Sofia Tel Fax 359 2 974 42 88 EGYPT ESAB Egypt Dokki Cairo Tel 20 2 390 96 69 Fax 20 2 393 32 13 ROMANIA ESAB Representative Office Bucharest Tel Fax 40 1 322 36 74 RUSSIA CIS ESAB Representative Office Moscow Tel 7 095 937 98 20 Fax 7 0
10. 95 937 95 80 ESAB Representative Office St Petersburg Tel 7 812 325 43 62 Fax 7 812 325 66 85 Distributors For addresses and phone numbers to our distributors in other countries please visit our home page www esab com ESAB AB F SE 695 81 LAXA SWEDEN Phone 46 584 81 000 www esab com 031021
11. CAT pe roro Voltages above 65V are defined as open circuit voltage Voltages below 45V are defined as welding voltages When the machine is in open circuit mode the current limit is at a low rate and the unit is ready for Hot Start Arc voltage limitation AIC Lenath Limit Te cmha e14 ar eee a e Nan a at an ks on Man a ee at inn J clhnidei This circuit which restrict the arc voltage and open circuit voltage assists in limiting the arc length when welding in the 20 50 A current range 11 6 Current reference TCO1 To Control gt gt Amplifier 1 I IC4 i ova i oo JA ki eee ee a me W ee ee ee eee r r e PR PA ARA E x510 026 E atl EED raise ke ti Pomote Ret a F H G cmha2e15 This circuit supplies a signal voltage to the current setting potentiometer and remote control unit It also modifies the current reference signal to a suitable level for the control amplifier 7 17 V from transformer TCOI is rectified and smoothed for supply to voltage regulator VR2 Potentiometer R21 adjusts the output voltage from VR2 for correct maximum current value from the current reference and control amplifier After adjustment the voltage between connection C03 and C05 must be 14 15 V Q10 R76 and R77 limit the current from VR2 to 60 mA The current limit protects the circuit board in the event of a short circuit in the cable to the remote control unit The reference inpu
12. S tester is a special instrument and can be ordered only from ESAB The part number is 0468 469 001 Connect the instrument as follows Disconnect the power unit from the mains Disconnect capacitor C02 and C03 Remove the gate connections from AP01 Connect the clip on the red wire to the red wire the gate wire on the transistor board Connect the clip on the yellow wire to the yellow wire the source on the transistor board Connect the black wire to the cooling fins drain Testing Press the pushbutton marked TEST If the board is healthy both the red and green LED s should flash alternately about once a second If the transistor board is short circuited the red LED will light continuously note that the green LED may also flash or be continuously lit If the transistor board is open circuited the green LED will be continuously lit Check that there is good electrical contact between the clip of the black wire and the cooling fins IMPORTANT Even if only one transistor board is indicated as faulty both boards must be replaced Check the gate pulses from APO1 before commissioning the new transistor boards see instructions on page 15 After replacement of the boards the machine must be soft started clhnidei 20 SOFT STARTING e Remove and insulate wires 007 and 008 from rectifier bridge V01 also remove and insulate wire 009 to rectifier bridge V02 see the circuit diagram on page 7 e Conne
13. Tel 45 36 30 01 11 Fax 45 36 30 40 03 FINLAND ESAB Oy Helsinki Tel 358 9 547 761 Fax 358 9 547 77 71 FRANCE ESAB France S A Cergy Pontoise Tel 33 1 30 75 55 00 Fax 33 1 30 75 55 24 GERMANY ESAB GmbH Solingen Tel 49 212 298 0 Fax 49 212 298 204 GREAT BRITAIN ESAB Group UK Ltd Waltham Cross Tel 44 1992 76 85 15 Fax 44 1992 71 58 03 ESAB Automation Ltd Andover Tel 44 1264 33 22 33 Fax 44 1264 33 20 74 HUNGARY ESAB Kit Budapest Tel 36 1 20 44 182 Fax 36 1 20 44 186 ITALY ESAB Saldatura S p A Mesero Mi Tel 39 02 97 96 81 Fax 39 02 97 28 91 81 THE NETHERLANDS ESAB Nederland B V Utrecht Tel 31 30 248 59 22 Fax 31 30 248 52 60 NORWAY AS ESAB Larvik Tel 47 33 12 10 00 Fax 47 33 11 52 03 POLAND ESAB Sp z 0 0 Warszaw Tel 48 22 813 99 63 Fax 48 22 813 98 81 PORTUGAL ESAB Lda Lisbon Tel 351 1 837 1527 Fax 351 1 859 1277 SLOVAKIA ESAB Slovakia s r o Bratislava Tel 421 7 44 88 24 26 Fax 421 7 44 88 87 41 SPAIN ESAB lb rica S A Alcobendas Madrid Tel 34 91 623 11 00 Fax 34 91 661 51 83 SWEDEN ESAB Sverige AB Gothenburg Tel 46 31 50 95 00 Fax 46 31 50 92 22 ESAB International AB Gothenburg Tel 46 31 50 90 00 Fax 46 31 50 93 60 SWITZERLAND ESAB AG Dietikon Tel 41 1 741 25 25 Fax 41 1 740 30 55 North and South America ARGENTINA CONARCO Buenos Aires Tel 54 11 4 7
14. YELLOW Les Gt gt RED MOTIAA LEZ 189 ceg 18r D X512 dlhn1e01 clhnidei 7 AP01 COMPONENT POSITIONS EBBE clhnie10 Circuit board AP01 0481 870 884 fitted before serial number 220 xxx xxxx WARNING high voltage in the shaded area clhnidei Circuit board AP01 0486 886 882 fitted from serial number 220 xxx xxxx WARNING high voltage in the shaded area From serial number 220 xxx xxxx circuit board 0486 886 882 is fitted in the machines The circuit board versions are fully interchangeable and can be used in any of the machines clhnidei AP0O1 DESCRIPTION OF OPERATION This description refers to the circuit diagram on page 7 and to the component position diagrams on pages 8 and 9 Only those items connected to the circuit board inputs and outputs are described here If the circuit board is faulty it must be replaced There are two versions of the circuit board this description applies to both versions The circuit boards are fully interchangeable After replacing the circuit board the machine must be soft started as described on page 21 1 LI 018 A06 2 Mi yen cmha2e10 HLO1 green A03 amp k UxS0D blue A04 Power supply Sis TCOI Rectifier bridge D1 D4 is supplied at 20 5 V from transformer TC01 The rectified voltage
15. ct an external power supply having a current limit of 1A to the positive and negative connections on V01 e Adjust the power supply voltage to 30V e Power the remaining parts of the unit from the normal power supply e Measure the output voltage from the machine This must be 5 5V 1V e Measure the secondary voltage from transformer TC02 With a voltage of 30V across the buffer capacitor the waveform must appear as shown below TT 48 5kHz 5ps 10ps 15ys 20ps 25ps aihn1po1 Secondary voltage at TCO2 for 30 V across the buffer capacitors e Measure the voltage with the oscilloscope probe connected to A and the screen to B according to the picture below Measuring points for the secondary voltage at TCO2 olhni poz Up to and including ser no O11 147 xxxx From serial no 011 148 xxxx clhnidei 21 ASSEMBLY DISASSEMBLY REMOVAL OF REAR PANEL AND CASING e Remove the strap from the rear panel 1 e Remove the cable bushing 2 and slide it back along the cable e Remove the two screws 3 e Remove switch knob 6 and screws 5 Remove the rear panel from the casing 7 e Pull the casing back over the rear panel and the mains cable REMOVAL OF FRONT PANEL e Remove the rear panel and casing Remove screws a e Remove the positive busbar from the rectifier unit Screw b is accessible from beneath the machine e Remove the two nuts c and remove the negative busbar from the shunt
16. ed to 48 5 kHz 0 5 kHz Maximum pulse time is 43 1 of the cycle time Maximum pulse time results in maximum current and arc voltage When no pulses are supplied by the pulse width modulator no welding current will flow IC3 controls the pulse frequency pulse time and blocking of pulses The reference voltage from IC3 is 5 1 V on circuit board 0486 886 882 On circuit board 0481 870 884 the voltage is 2 5 V Transistor Q5 controls the primary winding of the pulse transformer NOTE The frequency and pulse time are very important parameters If incorrectly adjusted they can result in transistor failure in the main circuit clhnide1 13 9 Gate circuit Li E01 red JA01 gate I l l 3 i X504 i pr ME j t4v 4 v l 11 l i a ka yi l 20 6 ps l i li E02 Y yellow 44A02 source is Sia me Se eh en anm ae 14V M et 20 615 chnie12 The driver stage for the MOSFET transistors provides control pulses to the gate source of the power transistors There is a separate output for each switching unit All gate circuits are galvanically isolated from other circuits on the board The insulation voltage between the pulse width modulator and the gate circuits is 4 kV WARNING the gate circuits are at mains voltage The two gate circuits are identical and so only one is described here When Q5 conducts a voltage pulse appears at the secondary winding of the
17. er and freewheel diodes VO3 rectifies the welding current During the time interval between two voltage pulses from transformer TCO2 the freewheel diodes V04 maintain the welding current from inductor LO1 There are 2 rectifier diodes and 4 freewheel diodes On the cooling fins are three diode modules mounted Each diode module has two diodes If one diode module is faulty all modules have to be replaced From serial number 011 148 xxxx a new diode module is used The rated current for the new module SCOMES MKK300 4 is 300 A The rated current for the old module Motorola MURP20040CT is 200 A Because of the higher rating only two modules are needed for the rectifier unit The ordering no for the new module is the same as for the old See page 23 for fitting instructions LED yellow Lit when thermal overload cutout STO1 opens due to high temperature Diode see L02 Sleeve connectors 12 pole Burndy connector for connection of remote control unit Welding terminals 2 OKC connectors WIRING DIAGRAM LHN 250 Caddy Professional 250 400V 3 WHITE rr En N BROWN ORANGE TI S 400V A Se 2 TODI 44 S 3 S Sas qe n a mo a m n f fa 2 1 3 l AP05 Ww XS10 p LALL 98 87 7 D _ _ 2882 o 026 a TJ 027 A 6 gt a x lt yo a o N 60 LOA ZO 011 Q 3 018 1 O16 1805 45 033 A 804 2 si H p x505 NN so s 7 ue Foz J
18. is stabilised by voltage regulator VR1 to 20 1 V All circuits on the circuit board except the current reference 6 and the gate circuit 9 are supplied from VR1 Connections A05 A06 supply 26 V DC 2 5 V to the cooling fan Thermal shutdown cmha2e11 clhnidei This circuit interrupts the gate pulses from the pulse width modulator if the machine is overloaded When it has not operated due to high temperature the thermal overload cutout normally short circuits inputs BO1 and B02 If the cutout contact opens IC1 lights LED VOS and the pulse width modulator 8 blocks the gate pulses See also STO1 in the component description The reference voltage to IC1 ref is generated by IC3 see page 13 10 016 B03 Arc Voltage Under voltage detector ere Under Voltage Detector 1 This circuit senses if the mains power supply voltage is fom l too low Loss of mains power supply for more than 10 ms or low voltage results in the pulse width modulator 8 fa blocking the gate pulses bam li li to PWM shut down The reference voltage to IC1 ref is generated by IC3 see page 13 cmhaze12 Open circuit voltage detector la Open Circuit Voltage Detector RII i 033 B04 not used n i I n i l 11 L Poo oE a e en l l 016 XB03 Arc Yoltage i t i t is d a l 5 Are Length Limit
19. l electronic training for help in connection with fault tracing and repair Use the wiring diagram as a form of index for the description of operation The circuit board is divided into numbered blocks which are described individually in more detail in the description of operation All component names in the wiring diagram are listed in the component description This manual contains details of all design changes that have been made up to and including April 2004 The manual is valid for LHN 250 and Caddy Professional 250 with serial numbers TAT XxX XXXX 011 xxx xxxx 220 xxx xxxx and 417 xxx xxxx From serial no 417 xxx xxxx Caddy Professional 250 is the only name of this product Rights reserved to alter specifications without notice clhnidei 2 The LHN 250 and Caddy Professional 250 are designed and tested in accordance with international and European standard IEC EN 60974 1 and 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 A WARNING A 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 e Install and earth the welding unit in accordance with applicable standards Do not touch live electrical parts
20. or arc welding The LHN 250 is a transistor controlled welding power source designed for welding with coated electrodes and for TIG welding touch start Equipment LHN 250 is equipped with a remote control socket which activates automatically when a remote control device is connected NOTE The contact pins L and M must be strapped in the remote device s connection cable for automatic activation to function The inverter is supplied with a 3 meter long mains cable LHN 250 is delivered with 5 meter long welding and return cables These are attached to cable connectors allowing quick change of polarity The manufacturer s serial number is stamped on the rating plate Field of application LHN 250 supply direct current which allows you to weld most alloyed and non alloyed steels stainless steels and cast iron With the LHN 250 you can use coated electrodes from 1 6 to 5 mm Tig welding TIG welding is particularly useful when high quality standards are required and when welding thin sheet Before using the LHN 250 for TIG welding it must be equipped with a TIG torch and gas valve a cylinder of argon an argon regulator tungsten electrodes and if necessary suitable filler metal The best method to use is the touch start where you gently stroke the tungsten electrode against the workpiece to establish the arc INSTALLATION WARNING This product is intended for repair and maintenance welding In domestic or office en
21. t has a separate power supply and high impedance input to the control amplifier protecting it against short circuits between the remote control unit cable and the welding circuit Changeover to remote control is arranged by short circuiting connections DO1 and D02 through insertion of the plug into the socket for the remote control unit The short circuit is in the form of a link between L and M in the plug The current reference signal is connected to C04 or D04 The reference signal voltage is 0 V at minimum current and 14 15 V at maximum current If inputs D01 and D02 are linked but no remote control unit is fitted resistor R74 holds the reference signal to the minimum level clhnidei 12 7 Control amplifier The control amplifier sets a suitable welding current in relation to the current setting and arc voltage The circuit can be divided up into two main parts e Average current control e Starting current control The level of the hot start current is depending on the level of the set current At 25A welding current the starting current is 25A At 250A the starting current is 300A The hot start time is about 0 5 seconds e Short circuit current limit 8 Pulse Width Modulator ref voltage control amplifier PWM shut down he cmha2e16 bee oe ee ee ne ee be See 4 The pulse width modulator determines the frequency and pulse time of the control pulses to the MOSFET transistors Pulse frequency is adjust
22. t hold the board 2 in position by prising them off with a screwdriver 1 between the cooling flange and the spring an ha2p31 Removal refitting of transistor circuit board REFITTING THE TRANSISTOR CIRCUIT BOARD When replacing the transistor circuit board both boards must always be replaced and new springs must be fitted Clean the contact surface 3 of the heat sink with extremely fine abrasive paper Apply a thin film of contact oil see item 506 in the spare parts list to the contact surfaces Place the circuit board 2 on the cooling fins Secure first one spring on each side of the board by pressing the spring down with a screwdriver 4 Then secure the remaining springs The springs must be fitted where there are components that are to be in contact with the heath sink Due to a change to transistors with higher current rating there might be less transistors on the spare part board than on the original board When fitting cable lugs and busbars to the boards it is important that the washers are fitted in the correct order Start by placing the lug on the foil and then fit a flat washer a spring washer and finally the screw clhnidei 24 Connections to circuit board AP03 cm ha2p29 Wire 031 to the connection between C02 and C03 Busbar connected to positive on C03 Busbar connected to negative on C02 Wire 013 from negative of rectifier VO2 Gate connection from circuit board APOI Oo a 90
23. t transient voltages Fan 24 VDC Indicating lamp 28 V white showing that the mains power supply is turned on Secondary inductor Inductor Together with COS and VO6 this forms an LC circuit which reduces the risk of the arc extinguishing at low welding currents Capacitor C05 in the LC circuit charges when VO3 conducts The circuit can temporarily maintain a high output voltage at low welding current reducing the risk of the arc being extinguished Diode V06 protects capacitor CO5 against negative voltage Coil EMC included in conductor 013 Ferrite ring core Protection against transient voltages Ferrite ring cores Protection against transient voltages Ferrite ring cores Protection against transient voltages Ferrite ring core included in APOS Ferrite ring core included in APOS Mains switch 3 pole Potentiometer for adjusting welding current 10 KQ 2 W Shunt 119 mV 1mV at 250A Thermal overload cutout fitted in the secondary inductor LO1 winding Interrupts at 130 C recloses at 100 C Control power supply transformer Primary side is supplied at 400V Dual secondary windings supply 20 5 V and 17 V to circuit board APO1 Main transformer see page 26 for installation instructions Mains rectifier diode bridge 35 A 1200 V After replacing the rectifier bridges the machine must be soft started see instructions on page 21 VO3 V04 VO5 VO6 XS01 XS13 XS11 XS12 clhnidei Rectifi
24. ument see MOS TESTER on page 20 for testing Due to a change to transistors with higher current rating transistor Q6 might not be fitted to the board Spare part boards may have 7 or 8 transistors 16 ye Si me sw T if Component positions circuit board AP02 clhn1p21 clhnidei 17 APO3 DESCRIPTION OF OPERATION Tann TCO2 HEAT SINK al Y Vo RI m N N w i Q2 aj R29 PLUS 4 pl an ls un l a a C7 1 c8 s E as RIB Fl R8 l red caot 4 l R28 y C035 314 A YM coz2 Oya l yellow CA02 4 i re 020 B01 4 E MINUS from VO1 gz 020 B02 1 C6 7 R23 TYI l D8 Lio W TO O D9 i kil DIO Y x ac Circuit diagram circuit board APO3 transistor board negative Individual transistors must not be replaced if the circuit board is faulty it must be replaced in its entirety In addition circuit board APO2 must also be replaced See on page 24 for instructions on removing and fitting the circuit board A01 A02 B01 B02 D1 D3 D5 D12 Q1 Q8 R21 clhnidei Connections A01 A02 are for the gate pulses from circuit board APO1 When the machine is loaded pulses from a trigger pulse winding on main transformer TCO2 are s
25. upplied to connections B01 and B02 for use as gate pulses in controlling thyristor TY 1 Transient voltage protection Back emf protection diode squelch diode for main transformer TCO2 when the transistors turn off See R29 MOSFET transistors These require a special instrument see MOS TESTER on page 20 for testing Due to a change to transistors with higher current rating transistor Q8 might not be fitted to the board Spare part boards may have 7 or 8 transistors Charging resistor 1292 10W for buffer capacitor C02 C03 When energising the power unit pulses from control circuit board AP01 are delayed by 300 ms to allow the buffer capacitor to charge 18 R26 R27 R29 TY1 Discharge resistor for buffer capacitor C03 Discharge time for the capacitor after turning off the mains power supply is about two minutes Discharge resistor for buffer capacitor C02 After turning off mains power supply discharge time for the capacitor is about two minutes R29 C7 C8 and D12 are limiting the peak voltage at transistors Q1 Q8 Thyristor for shunting charging resistor R21 when the machine is loaded If TY1 did not conduct resistor R21 would burn out when the unit is on load clhnte31 Component positions circuit board AP02 clhnidei 19 MOS TESTER The MO
26. vironment this product may cause radio interference It is the responsibility of the user to take adequate precautions Placing Place the machine so that there is nothing to prevent the cooling air from passing through it clhnide1 29 INSTRUCTIONS Connection To get maximum performance from the LHN 250 it must be fitted with a 16A slow fuse The LHN 250 have mains voltage compensation which means that 10 fluctuation in the supply voltage produces only 0 2 variation in the welding voltage LHN 250 is intended for 400V 3 phase supplies It can be used with 50 Hz or 60 Hz supplies OPERATION Start up The power switch is at the rear of the LHN 250 The white lamp on the front will glow when the power is on 1 Yellow light emitting diode indicates overtemperature 2 Welding current control 4 250 A 3 White lamp 4 Remote control socket bh11d001 Important Only use the accompanying welding cable and return cable with a cross sectional area of 35 mm2 See list of spare parts for order number Overload protection To save you worrying about overloading the LHN 250 it has a thermal cut out that will trip before the temperature becomes too high You can tell when the rectifier has been overloaded because the yellow light comes on and it will no longer be possible to weld clhnidei 30 INSTRUCTIONS FAULT TRACING Possible faults and measures to take No arc is generated by the welding power Make
27. z The conduction interval ranges between zero and 9 5 us depending on the welding current being supplied The conduction time and frequency are controlled by circuit board APO1 APO1 AP02 AP03 AP05 C01 C02 C03 C04 C05 clhnidei Main circuit board with control electronics See description on page NO TAG Circuit board with power transistors for the positive pole see description on page 16 WARNING these transistors are at mains voltage Circuit board with power transistors for the negative pole see description on page 18 WARNING these transistors are at mains voltage Suppression circuit board EMC Protects the environment from mains borne interference from the machine The ferrite cores LO9 and L10 are included in the circuit board The cores are mounted on the connection wires to the board KRETSKORT 48632 8892 L Circuit diagram and component positions circuit board APO5 Capacitor 0 1 uF 1000 VDC transient protection Capacitor 1000 uF buffer smoothing capacitors These capacitors takes about two minutes to discharge after disconnecting the equipment from mains Capacitor 0 1 UE 1000 VDC protects the equipment against RFI 2 capacitors 4 7 uF see L02 C06 EVO1 HLO1 Loi L02 L04 LO5 LO6 L07 LO8 LO9 L10 QF1 RPO1 RS01 STO1 TCO1 TCO2 VO1 V02 clhnidei 2 capacitors 1 nF Protection agains
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