Square TIG 255 User Manual

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SVM100-A

SQUARE WAVE TIG 255

Safety Depends on You

Lincoln arc welding and cutting equipment is designed and built with safety in mind. However, your overall safety can be increased by proper installation ... and thoughtful operation on your part. DO

NOT INSTALL, OPERATE OR REPAIR THIS EQUIPMENT WITHOUT READING THIS MANUAL AND THE SAFETY PRECAUTIONS CONTAINED THROUGHOUT. And, most

importantly, think before you act and be careful.

For use with machine Code Numbers

For use with machine Code Numbers For use with machine Code Numbers For use with machine Code Numbers For use with machine Code Numbers For use with machine Code Numbers

December 1995

10022 10023 10024 10025 10026 10134

View Safety Info View Safety Info View Safety Info View Safety Info

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World's Leader in Welding and Cutting Products Premier Manufacturer of Industrial Motors

SERVICE MANUAL

Sales and Service through Subsidiaries and Distributors Worldwide

22801 St. Clair Ave. Cleveland, Ohio 44117-1199 U.S.A. Tel. (216) 481-8100

SAFETY

WARNING

ARC WELDING can be hazardous.

PROTECT YOURSELF AND OTHERS FROM POSSIBLE SERIOUS INJURY OR DEATH. KEEP CHILDREN AWAY. PACEMAKER WEARERS SHOULD CONSULT WITH THEIR DOCTOR BEFORE OPERATING.

Read and understand the following safety highlights. For additional safety information, it is strongly recommended that you purchase a copy of “Safety in Welding & Cutting - ANSI Standard Z49.1” from the American Welding Society, P.O. Box 351040, Miami, Florida 33135 or CSA Standard W117.2-1974. A Free copy of “Arc Welding Safety” booklet E205 is available from the Lincoln Electric Company, 22801 St. Clair Avenue, Cleveland, Ohio 44117-1199.

BE SURE THAT ALL INSTALLATION, OPERATION, MAINTENANCE AND REPAIR PROCEDURES ARE PERFORMED ONLY BY QUALIFIED INDIVIDUALS.

ELECTRIC SHOCK can kill.

1.a. The electrode and work (or ground) circuits are electrically “hot” when the welder is on. Do not touch these “hot” parts with your bare skin or wet clothing. Wear dry, hole-free gloves to insulate hands.

1.b. Insulate yourself from work and ground using dry insulation. Make certain the insulation is large enough to cover your full area of physical contact with work and ground.

In addition to the normal safety precautions, if welding must be performed under electrically hazardous conditions (in damp locations or while wearing wet clothing; on metal structures such as floors, gratings or scaffolds; when in cramped positions such as sitting, kneeling or Iying, if there is a high risk of unavoidable or accidental contact with the workpiece or ground) use the following equipment:

• Semiautomatic DC Constant Voltage (Wire) Welder.

• DC Manual (Stick) Welder.

• AC Welder with Reduced Voltage Control.

1.c. In semiautomatic or automatic wire welding, the electrode, electrode reel, welding head, nozzle or semiautomatic welding gun are also electrically “hot”.

1.d. Always be sure the work cable makes a good electrical connection with the metal being welded. The connection should be as close as possible to the area being welded.

1.e. Ground the work or metal to be welded to a good electrical (earth) ground.

2.b. Use suitable clothing made from durable flame-resistant material to protect your skin and that of your helpers from the arc rays.

2.c. Protect other nearby personnel with suitable, non-flammable screening and/or warn them not to watch the arc nor expose themselves to the arc rays or to hot spatter or metal.

fumes and gases away from the breathing zone. When

welding with electrodes which require special ventilation such as stainless or hard facing (see instructions on container or MSDS) or on lead or cadmium plated steel and other metals or coatings which produce highly toxic fumes, keep exposure as low as possible and below Threshold Limit Values (TLV) using local exhaust or mechanical ventilation. In confined spaces or in some circumstances, outdoors, a respirator may be required. Additional precautions are also required when welding on galvanized steel.

ARC RAYS can burn.

2.a. Use a shield with the proper filter and cover plates to protect your eyes from sparks and the rays of the arc when welding or observing open arc welding. Headshield and filter lens should conform to ANSI Z87. I standards.

FUMES AND GASES can be dangerous.

3.a.Welding may produce fumes and gases hazardous to health. Avoid breathing these fumes and gases.When welding, keep your head out of the fume. Use enough ventilation and/or exhaust at the arc to keep

1.f.

Maintain the electrode holder, work clamp, welding cable and welding machine in good, safe operating condition. Replace damaged insulation.

1.g. Never dip the electrode in water for cooling.

1.h. Never simultaneously touch electrically “hot” parts of electrode holders connected to two welders because voltage between the two can be the total of the open circuit voltage of both welders.

1.i. When working above floor level, use a safety belt to protect yourself from a fall should you get a shock.

1.j. Also see Items 4.c. and 6.

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SQUARE WAVE TIG 255

3.b.

Do not weld in locations near chlorinated hydrocarbon coming from degreasing, cleaning or spraying operations. The heat and rays of the arc can react with solvent vapors form phosgene, a highly toxic gas, and other irritating products.

3.c. Shielding gases used for arc welding can displace air and cause injury or death. Always use enough ventilation, especially in confined areas, to insure breathing air is safe.

3.d. Read and understand the manufacturer’s instructions for this

equipment and the consumables to be used, including the material safety data sheet (MSDS) and follow your employer’s safety practices. MSDS forms are available from your welding distributor or from the manufacturer.

3.e. Also see item 7b.

vapors

Apr. ‘93

SAFETY

WELDING SPARKS can cause fire or explosion.

4.a.

Remove fire hazards from the welding area. If this is not possible, cover them to prevent the welding sparks from starting a fire.

materials from welding can easily go through small cracks and openings to adjacent areas. Avoid welding near hydraulic lines. Have a fire extinguisher readily available.

4.b. Where compressed gases are to be used at the job site, special precautions should be used to prevent hazardous situations. Refer to “Safety in Welding and Cutting” (ANSI Standard Z49.1) and the operating information for the equipment being used.

4.c. When not welding, make certain no part of the electrode circuit is touching the work or ground. Accidental contact can cause overheating and create a fire hazard.

4.d. Do not heat, cut or weld tanks, drums or containers until the proper steps have been taken to insure that such procedures will not cause flammable or toxic vapors from substances inside. They can cause an explosion even been “cleaned”. For information, purchase “Recommended Safe Practices for the Containers and Piping That Have Held Hazardous Substances”, AWS F4.1 from the American Welding Society

(see address above).

4.e. Vent hollow castings or containers before heating, cutting or welding. They may explode.

4.f.

Sparks and spatter are thrown from the welding arc. Wear oil free protective garments such as leather gloves, heavy shirt, cuffless trousers, high shoes and a cap over your hair. Wear ear plugs when welding out of position or in confined places. Always wear safety glasses with side shields when in a welding area.

4.g. Connect the work cable to the work as close to the welding area as practical. Work cables connected to the building framework or other locations away from the welding area increase the possibility of the welding current passing through lifting chains, crane cables or other alternate circuits. This can create fire hazards or overheat lifting chains or cables until they fail.

4.h. Also see item 7c.

Remember that welding sparks and hot

though

they have

Preparation

for Welding and Cutting of

CYLINDER may explode if damaged.

5.a. Use only compressed gas cylinders containing the correct shielding gas for the process used and properly operating regulators designed for the gas and

pressure used. All hoses, fittings, etc. should be suitable for the application and maintained in good condition.

5.b. Always keep cylinders in an upright position securely chained to an undercarriage or fixed support.

5.c. Cylinders should be located:

•Away from areas where they may be struck or subjected to

physical damage.

• A safe distance from arc welding or cutting operations and

any other source of heat, sparks, or flame.

5.d. Never allow the electrode, electrode holder or any other electrically “hot” parts to touch a cylinder.

5.e. Keep your head and face away from the cylinder valve outlet when opening the cylinder valve.

5.f. Valve protection caps should always be in place and hand tight except when the cylinder is in use or connected for use.

5.g. Read and follow the instructions on compressed gas cylinders, associated equipment, and CGA publication P-l, “Precautions for Safe Handling of Compressed Gases in Cylinders,” available from the Compressed Gas Association 1235 Jefferson Davis Highway, Arlington, VA 22202.

FOR ELECTRICALLY powered equipment.

6.a.Turn off input power using the disconnect switch at the fuse box before working on the equipment.

6.b. Install equipment in accordance with the U.S. National Electrical Code, all local codes and the manufacturer’s recommendations.

6.c. Ground the equipment in accordance with the U.S. National Electrical Code and the manufacturer’s recommendations.

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Mar. ‘93

SQUARE WAVE TIG 255

iii

SAFETY

FOR ENGINE powered equipment.

7.a. Turn the engine off before troubleshooting and maintenance work unless the maintenance work requires it to be running.

____________________________________________________

7.b. Operate engines in open, well-ventilated areas or vent the engine exhaust fumes outdoors.

____________________________________________________

7.c. Do not add the fuel near an open flame welding arc or when the engine is running. Stop the engine and allow it to cool before refueling to prevent spilled fuel from vaporizing on contact with hot engine parts and igniting. Do not spill fuel when filling tank. If fuel is spilled, wipe it up and do not start engine until fumes have been eliminated.

____________________________________________________

7.d. Keep all equipment safety guards, covers and devices in position and in good repair. Keep hands, hair, clothing and tools away from V-belts, gears, fans and all other moving parts when starting, operating or repairing equipment.

ELECTRIC AND MAGNETIC FIELDS may be dangerous

8.a. Electric current flowing through any conductor causes localized Electric and Magnetic Fields (EMF). Welding current creates EMF fields around welding cables and welding machines

8.b. EMF fields may interfere with some pacemakers, and welders having a pacemaker should consult their physician before welding.

8.c. Exposure to EMF fields in welding may have other health effects which are now not known.

8d. All welders should use the following procedures in order to

minimize exposure to EMF fields from the welding circuit:

8.d.1.

Route the electrode and work cables together - Secure them with tape when possible.

8.d.2. Never coil the electrode lead around your body.

8.d.3. Do not place your body between the electrode and

work cables. If the electrode cable is on your right side, the work cable should also be on your right side.

8.d.4. Connect the work cable to the workpiece as close as

possible to the area being welded.

8.d.5. Do not work next to welding power source.

____________________________________________________

7.e. In some cases it may be necessary to remove safety guards to perform required maintenance. Remove guards only when necessary and replace them when the maintenance requiring their removal is complete. Always use the greatest care when working near moving parts.

7.f. Do not put your hands near the engine fan. Do not attempt to override the governor or idler by pushing on the throttle control rods while the engine is running.

7.g. To prevent accidentally starting gasoline engines while turning the engine or welding generator during maintenance work, disconnect the spark plug wires, distributor cap or magneto wire as appropriate.

___________________________________________________

7.h. To avoid scalding, do not remove the radiator pressure cap when the engine is hot.

Mar. ‘93

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SQUARE WAVE TIG 255

SAFETY

PRÉCAUTIONS DE SÛRETÉ

Pour

votre propre protection lire et observer toutes les instructions et les précautions de sûreté specifiques qui parraissent dans ce manuel aussi bien que les précautions de sûreté générales suivantes:

Sûreté Pour Soudage A L’Arc

1. Protegez-vous contre la secousse électrique:

a. Les circuits à l’électrode et à la piéce sont sous tension

quand la machine à souder est en marche. Eviter toujours tout contact entre les parties sous tension et la peau nue ou les vétements mouillés. Porter des gants secs et sans trous pour isoler les mains.

b. Faire trés attention de bien s’isoler de la masse quand on

soude dans des endroits humides, ou sur un plancher metallique ou des grilles metalliques, principalement dans

les positions assis ou couché pour lesquelles une grande partie du corps peut être en contact avec la masse.

c. Maintenir le porte-électrode, la pince de masse, le câble

de soudage et la machine à souder en bon et sûr état defonctionnement.

d.Ne jamais plonger le porte-électrode dans l’eau pour le

refroidir.

e. Ne jamais toucher simultanément les parties sous tension

des porte-électrodes connectés à deux machines à souder parce que la tension entre les deux pinces peut être le total de la tension à vide des deux machines.

f. Si on utilise la machine à souder comme une source de

courant pour soudage semi-automatique, ces precautions pour le porte-électrode s’applicuent aussi au pistolet de soudage.

5. Toujours porter des lunettes de sécurité dans la zone de soudage. Utiliser des lunettes avec écrans lateraux dans les zones où l’on pique le laitier.

6. Eloigner les matériaux inflammables ou les recouvrir afin de prévenir tout risque d’incendie dû aux étincelles.

7. Quand on ne soude pas, poser la pince à une endroit isolé de la masse. Un court-circuit accidental peut provoquer un échauffement et un risque d’incendie.

8. S’assurer que la masse est connectée le plus prés possible de la zone de travail qu’il est pratique de le faire. Si on place la masse sur la charpente de la construction ou d’autres endroits éloignés de la zone de travail, on augmente le risque de voir passer le courant de soudage par les chaines de levage, câbles de grue, ou autres circuits. Cela peut provoquer des risques d’incendie ou d’echauffement des chaines et des câbles jusqu’à ce qu’ils se rompent.

9. Assurer une ventilation suffisante dans la zone de soudage. Ceci est particuliérement important pour le soudage de tôles galvanisées plombées, ou cadmiées ou tout autre métal qui produit des fumeés toxiques.

10. Ne pas souder en présence de vapeurs de chlore provenant d’opérations de dégraissage, nettoyage ou pistolage. La chaleur ou les rayons de l’arc peuvent réagir avec les vapeurs du solvant pour produire du phosgéne (gas fortement toxique) ou autres produits irritants.

11. Pour obtenir de plus amples renseignements sur la sûreté, voir le code “Code for safety in welding and cutting” CSA Standard W 117.2-1974.

2. Dans le cas de travail au dessus du niveau du sol, se protéger contre les chutes dans le cas ou on recoit un choc. Ne jamais enrouler le câble-électrode autour de n’importe quelle partie du corps.

3. Un coup d’arc peut être plus sévère qu’un coup de soliel, donc:

a. Utiliser un bon masque avec un verre filtrant approprié

ainsi qu’un verre blanc afin de se protéger les yeux du rayonnement de l’arc et des projections quand on soude ou quand on regarde l’arc.

b. Porter des vêtements convenables afin de protéger la

peau de soudeur et des aides contre le rayonnement de l‘arc.

c. Protéger l’autre personnel travaillant à proximité au

soudage à l’aide d’écrans appropriés et non-inflammables.

4. Des gouttes de laitier en fusion sont émises de l’arc de soudage. Se protéger avec des vêtements de protection libres de l’huile, tels que les gants en cuir, chemise épaisse, pantalons sans revers, et chaussures montantes.

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PRÉCAUTIONS DE SÛRETÉ POUR LES MACHINES À SOUDER À TRANSFORMATEUR ET À REDRESSEUR

1. Relier à la terre le chassis du poste conformement au code de l’électricité et aux recommendations du fabricant. Le dispositif de montage ou la piece à souder doit être branché à une bonne mise à la terre.

2. Autant que possible, I’installation et l’entretien du poste seront effectués par un électricien qualifié.

3. Avant de faires des travaux à l’interieur de poste, la debrancher à l’interrupteur à la boite de fusibles.

4. Garder tous les couvercles et dispositifs de sûreté à leur place.

Mar. ‘93

SQUARE WAVE TIG 255

RETURN TO MAIN INDEX

MASTER TABLE OF CONTENTS FOR ALL SECTIONS

Page

Safety .........................................................................................................................i-iv

Installation......................................................................................................Section A

Technical Specifications........................................................................................A-1

Location.................................................................................................................A-2

High Frequency Interference Protection................................................................A-2

Input Connections..................................................................................................A-3

Output Connections...............................................................................................A-4

Operation.........................................................................................................Section B

Safety Precautions.................................................................................................B-1

Graphic Symbols..........................................................................................B-2 – B-3

General Description...............................................................................................B-4

Design Features and Advantages .........................................................................B-4

Welding Capability.................................................................................................B-5

Limitations..............................................................................................................B-5

Controls and Settings ............................................................................................B-6

Hand and Foot Amptrol Operation.........................................................................B-8

Welding Operation .....................................................................................B-8 – B-11

Auxillary Power....................................................................................................B-11

Overload Protection.............................................................................................B-12

Accessories.....................................................................................................Section C

Maintenance ....................................................................................................Section D

Safety Precautions ................................................................................................D-1

Routine and Periodic Maintenance........................................................................D-1

General Assembly Exploded View ........................................................................D-2

Theory of Operation........................................................................................Section E

Power Supply Operation ...............................................................................E1 – E-5

SCR Operation ......................................................................................................E-6

Thermal Protection ................................................................................................E-7

Troubleshooting and Repair...........................................................................Section F

How To Use Troubleshooting Guide......................................................................F-1

PC Board Troubleshooting Procedures.................................................................F-2

Troubleshooting Guide...............................................................................F-3 – F-15

Test Procedures.......................................................................................F-17 – F-28

Oscilloscope Waveforms..........................................................................F-31 – F-39

Replacement Procedures.........................................................................F-40 – F-42

Re-Test After Repair............................................................................................F-44

Electrical Diagrams.........................................................................................Section G

Parts Manual..........................................................................................................P-241

SQUARE WAVE TIG 255

TABLE OF CONTENTS

- INSTALLATION SECTION -

Installation.......................................................................................................Section A

Technical Specifications........................................................................................A-1

Input and Output Specifications Cable and Fuse Sizes Physical Dimensions

Location.................................................................................................................A-2

Stacking ..........................................................................................................A-2

Tilting...............................................................................................................A-2

High Frequency Interference Protection................................................................A-2

Input Connections..................................................................................................A-3

Reconnect Procedure............................................................................................A-4

Output Connections...............................................................................................A-4

Section A

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SQUARE WAVE TIG 255

A-1

INSTALLATION

TECHNICAL SPECIFICATIONS – SQUARE WAVE TIG 255

INPUT - SINGLE PHASE ONLY

Standard

Voltage

208/230/460/1/60

230/460/575/1/60 200/240/400/1/50/60 220/380/440/1/50/60 380/415/500/1/50/60 220/380/415/1/50/60

Input Current at Rated Output

81/74/37 74/37/30 85/77/44 77/45/39 45/41/33 77/45/41

RATED OUTPUT

(1)

Code

Number

10022 10023 10024 10025 10026 10134

Duty Cycle

40% Duty Cycle

NEMA Class II (40)

60% Duty Cycle

100% Duty Cycle

Welding Current Range

(Continuous)

5-315 Amps

AC and DC

Fuse

Input

Voltage /

Frequency

208/60 230/60 460/60

575/60 200/50/60 220/50/60 380/50/60 400/50/60 415/50/60 440/50/60 500/50/60

(Super Lag)

or Breaker

Size

125 100

50 125 100

Amps

Volts at Rated Amperes

255 200

150

OUTPUT

Constant Open Circuit Voltage

115 Volts AC, 10 Amps

Stick OCV: 76

TIG OCV: 53

RECOMMENDED INPUT WIRE AND FUSE SIZES

For all Stick, DC TIG, and Balanced AC TIG

Welding at 255A/30V/40% Duty Cycle

Based on the 1993 US. National

Electrical Code

Type 75°C

Input

Ampere

Rating on

Nameplate

81 74 37 30 85 77 46 43 41 39 34

Type 75°C

Copper Wire in

Conduit AWG

(IEC) Sizes

6 (16mm2) 6 (16mm2) 10 (6mm2) 10 (6mm2) 6 (16mm2) 6 (16mm2) 8 (10mm2) 10 (6mm2) 10 (6mm2) 10 (6mm2) 10 (6mm2)

Copper Ground Wire in Conduit

AWG (IEC)

Sizes

6 (16mm2) 8 (10mm2) 10 (6mm2) 10 (6mm2) 6 (16mm2) 8 (10mm2) 8 (10mm2) 10 (6mm2) 10 (6mm2) 10 (6mm2) 10 (6mm2)

For Unbalanced AC TIG Welding Above 180

Amps, 255A/16V/40% Duty Cycle, Auto

Balance Based on the 1993 U.S. National

Electrical Code

Copper Wire in

Input

Amperes

102

92 46 37

105

96 55 53 51 48 42

Conduit AWG

30 28

Auxiliary Power

220Volts AC, 2 Amps

(50/60 Hz. machines only)

Type 75°C

(IEC) Sizes

4 (25mm2) 4 (25mm2) 8 (10mm2) 10 (6mm2) 4 (25mm2) 4 (25mm2) 8 (10mm2) 8 (10mm2) 8 (10mm2) 8 (10mm2) 10 (6mm2)

Copper Ground Wire in Conduit

AWG (IEC)

6 (16mm2) 6 (16mm2) 10 (6mm2) 10 (6mm2) 6 (16mm2) 8 (10mm2) 8 (10mm2) 10 (6mm2) 10 (6mm2) 10 (6mm2) 10 (6mm2)

Sizes

(1)

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Unbalanced TIG welding above 180 amps will draw higher input currents; see Supply Connections section.

SQUARE WAVE TIG 255

PHYSICAL DIMENSIONS

Height Width Depth Weight

30.5 in. 19.0 in. 30.0 in. (Lift bail, add 3.5 in) 300 lbs

(137 kg)

775 mm 485 mm 760 mm

(Lift bail, add 90 mm)

INSTALLATION

A-2

Read entire installation section before starting installation.

SAFETY PRECAUTIONS

WARNING

ELECTRIC SHOCK can kill.

• Only qualified personnel should

perform this installation.

• Turn the input power OFF at the disconnect switch or fuse box before working on this equipment.

• Do not touch electrically hot parts.

• Always connect the Square Wave TIG 255 grounding terminal (located on the bottom of the input connection box) to a good electrical earth ground.

SELECT SUITABLE LOCATION

HIGH FREQUENCY INTERFERENCE PROTECTION

The spark gap oscillator in the high frequency generator, being similar to a radio transmitter, can be blamed for many radio, TV and electronic equipment interference problems. These problems may be the result of radiated interference. Proper grounding methods can reduce or eliminate radiated interference.

Radiated interference can develop in the following four ways:

1. Direct interference radiated from the welder.

2. Direct interference radiated from the welding leads.

3. Direct interference radiated from feedback into the power lines.

4. Interference from re-radiation of “pickup” by ungrounded metallic objects.

Keeping these contributing factors in mind, installing equipment per the following instructions should minimize problems.

Place the welder where clean cooling air can freely circulate in through the rear louvers and out through the side louvers. Dirt, dust or any foreign material that can be drawn into the welder should be kept at a minimum. Failure to observe these precautions can result in excessive operating temperatures and nuisance shut-downs. Square Wave TIG 255 power sources carry an IP23 enclosure rating. They are rated for use in damp, dirty environments subject to occasional falling water such as rain.

STACKING

Square Wave TIG 255’s cannot be stacked.

TILTING

Each machine must be placed on a secure, level surface, either directly or on a recommended undercarriage. The machine may topple over if this procedure is not followed.

1. Keep the welder power supply lines as short as possible and completely enclose them in rigid metallic conduit or equivalent shielding for a minimum distance of 50 feet (15.2m). There should be good electrical contact between this conduit and the welder. Both ends of the conduit should be connected to a driven ground and the entire length should be continuous.

2. Keep the work and electrode leads as short as possible and as close together as possible. Lengths should not exceed 25 ft (7.6m). Tape the leads together when practical.

3. Be sure the torch and work cable rubber coverings are free of cuts and cracks that allow high frequency leakage. Cables with high natural rubber content, such as Lincoln Stable-Arc® better resist high frequency leakage than neoprene and other synthetic rubber insulated cables.

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SQUARE WAVE TIG 255

A-3

INSTALLATION

4. Keep the torch in good repair and all connections tight to reduce high frequency leakage.

5. The work terminal must be connected to a ground within ten feet of the welder, using one of the

following methods: a) A metal underground water pipe in direct

contact with the earth for ten feet or more.

b) A 3/4” (19mm) galvanized pipe or a 5/8”

(16mm) solid galvanized iron, steel or copper rod driven at least eight feet into the ground.

The ground should be securely made and the grounding cable should be as short as possible using cable of the same size as the work cable, or larger. Grounding to the building frame electrical conduit or a long pipe system can result in reradiation, effectively making these members radiating antennas.

6. Keep all access panels and covers securely in place.

FIGURE A.1 — REAR PANEL

7. All electrical conductors within 50 ft (15.2m) of the welder should be enclosed in grounded rigid metallic conduit or equivalent shielding. Flexible metallic conduit is generally not suitable.

8. When the welder is enclosed in a metal building, several good earth driven electrical grounds (as in 5 (b) above) around the periphery of the building are recommended.

Failure to observe these recommended installation procedures can cause radio or TV interference problems and result in unsatisfactory welding performance resulting from lost high frequency power.

INPUT CONNECTIONS

Be sure the voltage, phase, and frequency of the input power is as specified on the rating plate, located on the rear of the machine. Refer to Figure A.1.

1. RATING PLATE 4. 220V RECEPTACLE & BREAKER

2. INPUT ENTRY HOLE (50/60 HZ MACHINE ONLY)

3. RECONNECT PANEL 5. 115V RECEPTACLE & BREAKER

GROUND CONNECTION

The frame of the welder must be grounded. A ground terminal marked with the symbol is located at the bottom of the input box for this purpose. See your local and national electrical codes for proper grounding methods.

INPUT SUPPLY CONNECTIONS

Have a qualified electrician connect single phase input power leads to L1 and L2 of the input panel in accordance with all local codes and national electrical codes. Refer to the connection diagram located on the inside of the cover of the Reconnect Panel.

Welder supply line entry provision is in the case rear panel with a removable cover over the input connection panel area. Entry is through a 1.7 in (43mm) diameter hole in the case back. See Figure A.1.

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SQUARE WAVE TIG 255

INSTALLATION

A-4

RECONNECT PROCEDURE

On multiple input voltage welders, be sure the reconnect panel is connected per the following instructions for the voltage being supplied to the welder.

CAUTION

Failure to follow these instructions can cause immediate failure of components within the welder.

___________________________________________

Welders are shipped connected for the highest input voltage as listed on the rating Plate. To change this connection for a different input voltage, reconnect the power strap (P) to the terminal corresponding to the input voltage used. Designations on reconnect panel, LOW, MID and HIGH correspond to the nameplate input voltages of a triple voltage welder. Dual voltage welders use only LOW and HIGH. Single voltage welders use only HIGH.

EXAMPLE: On a 208/230/460 volt welder, LOW is

208V, MID is 230V, and HIGH is 460V.

Fuse the input circuit with the recommended super lag fuses or delay type1circuit breakers. Choose an input

and grounding wire size according to local or national codes, refer to Specification page at the beginning of this chapter. Using fuses or circuit breakers smaller than recommended may result in “nuisance” shut-offs from welder inrush currents even if not welding at high currents.

Unbalanced AC TIG welding draws higher input currents than those for stick, DC TIG, or Balanced AC TIG welding. The welder is designed for these higher input currents. However, where unbalanced AC TIG welding above 180 amps is planned, the higher input currents require larger input wire sizes and fuses. Refer to Specification page at the beginning of this chapter.

The Square Wave TIG 255 should be permanently wired into the power system. Plugs or connectors are not recommended.

Also called “inverse time” or “thermal/magnetic” circuit breakers; circuit breakers which have a delay in tripping action that decreases as the magnitude of the current increases.

FIGURE A.2. - FRONT PANEL

POWER

WATER

OUT

1. CONTROL AND DISPLAY AREA 5. OPTIONAL WATER SOLENOID

2. POWER SWITCH 6. GAS SOLENOID

3. THERMOSTATIC 7. WORK (LEFT) AND PROTECTION LIGHT ELECTRODE TERMINALS

4. POLARITY SWITCH 8. REMOTE RECEPTACLE

GAS

WORK

OUT

ELECTRODE

L9119-1

DO NOT SWITCH WHILE WELDING

WARNING

L9119-2

REMOTE

OUTPUT CONNECTIONS

WARNING

To avoid receiving a high frequency shock, keep the TIG torch and cables in good condition.

___________________________________________

See Figure A.2 for the location of the work and electrode terminals, the gas and optional water solenoids, and the Remote Receptacle.

TIG TORCH CONNECTION

TIG welding torches come with 12.5 ft (3.8m) and 25 ft (7.6m) cables. Use the shorter length whenever possible to minimize possible radio interference problems. With power source off, connect the torch cable to the “Electrode” terminal on the welder. Connect a separate work cable to the “Work” terminal of the welder. See Table A.1 for recommended work cable sizes. Both work and electrode cables should be routed through the cable strain relief holes provided in the base directly below the welding output terminals.

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SQUARE WAVE TIG 255

A-5

INSTALLATION

TABLE A.1

Cable Sizes for Combined Lengths of Copper

Electrode and Work Cable

Machine Size

255 Amp

40% Duty Cycle #2 (35mm2) #1 (45mm2) 1/0 (55mm2)

Connect the TIG torch gas and water fittings to the welder fittings. Any torch with fittings that conform to Compressed Gas Association (CGA) standards can be used.

The welder fittings have the following threads: Gas Inlet and Outlet: 5/8”-18 right-hand female; Water inlet and Outlet: 5/8”-18 left-hand female. The cylinder of inert shielding gas must be equipped with a pressure regulator and flow meter. Install a hose between the flow meter and gas inlet on the welder.

Lengths up to

100 ft 100 to 200 ft 200 to 250 ft

WARNING

Observe the safety precautions necessary for handling and using compressed gas containers. Contact your supplier for specific information.

___________________________________________

STICK ELECTRODE CABLE CONNECTION

Turn the Power switch Off. Run the electrode and work cables through the strain relief holes below the welding output terminals, and connect the cables to the proper terminals. This strain relief prevents damage to the welding output terminals if the cables are pulled excessively. Select cable size according to Table A.1.

WARNING

Do not connect a TIG torch and stick electrode cable at the same time. They will both be electrically HOT whenever the output contactor is energized.

___________________________________________

DO NOT operate a water-cooled torch unless water is flowing. Water doesn’t flow until solenoid is actuated.

If using a water-cooled torch with a Magnum water cooler, connect the cooler water outlet to the ‘Water Valve In” fitting. Connect the TIG torch inlet to the “Water Valve Out” fitting.

If using a water-cooled torch with a free-running water supply, install a water line between the welder “Water Inlet” and the supply. Include a strainer in the water supply line to prevent dirt particles from obstructing water flow in the valve and cooling chamber of the TIG torch. Failure to do so could result in water valve malfunction and overheating of the water-cooled torch. Connect the torch water line to the welder “Water Out” fitting. Use a nonmetallic drain line from the electrode connection to the drain or water recirculating pump.

For other water coolers or torches, consult the manufacturer’s instructions for the water cooler or TIG torch being used.

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SQUARE WAVE TIG 255

TABLE OF CONTENTS

- OPERATION SECTION -

Operation..........................................................................................................Section B

Safety Precautions.................................................................................................B-1

Graphic Symbols..........................................................................................B-2 - B-3

General Description ...............................................................................................B-4

Design Features and Advantages..........................................................................B-4

Welding Capability .................................................................................................B-5

Limitations..............................................................................................................B-5

Controls and Settings.............................................................................................B-6

Control Panel Keys .........................................................................................B-6

Case Front Controls........................................................................................B-7

Hand and Foot Amptrol Operation.........................................................................B-8

Welding Operation.......................................................................................B-8 - B-11

TIG Welding Guidelines..................................................................................B-8

TIG Welding Sequence of Operation (2-Step Mode)......................................B-9

TIG Welding Sequence of Operation (4-Step Mode)....................................B-10

Advanced Tig Welding Features...................................................................B-11

Auxillary Power ....................................................................................................B-11

Overload Protection .............................................................................................B-12

Section B

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SQUARE WAVE TIG 255

B-1

OPERATION

OPERATING INSTRUCTIONS

Read and understand entire section before operating machine.

GENERAL WARNINGS

SAFETY PRECAUTIONS

WARNING

ELECTRIC SHOCK can kill.

• Do not touch electrically live parts or electrode with skin or wet clothing.

• Insulate yourself from work and ground.

• Always wear dry insulating gloves.

FUMES AND GASES can be dangerous.

• Keep your head out of fumes.

• Use ventilation or exhaust to remove fumes from breathing zone.

WELDING SPARKS can cause fire or explosion

• Keep flammable material away.

• Do not weld on containers that have held combustibles.

ARC RAYS can burn.

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SQUARE WAVE TIG 255

• Wear eye, ear and body protection.

Observe additional Safety Guidelines detailed in the beginning of this manual.

OPERATION

GRAPHIC SYMBOLS THAT APPEAR ON

THIS MACHINE OR IN THIS MANUAL

B-2

TIG 2-STEP

TIG 4-STEP

STICK

CURRENT CONTROL

OUTPUT

LOCAL CUR-

RENT CON-

TROL

AFTERFLOW /

AFTERFLOW

TIME

CONTINUOUS

HIGH FRE-

QUENCY

START ONLY

HIGH FRE-

QUENCY

OFF

REMOTE CUR-

RENT CON-

TROL

INCREASE

OUTPUT

DECREASE

HIGH FRE-

QUENCY

CLEAN

(INCREASE

POSITIVE

POLARITY)

PENETRATE

(INCREASE

NEGATIVE

POLARITY)

TIG PULSER

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SQUARE WAVE TIG 255

B-3

OPERATION

GRAPHIC SYMBOLS THAT APPEAR ON

THIS MACHINE OR IN THIS MANUAL (CONT.)

AC WAVE BAL-

ANCE

GAS OUTPUT

PULSED PER

SECOND

OVER TEMPER-

ATURE

INPUT

POWER

DC+

POLARITY

DC-

POLARITY

DO NOT

GAS INPUT

ELECTRODE

CONNECTION

PROTECTIVE

GROUND

SINGLE PHASE TRANSFORMER AC & DC RECTI-

FIER POWER

SOURCE

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SWITCH

WHILE WELD-

ING

WARNING

WATER

(COOLANT)

OUTPUT

WATER

(COOLANT)

INPUT

TIG (GTAW)

SINGLE

PHASE

WORK CONNEC-

TION

AC POLARITY

SQUARE WAVE TIG 255

OPERATION

B-4

GENERAL DESCRIPTION

The Square Wave TIG 255 is a constant current, single range square wave AC/DC TIG (GTAW) arc welding power source with built-in high frequency stabilization. It also has stick (SMAW) capability. It is available from the factory in one model only; there are no factory installed options, only variations in input voltage and frequency.

The Square Wave TIG 255 includes advanced features such as Auto-Balance™, 2-Step/4-Step Arc Start Switch operation and a TIG pulser. In addition, fixed preflow and variable afterflow timers are included for shielding gas and cooling water control.

RECOMMENDED PROCESSES AND EQUIPMENT

The Square Wave TIG 255 is recommended for the TIG (GTAW) and stick (SMAW) welding processes within its output capacity of 5 to 315 amps, on both AC and DC polarity. It is compatible with all Magnum TIG accessories (see Accessory section in this manual), as well as many industry standard items, such as TIG torches, hoses, and water coolers.

• Welding current limit can be preset from 5 to 315 amps and is displayed on the Ammeter when not welding.

• Auto Balance circuitry automatically provides the proper amount of cleaning and penetration when AC TIG welding. Manual AC wave balance adjustment is also possible.

• 2-Step/4-Step Arc Start Switch Capability.

• TIG Pulser with On/Off Selection, and Pulses Per Second adjustment. Background current and duty cycle are automatically adjusted according to the peak welding current.

• Fixed preflow time of 0.5 seconds. Preflow time is eliminated if welding restarts during gas afterflow of previous weld. This avoids unnecessary delays when making repeated welds.

• Adjustable afterflow time control.

• Local/Remote current selection.

• Stick/TlG selection.

• Continuous/Start/Off High Frequency selection.

• DC+/AC/DC- Polarity Switch.

OPERATIONAL FEATURES AND CONTROLS

The Square Wave TIG 255 has the following controls as standard: TIG 2-Step/TlG 4-Step/Stick mode selection, Local/Remote current control selection, Continuous/Start Only/Off high frequency selection, Auto/Manual AC wave balance selection with the manual wave balance adjustment, TIG pulser On/Off selection with frequency adjustment, afterflow adjustment, and DC+/DC-/AC polarity selection.

DESIGN FEATURES AND ADVANTAGES

• Designed to NEMA EW-1 & International IEC-974 Standards.

• Single output range of 5-315 amps covers the majority of all TIG welding applications.

• Solid State Output Contactor: no noise, no parts to wear.

• Digital Ammeter and Voltmeter for precise readings

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from 5 to 315 amps welding.

•

Power Factor Correction for lower input currents and smaller input wire sizes.

• Remote Receptacle for Amptrol or Arc Start Switch.

• Low Voltage Arc Start Switch Circuit (24 V AC) for maximum operator safety.

• Gas and optional Water Valves: Inlet & outlet fittings conform to Compressed Gas Association (CGA) standards.

• Built-in High Frequency Generator.

• 115 Volt Receptacle with 10 amp Circuit Breaker.

• 220 Volt European (Schuko) type receptacle with 2 amp circuit breaker for water coolers (50/60Hz machines only).

• Excellent arc starting and stability up through 315 amps.

• High resistance to AC arc rectification.

• No tungsten spitting within current range of electrode.

• Compact size, requires only a 19 in x 30 in (485 mm x 760 mm) footprint.

SQUARE WAVE TIG 255

B-5

• Strain relief holes in base for welding cables, gas and water hoses and control cables.

• Easy access for input connections. Connections are simple strip and clamp of input wires (no lugs required).

• Low fan noise at idle.

• Modular construction for easy servicing.

• Simple keypad layout allows even novice users to operate with minimal instruction.

• Unused controls are automatically locked out to simplify setup. Examples: the AC wave balance control has no effect in DC; the High Frequency and gas and water valves do not operate in Stick mode; TIG Pulser is locked out in the Stick mode.

• Recessed panels protect controls, output terminals gas and water fittings.

OPERATION

• Large safety margins and protective circuits protect rectifiers from transient voltages and high currents.

• Line Voltage Compensated.

• Thermostatically Protected.

• Electronic Over Current Protection.

WELDING CAPABILITY

The Square Wave TIG 255 is rated at 255 amps, 30 volts, at 40% duty cycle on a ten minute basis. It is capable of higher duty cycles at lower output currents. If the duty cycle(s) are exceeded, a thermal protector will shut off the output until the machine cools to a reasonable operating temperature.

LIMITATIONS

The Square Wave TIG 255 is not recommended for arc gouging due to its limited output capacity.

The Square Wave TIG 255 is not recommended for AC TIG welding when high concentrations of helium are used for shielding; starting problems and arc rectification may occur.

The Square Wave TIG 255 is not recommended for pipe thawing.

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SQUARE WAVE TIG 255

OPERATION

B-6

CONTROLS AND SETTINGS

All operator controls and adjustments are located on the case front of the Square Wave TIG 255. Refer to Figures B.1, B.2.a and B.2.b and corresponding explanations.

FIGURE B.1 - CONTROL PANEL KEYS

CONTROL PANEL KEYS

The keys are grouped into six areas, described below and in Figure B.1. Some areas are active in both TIG and Stick, while others are active in TIG only. The red LED indicator lights are used to tell which functions are active, and the display (Item 1) is used to check the settings of the up/down keys.

1. WELD MODE KEYS: These keys select the Weld

Mode desired: TIG 2-Step, TIG 4-Step, or Stick. Read the complete Operating Instructions section for more information on TIG 2-Step and TIG 4Step.

2. CURRENT CONTROL: These keys select Local

or Remote and adjust the Amps Up or Amps Down. These keys are used to set thewelding current from 5 to 315 amps, as well as to select Local or Remote control. Local control allows the current to be adjusted only with the Amps Up/Amps Down keys. Remote control allows the use of a hand or foot operated remote control. Read the complete Operating Instructions on Local and Remote.

3. HIGH FREQUENCY: These keys are active in the

TIG mode only. Select from Continuous, Start Only, or Off. Read the TIG Welding Section for

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information on High Frequency.

THE LINCOLN ELECTRIC COMPANY CLEVELAND, OHIO USA

WELD MODE

TIG 2-STEP

TIG 4-STEP

STICK

CURRENT CONTROL

LOCAL

AMPS

LINCOLN

ELECTRIC

REMOTE

HIGH FREQUENCY

1. WELD MODE KEYS 5. TIG PULSER KEYS

2. CURRENT CONTROL KEYS 6. AFTERFLOW KEYS

3. HIGH FREQUENCY KEYS 7. DISPLAY

4. AC WAVE BALANCE KEYS

section for more information

CONTINUOUS

START ONLY

AFTERFLOW

SECONDS

G2612

AC/DC OUTPUT CAPACITY: 255 AMPS 30 VOLTS 40% DUTY CYCLE

AC WAVE BALANCE

MANUAL

AUTO-

BALANCE

CLEAN

OFF

PENETRATE

TIG PULSER

OFF

PULSES PER SECOND

4. AC WAVE BALANCE: These keys are active in the AC TIG mode only. They are used to set the amount of cleaning and/or penetration produced during an AC TIG weld. Auto Balance™ automatically sets the AC Wave Balance according to the welding current. If manual adjustment is desired, the Manual Balance key can be pressed, and the balance adjusted from +5 (cleaning) to -10 (penetration) with the Cleaning and Penetration keys. Read the Advanced Features section for a complete explanation of the AC Wave Balance.

5. TIG PULSER: These keys are active in the TIG mode only. The On/Off keys turn the TIG Pulser on and off. The Pulses Per Second keys adjust the pulsing frequency up and down, from 0.5 to 10 pulses per second. Read the Advanced Features section for more information on the TIG Pulser.

6. AFTERFLOW: These keys are active in the TIG mode only. They must adjust the afterflow time from 5 to 50 seconds for shielding gas and cooling water flow through solenoids located on the case front. As the Afterflow time is adjusted, the Afterflow time, in seconds, is shown in the Momentary Display.

SQUARE WAVE TIG 255

B-7

OPERATION

7. CONTROL PANEL: The display is divided into five sections. See Figures B.2.a and B.2.b.

FIGURE B.2.a - DISPLAY

A. AC/DC INDICATOR D. MOMENTARY DISPLAY B. VOLTMETER E. BAR GRAPH C. AMMETER

FIGURE B.2.b - DISPLAY

and on the Momentary Display. When the Momentary Display is blank (as in Figure B.2.a), the Display represents values shown on the

Bar Graph

ammeter. When a low value is shown on the ammeter, only a few “bars” will appear on the left hand side of the Bar Graph Display. As the ammeter value increases, more and more “bars” will appear. Whenever a value increases, more and more “bars” will appear. Whenever a value appears in the Momentary Display, the Bar Graph Display will represent the Momentary Display value, not the ammeter value.

CASE FRONT CONTROLS

Refer to Figure B.3 for the location of the following controls:

1. POWER SWITCH: Controls the input power to the Square Wave TIG 255.

2. OVER TEMPERATURE LIGHT: A yellow light which only lights when an over temperature situation occurs. See the Maintenance Section for more information on the thermostatic protection.

A. AC/DC INDICATOR: This symbol represents the

output polarity of the 255 . . . either AC or DC. AC is shown in Figure B.2.a; DC is shown in Figure B.2.b.

B. VOLTMETER: This meter displays open circuit

voltage as well as welding voltage, as measured on the output studs of the Square Wave TIG 255.

C. AMMETER: The ammeter can display preset

current (for setting the welding current before welding) and actual welding current (the value of the welding current during a weld).

D. MOMENTARY DISPLAY: This area is blank under

most conditions; see Figure B.2.a. Different values may be displayed here as certain keypad keys are pressed. See Figure B.2.b; the TIG Pulser is being adjusted, so the Pulse Frequency,

2.0 Hz, is being displayed. Information in the Momentary Display lasts for five seconds after a key is pressed. Read the complete Operating Instructions section for more information on the values that appear in the Momentary Display.

E. BAR GRAPH DISPLAY: This area provides a

graphical display of values shown on the Ammeter

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3. POLARITY SWITCH: Selects DC+, AC or DCwelding polarity. DO NOT SWITCH UNDER

LOAD.

FIGURE B.3 - CASE FRONT CONTROLS

POWER

WATER

OUT

GAS

WORK

OUT

1. POWER SWITCH

2. THERMOSTATIC PROTECTION LIGHT

3. POLARITY SWITCH

ELECTRODE

L9119-1

DO NOT SWITCH

WHILE WELDING

WARNING

L9119-2

REMOTE

SQUARE WAVE TIG 255

OPERATION

B-8

HAND AND FOOT AMPTROL

ACCESSORY OPERATION

Both the Hand and Foot Amptrol work in a similar manner. They are meant to be used for remote current control when Remote Current Control is selected. The TIG 2-Step mode must be selected when using an Amptrol for remote current control. As explained below, Amptrols can also be used as arc start switches if Local Current Control is selected.

For simplicity, the following explanation will refer only to “Amptrols”, meaning both Foot and Hand models. The term “minimum” refers to a Foot pedal in the “up” position, as it would be with no foot pressure, or a Hand Amptrol in the relaxed position, with no thumb pressure. “Maximum” refers to a fully depressed Foot Amptrol, or a fully extended Hand Amptrol.

The Amptrol is capable of controlling the output current from 5 amps to the preset current displayed on the ammeter. For example, if the ammeter is preset for 200 amps and the Current Control switch is in the REMOTE position, the Amptrol, when depressed just past its minimum position, will cause the Square Wave TIG 255 to weld at 5 amps. At the Amptrols maximum position, the output would be near 200 amps.

It is important to note that, for many applications, the tungsten will not start an arc at only 5 amps. To start an arc reliably, it is important to depress the Amptrol far enough so that the machine output current is near the tungsten operating range. In the example above, a 3/32” tungsten may be used on DC- to weld near 200 amps. To start the weld, the operator may have to depress the Amptrol approximately 1/4 of the way down, or to nearly 50 amps, in order to start the arc. Merely depressing the Amptrol to its 5 amp minimum position will not start the arc.

WELDING OPERATION

TIG WELDING

Familiarize yourself with the Controls and Display Section before attempting operation of the Square Wave TIG 255.

TIG WELDING GUIDELINES

TIG welding can be done in either the TIG 2-Step or the TIG 4-Step Weld Mode. TIG 2-Step is typically used with Hand or Foot Amptrols, with Remote Current control. TIG 4-Step is typically used with Arc Start switches and Local Current Control, because it provides a very brief current upslope, and a 5-second current downslope. TIG 4-Step also functions like a trigger interlock, making it unnecessary to hold down the Arc Start switch during a weld. Read the TIG Welding Sequence of Operation sections for more details on 2-Step and 4-Step Operation.

Refer to Table B.2 for guidelines on electrode sizes, torch nozzles and shielding gas flow rates.

TABLE B.1

RECOMMENDED POLARITY SETTINGS FOR

TIG WELDING

Type of Welding

Stainless Steel

Aluminum & Magnesium

Other Metals

Electrode

Polarity

DC-

High Frequency

Setting

START

CONTINUOUS

START

If the Current Control switch is set to the LOCAL position, an Amptrol can be used as an arc start switch. Depressing the Amptrol just past minimum will cause the Amptrols built-in arc start switch to close, and backing off completely causes the built-in start switch to open. The Amptrol will have no effect on the welding current when used as an arc start switch.

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SQUARE WAVE TIG 255

B-9

OPERATION

TABLE B.2

1%, 2%

2-15 5-20

15-80

70-150

(1)

FOR TUNGSTEN ELECTRODES

AC Approximate Argon

1%, 2%

Pure

Tungsten

2-15 10-20 20-30

30-80

60-130

100-180 100-240

190-300 250-400

Thoriated Tungsten

Zirconiated Aluminum

---

5-20

20-60

60-120

100-180 160-250

200-320 290-390 340-525

3-8 (2-4) 5-10 (3-5) 5-10 (3-5)

5-10 (3-5) 13-17 (6-8)

15-23 (7-11)

21-25 (10-12) 23-27 (11-13)

28-32 (13-15)

TYPICAL CURRENT RANGES

DCEN (-) DCEP ( +)

Tungsten Electrode

Diameter

in. (mm)

.010 (.25)

0.020 (.50)

0.040 (1.0) 1/16 (1.6) 3/32 (2.4)

1/8 (3.2) 5/32 (4.0)

3/16 (4.8) 1/4 (6.4)

(1) When used with argon gas. The current ranges shown must be reduced when using argon/helium or pure helium shielding gasses. (2) Tungsten electrodes are classified as follows by the American Welding Society (AWS):

Pure . . . . . . . . . . . . . . . EWP

1% Thoriated . . . . . . . . EWTh-1

2% Thoriated . . . . . . . . EWTh-2

Though not yet recognized by the AWS, Ceriated Tungsten is now widely accepted as a substitute for 2% Thoriated Tungsten in AC and DC applications. (3) DCEP is not commonly used in these sizes. (4) TIG torch nozzle “sizes” are in multiples of 1/16ths of an inch:

#10 = 5/8 in. (16 mm) (5) TIG torch nozzles are typically made from alumina ceramic. Special applications may require lava nozzles, which are less prone to breakage, but cannot with-

stand high temperatures and high duty cycles.

1%, 2% Thoriated Tungsten

2-15 5-20

15-80

70-150

150-250 250-400

400-500 500-750

750-1000

#4 = 1/4 in. (6 mm) #5 = 5/16 in. (8 mm) #6 = 3/8 in. (10 mm) #7 = 7/16 in. (11 mm) #8 = 1/2 in. (12.5 mm)

10-20 15-30

25-40 40-55

55-80

80-125

(3) (3) (3)

Unbalanced Wave Balanced Wave

Pure

Tungsten

Thoriated Tungsten

Zirconiated

2-15 5-15

10-60

50-100

100-160 150-210

200-275 250-350 325-450

140-235 225-325

300-400 400-500 500-630

(2)

Gas Flow Rate

C.F.H. (1/min.)

Stainless

Steel

3-8 (2-4) 5-10 (3-5) 5-10 (3-5)

9-13 (4-6) 11-15 (5-7)

11-15 (5-7) 13-17 (6-8)

18-22 (8-10)

23-27(11-13)

TIG Torch

Nozzle

(4), (5)

Size

#4, #5, #6

#5, #6

#6, #7, #8

#8, #10

TIG WELDING SEQUENCE OF OPERATION (2-STEP MODE)

In TIG 2-Step Mode the welding arc is established by depressing the Arc Start Switch or Amptrol (Step 1). Output continues as long as the switch or Amptrol is depressed. Releasing the switch or Amptrol (Step 2) turns off the arc. Hence the name 2-Step Mode.

1. Connect an Arc Start Switch or an Amptrol to the Remote Receptacle.

Turn on the welder, gas supply and water supply (if so

equipped). The Control Panel Display and

red LEDS will illuminate when the power is on.

3. Select the TIG 2-Step Weld Mode.

4. Select Local (if using an Arc Start Switch) or Remote (if using an Amptrol) current control. Set the output current using the Amps Up/Down keys. The output current setting will be displayed on the Ammeter.

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5. Select Continuous High Frequency if welding with AC polarity, or Start Only High Frequency if welding with DC- polarity. High Frequency Off can be used for scratch start welding.

6. Select AC or DC- electrode polarity. See Table B.1.

7. If welding with AC polarity, select Auto Balance™. This gives the optimum ratio between cleaning and penetration, automatically adjusted for the output current. If manual adjustment of the AC Wave Balance is desired, select Manual Balance, and adjust the wave balance with the Cleaning and Penetration keys. See the Advanced Features section for more information on setting and using the AC Wave Balance.

8. Select TIG Pulser On or Off. If the TIG Pulser is on, adjust the pulse frequency with the Pulses Per Second Up/Down keys. See the Advanced Features section for more information on setting and using the TIG Pulser.

SQUARE WAVE TIG 255

12/95

OPERATION

B-10

9. Set the Afterflow time with the Seconds Up/Down keys. Afterflow time provides shielding gas flow (and cooling water, if used) after the weld. Use short Afterflow times with low currents and small tungstens, use long afterflow times at high output currents with large tungstens.

10. Press and release the Arc Start Switch, and set the gas flow meter. The welder is now ready for welding.

11. Position the tungsten electrode at the start of the weld at a 65° to 75° angle with the horizontal so that the electrode is approximately 1/8” (4mm) above the work piece. Press the Arc Start Switch. This opens the gas and water valves to automatically purge air from the hose and torch. After a 0.5 second preflow time, the high frequency becomes available to strike the arc.

12. Hold the Arc Start Switch or Amptrol down until an arc is established. If using an Amptrol, read the section on Hand and Foot Amptrol Operation. Release the Arc Start Switch or Amptrol to stop the arc and start the Afterflow timer. After the Afterflow time has expired, the gas and water valves will close. To make another weld, repeat steps 11 and 12.

5. Select Continuous High Frequency if welding with AC polarity, or Start Only High Frequency if welding with DC- polarity. High Frequency Off can be used for scratch start welding.

6. Select AC or DC- electrode polarity. See Table B.1.

9. Set the Afterflow time with the Seconds Up/Down keys. Afterflow time provides shielding gas flow (and cooling water, if used) after the weld. Use short Afterflow times with low currents and small tungstens, long afterflow times at high output currents with large tungstens.

TIG WELDING SEQUENCE OF OPERATION (4-STEP MODE)

TIG 4-Step Mode funcitons like a trigger interlock, making it unnecessary to hold down the Arc Start Switch during welding. By depressing the Arc Start Switch a first time, the arc will start at a low current (step 1). By releasing the Arc Start Switch (step 2) the output ramps up to welding current. Depressing the Arc Start Siwtch a second time (step 3) initiates a welding current downslope. Releasing the Arc Start Switch (step 4) stops the arc. Hence the name “4-Step Mode”

1. Connect an Arc Start Switch to the Remote Receptacle.

Turn the welder, gas supply and water supply (if so equipped), on. The Control Panel Display and red lights will illuminate when the power is on.

3. Select the TIG 4-Step Weld Mode.

4. Select the Local current control. Set the output current current

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using the Amps Up/Down keys. The output setting will be displayed on the Ammeter.

10. Press and release the Arc Start Switch, and set the gas flow meter. The welder is now ready for welding.

12. Hold the Arc Start Switch down until an arc is established. The arc will start at a low current value. Release the Arc Start Switch. At this point, the Square Wave TIG 255 will quickly ramp up to the welding current, and the weld will continue indefinitely. Press the Arc Start Switch a second time to initiate a 5-second downslope. The current will go down to a crater fill current that is equal to 25% of the welding current. Release the Arc Start Switch to stop the arc and start the Afterflow timer. After the Afterflow time has expired, the gas and water valves will close. To make another weld, repeat steps 11 and 12.

SQUARE WAVE TIG 255

B-11

OPERATION

ADVANCED TIG WELDING FEATURES

AC WAVE BALANCE AND AUTO BALANCE™

AC Wave Balance is a feature unique to square wave TIG power sources. It is active only in AC TIG mode. It controls the amount of positive and negative current in the AC output.

The Square Wave TIG 255 allows the operator to select Auto Balance™. This selection provides automatic adjustment of the AC Wave Balance; it is suitable for most welding conditions. Auto Balance gives the ideal amount of cleaning and penetration, based on the welding current output.

Manual adjustment of the AC Wave Balance is also possible. Select the Manual Balance key, and the Balance setting will appear in the Momentary Display. Manual Balance settings vary from +5 (maximum cleaning) to -10 (maximum penetration). A setting of 0 yields a balanced output (equal amounts of cleaning and penetration). Use the following as a guide when setting the Balance manually:

BALANCED (0): The amounts of positive and

CLEANING (+1 to +5): Provides more positive

current than negative. Since the positive current produces the “cleaning” or oxide removal on aluminum, this setting is used for welding on heavily oxidized aluminum.

PENETRATION (-1 to -10): Provides more negative

current than positive. The arc plasma will be more concentrated and more easily directed to where the heat is needed. Higher penetration settings allow a given size of tungsten to carry more current.

CAUTION: Use only the amount of cleaning required because the greater amount of positive current will heat the tungsten more and possibly cause it to melt or “spit”. Also, the arc is usually more flared and less stable with more cleaning current.

In general, use just enough “cleaning” to remove oxides and to give good wetting to the puddle.

TIG PULSER

The Square Wave TIG 255 contains a unique TIG Pulser circuit. The TIG Pulser has On/Off selections, as well as adjustments for Pulses Per Second

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negative are the same.

Up/Down. Adjustment of the pulses per second (pulse frequency), allows for control of the heat input into the work piece. This adjustment can reduce distortion and burnthrough on thin guage base metal. When the Pulser is turned On, or when the are adjusted, the pulse frequency is Momentary Display. It can be varied from 0.5 Hz to 10 Hz in 0.5 Hz increments. (One Hertz {Hz} is equivalent to one pulse per second.) The background current (the welding current at the low point of the pulse cycle) is automatically adjusted from 40% to 60% of the peak current by the Square Wave TIG 255. The duty cycle (the ratio between that time spent at the peak current vs, the time spent at the background current) is fixed at 50%.

Pulses Per Second

shown in the

AUXILIARY POWER

ALL MACHINES

The Square Wave TIG 255 provides 10 amps of 115 volt AC power at a standard NEMA 5-15R receptacle, located on the lower case back of the machine. This circuit is protected from shorts and overloading by a 10 amp circuit breaker, located next to the receptacle. The auxiliary circuit is intended for running water coolers and small power tools, whose current draw is within the 10 amp rating.

CAUTION

Note that some types of equipment, especially pumps and large motors, have starting currents which are significantly higher than their running current. These higher starting currents may cause the circuit breaker to open. If this situation occurs, the user should refrain from using the Square Wave TIG 255 auxiliary for that equipment.

___________________________________________

50/60Hz MACHINES

Square Wave TIG 255 machines rated for 50/60Hz operation provide 2 amps of 220 volt AC power at a continental European (Schuko) type receptacle, located on the lower case back of the machine. This circuit is protected from shorts and overloading by a 2 amp circuit breaker, located above the receptacle. The auxiliary circuit is intended for running water coolers whose current draw is within the 2 amp rating of the receptacle.

SQUARE WAVE TIG 255

OPERATION

CAUTION

Note that some types of equipment, especially pumps and motors, have starting currents which are significantly higher than their running currents. These higher starting currents may cause the circuit breaker to open. If this situation occurs, the user should refrain from using the Square Wave TIG 255 auxiliary for that equipment.

___________________________________________

OVERLOAD PROTECTION

This welder has thermostatic protection from excessive duty cycles, overloads, loss of cooling, and high ambient temperatures. When the welder is subjected to an overload or loss of cooling, a thermostat will open. This condition will be indicated by the illumination of the yellow Thermostatic Protection Light on the case front (see Figure A.2). Also, the Display will be blank, and all of the red Control Panel lights will be out. The fan will continue to run to cool the power source. No welding is possible until the machine is allowed to cool and the Thermostatic Protection Light goes out.

B-12

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SQUARE WAVE TIG 255

B-13

NOTES

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SQUARE WAVE TIG 255

TABLE OF CONTENTS

- ACCESSORIES SECTION -

Accessories......................................................................................................Section C

Available Option and Accessories .........................................................................C-1

Undercarriage Function .........................................................................................C-1

Installation of Field Installed Options.....................................................................C-1

Section C

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SQUARE WAVE TIG 255

C-1

ACCESSORIES

OPTIONS / ACCESSORIES

• Hand Amptrol (K812)

• Foot Amptrol (K870)

• Arc Start Switch (K814)

• Magnum Cooler Horizontal TIG Mounting Bracket (K559-2)

• Undercarriage (K932-1)

UNDERCARRIAGE FUNCTION

The Square Wave TIG 255 is designed to be used with a Lincoln K932-1 Undercarriage. Complete installation instructions are included with the K932-1 undercarriage. When the undercarriage is properly installed, the Square Wave TIG 255 lift bail is nonfunctional. Do not attempt to lift the power source with the undercarriage attached. The undercarriage is designed for hand moving only; mechanized towing can lead to injury and/or damage to the Square Wave TIG 255.

INSTALLATION OF FIELD INSTALLED OPTIONS

Instructions for connecting the K932-1 Undercarriage and the K559-2 Magnum Cooler Horizontal TIG Mounting Bracket are included with those accessories.

Installation of the K812 Hand Amptrol, the K814 Arc Start Switch and K870 Foot Amptrol are as follows:

Lift the Output Cover Door (if so equipped) on the Square Wave TIG 255. Feed the cable up through the strain relief holes in the base, and connect the 6-pin MS-type (Amphenol) connector to the Remote Receptacle (See Figure A.2). Secure with the threaded collar.

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SQUARE WAVE TIG 255

TABLE OF CONTENTS

- MAINTENANCE SECTION -

Maintenance.....................................................................................................Section D

Safety Precautions.................................................................................................D-1

Routine and Periodic Maintenance........................................................................D-1

General Assembly Exploded View.........................................................................D-2

Section D

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SQUARE WAVE TIG 255

D-1

MAINTENANCE

SAFETY PRECAUTIONS

WARNING

ELECTRIC SHOCK can kill.

• Only qualified personnel should perform this maintenance.

• Turn the input power OFF at the disconnect switch or fuse box before working on this equipment.

• Do not touch electrically hot parts.

ROUTINE AND PERIODIC MAINTENANCE

WARNING

To avoid receiving a high frequency shock, keep the TIG torch and cables in good condition.

1. Disconnect power supply lines to machine before performing periodic maintenance.

2. Periodically clean the inside of the machine with a low pressure air system. Be sure to clean the following components thoroughly. See Figure D.1 for location of those components.

• Main Transformer

• Output Terminals

• Polarity Switch

• Rectifier Assembly

• Control Box Assembly

• Spark Gap Assembly

• Protection PC Board -

3. Inspect welder output and control cables for fraying, cuts, and bare spots.

4. Keep TIG torch and cables in good condition.

(Mounted to rear of control box assembly)

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SQUARE WAVE TIG 255

5. The fan motor has sealed ball bearings which require no maintenance.

6. Inspect spark gap spacing at regular intervals to maintain a 0.015 in (0.4mm) gap. (Smallest possible air gap consistent with good welding is desirable to minimize R.F.I. problems.) Dressing or any refinishing of the spark gap contacts is not recommended. If the contact surfaces become irregular or completely eroded, replacement of both electrodes is recommended.

+ 70 hidden pages

Square TIG 255 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

SAFETY