Thermal Arc 400MSTW CC User manual

A THERMADYNE®Company
INVERTER
ARC
WELDER
MODEL 400MSTW CC/CV
• STICK
•TIG - Lift Start
•MIG - Short Circuit
- Globular
- Spray
OPERATING MANUAL
July 1, 2001 Manual No. 430429-490

TABLE OF CONTENTS
1.0 GENERAL INFORMATION ...................................................2
1.01 Notes, Cautions and Warnings ...............................................2
1.02 Important Safety Precautions .................................................3
1.03 Publications ............................................................................6
1.04 Note, Attention et Avertissemen ............................................7
1.05 Precautions De Securite Importantes .....................................8
1.06 Documents De Reference .....................................................11
1.07 Statement of Warranty .............................................................12
2.0 INTRODUCTION AND DESCRIPTION .............................14
2.01 Description ...........................................................................14
2.02 Functional Block Diagrams .................................................15
2.03 Transporting Methods ..........................................................16
2.04 Electrical Input Connections ................................................16
2.05 Specifications .......................................................................19
2.06 Duty Cycle ...........................................................................20
3.0 OPERATOR CONTROLS .....................................................21
3.01 400MSTW Front & Rear Panels ..........................................21
3.02 Setup for Operation ..............................................................23
3.02.1 Selection of Welding Mode ...........................................23
3.02.2 Shielded Metal Arc Welding (SMAW) .........................25
3.02.3 Gas Tungsten Arc Welding (GTAW) Lift Start .............28
3.02.4 Gas Tungsten Arc Welding (GTAW) Scratch Start .......33
3.02.5 Carbon Arc Cutting (CAC) ...........................................38
3.02.6 Gas Metal Arc Welding (GTAW) ..................................40
3.02.7 Shutdown Operation ......................................................43
3.02.8 Electrode Selection Guide .............................................44
3.02.9 Welding Cable Selection Guide ....................................44
4.0 SAVE/LOAD OPERATION ...................................................45
4.01 Outline ......................................................................…..........45
4.02 SAVE Operation ......................................................................46
4.03 LOAD Operation .....................................................................47
4.04 SAVE/LOAD Data ..................................................................48
4.05 Initial Parameter Settings ........................................................50

5.0 BASIC TROUBLESHOOTING .............................................51
5.01 Common Welding Operation Faults .......................................51
5.02 Specific Problems ................................................................51
5.03 Error Code List ....................................................................54
6.0 PARTS LIST ............................................................................55
APPENDIX A – REMOTE 14-Pin CONNECTIONS ................59
APPENDIX B - ACCESORIES ....................................................60
APPENDIX C - INTERCONNECTION DIAGRAMS ..............61

MANUAL 430429-490 1 GENERAL
WARNING Read and understand this entire Operating Manual and your employer's safety
practices before installing, operating, or servicing the equipment.
WARNING While the information contained in this Operating Manual represents
our best judgement, Thermal Arc INC. assumes no
liability for its use.
Thermal Arc Models 400MSTW CC/CV Welder
Operating Manual Number 430429-490
Published by:
Thermal Arc INC.
2200 CORPORATE DRIVE
TROY, OHIO 45373-1085, USA
[phone]
Copyright 2001 by
Thermal Arc INC.
All rights reserved.
Reproduction of this work, in whole or in part, without written
permission of the publisher is prohibited.
The publisher does not assume and hereby disclaims any liability to any
party for any loss or damage caused by any error or omission in this
Operating Manual, whether such error results from negligence,
accident, or any other cause.
Printed in the United States of America
July 1, 2001

GENERAL 2 MANUAL 430429-490
1.0 GENERAL INFORMATION
1.01 NOTES, CAUTIONS AND WARNINGS
Throughout this manual, notes, cautions, and warnings are used to
highlight important information. These highlights are categorized as
follows:
NOTE An operation, procedure, or background information which requires
additional emphasis or is helpful in efficient operation of the system.
CAUTION A procedure which, if not properly followed, may cause damage to the
equipment.
WARNING A procedure which, if not properly followed, may cause injury to the
operator or others in the operating area.

MANUAL 430429-490 3 GENERAL
WARNING
1.02 IMPORTANT SAFETY PRECAUTIONS
OPERATION AND MAINTENANCE OF PLASMA ARC EQUIPMENT
CAN BE DANGEROUS AND HAZARDOUS TO YOUR HEALTH.
To prevent possible injury, read, understand and follow all warnings, safety precautions and
instructions before using the equipment. Call 1-937-440-0100 or your local distributor if you have any
questions.
GASES AND FUMES Gases and fumes produced during the plasma welding process can be
dangerous and hazardous to your health.
• Keep all fumes and gases from the breathing area. Keep your head out
of the welding fume plume.
• Use an air-supplied respirator if ventilation is not adequate to remove
all fumes and gases.
• The kinds of fumes and gases from the plasma arc depend on the kind
of metal being used, coatings on the metal, and the different
processes. You must be very careful when cutting or welding any
metals which may contain one or more of the following:
Antimony Chromium Mercury
Arsenic Cobalt Nickel
Barium Copper Selenium
Beryllium Lead Silver
Cadmium Manganese Vanadium
• Always read the Material Safety Data Sheets (MSDS) that should be
supplied with the material you are using. These MSDS’s will give you
the information regarding the kind and mount of fumes and gases
that may be dangerous to your health.
• For information on how to test for fumes and gases in your
workplace, refer to item I in the Publications Section in this manual.
Use special equipment, such as water or down draft cutting tables, to
capture fumes and gases.
• Do not use the plasma torch in an area where combustible or
explosive gases or materials are located.
• Phosgene, a toxic gas, is generated from the vapors of chlorinated
solvents and cleansers. Remove all sources of these vapors.
WARNING:
This product, when used for welding or cutting, produces
fumes or gases which contain chemicals known to the State of California
to cause birth detects and, in some cases, cancer.
(California Health & Safety Code Section 25249.5 et seq.)

GENERAL 4 MANUAL 430429-490
IMPORTANT SAFETY PRECAUTIONS (CONTINUED)
ELECTRIC SHOCK Electric Shock can injure or kill. The plasma arc process uses and
produces high voltage electrical energy. This electric energy can cause
severe or fatal shock to the operator or others in the workplace.
• Never touch any parts that are electrically "live" or "hot."
• Wear dry gloves and clothing. Insulate yourself from the work piece
or other parts of the welding circuit.
• Repair or replace all worn or damaged parts.
• Extra care must be taken when the workplace is moist or damp.
• Install and maintain equipment according to NEC code, refer to item 4
in the Publications section of this manual.
• Disconnect power source before performing any service or repairs.
• Read and follow all the instructions in the Operating Manual.
FIRE AND EXPLOSION Fire and explosion can be caused by hot slag, sparks, or the plasma arc.
• Be sure there is no combustible or flammable material in the
workplace. Any material that cannot be removed must be protected.
• Ventilate all flammable or explosive vapors from the workplace.
• Do not cut or weld on containers that may have held combustibles.
• Provide a fire watch when working in an area where fire hazards may
exist.
• Hydrogen gas may be formed and trapped under aluminum
workpieces when they are cut underwater or while using a water
table. DO NOT cut aluminum alloys underwater or on a water table
unless the hydrogen gas can be eliminated or dissipated. Trapped
hydrogen gas that is ignited will cause an explosion.
NOISE Noise can cause permanent hearing loss. Plasma arc processes can cause
noise levels to exceed safe limits. You must protect your ears from loud
noise to prevent permanent loss of hearing.
• To protect your hearing from loud noise, wear protective ear plugs
and/or ear muffs Protect others in the workplace.
• Noise levels should be measured to be sure the decibels (sound) do
not exceed safe levels.
• For information on how to test for noise, see item 1 in the Publications
section of this manual.

MANUAL 430429-490 5 GENERAL
IMPORTANT SAFETY PRECAUTIONS (CONTINUED)
PLASMA ARC RAYS Plasma Arc Rays can injure your eyes and burn your skin. The plasma
arc process produces very bright ultra violet and infra red light. These
arc rays will damage your eyes and bum your skin if you are not
properly protected
• To protect your eyes, always wear a welding helmet or shield. Also
always wear safety glasses with side shields, goggles or other
protective eye wear.
• Wear welding gloves and suitable clothing to protect your skin from
the arc rays and sparks.
• Keep helmet and safety glasses in good condition. Replace lenses
when cracked, chipped or dirty.
• Protect others in the work area from the arc rays. Use protective
booths, screens or shields.
• Use the shade of lens as recommended in the Operating Manual.

GENERAL 6 MANUAL 430429-490
1.03 PUBLICATIONS
Refer to the following standards or their latest revisions for more information:
1. OSHA, SAFETY AND HEALTH STANDARDS, 29CFR 1910, obtainable from the Superintendent
of Documents, U.S. Government Printing Office, Washington, D.C. 20402
2. ANSI Standard Z49.1, SAFETY IN WELDING AND CUTTING, obtainable from the American
Welding Society, 550 N.W. LeJeune Rd, Miami, FL 33126
3. NIOSH, SAFETYAND HEALTH IN ARC WELDING AND GASWELDING AND CUTTING,
obtainable from the Superintendent of Documents, U.S. Government Printing Office,
Washington, D.C. 20402
4. ANSI Standard Z87.1, SAFE PRACTICES FOR OCCUPATION AND EDUCATIONAL EYE AND
FACE PROTECTION, obtainable from American National Standards Institute, 1430 Broadway,
New York, NY 10018
5. ANSI Standard Z41.1, STANDARD FOR MEN'S SAFETY-TOE FOOTWEAR, obtainable from the
American National Standards Institute, 1430 Broadway, New York, NY 10018
6. ANSI Standard Z49.2, FIRE PREVENTION IN THE USE OF CUTTING AND WELDING
PROCESSES, obtainable from American National Standards Institute, 1430 Broadway, New York,
NY 10018
7. AWS Standard A6.0, WELDING AND CUTTING CONTAINERS WHICH HAVE HELD
COMBUSTIBLES, obtainable from American Welding Society, 550 N.W. LeJeune Rd, Miami, FL
331 26
8. NFPA Standard 51, OXYGEN-FUEL GAS SYSTEMS FOR WELDING, CUTTING AND ALLIED
PROCESSES, obtainable from the National Fire Protection Association, Batterymarch Park,
Quincy, MA 02269
9. NFPA Standard 70, NATIONAL ELECTRICAL CODE, obtainable from the National Fire
Protection Association, Batterymarch Park, Quincy, MA 02269
10. NFPA Standard 5lB, CUTTING AND WELDING PROCESSES, obtainable from the National Fire
Protection Association, Batterymarch Park, Quincy, MA 02269
11. CGA Pamphlet P-l, SAFE HANDLING OF COMPRESSED GASES IN CYLINDERS, obtainable
from the Compressed Gas Association, 1235 Jefferson Davis Highway, Suite 501, Arlington, VA 22202
12. CSA Standard Wl17.2, CODE FOR SAFETY IN WELDING AND CUTTING, obtainable from the
Canadian Standards Association, Standards Sales, 178 Rexdale Boulevard, Rexdale, Ontario,
Canada M9W 1R3
13. NWSA booklet, WELDING SAFETY BIBLIOGRAPHY obtainable from the National Welding
Supply Association, 1900 Arch Street, Philadelphia, PA 19103
14. American Welding Society Standard AWSF4.1, RECOMMENDED SAFE PRACTICES FOR THE
PREPARATION FOR WELDING AND CUTTING OF CONTAINERS AND PIPING THAT HAVE
HELD HAZARDOUS SUBSTANCES, obtainable from the American Welding Society, 550 N.W.
LeJeune Rd, Miami, FL 33126
15. ANSI Standard Z88.2, PRACTICE FOR RESPIRATORY PROTECTION, obtainable from
American National Standards Institute, 1430 Broadway, New York, NY 10018

MANUAL 430429-490 7 GENERAL
1.04 NOTE, ATTENTION ET AVERTISSEMENT
Dans ce manuel, les mots "note," "attention," et "avertissement" sont
utilisés pour mettre en relief des informations à caractère important. Ces
mises en relief sont classifiées comme suit:
NOTET oute opération, procédure ou renseignement général sur lequel il
importe d'insister davantage ou qui contribue à l'efficacité de
fonctionnement du système.
ATTENTION Toute procédure pouvant résulter l'endommagement du matériel en cas
de non-respect de la procédure en question.
AVERTISSEMENT Toute procédure pouvant provoquer des blessures de l'opérateur
ou des autres personnes se trouvant dans la zone de travail en cas de
non-respect de la procédure en question

GENERAL 8 MANUAL 430429-490
AVERTISSEMENT
1.05 PRECAUTIONS DE SECURITE IMPORTANTES
L'OPÉRATION ET LA MAINTENANCE DU MATÉRIEL DE SOUDAGE
À L'ARC AU JET DE PLASMA PEUVENT PRÉSENTER
DES RISQUES ET DES DANGERS DE SANTÉ.
Il aut communiquer aux opérateurs et au personnel TOUS les dangers possibles. Afin d'éviter les
blessures possibles, lisez, comprenez et suivez tous les avertissements, toutes les précautions de
sécurité et toutes les consignes avant d'utiliser le matériel. Composez le 1-937-440-0100 ou votre
distributeur local si vous avez des questions.
FUMÉE et GAZ La fumée et les gaz produits par le procédé de jet de plasma peuvent
présenter des risques et des dangers de santé.
• Eloignez toute fumée et gaz de votre zone de respiration.. Gardez votre
tête hors de la plume de fumée provenant du chalumeau.
• Utilisez un appareil respiratoire à alimentation en air si l'aération
foumie ne permet pas d'éliminer la fumée et les gaz.
• Les sortes de gaz et de fumée provenant de l'arc de plasma dépendent
du genre de métaI utillsé, des revêtements se trouvant sur le métal et
des différents procédés. Vous devez prendre soin lorsque vous coupez
ou soudez tout métal pouvant contenir un ou plusieurs des éléments
suivants:
antimoine cadmium mercure
argent chrome nickel
arsenic cobalt plomb
baryum cuivre sélénium
béryllium manganèse vanadium
• Lisez toujours les fiches de donn~es sur la sécurité des matières (sigle
américain "MSDS"); celles-ci devraient être foumies avec le matériel
que vous utilisez. Les MSDS contiennent des renseignements quant à
la quantité et la nature de la fumée et des gaz pouvant poser des
dangers de santé.
• Pour des informations sur la manière de tester la fumée et les gaz de
votre lieu de travail, consultez lparticle 1 et les documents cités à la
page 11.
• Utilisez un équipement spécial tel que des tables de coupe á débit
d'eau ou à courant descendant pour capter la fumée et les gaz.
• N'utilisez pas le chalumeau au jet de plasma dans une zone où se
trouvent des matières ou des gaz combustibles ou explosifs.
• Le phosgène, un gaz toxique, est généré par la fumée provenant des
solrants et des produits de nettoyage chlorés. Eliminez toute source
de telle fumée.

MANUAL 430429-490 9 GENERAL
PRECAUTIONS DE SECURITE IMPORTANTES
CHOC ELECTRIQUE Les chocs électriques peuvent blesser ou même tuer. Le procédé au jet
de plasma requiert et produit de l'énergie electrique haute tension. Cette
énergie électrique peut produire des chocs graves, voire mortels, pour
l'opérateur et les autres persormes sur le lieu de travail.
• Ne touchez jamais une pièce "sous tension" ou "vive"; portez des
gants et des vêtements secs. Isolez-vous de la pièce de travail ou des
autres parties du circuit de soudage.
• Réparez ou remplacez toute pièce usée ou endommagée.
• Prenez des soins particuliers lorsque la zone de travail est humide ou
moire.
• Montez et maintenez le matériel conformément au Code électrique
national des Etats-Unis. (Voir la page 6, article 9.)
• Débranchez l'alimentation électrique avant tout travail d'entretien ou
de réparation.
• Lisez et respectez toutes les consignes du Manuel de consignes.
INCENDIE ET
EXPLOSION Les incendies et les explosions peuvent résulter des scories chaudes, des
étincelles ou de l'arc de plasma. Le procédé à l'arc de plasma prodult du
métal, des étincelles, des scories chaudes pouvant mettre le feu aux
matières combustibles ou provoquer l'explosion de fumées
inflammables.
• Soyez certain qu'aucune matière combustible ou inflammable ne se
trouve sur le lieu de travail. Protégez toute telle matière qu'il est
impossible de retirer de la zone de travail.
• Procurez une bonne aération de toutes les fumées inflammables ou
explosives.
• Ne coupez pas et ne soudez pas les conteneurs ayant pu renfermer des
matières combustibles.
• Prévoyez une veille d'incendie lors de tout travail dans une zone
présentant des dangers d'incendie.
• Le gas hydrogène peut se former ou s'accumuler sous les pièces de
travail en aluminium lors'quelles sont coupeés sous l'eau ou sur une
table d'eau. NE PAS couper les aliiages en aluminium sous l'eau ou
sur une table d'eau h mains que le gas hydrogène peut s'échapper ou
se dissiper. Le gas hydrogène accumulé explosera si enflammé.

GENERAL 10 MANUAL 430429-490
PRECAUTIONS DE SECURITE IMPORTANTES
RAYONS D'ARC
DE PLASMA Les rayons provenant de l'arc de plasma peuvent blesser vos yeux et
brûler votre peau. Le procédé à l'rarc de plasma produit une lumière
in&a-rouge et des rayons ultra-violets très forts. Ces rayons d'arc
nuiront à vos yeux et brûleront votre peau si vous ne vous protégez pas
correctement.
• Pour protéger vos yeux, portez toujours un casque ou un écran de
soudeur. Fortez toujours des lunettes de sécurité munies de parois
latérales ou des lunettes de protection ou une autre sorte de protection
oculaire.
• Portez des gants de soudeur et un vêtement protecteur approprié
pour protéger votre peau contre les étincelles et les rayons de l'arc.
• Maintenez votre casque et vos lunettes de protection en bon état.
Remplacez toute lentille sale ou comportant fissure ou rognure.
• Protégez les autres personnes se trouvant sur la zone de travail contre
les rayons de l'arc en foumissant des cablnes ou des écrans de
protection.
• Respectez le teint de lentille recommandé dans le manuel de
consignes.
BRUIT Le bruit peut provoquer une perte permanente de l'ouYe. Les procédés
de soudage à l'arc de plasma peuvent provoquer des niveaux sonores
supérieurs aux limites normalement acceptables. Vous dúvez vous
protéger les oreilles contre les bruits forts afin d'éviter une perte
permanente de rouïe.
• Pour protéger votre ouïe contre les bruits forts, portez des tampons
protecteurs et/ou des protections auriculaires. Protégez également les
autres personnes se trouvant sur le lieu de travail.
• Il faut mesurer les niveaux sonores afin d'assurer que les d~cibels (le
bruit) ne dépassent pas les niveaux sûrs.
• Four des renseignements sur la manière de tester le bruit, consultez
l'article 1, page 11.

MANUAL 430429-490 11 GENERAL
1.06 DOCUMENTS DE REFERENCE
Consultez les normes suivantes ou les révisions les plus récentes ayant été faites à celles-ci pour de plus
ampies renseignements:
1. OSHA, NORMES DE SÉCURITÉ DU TRAVAIL ET DE PROTECTION DE LA SANTÉ, 29CFR
1910, disponible auprès du Superintendent of Documents, U.S. Government Printing Office,
Washington, D.C. 20402
2. Norme ANSI Z49.1, LA SÉCURITÉ DES OPÉRATIONS DE COUPE ET DE SOUDAGE,
disponible auprés de la Société Américaine de Soudage (American Welding Society), 550 N.W.
LeJeune Rd., Miami, FL 33126
3. NIOSH, LA SÉCURITÉ ET LA SANTÉ LOPS DES OPÉRATIONS DE COUPE ET DE SOLIDAGE
À U´ARC ET AU GAZ, disponible auprès du Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402
4. Norme ANSI Z87.1, PRATIQUES SURES POUR LA PROTECTION DES YEUX ET DU VISAGE
AU TRAVAIL ET DANS LES ECOLES, disponible de l'Institut Américain des Normes Nationales
(American National Standards Institute), 1430 Broadway, New York, NY 10018
5. Norme ANSI Z41.1, NORMES POUR LES CHAUSSURES PROTECTRICES, disponible auprès de
l'American National Standards Institute, 1430 Broadway, New York, NY 10018
6. Norme ANSI Z49.2, PRÉVENTION DES INCENT)IES LOPS DE L'EMPLOI DE PROCÉDÉS DE
COUPE ET DE SOUDAGE, disponible auprès de l'American National Standards Institute, 1430
Broadway, New York, NY 10018
7. Norme A6.0 de l'Association Américaine du Soudage (AWS), LE SOLIDAGE ET LA COUPE DE
CONTENEURS AYANT RENTERMÉ DES PRODUITS COMBUSTIBLES, disponible auprés de la
American Welding Society, 550 N.W. LeJeune Rd., Miami, FL 33126
8. Norme 51 de l'Assoclahon Améncaine pour la Protechon contre les Incendms (NFPA), LES
SYSTEMES À GAZ AVEC ALIMENTATION EN OXYGENE POUR LE SOUDAGE, LA COUPE
ET LES PROCÉDIÉS ASSOCIÉS, disponible auprès de la National Fire Protection Association,
Batterymarch Park, Quincy, MA 02269
9. Norme 70 de la NFPA, CODE ELECTRIQUE NATIONAL, disponible auprès de la National Fire
Protection Association, Batterymarch Park, Quincy, MA 02269
10. Norme 51B de la NFPA, LES PROCÉDÉS DE COUPE ET DE SOUDAGE, disponible auprès de la
National Fire Protection Association, Batterymarch Park, Quincy, MA 02269
11. Brochure GCA P-l, LA MANIPULATION SANS RISQUE DES GAZ COMPRIMÉS EN
CYLINDRES, disponible auprès de l'Association des Gaz Comprimés (Compressed Gas
Association), 1235 JeffersonDavis Highway, Suite 501, Arlington, VA 22202
12. Norme CSA W117.2, CODE DE SÉCURITÉ POUR LE SOUDAGE ET LA COUPE, disponible
auprès de l'Association des Normes Canadiennes, Standards Sales, 178 Rexdale Boulevard,
Rexdale, Ontario, Canada, M9W 1R3
13. ivret NWSA, BIBLIOGRAPHIE SUR LA SÉCURITÉ DU SOUDAGE, disponible auprès de
l'Association Nationale de Fournitures de Soudage (National Welding Supply Association), 1900
Arch Street, Philadelphia, PA 19103
14. Norme AWSF4.1 de l'Association Améncame de,Soudage, RECOMMANDATIONS DE
PRATIQUES SURES POUR LA PREPARATION À LA COUPE ET AU SOUDAGE DE
CONTENEURS ET TUYAUX AYANT RENFERMÉ DES PRODUITS DANGEREUX, disponible
auprès de la American Welding Society, 550 N.W. LeJeune Rd., Miami, FL 33126
15. Norme ANSI Z88.2, PRATIQUES DE PROTECTION RESPIRATOIRE, disponible auprès de
l'American National Standards Institute, 1430 Broadway, New York, NY 10018

GENERAL 12 MANUAL 430429-490
1.07 STATEMENT OF WARRANTY
LIMITED WARRANTY: Thermal Arc®, Inc., A Thermadyne Company, hereafter, “Thermal Arc” warrants to customers of
its authorized distributors hereafter “Thermal; Arc” that its products will be free of defects in workmanship or material.
Should any failure to conform to this warranty appear within the time period applicable to the Thermal Arc products as stated
below, Thermal Arc shall, upon notification thereof and substantiation that the product has been stored, installed, operated,
and maintained in accordance with Thermal Arc’s specifications, instructions, recommendations and recognized standard
industry practice, and not subject to misuse, repair, neglect, alteration, or accident, correct such defects by suitable repair or
replacement, at Thermal Arc’s sole option, of any components or parts of the product determined by Thermal Arc to be
defective.
THERMAL ARC MAKES NO OTHER WARRANTY, EXPRESS OR IMPLIED. THIS WARRANTY IS
EXCLUSIVE AND IN LIEU OF ALL OTHERS, INCLUDING, BUT NOT LIMITED TO ANY WARRANTY OF
MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE.
LIMITATION OF LIABILITY: Thermal Arc shall not under any circumstances be liable for special, indirect or
consequential damages, such as, but not limited to, lost profits and business interruption. The remedies of the Purchaser set
forth herein are exclusive and the liability of Thermal Arc with respect to any contract, or anything done in connection
therewith such as the performance or breach thereof, or from the manufacture, sale, delivery, resale, or use of any goods
covered by or furnished by Thermal Arc whether arising out of contract, negligence, strict tort, or under any warranty, or
otherwise, shall not, except as expressly provided herein, exceed the price of the goods upon which such liability is based. No
employee, agent, or representative of Thermal Arc is authorized to change this warranty in any way or grant any other
warranty.
PURCHASER'S RIGHTS UNDER THIS WARRANTY ARE VOID IF REPLACEMENT PARTS OR
ACCESSORIES ARE USED WHICH IN THERMAL ARC’S SOLE JUDGEMENT MAY IMPAIR THE SAFETY OR
PERFORMANCE OF ANY THERMAL ARC PRODUCT.
PURCHASER'S RIGHTS UNDER THIS WARRANTY ARE VOID IF THE PRODUCT IS SOLD TO PURCHASER
BY NON-AUTHORIZED PERSONS.
The warranty is effective for the time stated below beginning on the date that the authorized distributor delivers the products to
the Purchaser. Notwithstanding the foregoing, in no event shall the warranty period extend more than the time stated plus one
year from the date Thermal Arc delivered the product to the authorized distributor.
ALL OTHER P-WEE, PRO-LITES
POWER SUPPLIES POWER SUPPLIES PRO-PLUS, PRO-WAVE LABOR
MAIN POWER MAGNETICS (STATIC & ROTATING) 3 YEARS 2 YEAR 1 YEAR
ORIGINAL MAIN POWER RECTIFIER 3 YEARS 2 YEAR 1 YEAR
CONTROL PC BOARD 3 YEARS 2 YEAR 1 YEAR
ALL OTHER CIRCUITS AND COMPONENTS INCLUDING 1 YEAR 1 YEAR 1 YEAR
BUT NOT LIMITED TO, CONTACTORS, RELAYS,
SOLENOIDS, PUMPS, POWER SWITCHING SEMI-CONDUCTORS
ENGINES: ENGINES ARE NOT WARRANTED BY THERMAL ARC, ALTHOUGH MOST ARE WARRANTED
BY THE ENGINE MANUFACTURER, SEE THE ENGINE MANUFACTURES WARRANTY FOR DETAILS.
CONSOLES, CONTROL EQUIPMENT, HEAT 1 YEAR 1 YEAR 1 YEAR
EXCHANGES, AND ACCESSORY EQUIPMENT
TORCH AND LEADS 180 DAYS 180 DAYS 180DAYS
REPAIR/REPLACEMENT PARTS 90 DAYS 90 DAYS 90 DAYS
Warranty repairs or replacement claims under this limited warranty must be submitted to Thermal Arc by an authorized
Thermal Arc repair facility within thirty (30) days of purchaser’s notice of any Warranty Claim. No transportation costs of
any kind will be paid under this warranty. Transportation charges to send products to an authorized warranty repair facility
shall be the responsibility of the Purchaser. All returned goods shall be at the Purchaser’s risk and expense. This warranty
supersedes all previous Thermal Arc warranties.
Thermal Arc® is a Registered Trademark of Thermadyne Industries Inc.
Effective January 1, 2001

MANUAL 430429-490 13 INTRODUCTION
PAGE LEFT INTENTIONALY BLANK

14 MANUAL 430429-490
2.0 INTRODUCTION AND DESCRIPTION
2.01 Description
The Thermal Arc™ Model 400MSTW is a single or three-phase DC arc
welding power sources with Constant Current (CC) and Constant Voltage (CV)
output characteristics.
This unit is designed for use with Shielded Metal Arc Welding (SMAW), Gas
Metal Arc Welding (GMAW), and Gas Tungsten Arc Welding (GTAW)
processes. A digital amperage / voltage meter is standard.
Figure 1. 400MSTW model Volt-Ampere curve
NOTE Volt-Ampere curves show the maximum Voltage and Amperage output
capabilities of the welding power source . Curves of other settings will fall
between the curves shown.
5 150 400 420
19V
OCV Lessthan 80V
Arc Characterristics
"CURRENT" Control
25 150 420
19V
OCV Lessthan 80V
36V
OutputCurrent Limit 420A

MANUAL 430429-490 15 OPERATOR CONTROLS
2.02 Functional Block Diagrams
Figure 2 illustrates the functional block diagram of the 400MSTW power supply.
Figure 2. 400MSTW Model functional block diagram
Main
Circuit
Breaker
Input
Diode Inrush Current Suppressor Capacitor IGBTInverter Module
Thermal
Sensor
Output
Trans formers Output Diode Trans forme r
(CT-1)
Current Coupling
Coil
+
Control
Trans former
Drive Circuit
Voltage Sensor
DC Power
Supply for
Control Circuit
To each control circuit
+12VDC +20VDC
+24VDC +5VDC
Trouble
Sensing
Circuit
Sequence
Control
Reference
Adjustments &
Control Switches
Torch Control
Connection
(CON1)
Current
Adjustment
Circuit
Output
Voltage
Sensor
Primary
Current
Sensor
Thermal
Sensor
Circuit
Lift Tig Mode
Output Short
Sensing Circuit
Output
Inductor
-
-
+
+
Input
Power

OPERATOR CONTROLS 16 MANUAL 430429-490
2.03 Transporting Methods
These units are equipped with a handle for carrying purposes.
WARNING ELECTRIC SHOCK can kill.
• DO NOT TOUCH live electrical parts.
• Disconnect input power conductors from de-energized supply line
before moving welding power source.
WARNING FALLING EQUIPMENT can cause serious personal injury and equipment
damage.
• Lift unit with handle or shoulder strap on top of case.
• Use hand cart or similar device of adequate capacity.
• If using a fork lift vehicle, place and secure unit on a proper skid
before transporting.
2.04 Electrical Input Connections
WARNING ELECTRIC SHOCK can kill; SIGNIFICANT DC VOLTAGE is present after
removal of input power.
• DO NOT TOUCH live electrical parts.
• SHUT DOWN welding power source, disconnect input power
employing lockout/tagging procedures. Lockout/tagging
procedures consist of padlocking line disconnect switch in open
position, removing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting device.
Electrical Input Operate the welding power source from a single-phase 50/60 Hz, AC
Requirements power supply. The input voltage must match one of the electrical input
voltages shown on the input data label on the unit nameplate. Contact the
local electric utility for information about the type of electrical service
available, how proper connections should be made, and inspection
required.
The line disconnect switch provides a safe and convenient means to
completely remove all electrical power from the welding power supply
whenever necessary to inspect or service the unit.
NOTE These units are equipped with a three-conductor with earth power cable that
is connected at the welding power source end for single-phase and three-phase
electrical input power.