Arc Welding
Machines and Accessories
2020
© 2020 by
Pacific Vocational College Ltd.
Burnaby, British Columbia
All rights reserved. No part of this manual may be reproduced in any form, without
permission in writing from Pacific Vocational College Ltd.
Table of Figures
Figure 1 - AC Transformer Welder and DC Motor Generator Welder .......................................................... 1
Figure 2 - AC and DC Welders ....................................................................................................................... 3
Figure 3 - Welding Accessories ..................................................................................................................... 4
Machines and Accessories, Arc Welding
© Pacific Vocational College, 2020
i
Arc Welding Machines and Accessories
The success of welding as a metal-joining process rests on the fact that a good weld
with common steels is as strong as or stronger than the plate in which it is made. This
success has been established through the years by the gradual development of welding
machines, accessories and electrodes that satisfy the complex requirements of the arc
process.
Arc welding requires a continuous supply of electric current, sufficient in amount
(amperes) and of proper voltage to maintain an arc. This current may be either
alternating (AC) or direct (DC), but it must be provided through a source that can be
adjusted.
Several different types of welding machines are available for producing satisfactory
welding current. Alternating current is produced in special welding transformers. Direct
current is produced in either electric motor-generator sets, rectifier sets, or enginedriven generator sets. Combination welders, producing both AC and DC are basically
transformer-rectifier sets.
Figure 1 - AC Transformer Welder and DC Motor Generator Welder
Welding machines are rated according to their current output, voltage and duty cycle
and are available in a wide range of sizes. The National Electrical Manufacturers
Association establishes minimum standards for rating welding machines and most
manufacturers follow these standards. The standards are established on a conservative
basis, requiring a rating well below the maximum overload capacity of the machine so
that it will provide safe operation efficiently over a long period of time. Ratings are given
with a percentage duty cycle.
The duty cycle of a welder is the percentage of a ten-minute period that a welder can
operate at a given output current setting. If a welder is rated 300 amperes at a 60% duty
cycle, it means that the machine can be operated safely at 300 amperes welding current
for 6 out of every 10 minutes. If this duty cycle is reduced in actual operation, the
Machines and Accessories, Arc Welding
© Pacific Vocational College, 2020
1
maximum permissible current is increased. At 35% duty cycle, a 300-ampere machine
could be operated at 375 amperes.
Transformer welders are available for operation on single-phase power lines. They
transform high-voltage-low-amperage input current to a low-voltage-high-amperage
welding current. Current controls must be provided on the transformer to permit its use
for welding. There are three basically different types of current-control systems. One
type of current control is the movable iron core operated by a crank. This is a
continuous current control. A second type is the solid-state electrical circuitry, which is
also continuous control. The other is a tap-type control, in which the electrode leads are
plugged into different jacks, or taps, to obtain different settings. All accurately regulate
the welding current, with either, the operator can select just the welding heat he/she
wants.
Rectifier sets are basically three-phase or single-phase transformers to which have
been added silicon or other rectifiers to change the output current from alternating to
direct current. These machines have the basic control and output characteristics that
are inherent in transformers.
Direct-current generators use an armature rotating in an electrical field. Current is
generated in the armature and is taken off for the use through a commutator. The
armature is rotated either by an electric motor or an internal combustion engine. When
generators are engine-operated, they are independent of electric power and may be
operated in the field where power is not available.
Combination welders, producing both AC and DC current, are the most versatile of all
types of welders. They are basically a single-phase transformer and a rectifier from
which, by turning a switch, either alternating or direct welding current is available. With
DC, polarity can be switched to either electrode positive or electrode negative.
Several factors must be evaluated when selecting a welding power source. The size or
rated output of a machine required for a given job depends on the thickness of the metal
to be welded and the amount of welding to be done. There is no need to buy more
capacity than will be required by the job. Be sure, however, to check the duty cycle.
Machines with a low duty cycle should be used only for maintenance or intermittent
welding. 60% duty cycle is normal for industrial welders. Continued operation of a
machine beyond its rated capacity will shorten its service life.
Machines and Accessories, Arc Welding
© Pacific Vocational College, 2020
2
Figure 2 – AC and DC Welders
In selecting the welder, another consideration is the utility power available. Fortunately,
welders are made to be used with all types of power, but certain types are available for
only given conditions. Motor-generator sets are generally available for only three-phase
AC power, but can be ordered to different cycles and voltages. They are also available
for DC power. AC machines are generally available for only single-phase AC power in
various cycles, with or without power-factor correction in the machine. Fortunately, in
most manufacturing situations, the source of power does not present a limiting factor on
the selection of the welder. The decision can be made on the basis of what is the most
efficient and economical machine for a given job.
Also, consider what type machine will make the job easiest to do and enable better
welding to be done at lower costs. There is one best way to do every welding job.
Input power to the welder should be planned and installed only by qualified electricians.
Lines should be of the proper size and properly fused, according to local requirements
and current standards.
Current-carrying cables, cable lugs, electrode holder, work clamp, weld-cleaning
devices and protective equipment are essential for each welding machine and operator.
These are called accessories. For maximum safety and efficiency, good quality
accessories must be used.
Machines and Accessories, Arc Welding
© Pacific Vocational College, 2020
3
The welding current is conducted from the source of power to the electrode holder by an
insulated copper, extra-flexible cable. This cable is designed expressly for welding and
derives its flexibility from the thousands of very fine, almost hair-like wires enclosed in a
durable paper wrapping that allows the conductor to slip readily within its insulation
when the cable is bent. The high-grade insulation also contributes to flexibility. Wear
resistance is provided in this cable by an extra tough, braided cotton reinforcing and by
the special composition of the covering, which provides a smooth finish, highly resistant
to abrasion. For completing the welding circuit, a somewhat less flexible, but equally
wear-resistant cable is used.
Hand Shield
Figure 3 – Welding Accessories
The size (diameter) of the cables used in welding varies, depending upon the capacity
of the machine and the length of cable required. Cable size is selected carefully
because of its current carrying capacity.
The cable is generally connected to the welder by means of a copper terminal lug. This
lug is soldered or clamped to the end of the cable and fits on the welder terminal post.
The electrode holder grips the electrode during the welding process. This holder should
be reasonably light, well-insulated and sturdy enough to withstand the wear of continual
handling. The holder should be the correct size for maximum machine output. A springgrip holder for quick insertion or release of the electrode is best.
A work clamp fastened to the work or the table on which the work is mounted completes
the welding circuit. A spring-pressure work clamp is the quickest and easiest to use.
Magnetic clamps are available and may be necessary for a secure connection on broad
surfaces where it is difficult to use spring-pressure work clamps.
A shield for the face and eyes is necessary for protection from arc rays and heat and
the spatter of molten metal. This shield may have a head band for wearing on the head
or a handle attached for holding in the hand. The head shield is most commonly used
Machines and Accessories, Arc Welding
© Pacific Vocational College, 2020
4
for welding, as both hands are usually needed for the welding process. The shield
should have a number 10 or 12 filter glass for general purpose welding.
The more expensive filter glass should be protected by a clear cover-glass, which may
be replaced when covered with arc spatter.
Gloves and apron should be of chrome-tanned leather to protect the hands, body and
clothes from heat and spatter. If welding is done in positions other than flat, leather
shoulders and sleeves must be worn.
Safety glasses should be worn under the shield to protect the welder’s eyes when
chipping hot slag, grinding metal for joint preparation and cleaning metal with the wire
brush.
A chipping hammer and wire scratch brush should be used to thoroughly clean the
beads. A workbench soon becomes spattered and burned. This table should be steel for
fire-proofness and ease of grounding work. It may be easily made in the shop.
Protection for other persons working in the shop may be provided around the welding
area by a booth or shield of fireproof canvas, sheet metal, or transit. This might be a
permanent or portable unit, depending upon the work being done.
Machines and Accessories, Arc Welding
© Pacific Vocational College, 2020
5
Edits:
Last revision – March 4, 2021 by Alexandra Permiakova
March 10, 2020 by Richa Devgun
September 12, 2019 by Jennifer Bradbury
April 30th, 2019 by Sandor Rethy
Machines and Accessories, Arc Welding
© Pacific Vocational College, 2020
6