©
COPYRIGHT 1999 THE ESAB GROUP, INC. LESSON
I, PART B
1.9.3.1.1 The transformer
type produce only alternating current. They are commonly
called "Welding Transformers."
All AC types utilize single-phase primary power and are of
the constant current type.
1.9.3.1.2 The rectifier
types are commonly called "Welding Rectifiers" and produce
DC or, AC and
DC welding current. They may utilize either single phase or three phase
input power. They
contain a transformer, but rectify the AC or DC by the use of selenium
rectifiers, silicon diodes or silicon
controlled rectifiers. Available in either the constant
current or the constant voltage type,
some manufacturers offer units that are a combination of
both and can be used for coated electrode welding, non-consumable electrode welding
and for welding with solid or flux
cored wires. 1.9.3.2
Rotating
Types - Rotating type power sources may be divided
into two classifi- cations:
1. Motor-Generators
2. Engine
Driven 1.9.3.2.1 Motor-generator
types consist of an electric motor coupled to a generator or
alternator that produces the desired
welding power. These machines produced excellent welds,
but due to the moving parts, required considerable maintenance. Few, if
any, are being
built today. 1.9.3.2.2 Engine
driven types consist of a gasoline or diesel engine coupled to a generator
or alternator that produces the desired
welding power. They are used extensively on jobs beyond
commercial power lines and also as mobile repair units. Both rotating types
can deliver either
AC or DC welding power, or a combination of both. Both types are available
as constant current or constant voltage
models. 1.9.4
Power
Source Controls - Welding power sources differ
also in the method of controlling
the output current or voltage. Output may be controlled mechanically as
in machines having
a tapped reactor, a moveable shunt or diverter, or a moveable coil. Elec-
trical types of controls, such as magnetic
amplifiers or saturable reactors, are also utilized and
the most modern types, containing silicon controlled rectifiers, give precise
electronic control.
1.9.4.1 A
detailed discussion of the many types of welding power sources on the market
today is much too lengthy a subject
for this course, although additional information on the type
of power sources for the various welding processes will be covered in Lesson II.
1.9.4.2 Excellent
literature is available from power source manufacturers, however, and
should be consulted for further reference.
