Multiple operator welding apparatus

A multiple operator welding apparatus is disclosed which is particularly well suited for use in stick arc welding, GTAW, FCAW, ACAC, and GMAW arc welding processes. One or more welding modules are selectively mounted in a main power frame and connected to the power source by a knife blade connector which permits removal and replacement of one or more welding modules while the power source is in use. The knife blade connector also permits one or more welding modules to be removed from the main power frame and used at a remote location. The welding module for use with the multiple operator welding apparatus incorporates an inductor which permits use of a reduced incoming module voltage while producing a satisfactory weld. The reduced incoming module voltage results in significant energy savings.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a welding apparatus and, more particularly, to a 
welding apparatus suitable for use by multiple operators and for a welding 
apparatus suitable for use with a reduced input voltage. 
2. Description of Related Art 
There are numerous different welding processes utilized in the welding 
industry for welding various materials under different circumstances. 
These welding processes include stick arc welding, shielded metal arc 
welding (SMAW), gas tungsten arc welding (GTAW), flux core arc welding 
(FCAW), air carbon arc gouging and gas metal arc welding (GMAW). These 
several different welding processes are performed in numerous environments 
ranging from factories, construction sites to shipyards. Most arc welding 
operations are performed using direct current from either a DC power 
source or, more commonly, from an AC power source which has been converted 
from AC to DC. 
Multiple operator welding machines were developed to permit several welding 
arcs to be struck from a single common power supply. The power supply 
typically has a transformer and rectifier to step down and convert the 
power from AC to an acceptable DC level. The known multiple operator 
welding machines are a saturable reactor type welding unit having a 
plurality of welding modules. Each welding module corresponding to a 
single welding arc requires a magnetic amplifier for generation of an 
acceptable arc. Such a saturable reactor type unit with magnetic 
amplifiers in each module is extremely heavy and very difficult to 
transport around a job site or to a new job site. 
A further drawback of the known saturable reactor type multiple operator 
welding machine is that the welding processes which can be performed from 
the unit are limited. No known multiple operator welding machines can 
perform GMAW welding in addition to other welding processes such as stick, 
SMAW, GTAW or FCAW. GMAW operations on these welding machines must be 
performed with a voltage sensing wire feeder. In addition, none of the 
known multiple operator welding machines permit two or more different 
processes to be conducted from a single multiple operator welding machine 
at the same time absent the use of a voltage sensing wire feeder. 
In light of the deficiencies, the known multiple operator welding machines 
are limited in their flexibility and versatility of use. 
The arc voltage between a workpiece and a welding electrode is dependent 
upon the spacing between the two electrically charged members. As the 
spacing increases, the voltage increases and the current flow can 
decrease. When the spacing between the electrode and the workpiece is too 
great, an insufficient amount of current will flow, potentially resulting 
in defects such as spatter and lack of fusion. As the spacing increases, 
the arc will ultimately be extinguished. 
Conversely, as the spacing between the electrode and the workpiece 
decreases, the voltage decreases and the current increases. If the spacing 
between the electrode and the workpiece is too small, the voltage will 
drop to an unacceptable level and excessive current will flow to the 
workpiece. This can result in gouging the workpiece or short circuiting 
the arc. 
For most GMAW welding operations, it is desired to maintain a certain arc 
voltage and current flow, therefore, the spacing between the welding 
electrode and the workpiece must be maintained substantially constant. 
However, this spacing is constantly changing in light of globules of metal 
which drip from the welding electrode, the inability of the welder to hold 
the electrode steady and irregularities in the structure of the workpiece. 
Conversely, other welding procedures such as SMAW require varying the arc 
length to create different voltage, current and temperature levels. It is 
imperative that the arc not be extinguished or short circuit during these 
fluctuations in the arc length. 
An additional problem with the known welding apparatus is that each welding 
module is based on a welding module input voltage of 80 volts DC from the 
rectifier of the transformer of the power frame. 80 volts DC is generally 
regarded as the voltage required to produce a relatively stable arc, i.e. 
the current fluctuation as a result of change in the arc voltage is 
acceptable. This input voltage is required even though the arc voltage is 
typically in the range of 25 to 35 volts. The 80 volt welding module input 
voltage is commonly reduced to the lower arc voltage by resistors or other 
suitable means. The power lost in reducing the voltage from 80 volts to 25 
arc volts is significant. The lost power is converted into heat which must 
be vented from the machine. The power loss due to voltage reduction 
results in very uneconomical power usage and increases the likelihood of 
overheating of the welding units. 
SUMMARY OF INVENTION 
The multiple operator welding apparatus according to the invention improves 
the prior art multiple operator welding machines by creating a multiple 
operator, multiple process system contained in a single package. The 
multiple operator welding apparatus according to the invention can perform 
stick, SMAW, GTAW, FCAW, air arc and GMAW welding processes from a single 
unit. In addition, different welding processes can be performed at the 
same time from a single multiple operator welding apparatus according to 
the invention. 
The multiple operator welding machine according to the invention also 
permits the removal of one or more modules from the multiple operator unit 
without requiring the power to be turned off to the entire unit, thereby 
disrupting other welders operating from main power unit. Moreover, the 
multiple operator welding apparatus according to the invention permits use 
of 60 volts DC input into each module rather than 80 volts DC because of 
the incorporation of an inductor. The use of 60 volts DC drastically 
reduces lost power and increases the efficiency and economy of the 
multiple operator welding apparatus. 
The welding apparatus according to the invention comprises a welding module 
removably supported in a main power frame and a knife blade assembly 
connecting the module to an electrical bus bar mounted in the main power 
frame and electrically connected to the power source. Each knife blade 
assembly preferably comprises three knife blade connectors, corresponding 
to a positive, negative and common ground conduit. Each knife blade 
connector comprises a first connector member mounted to and electrically 
connected to the welding module and second connector member mounted to and 
electrically connected to the bus bar. The first connector member engages 
the second connector member to establish an electrical connection between 
the module and the bus bar when the module is inserted in the power frame. 
The welding module is provided with a welding module output terminal for 
connection to the welding electrode and a plurality of electrical elements 
connected between the first connector member and the welding module output 
terminal for providing suitable electrical power to the welding module 
output terminal. Advantageously, a welding module can be selectively 
disconnected from the power source and removed from the main power frame. 
The first connector member preferably comprises a knife blade and the 
second connector member preferably comprises an U-shaped clip. 
A multiple operator welding apparatus is created by mounting a plurality of 
welding modules in the main power frame, electrically connected to the 
main power frame by a plurality of knife blade assemblies. In one 
embodiment, eight welding modules are mounted in the main power frame. 
A dummy drawer, which can be selectively mounted in the main power frame in 
the place of a welding module provides connection between the main power 
frame and a welding module removed for use at a remote location. The dummy 
drawer has an output terminal and a connector member. The connector member 
on the dummy drawer is connected to the second connector member on the 
main power frame and the first connector member on the remote welding 
module is connected to the dummy drawer output terminal. A protective 
shell preferably substantially surrounds a removed welding module. A 
connector member on the protective shell can be selectively connected to 
the first connector member of the welding module. An input terminal on the 
protective shell, in electrical contact with the shell connector member, 
can be electrically connected to the dummy drawer output terminal by 
electrical cables. 
Variable current means can be incorporated in the welding module to vary 
the electrical current supply to the welding electrode. In one embodiment, 
the variable current means comprises a plurality of resistors and a 
switching box. 
The plurality of electrical components mounted in the welding module can 
also comprise an inductor electrically connected between the first 
connector member and the module output terminal. Preferably, the inductor 
is connected between the plurality of resistors and the welding module 
output terminal. 
The welding apparatus according to the invention can also comprise a source 
of electrical power, at least one welding electrode and a welding module 
electrical circuit. The welding electrode is electrically connected to the 
power source for striking an arc between the workpiece and the electrode. 
The welding module electrical circuit interconnects the welding electrode 
and the power source. The circuit comprises an inductor connected in 
series between the power source and the electrode. The inductor inhibits 
fluctuations in electrical current resulting from changes in the potential 
across the arc between the workpiece and the electrode. In one embodiment, 
the circuit has at least one resistor connected in series with the 
inductor between the power source and the electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings and to FIG. 1 in particular, the multiple 
operator welding apparatus according to the invention comprises a main 
power frame 12 having a plurality of welding modules 14 selectively 
mounted therein. The welding modules 14 and the main power frame 12 are 
supported by a power frame housing 16. A plurality of side panels 18 are 
selectively mounted to the power frame housing 16 by a plurality of 
fasteners 20. A plurality of front panels 22 and rear panels (not shown) 
are similarly selectively fastened to the power frame housing 16. A roof 
panel 27 is secured to the top of the power frame housing 16 to protect 
the main power frame from the elements. 
The main power frame housing 16 also includes a base 24 adapted for 
movement of the power frame 12 by a forklift and lifting eyes 26 Secured 
to the top of the housing 16 for movement of the power frame by a crane or 
other lifting device. 
In the preferred embodiment, a plurality of 115 V outlets 28 are mounted to 
the front of the main power frame 12 to supply power for a wide variety of 
accessory equipment such as wire feeders, lights, grinders, etc. Indicator 
lights 30 can be mounted to the front panels 22 to provide information 
regarding the status of the unit, such as an on/off power light and a 
light indicating that the unit is ready for the striking of an arc by one 
or more welders. A plurality of common ground connections 32 preferably 
extend from the front of the power frame 12. The common ground connections 
are electrically connected to the common ground of the main power frame 12 
as discussed below. 
In the preferred embodiment, as seen in FIG. 1, eight welding modules 14 
are selectively mounted within the main power frame 12. An alternative 
embodiment is seen in FIG. 2 wherein only four welding modules 14 are 
selectively mounted within the main power frame 12. It is to be understood 
that any combination of one or more welding modules 14 within a power 
frame come within the scope of this invention. 
FIG. 3 is a perspective view of the main power frame 12 of the preferred 
embodiment seen in FIG. 1, with the side panels 18 removed to expose the 
support structure and electrical connections for each welding module 14 to 
the main power frame 12. Each welding module 14 is supported and guided in 
the power frame housing 16 by module glides 36. The glides 36 permit the 
modules 14 to easily slide into and out of the power frame housing 16. 
As seen in FIGS. 3 and 4, bus bars 38 are mounted to the power frame 
housing 16 at the rear of the module glides 36. The bus bars 38 are 
preferably manufactured of copper or some other highly conductive material 
and comprise a common ground bar 40, a positive bar 42 and a negative bar 
44. The bus bars 38 are mounted to the a support panel 46 by a plurality 
of insulators 48. The support panel 46 is in turn mounted to the power 
frame housing 16. 
Each module 14 is selectively connected to the main power frame 12 by a 
knife blade assembly. Each knife blade assembly preferably comprises three 
knife blade connectors, a common ground, positive and negative knife blade 
connector. A knife blade connector preferably comprises a first connector 
member connected to the welding module 14 and a second connector member 
connected to the main power frame through the bus bars 38. Preferably, the 
second connector members comprise spring clips 50 mounted to the bus bars 
38. As seen in FIGS. 3 and 4, one spring clip 50 is mounted to each of the 
common ground, positive, and negative bus bars 40, 42 and 44 for each 
welding module 14 to be mounted in the power frame housing 16. The spring 
clips 50 are electrically connected to the bus bars 38 and comprise a pair 
of opposing side members biased by a spring 54 into engagement with one 
another. The outboard ends of the opposing side members preferably 
terminate in open flanges 56 to permit easy connection and disconnection 
of the knife blade connector. 
The first connector member preferably comprises a knife blade 60 mounted to 
the rear of each welding module 14 as seen in FIG. 5. A common ground 
knife blade 62, positive knife blade 64 and negative knife blade 66 are 
supported by insulating plates 68 at the rear of the welding module 
housing 70. The outboard end of each knife blade 62 is preferably beveled 
such that it can be easily received between the open flanges 56 of the 
spring clips 50. The spring clips 50 and knife blades 60 conduct the 
electrical power of the main power frame 12 from the bus bars 38 to the 
electrical circuit of the welding module 14, described below. 
As seen in FIG. 3, each welding module 14 can be removed from the power 
frame housing 16 by grasping the welding module handles 74 and pulling the 
welding module forward, disengaging the knife blades 60 from the spring 
clips 50. After the blades 60 have been removed from the clips 50 the 
welding module 14 can be slidably removed from the main power frame 
housing 16. The removed welding module 14 can be easily replaced by 
inserting a new welding module into the aperture of the power frame 
housing 16 and sliding the replacement welding module along the module 
glides 36 until the knife blades 60 engage the spring clips 50 at the rear 
of the module glides 36. Once the knife blades 60 are received within the 
spring clips 50, the welding module is completely installed and ready to 
operate. 
The knife blade connector construction according to the invention permits 
easy removal and replacement of a welding module. In addition, the knife 
blade connector structure according to the invention permits one or more 
welding modules 14 to be removed from the main power frame 12 without 
disrupting any of the other welding modules within the main power frame 
12. Therefore, if one of the welding modules 14 is not appropriate for the 
particular welding process, the user can remove the welding module 14 and 
replace it with an appropriate welding module without turning the power 
off to the main power frame 12 or otherwise disrupting the other welders 
operating from the main power frame 12. For example, if a welding module 
particularly suited for use with a stick electrode welding process is 
mounted in the main power frame 12, the user can quickly slidably remove 
the stick electrode welding module and substitute therefor a GMAW welding 
module for use in a GMAW welding process. As will be discussed further 
below, the welding apparatus according to the invention is suitable for 
use with one or more of several different welding modules adapted for 
particular welding processes or a combination thereof. 
Another benefit of the power frame 12 according to the invention is the 
ability to remove one or more modules 14 from the power frame housing 16 
and use it at a remote location. As seen in FIGS. 6-9, a welding module 14 
can be removed from the main power frame 12 and mounted within a 
protective shell 80 to create a remote welding module 78. The module 14 is 
slidably mounted in a front aperture (not shown) of the protective shell 
80 until the knife blades 60 at the rear of the module housing 70, engage 
connector members 94 of the protective shell 80. Preferably, the connector 
members 94 comprise spring clips 95 mounted at the rear of the protective 
shell 80 (FIG. 10). The spring clips 95 of the protective shell 80 are 
identical to the spring clips 50 previously described for the main power 
frame 12. The protective shell spring clips are electrically connected to 
terminals 82 mounted on the rear wall of the protective shell 80. The 
terminals 82 comprise a common ground terminal 84, a positive terminal 86 
and a negative terminal 88 which are adapted to engage electrical cables. 
Two cables 90 electrically connect the positive terminal 86 and negative 
terminal 88 of the remote welding module 78 to the positive terminal 96 
and negative terminal 98 of the dummy drawer 92 mounted in the main power 
frame 12. 
An alternative to connecting the cables 90 to a dummy drawer 92 is to 
connect the cables 90 directly to the rectifiers 144 and 146 behind the 
front panel 22. This procedure is not recommended because of the obvious 
electrical hazards. 
The common ground terminal 84 of the remote welding module 78 is connected 
to the common ground connection 32 of the main power frame 12 by a cable 
91. 
When one welding module 14 is removed and mounted within the protective 
shell 80, a dummy drawer 92 can be slidably mounted into the aperture of 
the removed module 14. As seen in FIG. 9, the dummy drawer 92 has output 
terminals comprising a positive terminal 96 and a negative terminal 98 
mounted on the front thereof. The terminals of the dummy drawer 92 are 
electrically connected to a dummy drawer connector member, preferably 
dummy drawer bus bars 100. The dummy drawer bus bars 100 extend from the 
terminals on the front of the dummy drawer 92 to the rear of the dummy 
drawer 92. Each dummy drawer bus bar 100 has a beveled edge knife blade 
102 at the rear terminal end thereof. The knife blades 102 engage the 
spring clips 50 of the main power frame 12 to electrically connect the 
remote welding module to the main power frame 12. The dummy drawer bus 
bars 100 are preferably made of copper or some other highly conductive 
material. 
Through the use of a remote welding module 78, a welder working some 
distance from the main power frame 12 can take his welding controls 
mounted on the welding module 14 with him. That is, each time the welder 
needs to adjust the current or polarity for the particular welding 
operation, each of these controls can be adjusted directly from the remote 
welding module 78 which is adjacent the welder. Therefore, a welder can be 
more efficient by spending more time welding rather than walking to and 
from the main power frame 12 to adjust the parameters of the welding arc. 
As mentioned previously, the main power frame 12 according to the invention 
is suitable for use with a combination of welding modules specially 
adapted for particular welding processes. For example, welding modules 
adapted for a stick welding process can be constructed significantly 
different from a welding module suitable for GMAW welding processes. 
However, each of the various welding modules 14 centers around a basic 
construction which comprises of a welding module housing 70, the 
previously described knife blades 60 and insulating plates 68, a plurality 
of resistors 110, a switching box 112 and an inductor 114. 
The welding module housing 70 comprises a plurality of support members 
which are assembled in a rectangular structure to support the various 
components of the welding module 14. A front panel 106 is supported on the 
front of the welding module housing 70. The knife blades 60 and insulating 
plates 68 are mounted at the rear of the welding module 14. A plurality of 
resistors 110 are mounted on insulating supports 116 which are in turn 
mounted to the housing 70. The switching box 112 and inductor 114 are 
mounted adjacent the front panel 106. 
As seen in FIG. 11, the front panel 106 of the welding module 14 has a pair 
of handles 74 mounted thereon for the user to grasp the welding module 
when removing it from the main power frame 12. An auxiliary plug 117 is 
mounted on the front panel 106 to provide electrical current for accessory 
equipment. A polarity switch 118, a coarse current adjusting knob 120, a 
fine current adjusting switch 122, and welding electrode terminals 124 are 
also mounted to the front panel 106. A cover 126 can be hingedly mounted 
above the welding electrode terminals 124 to protect the terminals 124 and 
avoid electrical shock. 
The structure and electrical circuit of the main power frame 12 can be seen 
in FIGS. 13, 14 and 15. Three phase line voltage enters the welding 
apparatus from an outside source through terminals 130. The preferred 
embodiment of the main power frame is adapted for hook up to one of 
several line voltages, such as 230 volts, 460 volts and 575 volts. 
Alternatively, the power frame can be wired for other line voltages such 
as 220 volts, 380 volts and 440 volts. Tap board links on tap boards 132 
and 134 are used to adjust the power to the power frame according to the 
incoming line voltage. 
Tap board links 158 are also used to adjust the power supplied to the 
primary contacts 160 and 162. The primary contacts 160 and 162 are 
energized by contactor coils 164 and 166. Current is applied to the coils 
164 and 166 from auxiliary transformer 167 when switch 128 is closed by 
manual operation. As a result, the primary contacts 160 and 162 will be 
operated, permitting the flow of current through the primary contacts 160 
and 162 to transformers 136 and 138. 
The transformers 136 and 138 comprise primary windings 168 and 170, 
transformer cores 176 and 178 and secondary windings 180 and 182, 
respectively. The amount of voltage step-down required from the 
transformers 136 and 138 varies depending upon the incoming line voltage. 
Therefore, the primary windings 168 and 170 have a plurality of 
sub-windings 172 and 174, respectively, which are selectively connected 
pursuant to the level of the incoming line voltage. The sub-windings 172 
and 174 are selectively connected through connections on the tap boards 
132 and 134. The tap board connections for the primary windings 168 and 
170 of the transformers 136 and 138 are conventional. 
The voltage passing through the primary windings 168 and 170 of the 
transformers is stepped-down to an acceptable level, preferably 45 volts, 
through the cooperation of the primary windings 168 and 170, the 
transformer cores 176 and 178 and the secondary windings 180 and 182. 
Current is also supplied to the auxiliary transformer 167 for the creation 
of 115 volts for use by the accessory equipment connected to the 115 volt 
outlets 28. 
From the secondary windings 180 and 182 of the transformers 136 and 138, 
the current flows to the rectifiers 144 and 146. The rectifiers 144 and 
146 convert the current from alternating current to direct current and 
have three incoming legs with six diodes 184 and 186. The rectifiers also 
incorporate conductor/heat sinks 188 and 190. The conductor/heat sinks 188 
and 190 collect the current flowing from the three legs of the diodes 184 
and 186 and conduct the resulting current to the parallelling panel 192. 
The resulting voltage as a result of rectification of the three phase 
current is 60 volts. The conductor/heat sinks 188 and 190 have a large 
surface area which can dissipate heat which can build in the rectifiers 
144 and 146. As seen in FIG. 14, electrical fans 156 are provided in the 
main power frame 12 to remove heat from the unit. 
The parallelling panel 192 collects the current from the two transformers 
136 and 138 and creates a dual polarity welding apparatus thereby 
permitting welders to convert the welding process at each module 14 from 
straight to reverse polarity, if desired. The positive terminal from the 
first rectifier 144 is connected to a positive member 194. The negative 
terminal from the second rectifier 146 is connected to a negative member 
196 of the parallelling panel 192. The negative terminal from the first 
rectifier 144 and the positive terminal from the second rectifier 146 are 
connected to common ground members 198 which are connected by a conducting 
member 200 to create the common ground of the main power frame 12. 
The electrical power of the main power frame 12 is conducted from the 
parallelling panel 192 to the bus bars 38 by a plurality of electrical 
cables 154. 
While the embodiment of the main power frame 12 discussed above includes 
two primary transformers 136 and 138 and an output paralleling panel 192, 
the welding apparatus according to the invention can be operated with a 
single transformer without the benefit of dual polarity welding capability 
or with a single transformer with two secondary windings. 
As seen in FIGS. 4 and 16, each welding module 14 receives electrical power 
from the bus bars 38 through the spring clips 50 and knife blades 60. 
Electrically connected to the positive and negative knife blades 64 and 66 
is a polarity switch 118 for converting the welding module from straight 
to reverse polarity, or vice versa. It is to be understood that the 
polarity switch 118 is optional for a welding module suitable for use in 
the welding apparatus according to the invention. 
When the welding module is used for straight polarity welding, as seen in 
FIG. 16, the workpiece 202 is electrically connected to the common ground 
terminal 32 of the main power frame 12, and the welding electrode 204 is 
electrically connected to the negative terminal via the polarity switch 
118. Conversely, when the welding module is used for reverse polarity 
welding, the welding electrode 204 is electrically connected to the 
positive terminal through the polarity switch 118. For reverse polarity 
welding the workpiece continues to be connected to the common ground 
terminal 32. 
In addition, the welding module 14 according to the invention preferably 
incorporates one or more demand pulse boards 206 which selectively 
supplies additional current to the welding arc in the event that the 
voltage drops below a desired level. The structure of the demand pulse 
boards 206 is described in U.S. Pat. No. 4,523,077 issued Jun. 11, 1985 to 
Hoyt, Jr. et al., which is expressly incorporated herein by reference. A 
welding module according to the invention having two demand pulse boards 
206 is particularly well suited for use in a GMAW welding process. A 
welding module 14 having a single demand pulse board 206 incorporated 
therein is particularly well suited for a FCAW welding process or some 
SMAW processes whereas a welding module 14 according to the invention 
having no demand pulse boards 206 incorporated therein is particularly 
well suited for other SMAW processes. 
As seen in FIG. 16, the switching box 112 cooperates with the plurality of 
resistors 110 to supply a variable amount of current from the main power 
frame to the welding electrode 204. The switching box is connected to the 
coarse current adjusting knob 120 (FIG. 11) and the fine current adjusting 
switch 122 (FIG. 11) to permit the welder to select the desired current 
level for the particular welding procedure. In the preferred embodiment, 
the coarse current adjusting knob 120 and switching box 112 adjust the 
current in fifty amp increments whereas the fine current adjusting switch 
122 and switching box adjust the current in five amp increments. The Table 
A provided below shows the resistance of the resistors contained in the 
electrical circuit of the preferred embodiment. The switching box 112 
permits adjustment of the current from 0 to 395 amps in 5 amp increments 
by selectively connecting the resistors 110 in the electrical circuit 
between the welding electrode 204 and the knife blades 60. 
TABLE A 
______________________________________ 
Resistor Number 
Resistance-Ohms 
______________________________________ 
210 0.7 
212 0.7 
214 0.7 
216 0.5 
218 0.5 
220 0.5 
222 7.0 
224 3.5 
226 2.3 
228 2.3 
______________________________________ 
Shown in FIG. 16 is an inductor 114 connected between certain terminals of 
the switching box 112 and electrode 204. In the preferred embodiment, only 
the first 145 amps of current supplied to the welding electrode 204 
through the switching box 112 pass through the inductor 114. Through 
experimentation, the inventors have discovered that the beneficial effects 
of the inductor 114 on the welding arc are predominate in the low current 
conditions. The preferred inductor 114 has an inductance of approximately 
1.8 milliHenrys for use with an incoming welding module voltage of 60 
volts. 
The welding module 14 according to the invention having the inductor 
incorporated therein provides two significant advantages. First, the 
inductor 114 dramatically stabilizes the welding arc, thereby reducing 
defects in the resulting weld bead. Secondly, the welding apparatus 
according to the invention results in significant power savings over known 
welding apparatuses due to the lower input voltage. 
The inductance of the inductor 114 resists changes in the current flow 
between the welding electrode 204 and the workpiece 202. This is of 
primary importance when the particular welding process employed demands 
rapid changes in the arc voltage. It also reduces the amount of spatter by 
opposing sudden current changes. For example, when a welder raises the 
welding electrode 204, the resistance of the arc between the workpiece 202 
and the electrode 204 increases, causing the current to decrease and the 
voltage to increase. Eventually, the resistance will be so great that the 
arc will be extinguished. The arc extinguishes more quickly for a lower 
input voltage such as 60 volts than for a higher voltage of 80 volts. 
Therefore, the standard input voltage, used in prior art systems, is 80 
volts. However, the incorporation of the inductor 114 in the electrical 
circuit of the welding apparatus according to the invention slows the 
change in current as well as changes in the arc voltage. Therefore, a 
welding module having an inductor 114 and an input voltage of 60 volts has 
substantially the same stability as the traditional 80 volt welding 
module. Through the use of a welding module having resistors 110 and the 
inductor 114 electrically connected therein, a constant current welding 
module which resists current change is created. 
The effect of the inductor 114 on the stability of the arc weld can be more 
easily understood by reference to FIG. 17, an example of a 
voltage-amperage curve for a preset current of 150 amps. This V-A curve is 
for a welding module not incorporating any of the demand pulse boards 206. 
A welding module according to the invention having an input voltage of 60 
volts is shown in solid lines whereas a welding module having an input 
voltage of 80 volts is shown in dashed lines. 
The stability of a welding arc is a function of the slope of the V-A curve. 
The slope is equal to the change in output or arc voltage over the change 
in the output current. The slope of the 60 volt welding module is less 
than the slope of the 80 volt welding module. Therefore, changes in the 
arc voltage have a more dramatic effect on the output current for the 60 
volt welding module than for the 80 volt welding module. 
The second benefit of the inductor is greater efficiency and significant 
power savings. The voltage within the welding module according to the 
invention is reduced from the incoming welding module voltage to the lower 
arc voltage by resistors 110 or other suitable means. Since electric power 
is a function of the voltage, it will be apparent that the power lost in 
reducing the voltage from 80 volts to 25 arc volts is far greater than the 
power lost in reducing the voltage from 60 volts to 25 arc volts. The 60 
volt system power losses are thirty-six percent (36%) less than the power 
losses of an 80 volt system. Therefore the 60 volt system is significantly 
more energy efficient. In addition, the resistors necessary to obtain the 
desired arc voltage from an 80 volt system are considerably larger and 
heavier than the resistors necessary to obtain the desired arc voltage in 
the 60 volt system. Therefore, the 60 volt system has significant energy 
efficiency and weight advantages over the 80 volt system. 
The welding module 14 according to the invention creates a satisfactory 
weld bead with an input welding module voltage of 60 volts because of the 
incorporation of the inductor 114. These advantages in addition to the 
ability to substitute and replace welding modules within a single main 
power frame create an efficient and highly improved multiple operator 
welding apparatus. 
The welding apparatus according to the invention creates the first true 
multiple operator/multiple process welding apparatus capable of GMAW. The 
welding apparatus according to the invention permits multiple welders to 
operate from a single main power frame. The welding apparatus according to 
the invention also permits welders from the same power frame to conduct 
different welding procedures. For example, one welder can utilize a stick 
electrode welding module while a second welder utilizes a GMAW welding 
module and yet a third welder utilizes a FCAW welding module. Moreover, 
one or more of the welding modules can be removed from the main power 
frame and replaced while the power frame is in operation without 
disturbing other welders which are operating from the main power frame. 
Yet another benefit of the welding apparatus according to the invention is 
the ability of one or more welders to remove the welding module from the 
main power frame and electrically connect the remote welding module to the 
main power frame to use it at a remote welding site. 
While particular embodiments of the invention have been shown, it will be 
understood, of course, that the invention is not limited thereto since 
modifications can be made by those skilled in the art, particularly in 
light of the foregoing teachings. Reasonable variation and modification 
are possible within the foregoing disclosure of the invention without 
departing from the spirit of the invention.