DESCRIPTION
ARC WELDING APPARATUS
TECHNICAL FIELD
The present invention relates to an arc welding apparatus in
whieh welding is carried out by using a non-consumable electrode.
BACKGROUND ART
Recently, with consideration for environment, an aluminum
material and a magnesium material, which have light weight and an
excellent recycling property, are commonly used for building structures,
vehicles, and the like. An alternating current (AC) arc welding
apparatus is commonly used for bonding the materials. The AC arc
welding apparatus carries out arc welding by alternately repeating the
negative polarity and the positive polarity (see, for example, Patent
Literature l).
In particular, in working sites for manufacturing large building
structures, in order to improve working efficiency, welding work with a
large electric current of 300 A or more and 500 A or less is carried out.
In conventional AC arc welding apparatuses (for example, a TIG
welding apparatus) outputting such a large electric current, thermal
loss of a semiconductor device that is operated mainly inside the
apparatus is increased. Therefore, in order to reduce on-loss (product
of on resistance and carried electric current of a main transistor), it is
necessary to employ a semiconductor device whose switching speed is
slow. As a result, a switching loss becomes large, and accordingly has

not been possible to enhance the inverter frequency. Therefore, a
circuit configuration that is operated at a relatively low inverter
frequency (for example, to about 10 kHz) is employed. Thus, it has
been necessary to mount a reactor having a large inductance value in
order to prevent arc interruption in a low current region (for example,
to about 10A).
Fig. 4 is a diagram showing a schematic configuration of a
conventional arc welding apparatus, and Fig. 5 is a graph showing a
change over time of a welding current waveform in a conventional arc
welding apparatus. With reference to Figs. 4 and 5, an operation of
an arc welding apparatus that has been conventionally commonly used
is described. Hereinafter, a non-consumable electrode type AC arc'
welding apparatus that carries out welding by repeating a negative
polarity period and a positive polarity period as an example.
In Fig. 4, arc welding apparatus 22 includes current detection
section 4 for detecting a welding current, high voltage generating
section 8, output section 19 for carrying out a welding output, control
section 20 for controlling output section 19, and reactor 21 provided
between output section 19 and welding torch 10. Herein, high voltage
generating section 8 applies a high voltage to between electrode 9
provided in welding torch 10 and base material 12 as a subject to be
welded. Furthermore, to arc welding apparatus 22, welding torch 10
provided with electrode 9 and base material 12 as a subject to be
welded are connected, and arc 11 is generated between electrode 9 and
base material 12 to carry out welding.
In Fig. 5 showing a change over time of a welding current and a
high voltage generating signal, IP denotes a peak current value, and IS

denotes a start current value. Furthermore, El denotes a welding
starting time point that is a time point at which welding is started, and
K2 denotes a current detection time point that is a time point at which
a current is detected by current detection section 4. Furthermore,
TUP3 denotes a rise time in a conventional arc starting time, and
TUP4 denotes a rise time in a conventional stationary welding time.
13 denotes a current value before the polarity of the welding current is
commutated from the positive polarity to the negative polarity.
In Fig. 4, a commercial voltage input (for example, 200 V is
used) supplied from an external device such as a power board is
supplied to output section 19 of arc welding apparatus 22. Output
section 19 outputs a welding current or a welding voltage suitable for
welding by an inverter control driven at an inverter frequency of about
10 kHz based on a welding control signal output by control section 20.
The welding current or the welding voltage output by output section 19
is smoothed via reactor 21, and supplied to welding torch 10 and base
material 12. Arc 11 is generated between the tip of electrode 9 and
base material 12, and thus alternating arc welding is carried out.
When the inverter frequency is about 10 kHz, in order to
prevent arc interruption at a low current (for example, about 10 A), an
inductance value of reactor 21 is required to be 200 μH or more. This
inductance value is determined based on, for example, experiment,
calculation, or the like.
Herein, control section 20 outputs a high voltage generating
signal to high voltage generating section 8 and turns on the high
voltage generating signal at a time when arc starting is initiated.
Thereafter, control section 20 receives an input of a current detection

signal output from current detection section 4, and it turns off a high
voltage generating signal when current detection section 4 detects a
current and control section 20 receives a signal from current detection
section 4 indicating that the current is detected.
High voltage generating section 8 generates a voltage that is
higher than a voltage in the stationary welding time (for example, 15
kV), applies a high voltage to between electrode 9 and base material 12
when the high voltage generating signal is on in the arc starting time,
and stops applying of a high voltage when a high voltage generating
signal is turned off.
Next, with reference to Fig. 5, a change over time of a welding
current waveform in a conventional arc welding apparatus is
described.
At welding starting time point El at which welding is started,
control section 20 turns on driving of output section 19 and a no-load
voltage is applied to between electrode 9 and base material 12 by
output section 19. Furthermore, control section 20 turns on a high
voltage generating signal so that a high voltage for arc starting is
applied by high voltage generating section 8. Thereafter, arc is
generated, and control section 20 turns off a high voltage generating
signal and stops applying of a high voltage at current detecting point
E2 at which current detection section 4 detects an electric current.
In arc starting, during rise time TUP3 in the arc starting time,
the welding current rises at 500 A/msec and reaches start current
value IS (for example, 350 A).
Furthermore, in a stationary welding period, during rise time
TUP4 from a zero crossing point when the polarity of the welding

current is commutated, the welding current rises at 500 A/msec, and
reaches absolute value IP of a peak current (for example, 350 A).
As mentioned above, the rise of the welding current in the arc
starting time and the rise of the welding current in the stationary
welding period are determined by the inductance value of reactor 21.
Herein, the rise denotes an amount of increase in the welding current
per unit time until it reaches the peak current.
Then, a current command of AC welding is generally in a pulse
state. It is common to think that the rise is preferably large so as to
form an actual current waveform in a pulse state.
When a reactor having a large inductance value (for example,
200 μH or more) is mounted on a conventional arc welding apparatus
22, a ripple of the welding current is suppressed, which is effective to
prevent arc interruption at a low current (for example, about 10 A).
However, on the other hand, the rise of the welding current becomes
slower, that is, the gradient is smaller and gentler, which makes an arc
starting property bad. Even if a rectangular command is given as a
current command, due to the inductance of the reactor, the rise is
slower in the executed welding current as compared with the
commanded current waveform. The tendency is stronger as the
inductance value is larger.
Recently, with the appearance of new inverter methods, in a
non-consumable electrode type arc welding apparatus (for example, a
TIG welding apparatus) for large electric current such as 500 A, it is
possible to increase an inverter frequency (for example, to about 40
kHz).
In a TIG welding apparatus driven by an inverter frequency of

40 kHz, a current ripple is small and arc interruption is difficult to
occur at a low current (for example, about 10 A). Accordingly, a
reactor having a small inductance value (for example, 100 μH or less)
can be mounted.
For example, when a reactor having an inductance value of 50
μH is mounted, the rise of a current becomes large (for example, 1500
A/msec or more), and the arc starting property is dramatically
improved.
However, in the TIG welding apparatus having a large rise of a
current (1500 A/msec or more), the rise of a current in the stationary
welding time is also large (1500 A/msec or more). This has revealed
that at the time of working with a large electric current (for example,
300 A or more), in an operation of inserting a filler wire, the filler wire
cannot be melted smoothly, thus deteriorating the workability.
That is to say, when a reactor having a small inductance value
is used, the arc starting property is improved, but the workability in
the stationary welding may be deteriorated.
[Citation List]
[Patent Literature]
PTL V Japanese Patent Application Unexamined Publication No.
H2-235574
SUMMARY OF THE INVENTION
The present invention provides an arc welding apparatus
having excellent arc starting performance, and having excellent
workability of a filler wire when welding is carried out with a large
electric current.

An arc welding apparatus of the present invention is a
non consumable electrode type arc welding apparatus for carrying out
welding by outputting an alternating current pulse having an absolute
value of a peak current of 300 A or more and 1500 A or less. The
apparatus includes an output section for outputting a welding current,
a control section for outputting a welding current control signal to the
output section for each cycle of the welding current to be controlled,
and a reactor having an inductance value of 10 μH or more and 100 μH
or less. The control section is configured to control the welding
current, by using a first rise time that is from a time at which the
welding current initiates arc starting to a time at which the welding
current reaches an absolute value of a peak current in arc starting
time, and a second rise time from a zero crossing point when a polarity
of the welding current is commutated to a time at which the welding
current reaches the absolute value of the peak current in a stationary
welding time after the arc starting, so that the second rise time is
longer than the first rise time.
With this configuration, it is possible to provide an arc welding
apparatus in which an arc starting property is improved at the time of
working with a large electric current, the workability of inserting a
filler wire is not deteriorated, and the filler wire can be melted
smoothly.
BRIEF DESCRIPTION OF DRAWINGS
Pig. 1 is a diagram showing a schematic configuration of an arc
welding apparatus in accordance with a first exemplary embodiment of
the present invention.

Fig. 2 is a graph showing a change over time of a welding
current waveform in accordance with the first exemplary embodiment
of the present invention.
Fig. 3 is a graph showing a correlation between a welding
current value and an amount of increase in the welding current value
per unit time of the welding current in accordance with the first
exemplary embodiment of the present invention.
Fig. 4 is a diagram showing a schematic configuration of a
conventional arc welding apparatus.
Fig. 5 is a graph showing a change over time of a welding
current waveform in the conventional arc welding apparatus.
DESCRIPTION OF EMBODIMENTS
Hereinafter, the exemplary embodiment of the present
invention is described with reference to drawings. In the following
drawings, the same reference numerals are given to the same
configuration and the description thereof is omitted.
FIRST EXEMPLARY EMBODIMENT
Fig. 1 is a diagram showing a schematic configuration of an arc
welding apparatus in accordance with a first exemplary embodiment of
the present invention. Fig. 2 is a graph showing a change over time of
a welding current waveform in accordance with this exemplary
embodiment. Fig. 3 is a graph showing a correlation between a
welding current value and an amount of increase in the welding
current value per unit time of the welding current in accordance with
this exemplary embodiment. An operation of the arc welding
apparatus configured as shown in Fig. 1 is described with reference to

Figs. 2 and 3.
Hereinafter, a non-consumable electrode type
alternating-current (AC) arc welding apparatus that carries out
welding by repeating a negative polarity period and a positive polarity
period as an example.
In Fig. 1, arc welding apparatus 1 includes output section 2
carrying out welding output, control section 3, current detection
section 4 for detecting a welding current, reactor 5 for smoothing the
output from output section 2, storage section 6, selection section 7 for
selecting the stored content of storage section 6, and high voltage
generating section 8 for outputting a high voltage. Herein, control
section 3 controls output section 2 by outputting a control signal to
output section 2 for each control cycle. Storage section 6 stores an
amount of increase in a welding current value per unit time of the
welding current with respect to the welding current value.
Note here that output section 2 includes rectifier section 14,
smoothing section 15, inverter control section. 13, transformer 16,
secondary rectifier section 17, and secondary inverter control section
18. Herein, smoothing section 15 smoothes an output of rectifier
section 14. Inverter control section 13 inverter-controls an output of
smoothing section 15. Transformer 16 transforms an output of
inverter control section 13. Secondary rectifier section 17 smoothes
an output of transformer 16. Secondary inverter control section 18
inverter-controls an output of secondary rectifier section 17.
Furthermore, arc welding apparatus 1 is coupled to welding
torch 10 provided with electrode 9 and base material 12 as a subject to
be welded via cables 10a and 12a and the like. Then, arc welding

apparatus 1 supplies electric power to between electrode 9 and base
material 12, thereby generating arc 11 between electrode 9 and base
material 12, Thus, welding is carried out.
In Fig. 2 showing a change over time of a welding current and
the like, IP denotes a peak current value of a welding current, and IS
denotes a start current value of the welding current. II denotes a
current value during rise, showing a first current value that is smaller
than peak current IP. 12 denotes a current value during fall, showing
a second current value that is smaller than peak current IP.
Furthermore. TUP1 denotes a first rise time that is from a time
at which the welding current is zero to a time at which the welding
current reaches start current IS, and TUP2 denotes a second rise time
that is from a time at which the welding current is commutated to zero
to a time at which the welding current reaches peak current IP. TDNl
denotes a first fall time during which the welding current lowers from
peak current IP to second current value 12, and TH denotes a
predetermined time that is a period during which second current value
[2 is maintained. TDN2 denotes a second fall time that is a time
combining first fall time TDNl and predetermined time TH.
Furthermore, DIl denotes an amount of increase in a welding
current value per unit time of a first welding current, and DI2 denotes
an amount of increase in a welding current value per unit time of a
second welding current that is different from the first welding current.
Furthermore, El denotes a welding starting time point that is a
time point at which welding is started, E2 denotes a current detection
time point that is a time point at which a current is detected, and E3
denotes an arc starting completion time point that is a time point at

which an arc starring period has been completed.
In Fig. 1, a commercial voltage input (for example, 200 V)
supplied from an external device such as a power board is supplied to
output section 2 of arc welding apparatus 1. Then, it is converted into
a direct current (DC) voltage by rectifier section 14 including a diode
and the like and smoothing section 15 including an electrolytic
capacitor and the like. Current detection section 4 including CT
(Current Transformer) and the like detects a welding current. To
control section 3 including CPU, DSP (Digital Signal Processor), ADC
(Analog to Digital Converter), and the like, an output from current
detection section 4 is input. Then, control section 3 forms an output
command suitable for welding in synchronization with control timing
of an inverter (for example, switching operation timing of the inverter),
carries out a current feedback operation based on an output target,
calculates a conduction width of the switching element of inverter
control section 13. and outputs a welding current control signal.
Inverter control section 13, which includes IGBT (Insulated
Gate Bipolar Transistor), MOSFET (Metal-Oxide Semiconductor device
Field Effect Transistor), and the like, driven by a PWM (Pulse Width
Modulation) operation or a phase shift operation based on a welding
current control signal output by control section 3, converts a DC
voltage, which has been inverter-driven and converted by rectifier
section 14 and smoothing section 15, into an AC voltage of high
frequency suitable for welding via transformer 16.
A no-load voltage output by transformer 16 is 80V.
Furthermore, transformer 16 operates in an inverter frequency of 40
kHz. The inverter is configured to include IGBT and a transformer,

and operates in a frequency of 40 kHz as a frequency of a transformer
current.
An AC voltage in a high frequency, which is output by
transformer 16, is rectified by secondary rectifier section 17 including
a diode and the like, and input into secondary inverter control section
18. Secondary inverter control section 18 is configured by a circuit
such as full bridge and half bridge by using IGBT and the like, and
switches the output polarity between the positive polarity and the
negative polarity.
Herein, the positive polarity refers to a case where a moving
direction in which electrons in arc plasma move is a direction from
electrode 9 to base material 12, and electrode 9 is negative and the
base material is positive. Furthermore, the negative polarity refers to
a case where a moving direction in which electrons in arc plasma move
is a direction from base material 12 to electrode 9, and electrode 9 is
positive and the base material 12 is negative.
A welding current or a welding voltage output by secondary
inverter control section 18 is smoothed via reactor 5, and supplied to
welding torch 10. Then, arc 11 is generated between the tip of
electrode 9 that is a non-consumable electrode made of tungsten and
the like, and base material 12 that is a subject to be welded, for
example, an aluminum material. Thus, AC arc welding is carried out.
Note here that an inductance value of reactor 5 is 100 (_iH or less,
for example, 50 u.H. A reactor having a smaller inductance value than
that of reactor 21 provided in conventional arc welding apparatus 22
described with reference to Fig. 4 is used. Thus, the amount of
increase- in the welding current value per unit time of the welding

current can be made to bo 1500 A/msec.
Furthermore, storage section 6 including CPU and the like
stores the amount of increase in the welding current per unit time of
the first welding current shown in Fig. 3 and the amount of increase in
the welding current per unit time of the second welding current shown
in Fig. 2 as amounts of increase in the welding current values per unit
time of the different welding currents with respect to the same welding
current value. Note here that not two but three or more of amounts of
increase in the welding current per unit time may be stored.
Furthermore, selection section 7 including CPU and the like
selects one amount of increase in the welding current value per unit
time of the welding current is selected from the plurality of amounts of
increase in the welding current values per unit time of the welding
currents stored in storage section 6, and inputs the selected amount
into control section 3. Note here that switching by selection section 7
may be carried out automatically according to the setting of a welding
current or the setting of frequency or the setting of a welding method.
Alternatively, the switching may be carried out manually according to
the preference of an operator who operates arc welding apparatus 1.
Control section 3 carries out output control by outputting a
control signal to the output section 2 based on the amount of increase
in the welding current value per unit time of the welding current
selected and output by selection section 7. Furthermore, control
section 3 can output a high voltage generating signal to high voltage
generating section 8, and turns on the high voltage generating signal
and outputs the signal to high voltage generating section 8 in the arc
starting time by, for example, pushing a torch switch (not shown)

provided on welding torch 10. Then, with a high voltage output by
high voltage generating section 8, an arc is generated between
electrode 9 and base material 12 and electric current flows. When
control section 3 receives a current detection signal from current
detection section 4 that detects this current, it turns off a high voltage
generating signal, and stops outputting of high voltage generating
section 8.
High voltage generating section 8 including a flyback
transformer and the like applies a voltage (for example, 15 kV) that is
higher than a voltage in the stationary welding time to between
electrode 9 and base material 12 during a time when the high voltage
generating signal output from control section 3 is on. On the other
hand, during a tunc when the high voltage generating signal output
from control section 3 is off, high voltage generating section 8 stops
applying of a high voltage.
The following is a description with reference to Fig. 2 of a
change over time of a welding current waveform from the start of
welding in the arc starting period to the rise of an AC welding current
pulse in the stationary welding time in a stationary welding period
after the arc starting period is described.
At welding starting time point El at which welding is started,
control section 3 turns on the drive of inverter control section 13, and
applies a no-load voltage (for example, 80 V) to between electrode 9 and
base material 12. Furthermore, control section 3 turns on the high
voltage generating signal and outputs the signal to high voltage
generating section 8, thereby applying a high voltage for arc starting
(for example, 15 kY) to between electrode 9 and base material 12.

Then, with this high voltage, an arc is generated and a welding current
flows. At current detection time point E2 at which current detection
section 4 detects an electric current, control section 3 turns off the high
voltage generating signal and outputs the signal to high voltage
generating section 8, thereby stopping applying of a high voltage.
In the arc starting, during-first rise time TUP1 (for example,
0.23 msec), the welding current rises in an amount of increase in the
welding current per unit time of 1500 A/msec, and reaches the start
current value IS (for example, 350 A).
Thereafter, at arc starting completion time E3 at which the arc
starting period is completed, the arc starting period shifts to the
stationary welding period. Note here that the completion of the arc
starting period may be a time point at which a predetermined time
period (for example, 100 msec) has passed from the arc starting.
Furthermore, the completion of the arc starting period may be a time
point at which the number of outputting times of AC pulses is
measured and pulses are output a predetermined number of times, for
example, a time point at which 5-pulse AC output is carried out.
Furthermore, during the stationary welding period,
commutation in which the positive polarity and the negative polarity
are changed is carried out, a welding current reaches peak current IP
(for example, 350 A) from the zero-crossing point at which the polarity
of welding current is comrautated after second rise time TUP2 (for
example, 0.85 msec) has passed.
Note here that during a period of second rise time TUP2, the
welding current rises at 500 A/msec as the amount of increase in the
welding current value per unit time until the welding current reaches

first current value JI (for example, 50 A). After the welding current
exceeds first current value 11 (for example, 50 A), the welding current
rises such that the amount of increase in the welding current value per
unit time is smaller than 500 A/msec and becomes lower as an absolute
value of the welding current is increased. For example, the absolute
value of the welding current is based on the amount of increase in the
welding current per unit time of the first welding current shown by a
solid line in Fig. 3.
As mentioned above, in a state in which reactor 5 having a
small inductance value is connected, in the arc starting time, the arc
starling performance is secured by allowing the welding current to rise
steeply by the rise of the welding current that depends on the
inductance value of reactor 5. At the same time, during the
stationary welding, by giving a welding current command to control
the rise of a welding current to be gentler as compared with the arc
starting time without depending upon the inductance value of reactor 5,
the workability of a filler wire can be made preferable.
Note here that during second rise time TUP2, until the welding
current reaches first current value II (for example, 50 A), the welding
current rises in the amount of increase in the welding current per unit
time of not 500 A/msec but 1500 A/msec. After the welding current
exceeds first current value II (for example, 50A), the welding current
may be controlled so that an increase in the welding current value per
unit time is reduced as an absolute value of the welding current is
increased.
Herein, 1500 A/msec is defined as a maximum amount of the
change per unit time determined by the inductance value of reactor 5.

which can he output by arc welding apparatus 1. Thus, in the initial
period of the increase in a current, a welding current may be allowed to
increase in a maximum amount of change per unit time.
Thai is to say. arc welding apparatus 1 of the present invention
is a non-consumable electrode type arc welding apparatus that carries
out welding by outputting an AC pulse having an absolute value of a
peak current of 300 A or more and 1500 A or less. Arc welding
apparatus 1 includes output section 2 for outputting a welding current,
control section 3 for outputting a welding current control signal to
output section 2 for each cycle of the welding current to be controlled,
and reactor 5 whose inductance value is 10 p.H or more and 100 uH or
less. Control section 3 of arc welding apparatus 1 is configured to
control the welding current by using first rise time TUP1 and second
rise time TUP2 so that second rise time TUP2 is longer than first rise
time TUP1. Herein, first rise time TUPl is a time from a time at
which the welding current initiates the arc starting to a time at which
the welding current reaches an absolute value of a peak current in the
arc starting time. Second rise time TUP2 is a time from the
zero-crossing point when the polarity of the welding current is
commutated to a time at which the welding current reaches the
absolute value of the peak current in the stationary welding time after
the arc starting.
With this configuration, it is possible to provide arc welding
apparatus 1 in which an arc starting property is improved at the time
of working with a large electric current, the workability of inserting a
filler wire is not deteriorated, and the filler wire can be m.elted
smoothly.

Furthermore, control section 3 may be configured to control the
welding current that increases during second rise time TUP2 so that
ihc increase in the welding current value per unit time is reduced as
an absolute value of the welding current becomes higher.
With this configuration, during the stationary welding, since
the welding is controlled by giving a welding current command so that
the rise of the welding current is allowed to be gentler as compared
with the arc starting time without depending upon the inductance
value of reactor 5. it is possible to improve the workability of the filler
wire.
Furthermore, control section 3 may be configured to control the
welding current that increases during second rise time TUP2 so that
the welding current is increased without changing the increase in the
welding current value per unit time until the welding current reaches
first current value 11, and the increase in the welding current value
per unit time is reduced as an absolute value of the welding current
becomes higher when the welding current excee-ds first current value
11.
With this configuration, in the arc starting time, the arc
starting performance is secured by allowing the welding current to rise
steeply by the rise of the welding current that depends upon the
inductance value of reactor 5, and in the stationary welding time, the
workability of the filler wire can be made preferable.
Furthermore, the output section 2 can output the welding
current in an amount of increase in the welding current value per unit
time of 1000 A/msec or more and 10000 A/msec or less. The output
section may be configured so that the amount of increase in the

welding current value per unit time in first rise time TUPl is 1000
A/ras or more and 10000 A/msec or less, and the amount of increase in
the welding current per unit time in second rise time TUP2 is 10
A/msec or more and 500 A/msec or less.
With this configuration, in the arc starting time, the arc
starting performance is secured by allowing the welding current to rise
steep]}- by the rise of the welding current that depends upon the
inductance value of reactor 5, and in the stationary welding time, the
workability of the filler wire can be made preferable.
Furthermore, the output section 2 can output the welding
current in an amount of increase in the welding current per unit time
of 1000 A/msec or more and 10000 A/msec or less. The output section
2 may be configured so that the amount of increase in the welding
current per unit time in first rise time TUPl is 1000 A/ms or more and
10000 A/msec or less^ the amount of increase in the welding current
per unit time in second rise time TUP2 until the welding current
reaches first current value II is 1000 A/msec or more and 10000 A/msec
or less? and amount of increase in the welding current per unit time is
L0 A/msec or more and 500 A/msec or less in the case where the
welding current exceeds first current value II in second rise time
TUP2.
With this configuration, in the arc starting time, the arc
starting performance is secured by allowing the welding current to rise
steeply by the rise of the welding current that depends upon the
inductance value of reactor 5, and in the stationary welding time, the
workability of the filler wire can be made preferable.
Furthermore, output section 2 may be configured to include

inverter control section 13, in which the inverter frequency of inverter
control section 13 is 40 kHz or more and 1 MHz or less.
With this configuration, a current ripple becomes smaller, and
arc interruption is difficult to occur at a low current (for example,
about 10 A).
Furthermore, a configuration may be employed, which includes
high voltage generating section 8 for applying a high voltage that is
higher than a voltage in the stationary welding time between the
n on-con sum able electrode and a subject to be welded in the arc
starting time, and a high voltage is applied to between the
non-consumable electrode and the subject to be welded so as to carry
out arc starting.
With this configuration, more preferable arc starting can be
achieved, and the base material and the electrode are not damaged in
the arc starting time.
As mentioned above, by increasing the rise of the welding
current in the vicinity of the zero-crossing point in commutation, it is
possible to prevent the occurrence of arc interruption at the time of
commutation. Note here that in conventional arc welding apparatus
22 described with reference to Fig. 4, since the rise of a current in the
vicinity of zero-crossing point is determined by the inductance value of
reactor 21, it has not been possible to increase the rise in the vicinity of
the zero-crossing point.
Next, with reference to Fig. 2, a change over time of a welding
current waveform at the time point at which the welding current falls
before commutation is described.
Control section 3 controls the welding current in the stationary

welding time so that it is decreased from peak current value IP (for
example, 350 A) to second current value 12 (for example, 100 A) in an
amount of decrease in the welding current per unit time of 800 A/msec,
and second current value 12 is maintained for a predetermined time
(for example, 0.1 msec) and then commutated. Note here that first
fall time TDN1 (for example, 0.32 msec) during which the current is
decreased from peak current value IP to second current value 12 is
allowed to be shorter than second rise time TUP2 (for example, 0.85
msec). Furthermore, control section 3 may control the welding
current in the stationary welding time so that second fall time TDN2
(for example, 0.42 msec) from the time point at which the welding
current starts to decrease from the peak welding current IP to the time
point at which the polarity of the welding current is commutated to the
zero-crossing point is shorter than the second rise time TUP2.
As mentioned above, by increasing the amount of decrease in
the current fall, second current value 12 that is a current value before
commuiation can be set lower than current value 13 (for example, 200
A) that is a value before commutation in conventional arc welding
apparatus 22, which is described with reference to Fig. 5. Thus, it is
possible to prevent a semiconductor device from being damaged by a
high serge voltage generated according to switching of a semiconductor
device (hat constitutes a secondary inverter in commutation.
Furthermore, current value 13 before commutation of
conventional arc welding apparatus 22 described with reference to Fig.
5 is determined by an inductance value of reactor 21 shown in Fig. 4.
Since current value 13 is determined by an amount of decrease in the
t'all of fhe current, it has not been possible to fall a current steeply

before commutation.
Following is a description with reference to Fig. 2 of a welding
current waveform of a welding current, which has a plurality of
amounts of increase in the welding current per unit time and in which
amounts of increase are switched.
Storage section 6 of arc welding apparatus 1 stores the amount
of increase in the welding current value per unit time of the first
welding current shown in Fig. 3 and the amount of increase in the
welding current value per unit time of the second welding current
shown in Fig. 2 as an amount of increase in the welding current value
per unit time of the second welding current with respect to the same
welding current value. Then, the stored content of storage section 6 is
switched and selected by selection section 7.
An example shown in Fig. 3 shows a case in which the reduction
degree of the amount of increase m the welding current per unit time
of the second welding current is larger than that of the first welding
current.
A case in which selection section 7 selects the amount of
increase in the welding current per unit time of the first welding
current is considered. At this time, the rise of the welding current
during second rise time TUP2 rises in the gradient shown by the
amount of increase Oil of the welding current per unit time of the first
welding current shown in Fig. 2. On the other hand, a case in which
selection section 7 selects the amount of increase in the welding
current per unit time of the second welding current is considered. At
this time, the rise of the welding current during second rise time TUP2
rises in the gradient shown by the amount of increase 1)12 of the

welding current per unit time of the second welding current.
Note here that the reduction degree of the amount of increase in
the welding current per unit time of the second welding current is
larger ihan that of the first welding current. This shows that the
welding current with the amount of increase DI2 per unit time of the
welding current of the second welding current of Fig. 2 rises more
gently. When the waveform of the rise of the welding current is
gentler, the arc is widened, and workability of a filler wire is improved.
On ihe other hand, it lacks in concentricity and so it is not suitable for
fillet welding. Therefore, it is desirable that respective suitable rises
are stored based on a subject to be welded or welding conditions, and
the like, and a suitable rise is selected, thereby canning out welding.
As mentioned above, by enabling the amount of increase in the
welding current value per unit time of the welding current to be
switched by selection section 7, the rise of the welding current during
second rise time TUP2 can be controlled. Thus, the workability of the
filler wire can be adjusted, and allowed to correspond to a variety of
working conditions or preferences of operators.
In the arc welding apparatus of the present invention, control
section 3 controls to decrease the welding current in the stationary
welding time from peak current value IP to second current value f.2
that is smaller than peak current value IP, second current value 12 is
maintained for predetermined time period TH, and then commutation
is carried out. Then, control section 3 is configured to control first fall
time TDN1 during which the welding current is decreased from peak
current value IP to second current value 12 is shorter .than second rise
nine TUP2.

With this configuration, by increasing the amount of decrease in
the fall of the current, second current value 12 that is a current value
before commutation can be set lower than current value 13 that is a
value before commutation in conventional arc welding apparatus 22.
Thus, it is possible to prevent a semiconductor device from being
damaged by a high serge voltage generated according to the switching
of the semiconductor device that constitutes a secondary inverter in
commutation.
Furthermore, in the stationary welding time, control section 3
is configured to control the welding current so that second fall time
TDN2 from the peak welding current IP to the zero-crossing point
when the polarity of the welding current is commutated is shorter than
the second rise time TUP2.
With this configuration, by increasing the amount of decrease in
the fall of the current, second current value 12 that is a current value
before commutation can be set lower than current value 13 that is a
value before commutation in conventional arc welding apparatus 22.
Thus, it is possible to prevent a semiconductor device from being
damaged by a high serge voltage generated according to the switching
of the semiconductor device that constitutes a secondary inverter in
commutation.
Furthermore, output section 2 can decrease the welding current
in an amount of decrease per unit time of the welding current of 800
A/msec or more and 10000 A/msec or less. In the configuration, the
amount of decrease in the welding current per unit time in first fall
time TDNJ or the amount of decrease in the welding current per unit
time in second fall time TDN2 is 800 A/msec or more and 10000 A/msec

or less.
With this configuration, by increasing the amount of decrease in
the fall of the current, second current value 12 that is a current value
before commutation can be set lower than current value 13 that is a
value before commutation in conventional arc welding apparatus 22.
Thus, it is possible to prevent a semiconductor device from being
damaged by a high serge voltage generated according to the switching
of the semiconductor device that constitutes a secondary inverter in
commutation.
Furthermore, storage section 6 for storing a plurality of
amounts of increase in welding current values per unit time of
different welding currents with respect to the same welding current
value, and selection section 7 for selecting an amount of increase in the
welding current value per unit time of the welding current from the
plurality of amounts of increase in welding current values per unit
time of the welding currents stored in storage section 6 are included.
With this configuration, by enabling the amount of increase in
the welding current value per unit time of the welding current to be
switched by selection section 7, the rise of the welding current during
second rise time TUP2 can be controlled. Thus, the workability of the
filler wire can be adjusted, and allowed to correspond to a variety of
working conditions or preferences of operators.
In Fig. 2, peak current value IP is the same value in the positive
polarity side and in the negative polarity side, but it may be different
values.
Furthermore, the reduction curve of the amount of increase in
the current, shown in Fig. 3 may be reduced linearly (a linear

expression), or reduced noivlinearly as in polynomial expression (for
example, a secondary expression).
Furthermore, the lower limit may be defined (minimum value is
• set,) at an arbitrary value (for example, 50 A/msec), the intermediate
point is provided if necessary, and the reduction property may be bent
noivlinearly.
Fig. 2 shows an example in which the arc starting is initiated
from the negative polarity side, but it may be initiated from the
positive polarity side.
Furthermore, Fig. 2 describes an example in which starting
current value IS and peak current value IP are the same value, but
they may be different values. In this case, first rise time TUP1 may
be TUP1 = (TUP 1 before conversion) x IS / IP, which is converted based
on a ratio of start current value IS to peak current value IP.
In this exemplary embodiment, an example in which high
frequency start is carried out by using high voltage generating section
8 in the arc starting time, but touch start may be used.
Furthermore, this exemplary embodiment describes AC arc
welding, but it may be applied to a waveform in rise of a pulse in a DC
non-consumable electrode type arc welding.
Furthermore, in this exemplary embodiment, as to the amount
of increase in the welding current per unit time of the welding current
in the rise of the welding current may use a reduction curve in which
the increase amount is the same in the positive polarity side and the
negative polarity side, but different properties maj^ be used.
Furthermore, as to the amount of increase in the welding
current per unit time of the welding current in the rise of the welding

current, Fig. 2 illustrates an example in which the increase is changed
during welding, but it may be set before arc starting and fixed during
welding.
Furthermore, Fig. 2 shows that the peak values of the positive
polarity and the negative polarity are arbitrary fixed values, but they
may be a welding current waveform that varies during the peak period.
Furthermore, finally, the relation between a peak current value
of the welding current and the workability of welding is shown in the
following Table 1. In Table, a mark "o" denotes that the workability is
good, and a mark "x" denotes that the workability is bad. A mark "A"
denotes that the workability is somewhat bad.
[Tabic ]]
As mentioned above, according to this exemplary embodiment,
the arc starting property can be improved and the workability of
welding m the stationary welding time can be also improved.
As mentioned above, according to the present invention, even
when a reactor having a small inductance value of 100 ΜH or less is
mounted and the current rise in the arc starting time is increased so as
to improve the arc starting property, a welding current is controlled so
that the second rise time is longer than the first rise time. With this
control, it is possible to provide an arc welding apparatus having
excellent workability in which the workability is not deteriorated in an
operation of inserting a filler wire even in the working time with a
large electric current.
INDUSTRIAL APPLICABILITY

As mentioned above, the present invention can provide an arc
welding apparatus having an excellent workability in which the
workability is not deteriorated in working of inserting a filler wire
even in working with a large electric current. Thus, the arc welding
apparatus of the present invention is industrially applicable as an arc
welding apparatus in the industries in which arc welding working is
carried out, for example, in plant construction industry in which a
particularly large aluminum member is welded with a large electric
current for production.
REFERENCE MARKS IN THE DRAWINGS
1 arc welding apparatus
2 output section
3 control section
4 current detection section
5 reactor
6 storage section
7 selection section
8 high voltage generating section
9 electrode

10 welding torch
10a, 12a cable
11 arc
1 2 base material
13 inverter control section
14 rectifier section
1 5 smoothing section

16 transformer
17 secondary rectifier section
18 secondary inverter control section

We Claim:
1. An arc welding apparatus that is a non-consumable electrode
type arc welding apparatus for carrying out welding by outputting an
alternating current pulse having an absolute value of a peak current of
300 A or more and 1500 A or less, the apparatus comprising:
an output section for outputting a welding current;
a control section for outputting a welding current control signal
to the output section for each cycle of the welding current to be
controlled; and
a reactor having an inductance value of 10 μH or more and 100
μH or less,
wherein the control section controls the welding current, by
using a first rise time from a time at which arc starting is initiated to a
time at which the welding current reaches an absolute value of a peak
current in arc starting time, and a second rise time from a
zero-crossing point when a polarity of the welding current is
commutated to a time at which the welding current reaches the
absolute value of the peak current in a stationary welding time after
the arc starting, so that the second rise time is longer than the first
rise time.
2. The arc welding apparatus of claim 1,
wherein the control section controls the welding current
increasing during the second rise time so that an increase in a welding
current value per unit time is reduced as the absolute value of the
welding current is higher.

3. The arc welding apparatus of claim 2,
wherein the control section controls the welding current
increasing during the second rise time so that the welding current is
increased without changing the increase in the welding current value
per unit time until the welding current reaches a first current value,
and the increase in the welding current value per unit time is reduced
as the absolute value of the welding current is higher when the
welding current exceeds the first current value.
1. The arc welding apparatus of claim 1,
wherein the output section can output the welding current in an
amount of increase in the welding current per unit time of 1000 A/msec
or more and 10000 A/msec or less, and wherein the amount of increase
in the welding current per unit time is 1000 A/msec or more and 10000
A/msec or less in the first rise time, and the amount of increase in the
welding current per unit time is 10 A/msec or more and 500 A/msec or
less in the second rise time.
5. The arc welding apparatus of claim 3,
wherein the output section can output the welding current in
the amount of increase in the welding current per unit time of 1000
A/msec or more and 10000 A/msec or less, and wherein the amount of
increase in the welding current per unit time is 1000 A/msec or more
and 10000 A/msec or less in the first rise time, the amount of increase
in the welding current per unit time is 1000 A/mses or more and 10000
A/msec or less until the welding current reaches the first current value

in the second rise time, and the amount of increase in the welding
current per unit time is 10 A/msec or more and 500 A/msec or less when
the welding current exceeds the first current value in the second rise
time.
6. The arc welding apparatus of claim 1,
wherein the control section controls the welding current in the
stationary welding time so that the welding current is reduced from
the peak current value to a second current value that is smaller than
the peak current value, and the second current value is maintained for
a predetermined period of time and then commutated, and wherein a
first fall time in which the welding current value is reduced from the
peak current value to the second current value is made to be shorter
than the second rise time.
7. The arc welding apparatus of claim 1,
wherein the control section controls the.welding current in the
stationary welding time so that a second fall time in which the welding
current reaches the zero-rcrossing point from the peak welding current
is made to be shorter than the second rise time.
8. The arc welding apparatus of claim 6 or 7,
wherein the output section can output a welding current in an
amount of decrease in the welding current per unit time of 800 A/msec
or more and 10000 A/msec or less, and wherein an amount of decrease
in the welding current per unit time in the first fall time or an amount
of decrease in the welding current per unit time in the second fall time

is 800 A/msec or more and 10000 A/msec or less.
9. The arc welding apparatus of claim 1, comprising:
a storage section for storing a plurality of amounts of increase
in the welding current value per unit time of different welding currents
with respect to the same welding current valuei and
a selection section for selecting an amount of increase in a
welding current value per unit time from the plurality of amounts of
increase in welding current value per unit time stored in the storage
section.
10. The arc welding apparatus of claim 1,
wherein the output section comprises an inverter control
section, and an inverter frequency of the inverter control section is 40
kHz or more and 1 MHz or less.
11. The arc welding apparatus of claim 1, comprising:
a high voltage generating section for applying a voltage that is
higher than a voltage in the stationary welding time to between a
non-consumable electrode and a subject to be welded in an arc starting
time,
wherein arc starting is carried out by applying a high voltage
between the non-consumable electrode and the subject to be welded.

ABSTRACT

In an arc welding apparatus of the present invention, even
when a reactor having a small inductance value of 100 μH or less is
mounted and the current rise in the arc starting time is increased so as
to improve the arc starting property, the control section controls the
welding current, by using first rise time and second rise time, so that
the second rise time is longer than the first rise time.