JP2022099368A - Pulse arc welding power supply - Google Patents

Abstract

To provide a method for preventing instability of a welding state during a transition period from an arc start, in a pulse arc welding in which output control is executed based on a welding voltage from which an abnormal voltage is removed.SOLUTION: A pulse arc welding power supply executes abnormal voltage removal control in which a welding wire 1 is fed, a welding current Iw formed of a peak current and a base current is supplied, a welding voltage Vw is detected, a detection value Vd of the welding voltage is limited within an allowable range that uses a reference voltage waveform as a central voltage value, and a voltage limit value Vft is calculated; and, based on the voltage limit value Vft, executes output control on the welding voltage Vw. In this pulse arc welding power supply, an allowable range ΔVc during an initial period after an arc start is set to a value smaller than that in a stationary period. In addition, when a short circuit occurs during the initial period, the allowable range ΔVc during the initial period is set to a value smaller than that during the stationary period.SELECTED DRAWING: Figure 5

Description

The present invention relates to a pulse arc welding power source that controls the output by removing an abnormal voltage from the welding voltage.

A pulse arc welding power source that conducts welding by energizing a welding current formed from a peak current and a base current is widely used. In consumable electrode type arc welding including pulse arc welding, it is good welding quality to maintain the apparent arc length (hereinafter, simply referred to as arc length), which is the shortest distance between the tip of the welding wire and the base metal, to an appropriate value. Is important to get. Therefore, the welding power supply is controlled by a constant voltage during the arc period. This utilizes the fact that the arc length and the welding voltage are in a proportional relationship, the arc length is detected by the welding voltage, and the welding voltage detection value is output so as to be equal to the voltage set value corresponding to the appropriate arc length. This is to maintain the arc length at an appropriate value by controlling it. Therefore, in order to stabilize the arc length control, it is necessary to detect the arc length with high accuracy by the welding voltage.

Since consumable electrode type arc welding is usually performed with an electrode positive polarity EP, an anode point is formed at the tip of the welding wire, a cathode point is formed on the surface of the base metal, and an anode point is formed between the anode point and the cathode point. An arc is generated. The anode point hardly moves in the state of being formed near the tip of the wire. On the other hand, the cathode point moves steadily toward the portion of the base material surface where the oxide film is present. Further, the cathode point fluctuates due to dirt on the surface of the base metal, the motion state of the molten pool, gas release from the molten pool, and the like. Even if the formation position of the cathode point changes in a short time, the apparent arc length does not change. This is because the apparent arc length changes depending on the difference between the wire feeding rate and the wire melting rate, so that it can change only slightly in a short time of a dozen ms or less. However, when the cathode point fluctuates due to the various causes described above, an abnormal voltage is superimposed on the welding voltage. This abnormal voltage is a voltage that is not proportional to the apparent arc length. Therefore, if the output is controlled based on the welding voltage on which this abnormal voltage is superimposed, the arc length control system becomes unstable and the welding quality deteriorates. Patent Document 1 discloses a method of removing an abnormal voltage from a welding voltage detection value to generate a welding voltage detection value proportional to an apparent arc length.

Japanese Patent No. 4263886

Welding voltage includes voltage fluctuations due to changes in arc length due to fluctuations in feed rate, torch height, fluctuations in molten pool state, etc., and abnormal voltages due to short-circuit periods, movement of cathode points, etc. Are superimposed. The voltage fluctuation accompanying the fluctuation of the arc length needs to be accurately detected in order to control the arc length. On the other hand, it is desirable to remove as much as possible the abnormal voltage that is not related to the fluctuation of the arc length in order to perform precise arc length control. For this reason, in the prior art, control is performed to remove the abnormal voltage superimposed on the welding voltage.

During the transition period from the arc start to the transition to the steady period, the arc generation state is also in the transient state, so that the abnormal voltage caused by the occurrence of a short circuit, the fluctuation of the cathode point, etc. is greatly superimposed on the welding voltage. In particular, when a short circuit occurs many times or a short circuit occurs for a long time, a large abnormal voltage is superimposed on the welding voltage. For this reason, even if the abnormal voltage removal control is performed during the transient period, the abnormal voltage superimposed on the welding voltage cannot be sufficiently removed, the arc length control becomes unstable, and the welding quality deteriorates. There is.

Therefore, in the present invention, in pulse arc welding in which the output is controlled based on the welding voltage from which the abnormal voltage is removed, it is possible to suppress the welding state from becoming unstable during the transient period from the arc start. The purpose is to provide.

In order to solve the above-mentioned problems, the invention of claim 1 is
The welding wire is fed, the welding current formed from the peak current and the base current is energized, the welding voltage is detected, and the detected value of the welding voltage is limited to the allowable range with the reference voltage waveform as the center voltage value. In a pulse arc welding power supply that performs abnormal voltage removal control to calculate the voltage limit value and outputs and controls the welding voltage based on the voltage limit value.
The tolerance is set to a value smaller during the initial period after the start of the arc than during the steady period.
It is a pulse arc welding power supply characterized by this.

The invention of claim 2 is
When a short circuit occurs during the initial period, the allowable range during the initial period is set to a value smaller than that during the steady period.
The pulse arc welding power source according to claim 1.

The invention of claim 3 is
When a short circuit of the reference time or more occurs during the initial period, the allowable range during the initial period is set to a value smaller than that during the steady period.
The pulse arc welding power source according to claim 1.

According to the present invention, in pulse arc welding in which the output is controlled based on the welding voltage from which the abnormal voltage is removed, it is possible to suppress the welding state from becoming unstable during the transient period from the arc start.

It is a waveform figure which shows the pulse arc welding method which concerns on embodiment. It is a figure which shows the setting method of the reference voltage waveform Vc used for removing an abnormal voltage which concerns on embodiment. FIG. 5 is a voltage waveform diagram when an abnormal voltage is generated due to an arc re-ignition immediately after the short circuit is released, according to the embodiment. FIG. 2 is a diagram showing a time change of a voltage limit value Vft for explaining a method of automatically setting the above-mentioned reference voltage waveform Vc in FIG. 2. It is a block diagram of the pulse arc welding power source which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a waveform diagram showing a pulse arc welding method according to an embodiment. The figure (A) shows the welding current Iw, and the figure (B) shows the welding voltage Vw. Hereinafter, description will be made with reference to the figure.

As shown in FIG. 3A, during the peak rise period Tup at time t1 to t2, the transition current rising from the base current Ib to the peak current Ip is energized, and then during the peak period Tp at time t2 to t3. Is, the peak current Ip is energized, and then, during the peak fall period Tdw from time t3 to t4, the transition current that descends from the peak current Ip to the base current Ib is energized, and then the time. During the base period Tb from t4 to t5, the above-mentioned base current Ib is energized. Further, in response to the energization of the welding current Iw, as shown in FIG. 3B, a transition voltage rising from the base voltage Vb to the peak voltage Vp is applied during the peak rise period Tup. Subsequently, during the peak period Tp, the peak voltage Vp is applied, and then, during the peak fall period Tdw, a transition voltage that drops from the peak voltage Vp to the base voltage Vb is applied. Then, during the base period Tb, the base voltage Vb is applied. Welding is performed by repeating the period from time t1 to t5 as one pulse period Tf. Numerical examples of the above parameters are described. Ip = 500A, Ib = 50A, Tp = 1.2ms, tup = 0.5ms, Tdw = 0.5ms, Tf = 3-10ms

Arc length control is performed to maintain the arc length at an appropriate value in order to obtain good welding quality. Normally, this arc length control utilizes the fact that the welding voltage Vw is substantially proportional to the arc length, and the pulse period is controlled so that the average value of the welding voltage Vw becomes equal to a predetermined voltage set value. .. This arc length control method is called a frequency modulation method. In this case, the peak period Tp, the peak current Ip, and the base current Ib are set to predetermined values and become pulse parameters. The peak current Ip is set to be equal to or higher than the critical value, and is called a unit pulse condition in combination with the peak period Tp. This unit pulse condition is set so as to have one pulse period and one droplet transition. The base current Ib is set to a small current value of about several tens of A, which is less than the critical value. The unit pulse condition and the base current Ib are set to appropriate values according to the material, diameter, feeding speed, etc. of the welding wire. The arc length control method includes a pulse width modulation method in addition to the frequency modulation method described above. In this pulse width modulation method, the pulse period Tf, the peak current Ip and the base current Ib are set to predetermined values, and the peak period Tp is controlled so that the average value of the welding voltage Vw becomes equal to the predetermined voltage set value. ..

In pulse arc welding, the cathode point of the arc has the property of being formed at the position where the oxide film on the surface of the base metal exists. Since the oxide film is removed (cleaned) by the arc, the cathode point is formed by moving to the peripheral portion in search of the place where the oxide film remains. As a result, the arc is in an unstable state where it is constantly moving, and a short circuit is likely to occur. Abnormal voltage when the welding wire and the base metal are short-circuited, the short circuit is released, and the arc reignites, or when the arc cathode point fluctuates due to the non-uniformity of the oxide film on the base metal surface. Will be superimposed on the welding voltage Vw. Since this abnormal voltage is a voltage that is not proportional to the arc length, it is necessary to remove the abnormal voltage superimposed on the welding voltage Vw in order to accurately detect the arc length. As a method for removing this, the reference voltage waveform Vc of the pulse waveform and the allowable range ΔVc are set, and the portion where the welding voltage Vw is out of the range of Vc ± ΔVc is cut as an abnormal voltage. Hereinafter, this abnormal voltage elimination control will be described.

FIG. 2 is a diagram showing a method of setting the above-mentioned reference voltage waveform Vc. First, as will be described later in FIG. 4, the reference peak voltage value Vpc, the reference base voltage value Vbc, and the allowable range ΔVc are set. Then, as shown in the figure, the reference voltage waveform Vc is defined by the elapsed time t with the start time of the peak rise period Tup as 0 seconds as shown in the following equation.
0≤t <Tup
Vc = ((Vpc-Vbc) / Tup) · t + Vbc (11) Equation Tup ≤ t <Tup + Tp
Vc = Vpc (12) Equation Tup + Tp≤t <Tup + Tp + Tdw
Vc = ((Vbc-Vpc) / Tdw) · (t-Tup-Tp) + Vpc (13) formula Tup + Tp + Tdw ≦ t <Tup + Tp + Tdw + Tb
Vc = Vbc (14) equation

For example, as shown in the figure, it is assumed that the welding voltage detection value at the elapsed time t = ta is Vd1. Since the elapsed time ta is when Tup + Tp ≦ ta <Tup + Tp + Tdw, substituting into the above equation (13), the center voltage value Vc1 of the reference voltage waveform becomes the following equation.
Vc1 = ((Vbc-Vpc) / Tdw) ・ (ta-Tup-Tp) + Vpc
Therefore, the welding voltage detection value Vd1 at the elapsed time ta is limited to the allowable range Vc1 ± ΔVc. That is, when Vd1 ≧ Vc1 + ΔVc, the voltage limit value is limited to Vft1 = Vc1 + ΔVc, and when Vd1 ≦ Vc1-ΔVc, it is limited to Vft1 = Vc1-ΔVc. The voltage limit value Vft calculated in this way is a voltage value substantially proportional to the arc length from which the abnormal voltage is substantially removed.

FIG. 3 is a voltage waveform diagram when an abnormal voltage is generated due to the arc re-ignition immediately after the short circuit is released. FIG. 6A shows the time change of the welding voltage Vw, and FIG. 6B shows the time change of the voltage limit value Vft after removing the abnormal voltage by the reference voltage waveform. As shown in FIG. 3B, the welding voltage Vw is limited to the allowable range Vc ± ΔVc with the reference voltage waveform as the center voltage value Vc. As a result, the voltage limit value Vft = Vc−ΔVc during the short-circuit period from time t1 to t2, and the voltage limit value Vft = Vc + ΔVc during the high voltage generation period accompanying the formation of the cathode point at time t2 to t3. In this way, it is possible to substantially eliminate abnormal voltages that are not related to the arc length, such as the voltage during the short-circuit period and the high voltage associated with the formation of the cathode point.

FIG. 4 is a diagram showing a time change of the voltage limit value Vft for explaining the method of automatically setting the reference voltage waveform Vc described above in FIG. 2. In the figure, the present time is the time nt, which is the start time of the nth pulse period Tf (n). Further, the average value of the voltage limit values only in the peak period in the n-1th pulse period Tf (n-1) is the peak voltage limit value Vpf (n-1), and the average value of the voltage limit values only in the base period. The value is the base voltage limit value Vbf (n-1). Similarly, the average value of the voltage limit values only during the peak period in the nmth pulse period Tf (n-m) is the peak voltage limit value Vpf (n-m), and the average value of the voltage limit values only during the base period is the base. The voltage limit value is Vbf (n-m). Here, m is an integer of 2 or more, and n is an integer of m + 1 or more.

At time tun, the peak voltage moving average value Vpr (n) is calculated as shown in the following equation by inputting the peak voltage limit value Vpf of the (n-1) to (nm) th times described above.
Vpr (n) = (Vpf (n-1) ＋… ＋ Vpf (nm)) / m Similar to the equation (21), the above-mentioned (n-1) to (nm) th base voltage limits at time tun. With the value Vbf as an input, the base voltage moving average value Vbr (n) is calculated as shown in the following equation.
Vbr (n) = (Vbf (n-1) + ... + Vbf (nm)) / m (22)

Then, in the above-mentioned equations (11) to (14), the above-mentioned peak voltage moving average value Vpr is substituted into the reference peak voltage value Vpc, and the above-mentioned base voltage moving average value Vbr is substituted into the reference base voltage value Vbc. Then, the reference voltage waveform during the nth pulse period Tf (n) period is automatically set as shown in the following equation.
0≤t <Tup
Vc (n) = ((Vpr (n) -Vbr (n)) / Tup) · t + Vbr (n) (31) Equation Tup≤t <Tup + Tp
Vc (n) = Vpr (n) (32) Equation Tup + Tp≤t <Tup + Tp + Tdw
Vc (n) = ((Vbr (n) -Vpr (n)) / Tdw) · (t-Tup-Tp) + Vpr (n) (33) Equation Tup + Tp + Tdw≤t <Tup + Tp + Tdw + Tb
Vc (n) = Vbr (n) (34)

As described above, the peak voltage moving average value Vpr and the base voltage moving average value Vbr are calculated at each start point of the pulse cycle, and the reference voltage waveform is automatically set by the above equations (31) to (34). To. In the above, when calculating the peak voltage moving average value Vpr, the peak voltage limit value Vpf may be calculated by weighting the moving average. Similarly, when calculating the base voltage moving average value Vbr, the base voltage limit value Vbf may be calculated by weighting the moving average. In addition, the length of the moving average period (predetermined period) is set to about several cycles to several tens of cycles in the past. This predetermined period is set to an appropriate value by an experiment according to the welding conditions such as the material, diameter, feeding speed, welding speed, and welded joint of the welding wire.

The peak voltage moving average value Vpr and the base voltage moving average value Vbr cannot be calculated based on the equations (21) and (22) until the pulse period Tf of m times elapses from the arc start. .. Therefore, during this period, the peak voltage initial value and the base voltage initial value are set in advance and used as the peak voltage moving average value Vpr and the base voltage moving average value Vbr. Further, from the arc start until the pulse period Tf elapses m times, the reference voltage waveform Vc is used by using the above-mentioned peak voltage moving average value Vpr and the above-mentioned base voltage moving average value Vbr calculated during the previous welding. May be formed.

As described above, the welding voltage Vw includes voltage fluctuations due to fluctuations in the arc length due to fluctuations in the feed rate, fluctuations in the torch height, fluctuations in the molten pool state, etc., short-circuit period, movement of the cathode point, etc. The abnormal voltage caused by the above is superimposed. The voltage fluctuation accompanying the fluctuation of the arc length needs to be accurately detected in order to control the arc length. On the other hand, it is desirable to remove as much as possible the abnormal voltage that is not related to the fluctuation of the arc length in order to perform precise arc length control.

FIG. 5 is a block diagram of a pulse arc welding power supply equipped with the above-mentioned abnormal voltage removal control in FIGS. 1 to 4 according to the embodiment. Hereinafter, each block will be described with reference to the figure.

When the start command signal On, which will be described later, changes to the High level (welding start) with a commercial power supply such as 3-phase 200V (not shown) as an input, the power supply main circuit PM controls the inverter according to the current error amplification signal Ei, which will be described later. Output control is performed, and the welding voltage Vw and the welding current Iw are output. Although not shown, the power supply main circuit PM includes a primary rectifier circuit that rectifies a commercial power supply, a capacitor that smoothes the rectified DC, an inverter circuit that converts the smoothed DC into high-frequency AC, and a high-frequency AC. Inverter transformer that steps down to a voltage value suitable for arc welding, a secondary rectifier circuit that rectifies stepped high-frequency alternating current, a reactor that smoothes the rectified DC, and PWM modulation control according to the current error amplification signal Ei described later. It is equipped with a drive circuit that drives the inverter circuit based on the result.

The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between the feeding tip (not shown) in the welding torch 4 and the base metal 2, and the welding current Iw is energized. Shielding gas is ejected from the tip of the welding torch 4 to shield the arc 3 from the atmosphere.

The start command circuit ON outputs a start command signal On, which is at the High level when welding is started and is at the Low level when welding is finished. The start command circuit ON corresponds to a start command switch provided in the welding torch 4, a circuit built in the robot control device in robot welding, and the like. ,

The voltage detection circuit VD detects the above welding voltage Vw and outputs a voltage detection signal Vd.

The current detection circuit ID detects the above welding current Iw and outputs a current detection signal Id.

The energization discrimination circuit CD takes the above current detection signal Id as an input, and when this value is equal to or higher than the energization discrimination value (about 10A), it determines that the welding current Iw is energized and becomes a high level energization discrimination signal. Output Cd.

The short-circuit discrimination circuit SD takes the above voltage detection signal Vd as an input, and when this value is less than the short-circuit discrimination value (about 10V), it determines that it is in the short-circuit period and becomes the High level. Is determined and the short-circuit determination signal Sd that becomes the Low level is output.

The initial period circuit TI receives the above-mentioned energization discrimination signal Cd as an input, and outputs an initial period signal Ti that becomes a high level during a predetermined initial period from the time when the energization discrimination signal Cd changes to the high level (energization). When the arc is started and the welding current Iw is energized, the energization discrimination signal Cd changes to the High level. The initial period is set as a period corresponding to the transition period from the arc start to the transition to the steady period. For example, the initial period is set to about 0.1 to 0.7 seconds. Since the pulse period is about 7 ms, a period of about 15 to 100 is included in the initial period.

The permissible range control circuit DC selects and processes any one of 1) to 3) shown below with the above initial period signal Ti and the above short circuit determination signal Sd as inputs, and performs processing, and the permissible range control signal Dc. Is output.
1) During the initial period when the initial period signal Ti becomes the High level, the allowable range control signal Dc which becomes the High level is output.
2) Tolerance control that becomes High level when the initial period signal Ti becomes High level and the short circuit discrimination signal Sd changes to High level (short circuit), and becomes Low level when the initial period ends. The signal Dc is output.
3) Initial period When the signal Ti is in the initial period when it reaches the High level and the short circuit discrimination signal Sd reaches the High level (short circuit) for the predetermined reference time (about 5 ms) or more, it becomes the High level and the initial period. When is completed, the allowable range control signal Dc that becomes the Low level is output.

The permissible range setting circuit ΔVC receives the above permissible range control signal Dc as an input, and when the permissible range control signal Dc is at the Low level, it becomes a predetermined normal permissible range, and when the permissible range control signal Dc is at the High level, it becomes the above-mentioned above. The allowable range setting signal ΔVc, which is a predetermined allowable range and is set to a value smaller than the normal allowable range, is output. For example, the normal allowable range is about ± 4V, and the initial allowable range is about ± 1V.

The voltage limit value calculation circuit FT limits the voltage detection signal Vd to within the limit range Vc ± ΔVc determined by the reference voltage waveform signal Vc and the allowable range setting signal ΔVc described later, and outputs the voltage limit value signal Vft. do.

The voltage moving average value calculation circuit VRA calculates the peak voltage moving average value signal Vpr and the base voltage moving average value signal Vbr with the above voltage limit value signal Vft as an input, as described above in FIG. These calculation methods are performed based on the above-mentioned equations (21) and (22).
The peak voltage moving average value Vpr and the base voltage moving average value Vbr cannot be calculated until the pulse period Tf of m times (m is an integer of 2 or more) elapses from the arc start. Therefore, during this period, the peak voltage initial value and the base voltage initial value are set in advance and used as the values of the peak voltage moving average value Vpr and the base voltage moving average value Vbr. Further, the above-mentioned peak voltage moving average value Vpr and the above-mentioned base voltage moving average value Vbr calculated during the previous welding may be used until the pulse period Tf of m times elapses from the arc start. ..

The reference voltage waveform setting circuit VC inputs the above-mentioned peak voltage moving average value signal Vpr and the above-mentioned base voltage moving average value signal Vbr, and outputs the above-mentioned reference voltage waveform signal Vc as described in FIG. The setting of the reference voltage waveform signal Vc is performed by the above-mentioned equations (31) to (34).

The voltage integration circuit SV integrates the above voltage limit value signal Vft from the start point of each pulse cycle (1 / t) ∫Vft · dt, and outputs the voltage integration value signal Sv. Here, t is the elapsed time (seconds) from the start time of each pulse cycle. Therefore, the value of the voltage integral value signal Sv is calculated every moment as the average value of the voltage limit value signal Vft.

The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The comparison circuit CM compares the above-mentioned voltage integration value signal Sv with the above-mentioned voltage setting signal Vr, and obtains a pulse period signal Tf which becomes a high level for a short time in order to end the pulse period when the same value is obtained. Output. When Sv = Vr, it means that the average value of the voltage limit value signal Vft in each pulse cycle becomes equal to the value of the voltage setting signal Vr. In this way, the arc length control described above is performed. Therefore, the interval at which the pulse period signal Tf changes to the High level for a short time is the length of each pulse period.

The elapsed time measurement circuit ST measures the elapsed time from the time when the pulse cycle signal Tf changes to the High level (the start time of each pulse cycle), and outputs the elapsed time signal St.

The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

The current control setting circuit IRC receives the above-mentioned elapsed time signal St, the above-mentioned peak current setting signal Ipr, and the above-mentioned base current setting signal Ibr as inputs, and each time the elapsed time signal St is reset to 0, a predetermined peak is set. During the rise period Tup, the current control setting signal Irc that rises from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr is output, and during the subsequent peak period Tp, the value of the peak current setting signal Ipr is output. Is output as the current control setting signal Irc, and during the subsequent peak fall period Tdw, the current control setting signal Irc that drops from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr is output. During the subsequent base period Tb, the value of the base current setting signal Ibr is output as the current control setting signal Irc.

The current error amplifier circuit EI amplifies the error between the current control setting signal Irc and the current detection signal Id, and outputs the current error amplification signal Ei.

The feed control circuit FC outputs a feed control signal Fc for feeding the welding wire 1 at a predetermined feed speed set value to the feed motor WM.

The action and effect of the above-described embodiment will be described.
1) When the start command signal On reaches the High level, the welding power supply starts output and starts feeding the welding wire 1.
2) When the welding wire 1 is fed and comes into contact with the base metal 2, the arc starts and the welding current Iw is energized.
3) The voltage limit value calculation circuit FT limits the voltage detection signal Vd within the limit range Vc ± ΔVc determined by the reference voltage waveform signal Vc and the allowable range setting signal ΔVc, and outputs the voltage limit value signal Vft. The value of the above allowable range setting signal ΔVc is a predetermined initial allowable range when a short circuit occurs during the initial period after the arc start, during the initial period, or when a short circuit longer than the reference time occurs during the initial period. It becomes. It is usually acceptable during the subsequent steady-state period.
4) The output of the welding power supply is controlled by frequency modulation control so that the average value of the voltage limit signal Vft and the predetermined voltage setting signal Vr become equal to each other.

According to the embodiment described above, the permissible range is set to a value smaller during the initial period after the arc start than during the steady period. During the transition period from the arc start to the transition to the steady period, the arc generation state is also in the transient state, so that the abnormal voltage caused by the occurrence of a short circuit, the fluctuation of the cathode point, etc. is greatly superimposed on the welding voltage. In particular, when a short circuit occurs many times or a short circuit occurs for a long time, a large abnormal voltage is superimposed on the welding voltage. In the present embodiment, during the initial period corresponding to the transient period, the allowable range is reduced and the abnormal voltage removal control is performed so that the abnormal voltage superimposed on the welding voltage is sufficiently removed. At this time, since the fluctuation of the welding voltage due to the fluctuation of the arc length is also removed a little, the transient response of the arc length control becomes a little slow. However, the effect of sufficiently removing the abnormal voltage is greater. Therefore, the allowable range is set to a normal value so as not to remove the welding voltage due to the fluctuation of the arc length during the steady period. As a result, in the present embodiment, in pulse arc welding in which the output is controlled based on the welding voltage from which the abnormal voltage is removed, it is possible to suppress the welding state from becoming unstable during the transient period from the arc start.

Further, according to the present embodiment, when a short circuit occurs during the initial period, it is preferable to set the allowable range during the initial period to a value smaller than that during the steady period. The reason why the abnormal voltage is generated during the initial period is that the short circuit often occurs many times because the arc generation state is in the transition state. Therefore, when a short circuit occurs during the initial period, the abnormal voltage is sufficiently removed by reducing the allowable range during the initial period. By doing so, when a short circuit does not occur during the initial period, the allowable range remains a normal value, so that the transient response of the arc length control is not impaired. As a result, in the present embodiment, the welding state during the transition period can be made more stable.

Further, according to the present embodiment, when a short circuit of the reference time or more occurs during the initial period, it is preferable to set the allowable range during the initial period to a value smaller than that during the steady period. The reason why the abnormal voltage is generated during the initial period is that the arc generation state is in the transition state, so that a long-term short circuit longer than the reference time often occurs. Therefore, when a short circuit of the reference time or longer occurs during the initial period, the abnormal voltage is sufficiently removed by reducing the allowable range during the initial period. In this way, when a long-term short circuit does not occur during the initial period, the allowable range remains a normal value, so that the transient response of the arc length control is not impaired. As a result, in the present embodiment, the welding state during the transition period can be made more stable.

1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding roll CD Currenting discrimination circuit Cd Currenting discrimination signal CM Comparison circuit DC Allowable range control circuit Dc Allowable range control signal EI Current error amplification circuit Ei Current error amplification signal FC Feed control Circuit Fc Feeding control signal FT Voltage limit value calculation circuit Ib Base current IBR Base current setting circuit Ibr Base current setting signal ID Current detection circuit Id Current detection signal Ip Peak current IPR Peak current setting circuit Ipr Peak current setting signal IRC Current control setting Circuit Irc Current control setting signal Iw Welding current ON Start command circuit On Start command signal PM Power supply Main circuit SD Short circuit discrimination circuit Sd Short circuit discrimination signal ST Elapsed time measurement circuit St Elapsed time signal SV Voltage integration circuit Sv Voltage integrated value signal t Elapsed time ta Elapsed time Tb Base period Tdw Peak fall period Tf Pulse period (signal)
TI initial period circuit Ti initial period signal Tp peak period Tup peak rise period Vb base voltage Vbc reference base voltage value Vbf base voltage limit value Vbr base voltage moving average value (signal)
VC reference voltage waveform setting circuit Vc reference voltage waveform (signal)
VD voltage detection circuit Vd voltage detection signal Vft voltage limit value (signal)
Vp peak voltage Vpc reference peak voltage value Vpf peak voltage limit value Vpr peak voltage moving average value (signal)
VR voltage setting circuit Vr voltage setting signal VRA voltage moving average value calculation circuit Vw Welding voltage WM Feed motor ΔVC Allowable range setting circuit ΔVc Allowable range (setting signal)

Claims (3)

The welding wire is fed, the welding current formed from the peak current and the base current is energized, the welding voltage is detected, and the detected value of the welding voltage is limited to the allowable range with the reference voltage waveform as the center voltage value. In a pulse arc welding power supply that performs abnormal voltage removal control to calculate the voltage limit value and outputs and controls the welding voltage based on the voltage limit value.
The tolerance is set to a value smaller during the initial period after the start of the arc than during the steady period.
It features a pulsed arc welding power supply. When a short circuit occurs during the initial period, the allowable range during the initial period is set to a value smaller than that during the steady period.
The pulse arc welding power source according to claim 1. When a short circuit of the reference time or more occurs during the initial period, the allowable range during the initial period is set to a value smaller than that during the steady period.
The pulse arc welding power source according to claim 1.

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