JP2001121264A - Method for controlling power supply for dc arc machining and power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a power supply for an arc machining by which method a contact of consumable electrode with a work is detected by applying a detecting voltage on the electrode, and to improve a power unit. SOLUTION: In the controlling method for a power source for a DC arc machining where a power supply circuit for the contact detection for a touch sensor is not used but shared with a power source for a welding, the voltage drop of the welding power supply under a no-load condition is detected by a beginning signal of a contact detection and the contact position of a consumable electrode with a work is determined, and a low electric current for detecting the contact is supplied from the welding power supply immediately after the contact of a consumable electrode with the work is detected, then the low electric current for detecting the contact is switched over to the welding current by a driving signal for the welding and the welding is started the power unit related to the above method is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a power supply device for arc processing for detecting that a consumable electrode is in contact with a workpiece by applying a detection voltage to the electrode.

[0002]

2. Description of the Related Art A wire touch sensor is used for positioning a welding robot. This wire touch sensor detects that the consumable electrode of the welding torch has come into contact with the workpiece.

FIG. 10 shows a conventional wire touch sensor. Reference numeral 1 denotes an AC power supply, and a three-phase AC commercial power supply is used. The primary rectifier circuit 2 rectifies and smoothes the output of the three-phase AC commercial power supply and converts it to DC power. The inverter circuit 3 converts the DC power of the primary rectifier circuit 2 into a high-frequency AC pulse voltage. Reference numeral 4 denotes a main transformer, and an inverter circuit 3
Is converted into a high-frequency AC pulse voltage suitable for arc machining. The secondary rectifier circuit 5 rectifies and smoothes the output of the main transformer and converts it to DC power. 6 is a DC reactor. As described above, the welding power supply circuit 57 is formed. Reference numeral 32 denotes a main control circuit.

As shown in FIG. 10, a constant current power supply circuit 51 serving as a detection voltage supply means is connected to a plus side (a welding torch 13 side) of an output terminal via a diode DR1. Therefore, when the welding power source is not outputting, the detection voltage is applied to the consumable electrode 14 at the tip of the welding torch 13 via the diode DR1 by the constant current power source 51.

When the consumable electrode 14 at the tip of the welding torch 13 comes into contact with the workpiece 15, a current flows and the voltage between the output terminals decreases. The AC amplifier 55 amplifies the voltage change between the output terminals. Short-circuit detection circuit 5 having a comparator function for converting this output into ON and OFF signals.
The contact signal S is transmitted via the control signal 6.

It is desirable that the voltage between the consumable electrode 14 and the workpiece 15 be as high as possible in order to enhance the contact detection capability. However, if the voltage is too high, the diode of the secondary rectifier circuit 5 is destroyed. Limited. Therefore, the voltage is set in consideration of the withstand voltage of the diode of the secondary rectifier circuit 5.
It is also conceivable to use a resistor to convert a change in current into a voltage.However, if a high resistance is used to increase sensitivity, the voltage for contact detection will be reduced. And the constant current power supply circuit 51 with a small detection voltage is used.

Generally, the internal circuit of a welding power source is not simple as shown in FIG. 10, but has various leakage currents. In addition, leakage current also exists in the cable on the welding torch 13 side and in the cable connecting the workpiece 15 and the welding power source, and these leak currents vary depending on the cable length and installation conditions. If the resistance between the welding torch 13 and the workpiece decreases due to these fluctuation factors, the voltage for contact detection also decreases and the detection sensitivity decreases. In order to solve the above problem, a constant current value automatic adjustment circuit 54 is provided. This monitors the detection voltage, and if the voltage is low for a predetermined period of time, increases the current set value of the constant current power supply 51, and serves to keep the detection voltage constant.

[0008] When the electric resistance between the welding torch 13 and the workpiece 15 is reduced, if the current of the constant current power supply 51 is increased without any limitation, the constant current power supply circuit 51 is destroyed by heat generation. Current limiting circuit 53
Is provided. This current limiting circuit 53 limits the maximum current of the constant current power supply circuit 51.

When the consumable electrode 14 comes into contact with the workpiece 15, the contact resistance becomes very small. When this state continues for a long time, the current value of the constant current power supply circuit 51 is maintained at the maximum state by the operation of the constant current value automatic adjustment circuit 54 and the current limiting circuit 53. Undesirable in terms. Therefore, it is detected that the consumable electrode 14 and the workpiece 15 are in contact with each other, and the constant current power supply circuit 51 is detected.
Short-circuit protection circuit 52 in order to suppress the current value of
Is provided.

Generally, when the metal surface of the workpiece 15 is covered with an oxide, conduction is extremely poor, but the oxide contains moisture and is not a perfect insulator. Therefore, even if a voltage is applied, a small amount of current flows, and by converting this current into a change in voltage and amplifying it, it has the same detection capability as when a high voltage is applied.

[0011]

In the conventional device shown in FIG. 10, it is necessary to detect the contact of the consumable electrode with the workpiece and determine the position of the contact of the consumable electrode with the workpiece. In addition, a contact detection power supply circuit 50 was required separately from the welding power supply. Further, when the output voltage from the welding power source is applied to the contact detection power supply circuit 50, a protection diode DR1 for protecting the circuit is required, and the contact detection power supply circuit 50 and the protection diode are further required. DR1 has to be separately installed outside the welding power source, so that the workability is very poor, and there is a disadvantage that it is expensive.

[0012]

SUMMARY OF THE INVENTION According to the method of the present invention, the welding power supply circuit 33 detects the position of the workpiece by detecting that the consumable electrode has contacted the workpiece. In a DC arc machining power supply control method for welding by applying a welding current, a contact detection power supply circuit 5 for a touch sensor is provided.
0 is a DC arc machining power supply control method that also serves as a welding power supply without using 0, wherein a no-load voltage Vo of the welding power supply circuit 33 is applied between the consumable electrode and the workpiece by a contact detection start signal, This is a DC arc machining power supply control method in which a welding current is supplied by a welding drive signal Sa after detecting that a consumable electrode has contacted a workpiece and determining a position of the workpiece.

In the method of the present invention, the consumable electrode contacts the workpiece and detects a low current flowing from the welding power supply circuit 33 to determine that the consumable electrode has contacted the workpiece. A method for controlling a DC arc machining power supply according to claim 1.

In the method of the present invention, the welding current is supplied from the welding power supply circuit 33 after detecting that the consumable electrode has contacted the workpiece and determining the position of the workpiece. In the DC arc machining power supply control method for welding, there is provided a DC arc machining power supply control method that also serves as a welding power supply without using a contact detection power supply circuit 50 for a touch sensor. V
o is detected, the position where the consumable electrode contacts the workpiece is determined, and a low current for contact detection is supplied from the welding power source immediately after detecting that the consumable electrode has contacted the workpiece. Then, this is a DC arc machining power supply control method for starting welding by switching the low current for contact detection to the welding current in accordance with the welding drive signal Sa.

According to the invention of claim 4 at the time of filing, the welding power supply circuit 33 is an inverter circuit, and supplies a low current for contact detection at a predetermined constant cycle from the welding power supply.
DC power source control method.

The invention of the method of claim 5 at the time of filing is defined by claim 4
The oscillation period tb and the stop period ta of the contact detection clock signal Sb that drives the inverter circuit
This is a DC arc machining power supply control method which is the cycle of the above.

The invention of the method of claim 6 at the time of filing is defined by claim 4
The oscillation period tb and the stop period ta of the contact detection clock signal Sb that drives the inverter circuit
The contact detection clock signal Sb immediately after detecting that the consumable electrode has contacted the workpiece.
Is reduced to a predetermined second oscillation period tc.

The invention of the method of claim 7 at the time of filing is described in claim 4
The oscillation period tb and the stop period ta of the contact detection clock signal Sb that drives the inverter circuit
The contact detection clock signal Sb immediately after detecting that the consumable electrode has contacted the workpiece.
This is a DC arc machining power supply control method for stopping the oscillation of the DC arc machining.

In the method of the invention, the welding power supply circuit 33 is an inverter circuit, and the output current value Ir of the inverter circuit when the consumable electrode contacts the workpiece.
And detecting an excessive current at the start of the contact detection low-current energization.
Or a DC arc machining power supply control method according to claim 7.

According to the invention of the ninth aspect of the present invention, a three-phase AC commercial power supply is rectified by a primary rectifier circuit 2 to obtain DC power, and the DC power is converted into a high-frequency AC pulse voltage by an inverter circuit 3. Each of the positive and negative voltages is output, and the main transformer 4 converts the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load.
In the DC arc machining power supply device for supplying DC power by rectifying the current, the detection and switching of the welding current and the low current for contact detection and the detection of the welding current switching signal St The clock signal Sb for contact detection is supplied by the low current supply command. The inverter circuit outputs an inverter drive signal Ps for driving the inverter from the PWM circuit to supply a low current for detection from the inverter, to detect a decrease in the no-load voltage Vo after the consumable electrode comes into contact with the workpiece, and to detect the consumable electrode. Judge the position where it touched the workpiece,
Next, a DC arc machining power supply for supplying a welding drive signal Sa according to a welding current supply command of the detection / welding current switching signal St, outputting an inverter drive signal Ps for driving the inverter from the PWM circuit, and supplying a welding current from the inverter. It is a control method.

According to a tenth aspect of the present invention, the inverter circuit 3 according to the ninth aspect is configured such that the oscillation period tb and the stop period of the contact detection clock signal Sb are controlled by the detection and welding current switching signal St detected low current energizing command. This is a DC arc machining power supply control method for generating a contact detection clock signal Sb that repeats at a cycle of ta.

According to the invention of claim 11 at the time of filing, the inverter circuit 3 according to claim 9 is configured such that the oscillation period tb and the stop period of the contact detection clock signal Sb in response to the detection / welding current switching signal St detection low current energization command. The pulse width of the contact detection clock signal Sb is set to a second predetermined value immediately after detecting a contact detection clock signal Sb that repeats at a cycle of ta and detecting that the consumable electrode has contacted the workpiece. This is a DC arc machining power supply control method for reducing the oscillation period tc.

According to a twelfth aspect of the present invention, the inverter circuit 3 according to the ninth aspect is configured such that the oscillation period tb and the stop period of the contact detection clock signal Sb are detected by the detection / welding current switching signal St detection low current energization command. DC arc machining power supply control for generating a contact detection clock signal Sb that repeats at a cycle of ta and stopping the oscillation of the contact detection clock signal Sb immediately after detecting that the consumable electrode has contacted the workpiece. Is the way.

According to the invention of claim 13 at the time of filing, the output current value Ir of the inverter circuit when the consumable electrode comes into contact with the workpiece is suppressed to suppress the excessive current at the start of the contact detection low current application. Claim 9 or Claim 10 or Claim 1
A DC arc machining power supply control method according to claim 1 or 12.

According to the invention of claim 14 at the time of filing, the output current value Ir of the inverter circuit when the consumable electrode comes into contact with the workpiece is detected, and the overcurrent for contact detection is detected by the detection / welding current switching signal St. By switching between the reference signal Ib and the welding overcurrent reference signal Ia, the output current I
r, and outputs an overcurrent detection signal Sc when it is larger than one of the reference signals to reduce the pulse period of the high-frequency AC pulse voltage output from the PWM circuit to reduce the excess current at the start of the contact detection low current application. A DC arc machining power supply control method according to claim 13 for suppressing.

The method according to claim 15 of the present invention is characterized in that a predetermined time td is set immediately after the consumable electrode comes into contact with the workpiece.
The DC arc machining power supply control method according to claim 9 or claim 10, wherein the position of the workpiece is determined after elapse.

[0027] At the time of filing, the invention of claim 16 is a primary rectifier circuit 2 for rectifying three-phase AC commercial power to obtain DC power.
An inverter circuit 3 that converts DC power into a high-frequency AC pulse voltage and outputs positive and negative voltages; a main transformer 4 that converts the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load; In a DC arc processing power supply device for rectifying the output of
A detection / welding changeover switch SW2 for controlling the PWM circuit 17 by switching between the output signal Sb of the contact detection clock circuit 21 and the output signal Sa of the welding drive circuit 20 according to the detection / welding current switching signal St; An output control changeover switch S for switching between the output setting signal Is of the output setting device 26 and the contact detection setting device 24 according to the switching signal St.
W3, and a PWM circuit 17 that modulates the pulse width in accordance with the contact detection reference signal Ic or the output setting signal Is selected by the output control changeover switch SW3 and controls the output,
This is a DC arc machining power supply device that controls the output of the inverter circuit 3 by an inverter drive signal Ps to switch between a low contact current for detection and a welding current.

The invention of the device according to claim 17 at the time of filing is a primary rectifier circuit 2 for rectifying three-phase AC commercial power to obtain DC power.
An inverter circuit 3 that converts DC power into a high-frequency AC pulse voltage and outputs positive and negative voltages; a main transformer 4 that converts the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load; In a DC arc processing power supply device for rectifying the output of
An overcurrent protection current detector 9 for detecting and outputting the output current value Ir of the inverter circuit; and an overcurrent reference signal changeover switch for selecting one of the contact detection overcurrent reference signal Ib and the welding overcurrent reference signal Ia. SW1 is compared with one of the reference signals selected by the overcurrent reference signal changeover switch SW1 and the output current value Ir of the inverter circuit. If the output current value Ir is larger than the one reference signal, the overcurrent detection signal Sc is output and PWM is output.
An overcurrent detection comparator 16 for controlling a circuit 17;
The output signal Sb of the contact detection clock circuit 21 and the output signal S of the welding drive circuit 20 are determined by the welding current switching signal St.
a, a detection / welding changeover switch SW2 for controlling the PWM circuit 17 by switching to a. An output control changeover switch SW3 for switching between the output setting signal Is of the output setting device 26 and the contact detection setting device 24 by the detection / welding current switching signal St.
And a PWM circuit 17 that modulates the pulse width according to the contact detection reference signal Ic or the output setting signal Is selected by the output control changeover switch SW3 and controls the output, and controls the output of the inverter circuit by the inverter drive signal Ps. A DC arc machining power supply device for switching between a contact low current for detection and a welding current.

The invention of the device according to claim 18 at the time of filing is a primary rectifier circuit 2 for rectifying three-phase AC commercial power to obtain DC power.
An inverter circuit 3 that converts DC power into a high-frequency AC pulse voltage and outputs positive and negative voltages; a main transformer 4 that converts the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load; In a DC arc processing power supply device for rectifying the output of
A detection / welding changeover switch SW2 for controlling the PWM circuit 17 by switching between the output signal Sb of the contact detection clock circuit 21 and the output signal Sa of the welding drive circuit 20 in response to the detection / welding current switching signal St; Output setting signal Is and output current I detected by output current detector 8
and an output waveform control circuit 22 for outputting the obtained output waveform control signal ΔV, a contact detection reference signal Ic of the contact detection setter 24 and an output waveform control signal Δ
An output control switch SW3 for selecting one of V, a PWM circuit 17 for modulating the pulse width according to the value of the contact detection reference signal Ic and the output waveform control signal ΔV selected by the output control switch SW3, and controlling the output. Inputting the output voltage signal Vo of the output voltage detector 7 and comparing a predetermined contact voltage detection reference value Va with the output voltage signal Vo;
The output voltage signal Vo is a predetermined reference value V for contact voltage detection.
a short-circuit detection circuit 23 which determines that the consumable electrode has come into contact with the workpiece when it is smaller than a and outputs an electrode contact signal So, and controls the output of the inverter circuit by the inverter drive signal Ps to detect the contact. This is a DC arc machining power supply device that switches between low current and welding current.

The invention of the apparatus according to claim 19 at the time of filing is a primary rectifier circuit 2 for rectifying three-phase AC commercial power to obtain DC power.
An inverter circuit 3 that converts DC power into a high-frequency AC pulse voltage and outputs positive and negative voltages; a main transformer 4 that converts the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load; In a DC arc processing power supply device for rectifying the output of
An overcurrent protection current detector 9 for detecting and outputting the output current value Ir of the inverter circuit; and an overcurrent reference signal changeover switch for selecting one of the contact detection overcurrent reference signal Ib and the welding overcurrent reference signal Ia. SW1 is compared with one of the reference signals selected by the overcurrent reference signal changeover switch SW1 and the output current value Ir of the inverter circuit. If the output current value Ir is larger than the one reference signal, the overcurrent detection signal Sc is output and PWM is output.
An overcurrent detection comparator 16 for controlling a circuit 17;
The output signal Sb of the contact detection clock circuit 21 and the output signal S of the welding drive circuit 20 are determined by the welding current switching signal St.
a, the detection / welding changeover switch SW2 for controlling the PWM circuit 17 by switching between the output setting signal Is of the output setting device 26 and the output current Io detected by the output current detector 8, and calculating the difference between them. An output waveform control circuit 22 for outputting the obtained output waveform control signal ΔV;
The output control switch SW3 for selecting one of the contact detection reference signal Ic and the output waveform control signal ΔV, and the contact detection reference signal I selected by the output control switch SW3.
c and a PWM circuit 17 that modulates the pulse width in accordance with the value of the output waveform control signal ΔV to control the output, and a contact voltage detection reference value Va that is input with the output voltage signal Vo of the output voltage detector 7 and is predetermined. And the output voltage signal Vo. When the output voltage signal Vo is smaller than a predetermined contact voltage detection reference value Va, it is determined that the consumable electrode has contacted the workpiece and the electrode contact signal So is output. A DC arc machining power supply device comprising a detection circuit 23 and controlling the output of the inverter circuit by an inverter drive signal Ps to switch between a low contact current for detection and a welding current.

According to the invention of the twentieth aspect of the invention, when the inverter circuit 3 detects the detection / welding current switching signal St and receives a low current energizing command, the second contact detection clock circuit 28
The contact detection clock signal Sb is generated immediately after detecting that the consumable electrode has come into contact with the workpiece by generating a contact detection clock signal Sb that repeats at the cycle of the oscillation period tb and the stop period ta of the output signal Sb. 20. The DC arc machining power supply device according to claim 18 or claim 19, wherein the pulse width of Sb is reduced to a predetermined value tc.

The invention according to claim 21 at the time of filing the invention is such that the inverter circuit 3 detects the detection / welding current switching signal St and outputs the third contact detection clock circuit 29 in response to the low current supply command.
The contact detection clock signal Sb is generated immediately after detecting that the consumable electrode has come into contact with the workpiece by generating a contact detection clock signal Sb that repeats at the cycle of the oscillation period tb and the stop period ta of the output signal Sb. 20. The DC arc machining power supply device according to claim 18 or claim 19, wherein oscillation of Sb is stopped.

The invention of the device according to claim 22 at the time of filing the invention determines the position of the workpiece after a predetermined contact detection inhibition period td immediately after the consumable electrode comes into contact with the workpiece. A DC arc machining power supply device according to claim 19, claim 20, or claim 21.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the present invention, as shown in the power supply unit connection diagram of FIG. 1 and a timing chart for explaining the operation of the connection diagram, FIG. A primary rectifier circuit that obtains power, an inverter circuit that converts DC power into a high-frequency AC pulse voltage and outputs positive and negative voltages, and a main transformer that converts the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load, In a DC arc machining power supply device that supplies DC power by rectifying the output of a main transformer with a secondary rectifier circuit, an output signal of a contact detection clock circuit and an output signal of a welding drive circuit are provided by a detection / welding current switching signal St. And a switch for controlling the PWM circuit by switching between them, and an output control for switching between the output setting signal Is of the output setting device and the contact detection setting device according to the detection / welding current switching signal. And change-over switch, PWM modulating output control to the pulse width in accordance with the selected contact detection reference signal Ic or the output setting signal Is by the output control changeover switch
A DC arc machining power supply device comprising a circuit and controlling an output of the inverter circuit by an inverter drive signal to switch between a contact low current for detection and a welding current.

[0035]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a control method and a power supply apparatus for a DC arc machining power supply using a touch sensor for determining a position at which a consumable electrode contacts a workpiece according to the present invention;

FIG. 1 is a power supply apparatus connection diagram showing an embodiment of a DC arc processing power supply apparatus for detecting that a consumable electrode has contacted a workpiece.

In FIG. 1, reference numeral 1 denotes an AC power supply, and a three-phase AC commercial power supply is used. The primary rectifier circuit 2 rectifies and smoothes the output of the three-phase AC commercial power supply and converts it to DC power. The inverter circuit 3 converts the DC power of the primary rectifier circuit 2 into a high-frequency AC pulse voltage. Reference numeral 4 denotes a main transformer, which converts the output of the inverter circuit 3 into a high-frequency AC pulse voltage suitable for arc machining. The secondary rectifier circuit 5 rectifies and smoothes the output of the main transformer and converts it to DC power. 6 is a DC reactor.

The output voltage detector 7 detects the voltage between the output terminals and outputs an output voltage signal Vo as shown in FIG. The output current detector 8 detects an output current and outputs an output current signal Io. Current detector 9 for overcurrent protection
Outputs an output current value Ir of the inverter circuit.

The overcurrent protection circuit 10 includes an overcurrent detection comparator 16, an overcurrent reference signal switch SW1, a welding overcurrent reference signal 18, and a contact detection overcurrent reference signal 1.
9, the output current value Ir of the inverter circuit in the overcurrent detection comparator 16 and the welding overcurrent reference signal Ia and the contact detection overcurrent reference signal Ib selected by the overcurrent reference signal changeover switch SW1. And outputs an overcurrent detection signal Sc when Ir <Ia and Ir <Ib.

The main control circuit 11 includes a PWM control circuit 17,
The PWM control circuit 17 includes an output control switch SW3, an output waveform control circuit 22, and a contact detection setting unit 24. The PWM control circuit 17 outputs the output waveform control signal ΔV and the contact detection reference signal Ic selected by the output control switch SW3.
, The pulse width of the inverter drive signal Ps is controlled.

Driver circuit 12 converts inverter drive signal Ps to a signal level corresponding to inverter circuit 3 and outputs an inverter control signal Ds. Reference numeral 13 denotes a welding torch, 14 denotes a consumable electrode, and 15 denotes a workpiece.

The detection / welding changeover switch SW2 selects the welding drive signal Sa of the welding drive circuit 20 and the contact detection clock signal Sb of the contact detection clock circuit 21 by the detection / welding current switching signal St, and performs PWM control. Circuit 1
7, and controls the oscillation period and the stop period of the PWM control circuit 17 in accordance with the above signals.

The short-circuit detecting circuit 23 receives the output voltage signal Vo and compares it with a predetermined reference value Va for contact voltage detection (not shown).
4 is in contact with the workpiece 15 and the electrode contact signal S
o is output outside the welding power source.

Reference numeral 25 denotes a start switch which outputs a start signal S1. 26 is an output setting device which outputs an output setting signal Is.

FIG. 2 is a timing chart for explaining the operation of the power supply device shown in FIG. 1. The operation of the embodiment shown in FIG. 1 will be described with reference to the timing chart of FIG. FIG. 2A shows the activation signal S1, which has a contact detection period T1 and a welding period T2. FIG. 2 (B) shows the detection and
FIG. 2 (C) shows a welding drive signal Sa, FIG. 2 (D) shows a contact detection clock signal Sb, and FIG. 2 (E) shows an output voltage detector. 7 shows an output voltage signal Vo output from the reference numeral 7. FIG. 2F shows the output current value Ir of the inverter circuit output from the overcurrent protection current detector 9, and FIG. 2G shows the overcurrent detection signal Sc output from the overcurrent detection comparator 16. Is shown. FIG.
(H) shows the electrode contact signal So output from the short-circuit detection circuit 23.

When the start signal S1 shown in FIG. 2A is output from the start switch 25, the PWM control circuit 17 waits in an operable state. Further, at the time of detection, the overcurrent reference signal changeover switch SW1, the detection and welding changeover switch SW2, and the output control changeover switch SW3 are all set to the b side by the detection and welding current changeover signal St.

When the overcurrent reference signal changeover switch SW1 is on the b side, the contact detection overcurrent reference signal Ib is selected and input to the overcurrent detection comparator 16. When the consumable electrode 14 comes into contact with the workpiece 15 and the set output current is large, the workpiece 15 is damaged by welding or sparking. Therefore, the value of the overcurrent reference signal Ib at the time of contact detection is set in a range of a predetermined value Ib = 1A to 3A in order to prevent the above.

When the detection / weld changeover switch SW2 is on the side b, the contact detection clock signal Sb shown in FIG. 2D is selected and input to the PWM control circuit 17. The PWM control circuit 17 oscillates in synchronization with the oscillation period tb of the input signal Sb.

During the stop period ta of the contact detection clock signal Sb shown in FIG.
Even if it touches No. 5, the output of the electrode contact signal So is delayed because the contact is not determined. Therefore, the above-described delay is dealt with by appropriately increasing the cycle of the oscillation period tb and the stop period ta of the contact detection clock signal Sb.

When the output control changeover switch SW3 is on the b side, the contact detection reference signal Ic from the contact detection setter 24 is selected and input to the PWM control circuit 17. Further, the contact detection reference signal Ic is set to a predetermined value that does not damage the workpiece 15 when the consumable electrode 14 contacts the workpiece 15.

At time t = t1 shown in FIG.
When the consumable electrode 14 contacts the workpiece 15, the contact detection starts from the second oscillation period tb in FIG. 2D.

The output voltage detector 7 inputs the output voltage signal Vo shown in FIG. The short-circuit detection circuit 23 compares the output voltage signal Vo with a predetermined contact voltage detection reference value Va, and determines that the consumable electrode 14 has come into contact with the workpiece 15 when Va> Vo. 2
An electrode contact signal So shown in (H) is output outside the welding power source.

The overcurrent protection current detector 9 is shown in FIG.
Is input to the overcurrent detection comparator 16. The overcurrent detection comparator 16 compares the output current value Ir of the inverter circuit with the overcurrent reference signal Ib at the time of contact detection, and when Ib <Ir, determines that an overcurrent has occurred. The overcurrent detection signal Sc is output, and the oscillation of the PWM control circuit 17 is temporarily stopped during the period when the overcurrent detection signal Sc is output to control the output current value.

At time t = t2 shown in FIG.
When the consumable electrode 14 is released from the workpiece 15, determination of contact or release is started from the fourth transmission period tb of the contact detection clock signal Sb in FIG. 2D.

The fourth output voltage signal V shown in FIG.
is input to the short-circuit detection circuit 23, the short-circuit detection circuit 2
3 compares the output voltage signal Vo with a predetermined reference value Va for contact voltage detection and determines that the consumable electrode 14 has opened from the workpiece 15 when Va <Vo.
The electrode contact signal So shown in (H) is set to Low.

In the overcurrent protection current detector 9, since the consumable electrode 14 is open from the workpiece 15,
The output current value Ir of the inverter circuit shown in FIG. The overcurrent detection comparator 16 compares the output current value Ir of the inverter circuit with the overcurrent reference signal Ib at the time of contact detection, so that Ib> Ir, and the output of the overcurrent detection signal Sc shown in FIG. To stop.

At time t = t3 at which the contact detection period T1 of the start signal S1 shown in FIG. 2A ends, the overcurrent reference signal switch SW1 and the detection / weld switch SW2 are switched by the detection / welding current switching signal St. And all the output control changeover switches SW3 are set to the a side. Also, the welding period T
2 shows a no-load state at the time of welding.

When the overcurrent reference signal changeover switch SW1 is switched to the a side, the welding overcurrent reference signal Ia is selected and input to the overcurrent detection comparator 16. If an overcurrent flows during welding, the power supply device is broken and the workpiece 15 is damaged. Therefore, the value of the welding overcurrent reference signal Ia is set to a predetermined value that can prevent the above.

When the detection / weld changeover switch SW2 is switched to the side a, the welding drive signal Sa shown in FIG. 2C is selected and input to the PWM control circuit 17. The PWM control circuit 17 oscillates while the input signal Sa is being input.

When the output control changeover switch SW3 is switched to the side a, feedback control is started, and the output setting signal Is and the output current signal Io are output from the output waveform control circuit 22.
And the difference is determined, and the determined output waveform control signal ΔV is input to the PWM control circuit 17. The PWM control circuit 17 controls the output signal Ps of the PWM control circuit 17 so that the output setting signal Is and the output current signal Io become equal.
Control the pulse width of

FIG. 3 is a power supply unit connection diagram showing a second embodiment of a DC arc processing power supply unit for detecting that a consumable electrode has contacted a workpiece. In this figure, the same reference numerals as those in FIG. 1 perform the same operations as those in FIG. When the output voltage signal Vo is input, the short-circuit detection activation circuit 23 shown in FIG. 3 compares the output voltage signal Vo with a predetermined reference value Va for contact voltage detection, and when Va> Vo, the consumable electrode 14 When it is determined that the contact has been made, the electrode contact signal So is input to the second contact detection clock circuit 28, and the electrode contact signal So is also output outside the welding power supply.

FIG. 4 is a timing chart for explaining the operation of the power supply device shown in FIG. FIG. 4 (A)
The start signal S1 indicates a contact detection period T1 and a welding period T2.
And have a period. FIG. 4B shows a detection / welding current switching signal St, FIG. 4C shows a welding drive signal Sa, and FIG. 4D shows a second contact detection clock signal Sb.
FIG. 4E shows an output voltage signal Vo output from the output voltage detector 7. FIG. 4F shows an output current value Ir of the inverter circuit output from the overcurrent protection current detector 9, and FIG. 4G shows an overcurrent detection signal Sc output from the overcurrent detection comparator 16. Is shown. FIG. 4 (H)
5 shows an electrode contact signal So output from the short circuit detection circuit 23.

At time t = t1 shown in FIG.
When the consumable electrode 14 comes into contact with the workpiece 15, the output voltage detector 7 inputs the output voltage signal Vo shown in FIG. The short-circuit detection circuit 23 compares the output voltage signal Vo with a predetermined contact voltage detection reference value Va, and determines that the consumable electrode 14 has contacted the workpiece 15 when Va> Vo. The electrode contact signal So shown in FIG. 4H is output, input to the second contact detection clock circuit 28, and output to the outside of the welding power source.

The second contact detection clock circuit 28 outputs the contact detection clock signal Sb shown in FIG. 4D after a predetermined second oscillation period tc has elapsed after the electrode contact signal So rises to High. Is set to Low, and the oscillation of the PWM control circuit 17 is stopped. As described above, the output current period during which the consumable electrode 14 is in contact with the workpiece 15 is shortened.

When the consumable electrode 14 is in contact with the workpiece 15 during the period from time t = t1 to t2 shown in FIG. 4D, the second contact detection clock circuit 28
The oscillation period tb of the contact detection clock signal Sb shown in (D)
Is changed to the second oscillation period tc to shorten the output current period at the time of contact. The description of the other circuits is the same as that of FIG.

FIG. 5 is a power supply device connection diagram showing a third embodiment of a DC arc processing power supply device for detecting that a consumable electrode has contacted a workpiece. In this figure, the same reference numerals as those in FIG. 1 perform the same operations as those in FIG. The short-circuit detection activation circuit 23 shown in FIG. 5 receives the output voltage signal Vo and compares it with a predetermined reference value Va for contact voltage detection. When Va> Vo, the consumable electrode 14 is attached to the workpiece 15. When it is determined that the contact has occurred, the electrode contact signal So is input to the third contact detection clock circuit 29, and the electrode contact signal So is also output outside the welding power source.

FIG. 6 is a timing chart for explaining the operation of the power supply device shown in FIG.
Only the differences from the timing chart of FIG. 2 will be described. FIG. 6D shows the contact detection clock signal Sb of the third contact detection clock circuit 29, and FIG. 6E shows the output voltage signal Vo output from the output voltage detector 7. FIG.
(H) shows the electrode contact signal So output from the short-circuit detection circuit 23.

At time t = t1 shown in FIG.
When the consumable electrode 14 comes into contact with the workpiece 15, the output voltage detector 7 inputs the output voltage signal Vo shown in FIG. The short-circuit detection circuit 23 compares the output voltage signal Vo with a predetermined contact voltage detection reference value Va, and determines that the consumable electrode 14 has come into contact with the workpiece 15 when Va> Vo. 6 (H), the electrode contact signal So is set to High, input to the third contact detection clock circuit 29, and output to the outside of the welding power source.

The third contact detection clock circuit 29 outputs the contact detection clock signal Sb shown in FIG. 6D after a predetermined second oscillation period tc has elapsed after the electrode contact signal So rises to High. At this time, the oscillation of the PWM control circuit 17 is stopped. As described above, the output current period during which the consumable electrode 14 is in contact with the workpiece 15 is shortened.

If the consumable electrode 14 is in contact with the workpiece 15 during the period from time t = t1 to t2 shown in FIG. 6E, the third contact detection clock circuit 29
The oscillation period tb of the contact detection clock signal Sb shown in (D)
Is stopped, and the oscillation of the PWM control circuit 17 is stopped. The description of the other circuits is the same as that of FIG.

FIG. 7 is a power supply device connection diagram showing a fourth embodiment of a DC arc processing power supply device for detecting that a consumable electrode has contacted a workpiece. In this figure, the same reference numerals as those in FIG. 1 perform the same operations as those in FIG. The second short-circuit detection activation circuit 27 shown in FIG. 7 receives the output voltage signal Vo, compares it with a predetermined contact voltage detection reference value Va after the elapse of the contact detection prohibition period td, and when Va> Vo. It is determined that the consumable electrode 14 has come into contact with the workpiece 15 and the electrode contact signal So
Is input to the third contact detection clock circuit 29, and
The electrode contact signal So is also output outside the welding power source.

FIG. 8 is a timing chart for explaining the operation of the power supply device shown in FIG. In the figure,
Only the differences from the timing chart of FIG. 2 will be described. 8D shows the contact detection clock signal Sb of the third contact detection clock circuit 29, and FIG. 8E shows the output voltage signal Vo output from the output voltage detector 7. FIG.
(H) shows the electrode contact signal So output from the second short-circuit detection circuit 27.

FIG. 9 is a detailed diagram of the timing chart shown in FIG. FIG. 9A shows details of the contact detection clock signal Sb of the third contact detection clock circuit 29, and FIG. 9B shows details of the output voltage signal Vo output from the output voltage detector 7. Show. FIG. 9C shows the electrode contact signal So output from the second short-circuit detection signal 27.

At time t = t1 shown in FIG.
When the consumable electrode 14 comes into contact with the workpiece 15, the output voltage detector 7 outputs the output voltage signal Vo shown in FIG.
To the short circuit detection circuit 27 of FIG. Second short circuit detection circuit 2
Reference numeral 7 indicates that at time t = t5 when the output voltage signal Vo rises as shown in FIG. 9B, the second short-circuit detection circuit 27 starts operating, and as a result, Va> Vo, and the contact is established. Although there is no contact, it judges as contact and malfunctions, and FIG. 9 (C)
The malfunctioning electrode contact signal So indicated by the dotted line is output.

The second short-circuit detection circuit 27 receives the output voltage signal Vo to prevent the above-described malfunction, and sets a predetermined contact detection inhibition period td from time t = t5 shown in FIG. 9B.
Immediately after the elapse of the contact detection prohibition period td, the output voltage signal Vo is compared with a predetermined reference value Va for contact voltage detection to determine that the consumable electrode 14 has correctly contacted the workpiece 15. Then, the electrode contact signal So shown as a solid line in FIG. 9 (C) is set to High, input to the contact detection clock circuit 29, and output to the outside of the welding power source.

The contact detection clock circuit 29 changes the contact detection sequence signal Sb shown in FIG. 8 (D) to Low after a predetermined second oscillation period tc has elapsed after the electrode contact signal So has risen to High. , PWM control circuit 1
7 is stopped.

In the period from time t = t1 to t2 shown in FIG. 8D, when the consumable electrode 14 is in contact with the workpiece 15, the third contact detection clock circuit 29
The oscillation period tb of the contact detection clock signal Sb shown in (D)
Is stopped, and the oscillation of the PWM control circuit 17 is stopped.

At time t = t2 shown in FIG.
When the consumable electrode 14 is released from the workpiece 15, FIG.
At time t = t4 in (D), determination of whether the contact or the release is started.

The output voltage detector 7 converts the output voltage signal Vo shown in FIG. 8E into a short-circuit detection circuit in synchronization with the oscillation period tb at time t = t4 of the contact detection clock signal Sb in FIG. Enter 27. The second short-circuit detection circuit 27 compares the output voltage signal Vo with the predetermined contact voltage detection level Va immediately after the predetermined contact detection prohibition period td elapses, and when Va <Vo, the consumable electrode 14 is processed. When it is determined that the object 15 has been released, the electrode contact signal So shown in FIG. 8H is set to Low, and the contact detection ends. The description of the other circuits is the same as that of FIG.

[0080]

(1) The power supply circuit of the welding power supply can be used as it is as the power supply for contact detection, so that it is not necessary to separately install a power supply circuit for short-circuit detection and a protection diode in the power supply device as in the prior art, and the power supply is consumed. Since the contact of the conductive electrode with the workpiece can be easily detected, workability can be significantly improved. (2) In the invention of the second embodiment, the output current period of the low current for contact detection can be reduced during the period when the consumable electrode is in contact with the workpiece, so that the workpiece is damaged by the low current for contact detection. Can be reduced. (3) In the invention of the third embodiment, since the output current period of the low current for contact detection is eliminated immediately after detecting that the consumable electrode has contacted the workpiece, the processing by the low current for contact detection is performed. Damage to objects can be further reduced. (4) In the invention of the fourth embodiment, a malfunction in contact detection at the time of the rise of the output voltage can be prevented by providing the contact detection prohibition period at the time of the rise of the output voltage.

[Brief description of the drawings]

FIG. 1 is a power supply device connection diagram showing an embodiment of a power supply device for performing a DC arc machining method for detecting that a consumable electrode has contacted a workpiece.

FIG. 2 is a timing chart for explaining the operation of the power supply device shown in FIG.

FIG. 3 is a power supply device connection diagram showing a second embodiment of a power supply device for performing a DC arc machining method for detecting that a consumable electrode has contacted a workpiece.

FIG. 4 is a timing chart for explaining the operation of the power supply device according to the second embodiment shown in FIG. 3;

FIG. 5 is a power supply device connection diagram showing a third embodiment of a power supply device for performing a DC arc machining method for detecting that a consumable electrode has contacted a workpiece.

FIG. 6 is a timing chart for explaining the operation of the power supply device according to the third embodiment shown in FIG. 5;

FIG. 7 is a power supply device connection diagram showing a fourth embodiment of a power supply device for performing a DC arc machining method for detecting that a consumable electrode has contacted a workpiece.

FIG. 8 is a timing chart for explaining the operation of the power supply device according to the fourth embodiment shown in FIG. 7;

FIG. 9 is a detailed timing chart shown in FIG.

FIG. 10 is a connection diagram of a conventional DC arc machining power supply device in which a short-circuit detection circuit and the like are provided outside a welding power supply.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-phase AC commercial power supply 2 Primary rectifier circuit 3 Inverter circuit 4 Main transformer 5 Secondary rectifier circuit 6 DC reactor 7 Output voltage detector 8 Output current detector 9 Current detector for overcurrent protection 10 Overcurrent protection circuit 11 Main Control circuit 12 Driver circuit 13 Welding torch 14 Consumable electrode 15 Workpiece 16 Overcurrent detection comparator 17 PWM control circuit 18 Welding overcurrent reference signal 19 Contact detection overcurrent reference signal 20 Welding drive circuit 21 Contact detection clock circuit 22 Output waveform control circuit 23 Short circuit detection circuit 24 Contact detection setting device 25 Start switch 26 Output setting device 27 Second short detection circuit 28 Second contact detection clock circuit 29 Third contact detection clock Circuit 32 Main control circuit 33 Welding power supply circuit 50 Contact detection power supply circuit 51 Constant current power supply circuit 52 Short circuit protection Protection circuit 53 current limiting circuit 54 constant current automatic adjustment circuit 55 AC amplifier 56 short circuit detection circuit 57 welding power supply circuit 58 welding control circuit DR1 diode Ds inverter control signal Ps inverter drive signal Ia welding overcurrent reference signal Ib contact detection overcurrent Reference signal Ic Contact detection reference signal Io Output current signal Ir Output current value of inverter circuit Is Output setting signal Sa Welding drive signal Sb Contact detection clock signal Sc Overcurrent detection signal So Electrode contact signal St Detection / welding current switching signal S1 Start signal SW1 Overcurrent reference signal changeover switch SW2 Detection / weld changeover switch SW3 Output control changeover switch T1 Contact detection period T2 Welding period Ta Consumable electrode non-contact period Tb Consumable electrode contact period ta Stop period tb Oscillation period tc Second Oscillation period td contact Touch detection prohibition period t1 Contact start time t2 Contact end time t3 Detection / weld switching time Va Contact voltage detection reference value Vo Output voltage signal (no load voltage) Vr Short circuit reference signal ΔV Output waveform control signal

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[Procedure amendment]

[Submission date] January 24, 2000 (2000.1.2
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 9

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] Claim 15

[Correction method] Change

[Correction contents]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Claim 18

[Correction method] Change

[Correction contents]

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

According to the invention of the ninth aspect of the present invention, a three-phase AC commercial power supply is rectified by a primary rectifier circuit 2 to obtain DC power, and the DC power is converted into a high-frequency AC pulse voltage by an inverter circuit 3. Each of the positive and negative voltages is output, and the main transformer 4 converts the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load.
Arc machining power supply control that supplies DC power by rectifying by DC
In the method, the detection and the welding current switching signal St are switched between the low current for contact detection and the welding current.
Inverter drive signal Ps for driving the inverter from the circuit
To output a low current for detection from the inverter, detect a drop in the no-load voltage Vo after the consumable electrode comes into contact with the workpiece, determine the position at which the consumable electrode has contacted the workpiece, Next, a DC arc machining power supply for supplying a welding drive signal Sa according to a welding current supply command of the detection / welding current switching signal St, outputting an inverter drive signal Ps for driving the inverter from the PWM circuit, and supplying a welding current from the inverter. It is a control method.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Go Miyagawa 2-1-1-11 Tagawa, Yodogawa-ku, Osaka-shi Inside Daihen Co., Ltd. (72) Inventor Ichiro Umezawa 2-1-1-11 Tagawa, Yodogawa-ku, Osaka-shi Stock Association F-term (reference) in Daihen Corporation 4E082 AA01 CA01 DA01 EC05 EC16 EF07

Claims (22)

[Claims] 1. A DC arc machining power supply control method for welding by applying a welding current from a welding power supply circuit after detecting that a consumable electrode has contacted a workpiece and determining a position of the workpiece. What is claimed is: 1. A DC arc machining power supply control method in which a contact detection power supply circuit for a touch sensor is used without using a welding power supply, wherein a no-load voltage of the welding power supply circuit is reduced by a contact detection start signal. DC arc machining power supply control method for applying a welding current by a welding drive signal after detecting that the consumable electrode has contacted the workpiece and determining the position of the workpiece. . 2. The DC arc machining according to claim 1, wherein the consumable electrode contacts the workpiece and detects a low current flowing from the welding power supply circuit to determine that the consumable electrode has contacted the workpiece. Power control method. 3. A DC arc machining power supply control method for welding by applying a welding current from a welding power supply circuit after detecting that the consumable electrode has contacted the workpiece and determining the position of the workpiece. What is claimed is: 1. A method for controlling a DC arc machining power supply which also serves as a welding power supply without using a contact detection power supply circuit for a touch sensor, comprising: detecting a decrease in a no-load voltage of the welding power supply by a contact detection start signal; Judge the position of contact with the workpiece, and immediately after detecting that the consumable electrode has contacted the workpiece, apply a low current for contact detection from the welding power source, and then drive the welding drive signal. This is a DC arc machining power supply control method in which a low current for contact detection is switched to a welding current to start welding. 4. The DC arc machining power supply control method according to claim 3, wherein the welding power supply circuit is an inverter circuit, and a low current for contact detection is supplied from the welding power supply at a predetermined constant cycle. 5. The DC arc machining power supply control method according to claim 4, wherein the predetermined fixed cycle is a cycle between an oscillation period and a stop period of the contact detection clock signal for driving the inverter circuit. 6. A predetermined fixed cycle is a cycle between an oscillation period and a stop period of a contact detection clock signal for driving an inverter circuit, and immediately after detecting that a consumable electrode has contacted a workpiece. And reducing the pulse width of the contact detection clock signal to a predetermined second oscillation period.
DC arc machining power supply control method. 7. A method according to claim 6, wherein the predetermined period is a period between an oscillation period and a stop period of the contact detection clock signal for driving the inverter circuit, and immediately after detecting that the consumable electrode has contacted the workpiece. 5. The method according to claim 4, wherein the oscillation of the contact detection clock signal is stopped. 8. The welding power supply circuit is an inverter circuit, and detects an output current value of the inverter circuit when the consumable electrode comes into contact with a workpiece to suppress an excessive current at the start of contact detection low current energization. The DC arc machining power supply control method according to claim 3 or claim 4 or claim 5 or claim 6 or claim 7. 9. A three-phase AC commercial power supply is rectified by a primary rectifier circuit to obtain DC power, and the DC power is converted into a high-frequency AC pulse voltage by an inverter circuit to output positive and negative voltages. In the DC arc machining power supply device for converting a high-frequency AC pulse voltage into an AC pulse voltage suitable for a load and rectifying the AC pulse voltage with a secondary rectifier circuit to supply DC power, a low current for contact detection and a welding current Detection and detection of the welding current switching signal.
An inverter drive signal for driving the inverter is output from the M circuit, a low current for detection is supplied from the inverter, and a decrease in no-load voltage after the consumable electrode comes into contact with the workpiece is detected. Judgment of the position of contact with the workpiece, then energizing the welding drive signal according to the welding current energizing command of the detection / welding current switching signal, outputting an inverter drive signal for driving the inverter from the PWM circuit, and welding from the inverter. DC arc machining power supply control method for applying current. 10. A contact detection clock signal which repeats in a cycle of an oscillation period and a stop period of a contact detection clock signal in response to a detection / welding current switching signal detection low current conduction command. 9. DC arc machining power supply control method. 11. An inverter circuit generates a contact detection clock signal that repeats in a cycle of an oscillation period and a stop period of a contact detection clock signal in response to a detection low current conduction command of a detection / welding current switching signal, and The DC arc machining power supply control method according to claim 9, wherein the pulse width of the contact detection clock signal is reduced to a predetermined second oscillation period immediately after detecting that the conductive electrode has come into contact with the workpiece. 12. An inverter circuit generates a contact detection clock signal that repeats in a cycle of an oscillation period and a stop period of a contact detection clock signal in response to a detection and welding current switching signal detection low current energization command. 10. The method of controlling a DC arc machining power supply according to claim 9, wherein the oscillation of the contact detection clock signal is stopped immediately after detecting that the contact with the workpiece has occurred. 13. The method according to claim 9, wherein an output current value of the inverter circuit when the consumable electrode comes into contact with the workpiece is detected to suppress an excessive current at the start of the contact detection low-current energization. Item 13. The DC arc machining power supply control method according to claim 11 or 12. 14. An overcurrent reference signal for contact detection and an overcurrent reference signal for welding are detected by a detection / welding current switching signal by detecting an output current value of the inverter circuit when the consumable electrode contacts the workpiece. Switch and compare with the output current value of the inverter circuit, and when it is larger than one of the reference signals, output an overcurrent detection signal to reduce the pulse period of the high-frequency AC pulse voltage output by the PWM circuit and supply a low current for contact detection. 14. The DC arc machining power supply control method according to claim 13, wherein a transient current at the time of starting is suppressed. 15. The method according to claim 9, wherein the position of the workpiece is determined after a lapse of a predetermined time immediately after the consumable electrode comes into contact with the workpiece. DC power source control method. 16. A primary rectifier circuit for rectifying a three-phase AC commercial power supply to obtain DC power, an inverter circuit for converting DC power to a high-frequency AC pulse voltage and outputting positive and negative voltages, and a high-frequency AC pulse voltage A main transformer for converting the output into an AC pulse voltage suitable for the load, and a DC arc machining power supply device for rectifying an output of the main transformer with a secondary rectifier circuit and supplying DC power, by a detection / welding current switching signal. A detection / welding changeover switch for controlling a PWM circuit by switching between an output signal of a contact detection clock circuit and an output signal of a welding drive circuit; and an output setting signal of an output setting device and a contact detection by the detection / welding current switching signal. An output control changeover switch for switching between a setter and a pulse width according to a contact detection reference signal or an output setting signal selected by the output control changeover switch. A DC arc machining power supply device comprising a PWM circuit for adjusting and controlling the output and switching between a contact low current for detection and a welding current by controlling an output of the inverter circuit by an inverter drive signal. 17. A primary rectifier circuit for rectifying a three-phase AC commercial power supply to obtain DC power, an inverter circuit for converting DC power to a high-frequency AC pulse voltage and outputting positive and negative voltages, and a high-frequency AC pulse voltage In a main transformer that converts the output into an AC pulse voltage suitable for a load, and a DC arc machining power supply that supplies DC power by rectifying the output of the main transformer with a secondary rectifier circuit, the output current value of the inverter circuit is An overcurrent protection current detector for detecting and outputting, an overcurrent reference signal changeover switch for selecting one of a contact detection overcurrent reference signal and a welding overcurrent reference signal, and a selection made by the overcurrent reference signal changeover switch Comparing the output current value of the inverter circuit with one of the reference signals and outputting an overcurrent detection signal when the output signal is larger than the one reference signal to control the PWM circuit. A comparator, a detection / welding changeover switch for controlling a PWM circuit by switching between an output signal of a contact detection clock circuit and an output signal of a welding drive circuit by a detection / welding current switching signal, and the detection / welding current switching signal An output control switch for switching between the output setting signal of the output setting device and the contact detection setting device, and a PWM circuit for controlling the output by modulating the pulse width according to the contact detection reference signal or the output setting signal selected by the output control switching switch. A DC arc machining power supply device that controls an output of an inverter circuit by an inverter drive signal to switch between a contact low current for detection and a welding current. 18. A primary rectifier circuit for rectifying a three-phase AC commercial power supply to obtain DC power, an inverter circuit for converting DC power to a high-frequency AC pulse voltage and outputting each positive and negative voltage, and the high-frequency AC pulse voltage A main transformer that converts the output into an AC pulse voltage suitable for the load, and a DC arc machining power supply that supplies DC power by rectifying the output of the main transformer with a secondary rectifier circuit, using a detection / welding current switching signal. A detection / weld changeover switch for controlling a PWM circuit by switching between an output signal of a contact detection clock circuit and an output signal of a welding drive circuit, an output setting signal of an output setting device and an output current detected by an output current detector; The output waveform control circuit that outputs the obtained output waveform control signal, and selects one of the contact detection reference signal and the output waveform control signal of the contact detection setting unit An output control switch, a PWM circuit that modulates a pulse width according to a value of a contact detection reference signal and an output waveform control signal selected by the output control switch, and controls an output, and an output voltage signal of an output voltage detector The input voltage is compared with a predetermined contact voltage detection reference value and an output voltage signal, and when the output voltage signal is smaller than the predetermined contact voltage detection reference value, the consumable electrode contacts the workpiece. A DC arc machining power supply device comprising: a short-circuit detection circuit that outputs an electrode contact signal upon determination, and controls an output of the inverter circuit by an inverter drive signal to switch between a low contact current for detection and a welding current. 19. A primary rectifier circuit that rectifies a three-phase AC commercial power supply to obtain DC power, an inverter circuit that converts DC power into a high-frequency AC pulse voltage and outputs positive and negative voltages, and a high-frequency AC pulse voltage. In a main transformer that converts the output into an AC pulse voltage suitable for a load, and a DC arc machining power supply that supplies DC power by rectifying the output of the main transformer with a secondary rectifier circuit, the output current value of the inverter circuit is An overcurrent protection current detector for detecting and outputting, an overcurrent reference signal changeover switch for selecting one of a contact detection overcurrent reference signal and a welding overcurrent reference signal, and a selection made by the overcurrent reference signal changeover switch Comparing the output current value of the inverter circuit with one of the reference signals and outputting an overcurrent detection signal when the output signal is larger than the one reference signal to control the PWM circuit. A comparator, a detection / welding changeover switch for controlling a PWM circuit by switching between an output signal of a contact detection clock circuit and an output signal of a welding drive circuit by a detection / welding current switching signal, and an output setting signal of an output setting device And an output current detected by the output current detector to determine the difference between the two, and an output waveform control circuit that outputs the obtained output waveform control signal; and a contact detection reference signal and an output waveform control signal of the contact detection setting device. An output control changeover switch for selecting one of the output control switches, a PWM circuit for modulating a pulse width according to the value of the contact detection reference signal and the output waveform control signal selected by the output control changeover switch and controlling the output, and an output voltage detector. An output voltage signal is input, a predetermined contact voltage detection reference value is compared with the output voltage signal, and the output voltage signal is smaller than a predetermined contact voltage detection reference value. A short-circuit detection circuit that determines that the consumable electrode has come into contact with the workpiece and outputs an electrode contact signal, and controls the output of the inverter circuit by an inverter drive signal to detect a low contact current and a welding current. DC machining power supply unit that switches between 20. A contact detection clock signal that repeats in a cycle of an oscillation period and a stop period of an output signal of a second contact detection clock circuit in response to a low-current energization command detected by an inverter circuit of a detection / welding current switching signal. 20. The direct current according to claim 18 or claim 19, wherein the pulse width of the contact detection clock signal is reduced to a predetermined second oscillation period immediately after the occurrence and detection of the contact of the consumable electrode with the workpiece. Arc processing power supply. 21. A contact detection clock signal which repeats in a cycle of an oscillation period and a stop period of an output signal of a third contact detection clock circuit in response to a low-current energizing command detected by an inverter circuit and a detection / welding current switching signal. 20. The DC arc machining power supply device according to claim 18 or claim 19, wherein the oscillation of the contact detection clock signal is stopped immediately after the generated consumable electrode contacts the workpiece. 22. The method according to claim 18, wherein the position of the workpiece is determined immediately after the consumable electrode comes into contact with the workpiece and after a predetermined contact detection inhibition period has elapsed.
22. The direct current arc machining power supply device according to claim 21.