JPH10235473A - Power source device for arc working - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the sufficient output even at the place where a power facility is poor by converting the output of a first rectifying circuit into AC by an inverter circuit, converting the voltage to the prescribed value by a transformer during the working, rectifying and accumulating the output of the transformer during the non-working, converting the accumulated power into the prescribed voltage by a DC/DC converting circuit during the working, superposing the converted power on the output of a second rectifying circuit, and supplying the superposed output to a load. SOLUTION: An AC power source 1 is supplied from an AC 100V power supply for the commercial power supply for electric lamps. An inverter circuit 3 converts the output of a first rectifying circuit 2 into AC of several kHz to tens of kHz of the voltage suitable for the arc working by a transformer 4. Thyristors 5a, 5b and diodes 6a, 6b constitute a second rectifying circuit to perform the full-wave rectification of the output of the transformer 4 and supply the DC output to an arc working load. A power accumulator 8 rectifies the output of the transformer 4 together with thyristors 7a, 7b and diodes 6a, 6b, and the accumulated power of the power accumulator 8 is converted into the power suitable for the arc working by a DC/DC converting circuit 9.

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 used for arc machining such as arc welding, arc cutting, plasma arc cutting, and the like, and more particularly, to obtaining a sufficient output even in a place where power equipment is poor. The proposed device has been proposed.

[0002]

2. Description of the Related Art In general, a power supply device for arc processing used for arc welding, plasma arc cutting, and the like is capable of appropriately transforming a commercial AC power supply with a transformer and having characteristics suitable for a target arc processing, such as constant current characteristics and drooping characteristics. For example, a device that controls output using a semiconductor element is used. In recent years, AC power has been once rectified to DC, and this DC is converted to AC of several tens of kHz by an inverter circuit using semiconductor switching elements, and then converted to a voltage suitable for arc processing by a high-frequency transformer, and then rectified again. A method of supplying a direct current to a workpiece as a direct current has also been put to practical use.

[0003] However, in the arc machining power supply devices described above, since all of them process electric power supplied from a commercial AC power supply, the power supply capacity is several KVA.
The above capacity is required. For this reason, in a small-scale building site or a place where power supply equipment such as repair work is not fully equipped, the capability cannot be sufficiently exhibited, and a welding defect may occur. Where there is no power supply at all, an engine welder using an engine generator will be used, but in such a place, electricity is naturally required for other tools, etc., and only for welding and cutting. It was extremely uneconomical to provide extra large generators.

On the other hand, in order to cope with this, a single-phase 1
There are also arc welding machines that obtain power from a 00V power supply, but these power supplies have a permissible range of up to 15A per line, and can perform extremely small capacity processing, and their application range is extremely limited. Met.

In order to solve the above-mentioned problems, an AC power supply is rectified to DC, a DC output is used to charge a large-capacity capacitor, and the DC output and the charged capacitor are connected in parallel. Thus, the system shown in FIG. 4 has been proposed in which the total output is led to an arc welding load through a current controller. (Japanese Patent Laid-Open No. 6-238443)

In FIG. 1, reference numeral 101 denotes an AC power supply.
Usually, it is a commercial AC power supply, for example, a power supply for lamps of AC100V. Reference numeral 102 denotes a power supply circuit.
A device that obtains a DC output by rectifying again after appropriately converting the voltage with a transformer is used. Reference numeral 103 denotes a capacitor connected to the DC output terminal of the power supply circuit 102, and a large-capacity capacitor of about several tens F to several thousand F is used. An output current limiting element 104 is formed of a semiconductor element such as a transistor, and limits an output current to a predetermined value. Reference numeral 105 denotes a welding load including the electrode and the workpiece.

In the apparatus shown in FIG. 1, the power from an AC power supply 101 is rectified by a power supply circuit 102 to become a DC of a predetermined voltage, which charges a large-capacity capacitor 103 and is current-limited by an output current limiting element 104. And supplied to the welding load 105.

[0008]

However, in the system shown in FIG. 4, the output of the power supply circuit 102 for rectifying the power supplied from the AC power supply 101 to obtain the DC power supplied to the welding load is simultaneously output to the capacitor 103. , The electric power is supplied to the arc welding load 105 from the output of the power supply circuit 102 and the capacitor 103 connected in parallel with the output. The output current is controlled by the output current limiting element 1 connected to the output terminal side from the capacitor 103.
04. Therefore, the capacitor 10
No. 3 can be discharged only while its terminal voltage is higher than the output voltage of the power supply circuit 102. If the terminal voltage is lower than this, the remaining accumulated charge cannot be released, and conversely, power is supplied from the power supply circuit.

If the output voltage of the power supply circuit 102 at the time of no load and non-welding is the same as the output voltage at the time of welding, the capacitor 103 does not exhibit its effect at all, and simply the power supply circuit 103 Has only a function as a capacitor for the output waveform smoothing means. Also,
Even when the capacitor 103 is charged higher than the power supply circuit during welding at the time of non-welding, it is possible to contribute to the output by the voltage of the difference between the charging voltage at the time of non-welding and the output voltage of the power supply circuit at the time of welding. The discharge proceeds and the terminal voltage of the capacitor 103 becomes equal to the power supply circuit 1 at the time of welding.
When the output voltage becomes lower than the output voltage of No. 02, the discharge stops, and power is supplied exclusively from the power supply circuit 102 only. For this reason, only a very small part of the charge charged in the capacitor 103 is used, and the effect of providing a large-capacity capacitor is hardly exhibited.

[0010]

SUMMARY OF THE INVENTION The present invention provides a first rectifier circuit for converting electric power from an AC power supply to DC, an inverter circuit for converting the output of the rectifier circuit to AC, and an arc output for the inverter circuit. A transformer for converting to a voltage suitable for processing, a second rectifier circuit for supplying an output of the transformer to a load during arc processing, and a power storage means for rectifying the output of the transformer and storing the output during non-processing. A DC / DC conversion circuit which converts the stored power of the power storage means into power having characteristics suitable for arc processing during arc processing, and superimposes the output on the output of the second rectifier circuit to supply the output to a load. A power supply device for processing is proposed.

In addition, the inverter circuit includes a circuit for limiting any one or more of input power, output power, and input current to a predetermined limit value or less, thereby limiting the power capacity. The present invention proposes a device that can be used safely even with an AC power supply having a power supply.

[0012]

FIG. 1 is a connection diagram showing an embodiment of a power supply device for arc machining according to the present invention. In the figure, 1
Is an AC power supply, which is supplied from, for example, an AC 100 V power supply for a power line. 2 is a first rectifier circuit, 3 is an inverter circuit for converting the first rectifier circuit into AC of several KHz to several tens KHz, and 4 is a transformer for converting the output of the inverter circuit 3 to a voltage suitable for arc machining. It is. 5a and 5b are thyristors, 6a and 6b are diodes, and the thyristors 5a and 5b and the diodes 6a and 6b are connected so as to form a mixed bridge type rectifier circuit. A second rectifier circuit that supplies a direct current to the arc processing load is configured. Reference numerals 7a and 7b denote thyristors, which are connected together with the diodes 6a and 6b so as to constitute another mixed-bridge type double-wave rectifier circuit. Reference numeral 8 denotes a huge capacitance of about several tens to 1000F such as an electric double-layer capacitor. It is a power storage device such as a capacitor or a storage battery, and constitutes power storage means for rectifying and storing the output of the transformer 4 together with the thyristors 7a and 7b and the diodes 6a and 6b. 9 is a power storage 8
A DC / DC conversion circuit that converts the power stored in the DC / DC converter into power suitable for arc machining, that adjusts the output by chopper control using a semiconductor switching element, that controls analog by a series transistor, or that is temporarily controlled by an inverter circuit. A known conversion circuit such as one that obtains a DC or pulsating output having desired characteristics through a transformer and a rectifier circuit after conversion into AC is used. Reference numeral 10 denotes an output smoothing DC reactor, and reference numeral 11 denotes an arc processing load such as an arc welding machine or an arc cutting machine, and includes, for example, an electrode 11a and a workpiece 11b. 12 is an output current setting device, 13 is a charging current setting device for setting a charging current to the power storage device 8,
14 is an input current limit value setting device, 15 is an output current detector,
Reference numeral 16 denotes a charging current detector, and 17 denotes an input current detector.
Reference numeral 18 denotes a comparator which inputs a set value Iro of the output current setting unit 12 and a detection value Ifo of the output current detector 15, and outputs a difference signal ΔIo = Iro−Ifo. Reference numeral 19 denotes a comparator which receives a set value Irc of the charging current setting unit 13 and a detection value Ifc of the charging current detector 16 and outputs a difference signal ΔIc = Irc−Ifc. 20 is the set value Iim of the input current limit value setting device 14
And the detected value Ifi of the input current detector 17 as input, the difference Δ
This comparator calculates Ii = Ifi-Iim, outputs a signal of zero or low level while ΔIi ≦ 0, and outputs a high level signal when ΔIi> 0. Reference numerals 21a and 21b denote diodes, and reference numeral 22 denotes a pulse width control circuit for supplying a drive signal to the inverter circuit 3, which outputs a pulse signal having a conduction time rate corresponding to the input signal. Reference numeral 23 denotes a DC / DC conversion control circuit that supplies a drive signal for the DC / DC conversion circuit 9, and is configured to provide an output corresponding to an input signal according to the configuration of the DC / DC conversion circuit 9. For example, DC /
When the DC conversion circuit 9 is a chopper circuit or an inverter circuit, a pulse width control circuit that outputs a pulse signal having a conduction time rate corresponding to the magnitude of an input signal is used, and a DC / D
When the C conversion circuit 9 is an analog transistor,
An amplifier that outputs a transistor drive signal having a magnitude corresponding to the input signal may be used. Reference numerals 24 to 26 denote analog switches, which use switching transistors. Reference numerals 27 and 28 denote OR gates, and reference numerals 30 to 32 denote polarity inverting inverter gates. Reference numeral 33 denotes a start command switch for starting arc machining, which always outputs a high level signal during arc machining. 34 to 3
Reference numeral 7 denotes a firing circuit for firing the thyristors 5a, 5b or 7a, 7b by a signal of the start command switch 33 or a signal obtained by inverting the output signal of the start command switch 33 by the inverter gate 31; A known drive circuit that supplies a gate drive signal to the thyristor in response to a signal is used. 38,39
Are amplifiers, each of which has an output ΔIo = I
It amplifies ro-Ifo and outputs signals ΔIo1 and ΔIo2. S is a switch for turning on and off the AC power.

In the apparatus shown in FIG. 1, after the switch S is closed, the output of the start command switch 33 is output to the inverter gate 30, until the start command switch 33 is closed.
Analog switch 2 by the signal inverted by
The signals ΔIo1 and ΔIo2 are grounded and are not transmitted to the pulse width control circuit 22 and the DC / DC conversion control circuit 23, regardless of the magnitude of the output of the comparator 18. Further, since the signal from the start command switch 33 is at a low level, the thyristors 5a and 5b maintain the cutoff state, and the DC / DC conversion circuit 9 also stops operating, so that power is supplied to the arc machining load 11. Not done.

On the other hand, the analog switch 25 to which the output of the start command switch 33 is directly supplied is in a cut-off state, and the ignition circuits 36 and 37 to which the signal inverted to a high level by the inverter gate 31 are supplied. When activated, the thyristors 7a and 7b are turned on. As a result, the output ΔIc = Irc−Ifc of the comparator 19 becomes the pulse width control circuit 2
2 and the inverter circuit 3 is activated.

The output of the inverter circuit 3 is turned on after the voltage is appropriately converted by the transformer 4.
Double-wave rectification is performed by a mixed bridge circuit composed of a diode 7b and diodes 6a and 6b, and stored in the power storage 8.
The charging current for the power storage 8 is the charging current detector 1
6 and becomes a signal Ifc, which is compared with a set value Irc of the charging current setter 13 by a comparator 19 to obtain a difference signal ΔIc.
= Irc-Ifc and is supplied to the pulse width control circuit 22. As a result, the charging current is controlled so as to maintain a value corresponding to the set value Irc.

On the other hand, at this time, the input current from the AC power supply 1 is detected by the input current detector 17 and becomes Ifi, and is compared by the comparator 20 with the set value Iim of the input current limit value setter 14. The comparator 20 calculates the difference signal ΔIi = Ifi−Iim, and outputs a zero or low level output while ΔIi ≦ 0.
While ΔIi> 0, the high level signal is supplied to the OR gate 2
7 and 28 to analog switches 25 and 26.

Since the input current is small and ΔIi ≦ 0 during Ifi ≦ Iim, the analog switch 25 remains off and the inverter circuit 3 outputs the output signal Δ
It operates at a conduction time rate determined by Ic, and charges the power storage 8 through the transformer 4, the thyristors 7a and 7b, and the diodes 6a and 6b. When the input current becomes excessive and Ifi> Iim, ΔIi> 0, and the comparator 20 outputs a high-level signal to make the analog switch 25 conductive. The conduction of the analog switch 25 causes the comparator 1
9 is grounded and is no longer supplied to the pulse width control circuit 22, and the inverter circuit 3 stops operating.
When the operation of the inverter circuit 3 stops, the input current sharply decreases, and ifi <Iim, and the output of the comparator 20 returns to the low level again. As a result, the analog switch 25 is turned off, the output signal ΔIc of the comparator 19 is supplied to the pulse width control circuit 22 again, and the operation of the inverter circuit 3 is restarted. If the setting is such that the input current exceeds the limit value, the above is repeated to limit the input current to be substantially equal to the limit value.

After the power accumulator 8 is sufficiently charged, a start command switch 33 for commanding the start of arc machining.
Is closed, the thyristors 7a and 7b are cut off, and the thyristors 5a and 5b are turned on. As a result, the accumulation of electric power in the electric power storage 8 is interrupted. The analog switch 25 is turned on, and the analog switches 24, 2
6 is shut off. As a result, the pulse width control circuit 22 is activated, and the output of the comparator 18 is amplified by the amplifier 38 by Δ
A drive pulse corresponding to Io1 is supplied to the inverter circuit 3 to operate it. The output of the comparator 18 is an amplifier 39
The DC / DC conversion circuit 9 is amplified and supplied to the DC / DC conversion control circuit 23 to start it. The DC / DC conversion circuit 9 thereby converts the power stored in the power storage 8 into power suitable for arc machining. The electric power is supplied to the arc processing load 11 through the DC reactor 10.

The output of the inverter circuit 3 is connected to the transformer 4 and the thyristors 5a, 5b,
The power converted by the mixed bridge circuit including the diodes 6a and 6b is supplied through the DC reactor 10.

At this time, the output current to the arc machining load 11 is detected by the output current detector 15 and becomes Ifo, and the comparator 18 sets the output current Iro of the output current setting unit 12 to Iro.
And the difference signal ΔIo = Iro−Ifo is calculated.
This difference signal ΔIo is amplified by amplifiers 38 and 39 to become ΔIo1 and ΔIo2, respectively.
2 and is supplied to the DC / DC conversion control circuit 23 to control the output current to be maintained at a value corresponding to the set value. Also at this time, the input current from the AC power supply 1 is detected by the input current detector 17 and compared with the set value Iim of the input current limit value setting device 14, and the input current Ifi is set to the limit value Iim.
Is exceeded, a high level signal is output from the comparator 20 to make the analog switch 26 conductive. Due to the conduction of the analog switch 26, the inverter circuit 3 stops,
Limit the input current so that it does not exceed the limit value.

In FIG. 1, by setting the amplification factors of the amplifiers 38 and 39 to different values, it is possible to make the output burden ratio at the time of arc machining different between the AC power supply side and the power storage means side. Of course, these amplifiers are not always necessary, and one or both of them can be omitted.

FIG. 2 is a connection diagram showing another embodiment of the present invention. In the figure, the DC / D of the embodiment shown in FIG.
As the C conversion circuit 9, an inverter circuit 9a, a transformer 9b
And the output rectifier circuit 9c. Further, the terminal voltage of the power accumulator 8 is detected by the voltage detector 43,
The detected value Efc is compared with the set value Erc of the charging voltage setter 41 by the comparator 42, and the difference signal ΔEc = Erc−Efc is used as a signal for the pulse width control circuit 22. DC /
Since the DC conversion circuit 9 is constituted by the inverter circuit 9a, the transformer 9b and the output rectification circuit 9c, the DC / DC
As the conversion control circuit 23, the output signal ΔIo2 of the amplifier 39
Is input, and a pulse width control circuit that outputs a pulse signal having a duty corresponding to the input signal is used.

The operation of the apparatus shown in FIG. 2 is the same as that of the first embodiment except that the DC / DC conversion circuit is of the inverter type and that the power storage 8 is charged at a constant voltage according to the set value Erc of the charging voltage setting unit 41. This is similar to the device shown in FIG.

In the apparatus shown in FIG. 2, the electric power stored in the electric power accumulator 8 is converted into a voltage by the transformer 9b of the DC / DC conversion circuit 9, so that the electric power stored in the electric power accumulator 8 Can be arbitrarily selected, so that there is no limitation on the rated voltage of the power storage device to be used. As a result, the circuit design becomes easier when a large-capacity capacitor such as an electric double-layer capacitor having a relatively low rated voltage is used as the power storage 8.

FIG. 3 is a connection diagram showing an example in which the apparatus of FIG. 1 is modified to apply the present invention to a plasma arc cutting apparatus. In FIG. 1, a workpiece 11b and a plasma arc cutting torch including an electrode 11a, a nozzle electrode 11c including the electrode 11a, and having a gas ejection port at a tip end are shown as the arc processing load 11. In addition, a current limiting resistor 44 for starting a small current pilot arc is provided between the nozzle electrode 11c and the electrode 11a at the start of cutting, and connected between the plus output terminal and the nozzle electrode 11c. Further, unlike the apparatus shown in FIG. 1, the plus output is connected to the workpiece 11b and the minus output is connected to the electrode 11a. The other components having the same functions as those of the device shown in FIG.

In the apparatus shown in FIG. 3, until the start command switch 33 for starting command is closed, the inverter circuit 3 operates and the thyristor 7 operates in the same manner as in the apparatus shown in FIG.
a and 7b conduct to charge the power accumulator 8. When the start command switch 33 is closed, the thyristors 7a and 7b are cut off, and the thyristors 5a and 5b conduct. Also DC
The / DC conversion circuit 9 also starts the conversion operation, converts the stored power of the power storage 8 into DC power suitable for arc processing, and supplies the DC power together with the outputs from the thyristors 5a and 5b to the arc processing load 11. These two outputs are supplied to the arc processing load 11 with a polarity such that the workpiece 11b side is positive and the electrode 11a side is negative, and a nozzle provided to surround the electrode 11a through a current limiting resistor 44 from a positive terminal. It is supplied to the electrode 11c.

When the start command switch 33 is closed, this signal causes a high voltage for arc ignition to be applied between the electrode 11a and the nozzle electrode 11c from a high-frequency high voltage supply circuit for arc ignition or a DC high voltage supply circuit (not shown). Applied, thereby breaking the insulation between the electrode 11a and the nozzle electrode 11c and activating a small current pilot arc limited by the resistor 44. On the other hand, at the same time as the supply of the high voltage for arc ignition by the start signal from the start command switch,
Alternatively, prior to this, a gas for plasma generation is supplied between the electrode 11a and the nozzle electrode 11c, and the gas is ionized by a pilot arc of a small current generated between the nozzle electrode 11c and the electrode 11a. The discharged gas is ejected from a gas ejection port provided at the tip of the nozzle electrode 11c. In this state, the electrode 11a and the nozzle electrode 11c
When the cutting torch is moved closer to the workpiece, an arc discharge is established between the electrode 11a and the workpiece 11b when the plasma generated gas ionized by the pilot arc touches the workpiece. Since the current of this arc discharge does not pass through the resistor 44, the current is not limited by this, but rapidly increases to the value set by the output current setting unit 12 to melt and cut the workpiece 11b. Can be.

Before and after the start command switch 33 is closed, the output current is determined by the set value Irc or Iro until the input current exceeds the limit value Iim, and the inverter circuit 3 is stopped when Ifi> Iim. The input current is limited so as to be equal to or less than the limit value in the same manner as in the apparatus shown in FIG.

In the embodiments shown in FIGS. 1 and 3, an example of the constant current charging circuit which detects the charging current to the power storage means 4 and keeps this charging current at a set value has been described. Power storage means 4 instead of current detector 16
A constant voltage charging circuit may be used which detects the terminal voltage of the terminal and charges the terminal until the terminal voltage reaches a set value.

Further, an output voltage detector is provided in place of the output current detector 15, and the pulse width control circuit 22 or the DC / DC conversion control circuit 23 is controlled so that the detection value of this detector becomes a set value. A constant voltage output characteristic may be obtained.

Further, an input power detector is provided in place of the input current detector 9, and the detection output of this detector is compared with the set value of the input power limit value setting device, and the input power exceeds the limit value. At this time, the output of each inverter circuit may be stopped.

Further, utilizing the fact that the input current or input power is substantially proportional to the output power, an output power detector of the inverter circuit 3 is provided, and this detected output is compared with the set value of the limit value setting device. These power conversion means may be stopped by the difference signal.

[Brief description of the drawings]

FIG. 1 is a connection diagram illustrating an embodiment of the present invention.

FIG. 2 is a connection diagram showing another embodiment of the present invention.

FIG. 3 is a connection diagram showing an example when the present invention is applied to a plasma cutting device.

FIG. 4 is a connection diagram showing an example of a conventional device.

[Explanation of symbols]

 Reference Signs List 1 AC power supply 2 Rectifier circuit 3, 9a Inverter circuit 4, 9b Transformer 5a, 5b, 7a, 7b Thyristor 6a, 6b Diode 8 Power storage device 9 DC / DC conversion circuit 9c Output rectification circuit 10 DC reactor 11 Arc processing load 11a Electrode 11b Workpiece 11c Nozzle electrode 12 Output current setting device 13 Charging current setting device 14 Input current limit value setting device 15 Output current detector 16 Charging current detector 17 Input current detector 18, 19, 20 Comparator 21a, 21b Diode 22 Pulse width control circuit 23 DC / DC conversion control circuit 24, 25, 26 Analog switch 27, 28 OR gate 30, 31, 32 Inverter gate 33 Start command switch 34, 35, 36, 37 Ignition circuit 38, 39 Amplifier 41 Charge voltage setting device 42 Comparator 43 Charge Voltage detector 44 resistor

Claims (4)

[Claims] 1. A first rectifier circuit for rectifying electric power supplied from an AC power supply to DC, an inverter circuit for converting an output of the rectifier circuit to AC, and an output of the inverter circuit suitable for arc machining. A transformer for converting the output of the transformer into a voltage, a second rectifier circuit for supplying an output of the transformer to a load at the time of arc machining, power storage means for rectifying the output of the transformer and storing the output during non-machining, A DC / DC conversion circuit for converting the power stored in the storage means into power having characteristics suitable for arc processing during arc processing and superimposing the power on the output of the second rectifier circuit to supply the load to a load. apparatus. 2. An inverter circuit comprising: a detector for detecting any one of input power, output power, and input current; and a comparator for outputting a signal when an output of the detector exceeds a limit value. 2. The power supply device for arc machining according to claim 1, further comprising a circuit for limiting an output of said inverter circuit by an output of said comparator. 3. The arc machining power supply device according to claim 1, wherein the second rectifier circuit is a mixed bridge type control rectifier circuit including a thyristor and a diode that are turned on by an arc machining command signal. . 4. The power storage means comprises a mixed-bridge control rectifier circuit composed of a thyristor and a diode that conducts the output of the transformer while the arc processing command signal is extinguished, and a large-capacity capacitor. Claim 1
The power supply device for arc machining according to any one of claims 1 to 3.