JP3881416B2 - Arc machining power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a power supply device used for arc processing such as arc welding, arc cutting, and plasma arc cutting, and particularly proposes a device that can obtain a sufficient output even in a poor place of power equipment. is there.
[0002]
[Prior art]
In general, a power supply device for arc machining used for arc welding, plasma arc cutting, or the like appropriately transforms a commercial AC power source with a transformer and has characteristics suitable for a desired arc machining, such as constant current characteristics and drooping characteristics. A device that controls output using a semiconductor element is used. In recent years, the AC power supply is once rectified to direct current, and this direct current is converted to AC of several tens of kHz by an inverter circuit using a semiconductor switching element, then converted to a voltage suitable for arc machining by a high frequency transformer, and then rectified again. A method of supplying a direct current to a workpiece has also been put into practical use.
[0003]
However, since all of the arc machining power supply devices described above process power supplied from a commercial AC power supply, a capacity of several KVA or more is required as the power supply capacity. For this reason, in a place where power facilities such as a small-scale construction site and repair work are not fully equipped, the ability cannot be fully exhibited and a welding defect may occur. Where there is no power supply equipment, an engine welder using an engine generator will be used. However, in such a place, power is also necessary for other tools, and only for welding and cutting. It was extremely uneconomical to prepare an extra large generator.
[0004]
On the other hand, to cope with this, there is an arc welding machine that obtains electric power from a single-phase 100V power supply for electric lamps. However, these power supplies have an allowable range of up to 15A per line, and can process extremely small capacities. However, the application range was extremely limited.
[0005]
Therefore, to solve the above problems, the AC power supply is rectified to be DC, and a large-capacity capacitor is charged with this DC output, and this DC output and the charged capacitor are connected in parallel. The system of FIG. 7 has been proposed in which the output is led to an arc welding load through a current controller. (Japanese Patent Laid-Open No. 6-238443)
[0006]
In the figure, reference numeral 101 denotes an AC power source, which is a normal commercial AC power source, for example, a power source for an AC 100V lamp. Reference numeral 102 denotes a power supply circuit. For example, a power supply circuit that rectifies an alternating current power supply to obtain a direct current, then converts it to a high frequency alternating current by an inverter circuit, converts the voltage appropriately by a transformer, and rectifies again to obtain a direct current output. Reference numeral 103 denotes a capacitor connected to the DC output terminal of the power supply circuit 102, and a capacitor having a large capacity of several tens of F to several thousand F is used. Reference numeral 104 denotes an output current limiting element, which is composed of a semiconductor element such as a transistor, and limits the output current to a predetermined value. Reference numeral 105 denotes a welding load composed of an electrode and a workpiece.
[0007]
In the apparatus shown in the figure, the power from the AC power supply 101 is rectified by the power supply circuit 102 to become a direct current of a predetermined voltage, charges the large-capacity capacitor 103 and is current-limited by the output current limiting element 104 and is welded. 105.
[0008]
[Problems to be solved by the invention]
However, in the system of FIG. 7 described above, the output of the power supply circuit 102 that rectifies the power supplied from the AC power supply 101 and obtains the DC power supplied to the welding load simultaneously charges the capacitor 103, so that arc welding is performed. Electric power is supplied to the load 105 from the output of the power supply circuit 102 and the capacitor 103 connected in parallel thereto. The output current is controlled by the output current limiting element 104 connected to the output terminal side from the capacitor 103. Therefore, the capacitor 103 can be discharged only while the terminal voltage thereof is higher than the output voltage of the power supply circuit 102. When the capacitor voltage is lower than this, the remaining accumulated charge cannot be discharged, and conversely, power can be supplied from the power supply circuit. become.
[0009]
If the output voltage of the power supply circuit 102 at the time of no load and non-welding and the output voltage at the time of welding are the same, the capacitor 103 does not exhibit the effect at all, and the output waveform of the power supply circuit 103 is simply It only has a function as a capacitor for the smoothing means. In addition, even when the capacitor 103 is charged higher than the power circuit during welding during non-welding, it is possible to contribute to the output because of the difference between the charging voltage during non-welding and the output voltage of the power circuit during welding. When the discharge progresses and the terminal voltage of the capacitor 103 becomes lower than the output voltage of the power supply circuit 102 during welding, the discharge stops and power is supplied exclusively from the power supply circuit 102. It will be. For this reason, only a very small part of the electric charge charged in the capacitor 103 is used, and the effect of providing a large-capacity capacitor can hardly be exhibited.
[0010]
[Means for Solving the Problems]
The present invention provides a first power conversion unit that converts electric power supplied from an AC power source into electric power suitable for arc machining, and rectifies the electric power supplied from the AC power source during non-processing and stores the electric power in the power storage unit. A second power conversion means; and a third power conversion means for converting the power stored in the power storage means into a power suitable for arc machining. The output of the first power conversion means and the third power conversion means The power supply device for arc processing is proposed in which the output of the power conversion means is superimposed on the workpiece and supplied to the workpiece.
[0011]
Furthermore, the first and second power conversion means can limit the power capacity by using any one of input power, output power, and input current as a conversion means that restricts one or more of them to a predetermined limit value or less. We proposed a device that can be used safely with some AC power supply.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a connection diagram showing an arc machining apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an AC power source, which is supplied from, for example, a power line AC100V power source. Reference numeral 2 denotes a first power conversion means which is activated by an arc machining command and converts the power supplied from the AC power source 1 into power suitable for arc machining. Reference numeral 3 denotes a second power conversion circuit for converting the output of the AC power source 1 into a DC voltage suitable for charging the power storage means 4. Reference numeral 4 denotes power storage means. For example, a huge capacity capacitor or storage battery called an electric double layer capacitor capable of rapid charging / discharging at several tens of F to 1,000 F can be used. Reference numeral 5 denotes third power conversion means for converting the electric power stored in the power storage means 4 into an output having characteristics suitable for arc machining at the time of arc machining, and reference numeral 6 denotes the output of the first power conversion means 2 and the third output. Output superimposing means for superimposing the output of the power conversion means 5 on each other, and as outlined in the figure, each output is connected in parallel with a diode, or these are connected in series to provide a total output. It is the circuit which obtains. An arc machining load 7 includes an electrode 7a and a workpiece 7b. A start command switch 11 continuously outputs a high level signal during arc machining. 12 is an inverter gate that inverts the output signal of the start command switch 11 and supplies the start signal to the second power conversion means at the time of non-machining, and 13 is suitable for arc machining to reduce the output current ripple and change the output current. This is a direct current reactor for providing a constant time constant.
[0013]
The output superimposing means 6 simply outputs the outputs of the first power converting means 2 and the third power converting means 5 when the first power converting means 2 and the third power converting means 5 have sufficient reverse breakdown voltage. It can be omitted because it only needs to be connected in parallel or in series.
[0014]
In the apparatus of FIG. 1, the first and second power conversion means 2, 3 may be any one that converts power from the AC power source 1 into power suitable for arc machining and charging the power storage means 4, For example, as briefly shown in the figure, a known circuit such as a control rectifier circuit using a transformer 2a, 3a and a thyristor that rectifies the output of the transformer to adjust it to a predetermined current can be used. The third power conversion means 5 may be any one that converts the DC output of the power storage means 4 into a predetermined output by chopper control or the like.
[0015]
In the apparatus of FIG. 1, when the switch S is closed, the output of the AC power supply 1 is supplied to the first power conversion means 2 and the second power conversion means 3, and among these, the first power conversion means is the start command. It is stopped until the switch 11 is closed. On the other hand, until the start command switch 11 is closed, the second power conversion means 3 converts the power because the high level signal obtained by inverting the output of the start command switch 11 by the inverter gate 12 is supplied. The input voltage is converted into a predetermined DC voltage by the transformer 3a and the control rectifier circuit 3b and output to the power storage means 4.
[0016]
When the start command switch 11 is closed during arc machining, the inverter gate 12 inverts the high level signal from the start command switch 11 and supplies it to the second power conversion means 3 as a low level, so that the second power conversion means 3 stops the operation and stops charging the power storage means 4.
[0017]
At the same time, the high-level signal of the start command switch 11 is supplied to the first power conversion means 2 and the third power conversion means 5 to start it, and the first power conversion means 2 is the power supplied from the AC power supply 1. Is converted into electric power suitable for arc machining and output, and the third power conversion means 5 converts the electric power stored in the power storage means 4 into electric power suitable for arc machining and outputs the electric power. The outputs of the first and third power conversion means are superimposed by the power superimposing means 6 and supplied to the arc machining load 7 through the DC reactor 13.
[0018]
Since the apparatus of FIG. 1 operates as described above, all of the electric power supplied from the AC power source 1 is charged to the power storage means when arc machining is not performed, and is all supplied to the arc machining load during arc machining. Therefore, the power capacity of the AC power source can be used effectively. Furthermore, during arc machining, machining is performed with the power superimposed from the power from the AC power supply and the power stored in the power storage means, so even when the capacity of the AC power supply is small, it is possible to secure the power necessary for arc machining. it can.
[0019]
FIG. 2 shows an example when the second invention of the present invention is implemented. Unlike the apparatus shown in FIG. 1, the first and third power conversion means 2 and 5 are always kept in an operating state. The output is supplied in parallel to the arc machining load through the semiconductor switching element. Therefore, in the apparatus of FIG. 2, the power superimposing means 6 is constituted by using a semiconductor switching element such as a thyristor or a switching transistor, and this switching element is used when the start command switch is closed during arc machining. It is made to conduct. The rest is the same as the apparatus shown in FIG.
[0020]
FIG. 3 shows a specific embodiment of the present invention. In the figure, reference numeral 1 denotes an AC power source, which is supplied from, for example, a power line AC100V power source. Reference numeral 2 denotes a first power conversion means which is activated by an arc machining command and converts the power supplied from the AC power source 1 into power suitable for arc machining. Reference numeral 3 denotes a second power conversion circuit for converting the output of the AC power source 1 into a DC voltage suitable for charging the power storage means 4. Reference numeral 4 denotes power storage means. For example, an electric double layer capacitor or a storage battery capable of rapid charging / discharging at about several tens of F to 1000F can be used.
[0021]
Reference numeral 5 denotes third power conversion means for converting the electric power stored in the power storage means 4 into an output having characteristics suitable for arc processing at the time of arc processing. The output of the first power conversion means 2 and the third power conversion The outputs of the means 5 are connected in parallel so as to be superimposed on each other to obtain a total output. An arc machining load 7 includes an electrode 7a and a workpiece 7b. 8 is an output current detector, 9 is an input current detector for detecting the input current to the first power conversion means, 10 is a charge current detector for the power storage means 4, and 11 is a start command switch for start command. The high level signal is output continuously during arc machining.
[0022]
Reference numeral 13 denotes a direct current reactor for reducing the ripple of the output current and giving the change of the output current a time constant suitable for arc machining. An output current setting unit 14 outputs a reference signal Iro. Reference numeral 15 denotes an input current limit value setter which outputs a reference signal Iim for determining the maximum allowable input current. Reference numeral 16 denotes a charging current setter that determines a current value to be supplied to the power storage means 4 and outputs a reference signal Irc. Reference numerals 17, 18, and 19 denote comparators. The comparator 17 outputs a difference signal ΔIo = Iro−Ifo, the comparator 19 outputs a difference signal ΔIc = Irc−Ifc, and the comparator 18 calculates ΔIi = Ifi−Iim. , .DELTA.Ii.ltoreq.0, use a 0 or low level signal, and when .DELTA.Ii> 0, use a high gain comparison amplifier that outputs a high level signal.
[0023]
In the figure, a first power conversion means 2 includes a primary rectifier circuit 201 that rectifies the output of the AC power source 1 to make a DC, an inverter circuit 202 that converts the output of the rectifier circuit 201 into a high-frequency AC, and the inverter A transformer 203 that converts the output of the circuit 202 into a voltage suitable for arc machining, a secondary rectifier circuit 204 that rectifies the output of the transformer 203 again into a direct current, and a pulse width control circuit 205 for the inverter circuit 202 including. 206 is an analog switch for grounding the input signal to the pulse width control circuit 205, 207 is an OR gate, 208 is the output of the start command switch 11, and outputs a high level signal when the start command switch is not closed. This is an inverter gate.
[0024]
The second power conversion means 3 is for the inverter circuit 302 that converts the direct current output of the primary rectifier circuit 201 of the first power conversion means 2 into a high frequency alternating current, the transformer 303, the secondary rectifier circuit 304, and the inverter circuit 302. Pulse width control circuit 305. An analog switch 307 for grounding an input signal to the 306 pulse width control circuit 305 is an OR gate.
[0025]
Further, the third power conversion means 5 includes an inverter circuit 502 that converts the direct current output of the power storage means 4 into high frequency alternating current, a transformer 503, a rectifier circuit 502, and a pulse width control circuit 505 for the inverter circuit 502. Reference numeral 506 denotes an analog switch that grounds an input signal to the pulse width control circuit 505 and stops this operation. Reference numeral 508 denotes an inverter gate that inverts a signal from the start command switch 11.
[0026]
In the apparatus of FIG. 3, the first power conversion means 2 and the third power conversion means 5 have sufficient reverse breakdown voltage because the outputs are rectified by the secondary rectifier circuits 204 and 504, respectively. The output superimposing means indicated by 1 is omitted, and the outputs of the first power converting means 2 and the third power converting means 5 are directly connected in parallel.
[0027]
In the apparatus of FIG. 3, when the switch S is closed, the output of the AC power supply 1 is rectified by the primary rectifier circuit 201 of the first power converter 2 and supplied to the inverter circuit 202 and the second power converter circuit 3. Until the start command switch 11 for the arc machining start command is closed, the low level signal from the start command switch 11 is inverted by the inverter gates 208 and 508 and becomes high level, and the analog switches 206 and 406 are turned on. Yes. For this reason, the pulse width control circuits 205 and 505 do not generate drive pulses regardless of the magnitude of the error signal output from the comparator 17 because the output command signal is grounded and becomes zero. For this reason, the inverter circuits 202 and 502 are stopped, the first and third power conversion means do not generate output, and arc machining is not performed.
[0028]
On the other hand, since the analog switch 306 is cut off while the output of the start command switch 11 is at a low level, the pulse width control circuit 305 of the second power conversion circuit 3 has a duty driving pulse corresponding to the output signal of the comparator 19. Is supplied to the inverter circuit 302. By this drive pulse, the second power conversion means 3 starts the operation of the inverter circuit 302 that receives the output of the primary rectifier circuit 201 of the first power conversion means 2, and the direct current output via the transformer 303 and the rectifier circuit 304. And the power storage means 4 is charged. The output of the second power converter 3, that is, the output current Ifc of the rectifier circuit 304 is detected by the charging current detector 10 and compared with the set value Irc of the charging current setter 16 by the comparator 19 to obtain a difference signal. ΔIc = Irc−Ifc is supplied to the pulse width control circuit 305 as an output command signal. The input current from the AC power source 1 is detected by the input current detector 9 and becomes Ifi, and the comparator 18 compares it with the set value Iim of the input current limit value setter 15 to obtain the difference signal ΔIi = Ifi−Iim. When ΔIi ≦ 0, a zero or low level signal is output, and when ΔIi> 0, a high level signal is output. As a result, until the input current Ifi exceeds the set value Iim of the input current limit value setter 15, that is, when ΔIi ≦ 0, the analog switch 306 remains cut off, and the inverter circuit 302 causes the error signal ΔIc = Irc−Ifc. The duty ratio is determined such that the power storage means 4 is charged with a constant current corresponding to the set charging current set value Irc.
[0029]
Conversely, when the input current becomes excessive and ΔIi> 0, that is, Ifi> Iim, the comparator 18 outputs a high level signal, whereby the analog switch 306 becomes conductive, and the pulse width control circuit makes the input signal grounded. Then, since it becomes zero, the drive pulse is not output, and the inverter circuit 302 stops. As a result, the second power conversion means 3 operates by normal feedback control until the input current exceeds the set value Iim, and charges the power storage means 4 with a constant current corresponding to the set value Irc. On the other hand, when the input current exceeds the set value Iim, the analog switch 306 is turned on and the inverter circuit 302 stops operating. However, when the operation is stopped, the input current rapidly decreases and Ifi <Iim, that is, ΔIi ≦ 0, again. The analog switch 306 is cut off, and the inverter circuit 302 generates an output again to resume charging the power storage unit 4. By repeating the above, eventually, an operation is performed in which the input current is limited to Iim or less.
[0030]
When the start command switch 11 is closed after the power storage means is sufficiently charged, the analog switch 306 is turned on by the high level signal from the start command switch 11 and the input signal of the pulse width control circuit 305 is made zero. Therefore, the second power conversion unit 3 stops its operation and stops charging the power storage unit 4.
[0031]
On the other hand, the high level signal from the start command switch 11 is inverted by the inverter gates 208 and 508 to become a low level, and the analog switches 206 and 506 are shut off. As a result, the error signal ΔIo = Iro−Ifo from the comparator 17 is supplied to the pulse width control circuits 205 and 505, respectively, and a drive pulse having a duty corresponding to each input signal is output to the inverter circuits 202 and 502. The inverter circuits 202 and 502 operate in this way, respectively converting DC input to high frequency AC, and the respective outputs are converted into voltages suitable for arc machining by the transformers 203 and 503, and then the secondary rectifier circuits 204 and 504. The current is rectified again and becomes direct current.
[0032]
The outputs of the secondary rectifier circuits 204 and 504 are superimposed because their output terminals are commonly connected, and are supplied to the arc machining load 7 having the electrode 7a and the workpiece 7b through the DC reactor 13. This output current is detected by the output current detector 8 to become a signal Ifo, and the comparator 17 compares it with the set value Iro of the output current setter 14 to calculate the error signal ΔIo = Iro−Ifo. At this time, the input current is detected by the input current detector 9 to become the signal Ifi, and the comparator 18 compares the input current with the output Iim of the input current limit value setting unit 15 to calculate the difference signal ΔIi = Ifi−Iim. Is done.
[0033]
Here, while ΔI i ≦ 0, that is, while the input current Ifi does not exceed the limit value Iim, the analog switches 206 and 506 are turned on / off only in response to the signal from the start command switch 11, but ΔI i> 0. In this case, the analog switches 206 and 506 are turned on regardless of the signal from the start command switch 11, and the command signals for the pulse width control circuits 205 and 505 are grounded. Therefore, until the input current exceeds the limit value Iim, the arc machining load 7 is supplied with power from both the first power conversion circuit 2 and the third power conversion circuit 5 and is set by the output current setting unit 14. A current of the specified value is supplied. However, in a state where the input current exceeds the limit value Iim, the output of the first power conversion circuit 2 stops when ΔIi> 0, and when ΔIi ≦ 0 due to the stop, the first power conversion circuit 2 is repeatedly started again. Therefore, when the setting is such that the input current exceeds Iim after all, the first power conversion circuit 2 operates in the output state where the input current is limited to the output current having a value at which the input current becomes the limit value Iim, regardless of the output setting value. The remaining output is covered by the output of the third power conversion means 5.
[0034]
Here, as the transformer 303 of the second power conversion means 3, a transformer that converts the output voltage of the inverter 302 into a voltage suitable for the rated voltage of the power storage means 4 is used. As the device 503, the rated voltage of the power storage unit 4 is required by using a converter that converts a high-frequency AC voltage obtained by converting the output voltage of the power storage unit 4 by the inverter circuit 502 into a desired voltage suitable for arc machining. It can be arbitrarily selected regardless of the arc machining voltage. For this reason, it is easy to use a capacitor having a large capacity such as an electric double layer capacitor having a small, light, long life but relatively low rated voltage as the power storage means 4.
[0035]
FIG. 4 is a connection diagram showing another embodiment of the present invention and corresponds to the second invention of the present invention. In the figure, reference numerals 6a and 6b denote control rectifier circuits that serve as both secondary rectifier circuits and output superimposing means, and thyristors 61a, 61b, 62a, and 62b are shown for transformers 203 and 503 having center taps, respectively. Thus, the cathode side of the thyristors 61a and 61b and the thyristors 62a and 62b are connected in common and are both connected to one terminal of the DC reactor 13. The output of the start command switch 11 is supplied to thyristors 61a, 61b, 62a, and 62b, respectively, to make them conductive during processing.
[0036]
In FIG. 4, the output of the start command switch 11 is supplied to the control rectifier circuits 6 a and 6 b to turn on and off the control rectifier circuits 6 a and 6 b, and is only supplied to the OR gate 307. 508, OR gate 207 and analog switch 506 are not provided. Accordingly, the output of the comparator 18 is directly supplied to the analog switch 206, and the pulse width control circuit 505 is always in an operating state.
[0037]
In the figure, before the start command switch 11 is closed, the power storage means 4 is charged with the set value of the charging current setter 16 in the same manner as in the apparatus of FIG. 3, and the input current Ifi at this time is the limit value Iim. It is controlled not to exceed. During this time, the ignition command signal is not supplied to the thyristors 61a, 61b, 62a, and 62b, so that the thyristors 61a, 61b, 62a, and 62b are cut off, and no electric power is supplied to the arc machining load 7.
[0038]
When the start command switch 11 is closed, the control rectifier circuits 6a and 6b are supplied with a signal from the start command switch 11 and supplied with an ignition signal to the thyristors 61a, 61b, 62a and 62b to be conducted. . At this time, the detected value Ifo of the output current detector 8 is compared with the set value of the output current setter 14 by the comparator 17 to calculate the error signal ΔIo = Iro−Ifo and supply it to the pulse width control circuits 205 and 505. Then, the outputs of the inverter circuits 202 and 502 are determined accordingly, and the output current is maintained at a value corresponding to the set value. On the other hand, at this time, the output of the start command switch 11 makes the analog switch 306 conductive through the OR gate 307 and stops the operation of the pulse width control circuit 302. At this time, the input current is detected by the detector 9 and compared with the set value of the input current limit value setter 15 by the comparator 18 to calculate the difference signal ΔIi = Ifi−Iim. As described in the example, when the input current becomes excessive and ΔI i> 0, the analog switch 206 is turned on, the output command signal for the pulse width control circuit 205 is grounded, and the inverter circuit 202 is stopped. The inverter circuit 202 is operated so that the input current value becomes Iim or less.
[0039]
3 and 4, the example of the constant current charging circuit in which the charging current for the power storage means 4 is detected and the charging current is maintained at the set value is shown. Instead of 10, a constant voltage charging circuit may be used in which the terminal voltage of the power storage means 4 is detected and charging is performed until the terminal voltage reaches a set value.
[0040]
In addition, an output voltage detector is provided in place of the output current detector 8, and the pulse width control circuits 206 and 506 are controlled to obtain a constant voltage output characteristic so that the detection value of the detector becomes a set value. Also good.
[0041]
Furthermore, 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 setter. When the input power exceeds the limit value, each The output of the inverter circuit may be stopped.
[0042]
Further, by utilizing the fact that the input current or the input power and the output power are approximately proportional, an output power detector of the first power conversion means or the second power conversion means is provided, and this detection output is set as a limit value setting device. These power conversion means may be stopped by a difference signal in comparison with the set value.
[0043]
Furthermore, as the first to third power conversion means 2, 3 and 5, in addition to the apparatus shown in the figure, any or all of these are obtained by a thyristor and a transformer to obtain a necessary voltage and output. Known means such as one constituted by a phase control rectifier circuit can be used.
[0044]
Needless to say, the second power conversion means 3 may be provided with a primary rectifier circuit in the same manner as the first power conversion means 2 so as to obtain power directly from the AC power source 1.
[0045]
FIG. 5 shows another embodiment of the present invention. In the figure, reference numerals 1 to 12 denote the same functions as those in the embodiment shown in FIG. In the figure, 20 is a polarity switching circuit provided between the DC reactor 13 and the arc machining load 7, and 21 is for supplying the polarity switching circuit 20 with forward and reverse drive signals at a predetermined cycle and rate. The polarity switching control circuits 21 a and 21 b are setters for setting the lengths of the positive polarity period and the reverse polarity period for the polarity switching control circuit 21.
[0046]
FIG. 6 shows a specific example of the polarity switching circuit. In the figure, reference numerals 20a to 20d denote bridge-connected semiconductor switching elements, and the switching elements 20a and 20b are turned on simultaneously or the switching elements 20c and 20d are turned on simultaneously by a drive signal from the polarity switching control circuit 21. Reference numerals 20e to 20h denote switching element protection diodes.
[0047]
5 and 6, the polarity switching control circuit 21 is activated when the activation command switch 11 is closed, and the rectangular wave pulse signal s according to the period and ratio determined by the setting devices 21a and 21b. ₁ , S ₂ Are alternately output and supplied to the switching elements 20a, 20b and 20c, 20d to alternately conduct them. A known timed circuit, mono-multivibrator, or the like can be used. As a result, the outputs of the first and third power conversion means superimposed by the output superimposing means 6 become an output having a polarity in which the electrode 7a is positive during the period in which the switching elements 20a and 20b are conductive, and the switching element 20c. , 20d is in a conductive period, the electrode 7a has a negative polarity output. Therefore, the setting signals 21a and 21b are adjusted to drive signal s. ₁ , S ₂ When the length and the ratio of are changed, the output to the arc machining load 7 can be an alternating current with an arbitrary positive / reverse ratio. Also signal s ₁ Output only the signal s ₂ Is stopped, the electrode 7a converts the positive polarity DC output to the signal s. ₂ When only the output is made, the electrode 7a can obtain a direct current output having a negative polarity.
[0048]
【The invention's effect】
As described above, since the power supply device for arc machining of the present invention is charged only when arc machining is not performed, the power capacity of the AC power supply can be used effectively. In addition, the power stored in the power storage means is converted into power having characteristics suitable for arc machining by the power conversion means different from the power stored in advance in the power storage means and the power from the AC power supply. As a result, it is possible to secure electric power necessary for processing even at a work site where the input power capacity is limited.
[Brief description of the drawings]
FIG. 1 is a connection diagram illustrating an example of an embodiment of the present invention.
FIG. 2 is a connection diagram showing another example of an embodiment of the present invention.
FIG. 3 is a connection diagram showing a specific embodiment of the present invention.
FIG. 4 is a connection diagram showing another specific embodiment of the present invention.
FIG. 5 is a connection diagram showing an example of still another embodiment of the present invention.
6 is a connection diagram showing a specific example of a polarity switching circuit used in the embodiment of FIG.
FIG. 7 is a connection diagram showing an example of a conventional apparatus.
[Explanation of symbols]
1 AC power supply
2 First power conversion means
2a, 3a transformer
2b, 3b Control rectifier circuit
3 Second power conversion means
4 Power storage means
5 Third power conversion means
6 Power superposition means
7 Arc machining load
7a electrode
7b Workpiece
8 Output current detector
9 Input current detector
10 Charging current detector
11 Start command switch
12, 208, 508 Inverter gate
13 DC reactor
14 Output current setting device
15 Input current limit value setter
16 Charge current setting device
17, 18, 19 Comparator
20 Polarity switching circuit
20a to 20d switching element
21 Polarity switching control circuit
201 Primary rectifier circuit
202, 302, 502 Inverter circuit
203, 303, 503 Transformer
204, 304, 504 Secondary rectifier circuit
205, 305, 505 Pulse width control circuit
206, 306, 506 Analog switch
207, 307 or gate
61, 62 Diode
61a, 61b, 62a, 62b thyristor

Claims (3)

A first power conversion means for converting electric power supplied from an AC power source into electric power suitable for arc machining at the time of machining, and an electric power storage inverter at the time of non-machining to convert the electric power supplied from the AC power source into high frequency AC A second power conversion means for rectifying the high-frequency alternating current converted by the power storage transformer and storing the power rectified during non-processing in the power storage means; and the electric power stored in the power storage means for arc processing during processing Arc processing comprising: third power conversion means for converting into power having suitable characteristics, wherein the output of the first power conversion means and the output of the third power conversion means are superimposed and supplied to the workpiece Power supply. First power conversion means for converting power supplied from an AC power source into power suitable for arc machining, and operating a power storage inverter during non-machining to convert power supplied from the AC power source into high frequency AC power Suitable for arc machining at the time of arc machining, the second power conversion means for rectifying the high-frequency alternating current converted by the storage transformer and storing the power rectified at the time of non-processing in the power storage means, and the power stored in the power storage means Third power conversion means for converting the power into the characteristic power, and output superimposing means for superimposing the output of the first power conversion means and the output of the third power conversion means upon processing to supply to the workpiece Power supply device for arc processing equipped with. 3. The arc machining power source according to claim 1, wherein electric power is supplied to the arc machining load through a polarity switching circuit that switches the output polarity of the superimposed output to an alternating current of normal, reverse, or a predetermined normal / reverse ratio. apparatus.

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