JP2564453B2 - Power supply for plasma processing machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of characteristics when a plasma arc is generated in a power supply device for a plasma processing machine.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram of a conventional power supply device for a plasma processing machine. A conventional plasma processing machine power supply device, an input unit that transforms an input voltage, a rectifying unit that rectifies the output of the input unit, a processing unit that performs plasma arc processing, a control unit that controls the output of the rectifying unit, And a pilot arc power source for generating a pilot arc. The input unit includes an input terminal 41 and a transformer 42 that transforms the input voltage input from the input terminal 41. The rectification unit is configured by a full-wave rectification circuit 43 that rectifies the output of the transformer 42 and a DC reactor 44 that smoothes the output of the full-wave rectification circuit 43. The processing part is a workpiece 45 to which the + side output of the DC reactor 44 is connected,
Main electrode 4 to which the minus output of DC reactor 44 is connected
6. The nozzle electrode 47 is connected to the + side output of the pilot arc power source. The control unit is a thyristor control that controls the output of the full-wave rectification circuit 43 by inputting the detection amounts of the plasma arc current detection circuit 48 and the plasma arc current detection circuit 48 that detect the currents flowing through the main electrode 46 and the workpiece 45. It is composed of a circuit 49. Further, the pilot arc power supply includes a transformer 51 that transforms the input voltage input from the input terminal 41, and the transformer 5 described above.
1. A rectifying circuit 52 for rectifying the output of No. 1, a smoothing reactor 53 for smoothing the output of the rectifying circuit 52, and a high frequency generating circuit 5 for applying a high frequency between the main electrode 46 and the nozzle electrode 47.
4 and a current limiting resistor 55.

Next, the operation will be described. Input terminal 41
The AC power is input to the transformer 42, is transformed by the transformer 42, and is input to the full-wave rectifier circuit 43. The full-wave rectifier circuit 43 is composed of a thyristor and is smoothed by the DC reactor 44 after rectification. Further, since the output of the DC reactor 44 is connected to the workpiece 45 on the + side and the main electrode 46 on the − side, a high no-load voltage is applied between the workpiece 45 and the main electrode 46. No current is flowing through. On the other hand, the output that has been transformed by the transformer 51, rectified by the rectifier 52, and smoothed by the smoothing reactor 53 has the + side on the nozzle electrode 47.
Since the negative side is connected to the main electrode 46, the nozzle electrode 4
A high no-load voltage is applied between 7 and the main electrode 46, but no current flows during this time. Then, by operating the high frequency generation circuit 54, a pilot arc is generated between the nozzle electrode 47 and the main electrode 46, and a pilot arc current flows. After the pilot arc is generated, the main electrode 46
Is brought closer to the workpiece 45, a plasma arc is generated between the workpiece 45 and the main electrode 46, and a plasma arc current flows.

[0004]

However, when a high no-load voltage is applied between the workpiece 45 and the main electrode 46 and the plasma arc current is not flowing, the detection amount of the plasma arc current detection circuit 48 is Since it becomes 0, the thyristor control circuit 49 controls the thyristor so that the maximum output of the full-wave rectification circuit 43 can be output. Therefore, an excessive plasma arc current flows at the same time when the plasma arc is generated. Further, generally, the AC power source input to the input terminal 41 uses a commercial power source, so the frequency thereof is 50 Hz or 60 Hz, and the DC reactor 44 is large, so that the response speed becomes slow and becomes excessive after the plasma arc is generated. The plasma arc current flows for a long time, so that the main electrode 46 is largely damaged.

An object of the present invention is to provide a power supply device for a plasma processing machine which does not flow an excessive plasma arc current when a plasma arc is generated and has a fast response speed.

[0006]

A power supply device for a plasma processing machine according to the present invention includes a rectifier circuit for rectifying an input AC power source, an inverter for converting an output of the rectifier circuit into an AC current as an input, and an inverter for the inverter. A transformer that transforms the output, a rectifier that rectifies the transformed voltage, and a plasma arc current detection circuit that detects the output of the rectifier.The inverter is feedback-controlled by the detection amount of the plasma arc current detection circuit. In two constant-current plasma arc power supplies having a control circuit for making a current constant, an output winding is added to one of the transformers of the constant-current plasma arc power supply, and the output of the windings is rectified. Pyroscope equipped with a rectifier circuit and a high frequency generation circuit for generating a pilot arc current at its output Characterized in that it is constituted by Toaku power.

Further, the present invention is characterized by having a switch means for cutting off the pilot arc current after the pilot arc is generated.

[0008]

In the power supply device for the plasma processing machine of the present invention, the input AC power is rectified by the rectifier circuit and converted into high frequency AC by the inverter. A plasma arc power supply having a pilot arc power supply applies a no-load voltage to the main electrode and the nozzle electrode. A pilot arc is generated by applying a high frequency high voltage between the main electrode and the nozzle electrode by the high frequency generating circuit. When the pilot arc is generated, the inverter is controlled by the detection amount of the pilot arc current detection circuit to control the pilot arc current at a constant current. The other plasma arc power source applies a no-load voltage between the main electrode and the workpiece, while the one plasma arc power source that shares the transformer with the pilot arc power source uses the pilot arc for constant current control. The output voltage is not large enough to generate a plasma arc. In this state, if the main electrode is brought close to the work piece while the pilot arc is generated, the other plasma arc power source (the one that does not share the transformer with the pilot arc power source) has a high no-load voltage. A plasma arc is generated by the other plasma arc power source. Then, the plasma arc current in this power supply is
The plasma arc current is detected by the plasma arc current detection circuit, and the inverter is controlled by the detected amount to control the plasma arc current at a constant current. After that, the one plasma arc power source is also operated, and the arc machining can be performed by the parallel operation.
In such a power supply device, since the pilot arc power supply shares the transformer of one plasma ark power supply, it is possible to avoid an increase in size of the power supply device. Further, each plasma arc power source may have a small capacity, and since each power source is controlled by constant current, the main electrode is not damaged when the plasma arc is generated. Further, by cutting off the pilot arc current by the switch after the plasma arc is generated, it is possible to prevent unnecessary loss due to the pilot arc after the plasma arc is generated.

[0009]

1 is a circuit configuration diagram of a power source device for a plasma processing machine according to an embodiment of the present invention. A power supply device for a plasma processing machine according to the present invention includes an input unit for inputting a commercial power supply, two plasma arc power supplies having a common input unit and having output sides commonly connected to enable parallel operation, and a transformer for the plasma arc power supply. It is composed of a pilot arc power supply that shares a vessel and generates a pilot arc, and a processing unit that performs processing with a plasma arc. The plasma arc power supply includes an inverter unit that converts an input power supply into a high-frequency AC voltage, a rectification unit that rectifies the output of the inverter unit, and a control unit that detects the plasma arc current and controls the inverter unit. The pilot arc power supply is composed of a rectification unit that rectifies the output of the inverter unit of the plasma arc power supply, a switch unit that turns on and off the output of the rectification unit, and a pilot arc generator unit. The input section includes an input terminal 1 and a rectifying circuit 2 that rectifies the commercial power source input from the input terminal 1. The inverter unit in the plasma arc power supply is composed of an inverter circuit 3.21 for converting the output of the rectifier circuit 2 into high frequency AC and a transformer 4.22 for converting the output of the inverter circuit 3.21. The rectification unit is a rectification circuit 5 that rectifies the outputs of the transformers 4 and 22.
23 and a smoothing reactor 6.24 for smoothing the output of the rectifying circuit 5.23. The control unit includes plasma arc current detection circuits 11 and 25 for detecting plasma arc current and the plasma arc current detection circuit 11 described above.
・ Inverter control circuits 12 and 26 for controlling the inverter circuits 3 and 21 according to the detected amount of 25. The rectifying unit in the pilot arc power supply is composed of a rectifying circuit 15 for rectifying the output of the tertiary winding 4 _c of one transformer 4 of the plasma arc power supply and a smoothing reactor 17 for smoothing the output of the rectifying circuit 15. ing. The switch section includes a switching element 16 that limits the output of the rectifier circuit 15 to the input to the smoothing reactor 17, and a switching element control circuit 19 that controls the switching element 16. The pilot arc generator section includes a pilot arc current detection circuit 18 for detecting a pilot arc current and a high frequency generation circuit 30 for applying a high frequency to the main electrode 8 and the nozzle electrode 9 when a pilot arc is generated. The processed portion is composed of the workpiece 7, the main electrode 8 and the nozzle electrode 9.

Next, the operation will be described. FIG. 2 shows a time chart at the time of startup in the embodiment. Figure 2
When the AC power is input to the input terminal 1 at T _{0 in} rectification, the rectification circuit 2 rectifies the AC power. The output of the rectifier circuit 2 is converted into a high frequency AC voltage by the inverter circuits 3 and 21. The output of the inverter is transformed by the transformers 4 and 22 and input to the rectifier circuits 5 and 23. The outputs rectified by the rectifier circuits 5 and 23 are smoothed by the smoothing reactors 6 and 24, and a high no-load voltage is applied between the workpiece 7 and the main electrode 8.

The pilot arc power source is the transformer 4
The output of the third winding 4 _c of the above is rectified by the rectifier circuit 15.
The switching element 16 is the switching element control circuit 1
It is in a closed state by 9. The output of the rectifier circuit 15 passes through the switching element 16 and is smoothed by the smoothing reactor 17 to apply a no-load voltage between the main electrode 8 and the nozzle electrode 9. At this time, since the pilot arc current is not flowing, the detection amount of the current detection circuit 18 is zero. Similarly, since the plasma arc current is not flowing, the detection amount of the current detection circuits 11 and 25 is 0. In such a state, the inverter control circuits 12 and 26 are controlled so that the outputs of the inverter circuits 3 and 21 become maximum.

After that (at T ₁ in FIG. 2), the high frequency generating circuit 30 is turned on to generate a pilot arc and a pilot arc current flows. Further, the pilot arc current is detected by the current detection circuit 18, and the inverter control circuit 12 controls the inverter circuit 3 by the detected amount to control the pilot arc current at a constant current. Further, when the pilot arc current is detected, the high frequency generation circuit 30 is also turned off. In this state, the no-load voltage applied between the workpiece 7 and the main electrode 8 by the inverter circuit 3 is low due to the constant current control of the pilot arc current, and this output alone does not affect the plasma arc. The migration is no longer possible.

In order to help this, the inverter circuit 21
With the other plasma arc power source having the above, a high no-load voltage is applied between the workpiece 7 and the main electrode 8 to facilitate the transition to the plasma arc.

[0014] at T ₂ in FIG. 2, when brought close to the main electrode 8 to the object 7 plasma arc, generated plasma arc current is detected by the current detection circuit 25 flows. The inverter control circuit 26 controls the inverter circuit 21 by the detected amount to make the plasma arc current constant.
Further, since the inverter control circuit 12 of the plasma arc power supply having the pilot arc power supply makes the pilot arc current a constant current, the output of the inverter circuit 3 is low. Therefore, the plasma arc current when the plasma arc is generated has a maximum current value that does not damage the main electrode 8.

The pilot arc helps to generate a plasma arc. As a result, the pilot arc becomes unnecessary after the plasma arc is generated. Moreover, the efficiency is poor due to losses due to the pilot arc current.
At T ₃ in FIG. 2, to stop the inverter circuit 3 sends a signal from the current detecting circuit 25 to the inverter stop circuit 12a of the inverter control circuit 12 in order to increase the efficiency.
Further, the timer circuit 12b in the inverter control circuit 12 is started at the same time as the stop. By stopping the inverter circuit 3, the pilot arc disappears and the pilot arc current becomes zero.

Further, the timer circuit 12b sends a signal to the inverter control circuit 12 when a set time has elapsed after starting (at T ₄ in FIG. 2), and the inverter control circuit 12 restarts the inverter circuit 3 by this signal. Let
After that, the plasma arc current is set to the final setting value (arc current value during processing) by parallel operation of the two plasma arc power supplies.
Performs constant current control. At that time, in the restarted inverter circuit 3, the plasma arc current rises as shown in FIG. 2 due to the delay time of the system due to the integrator / capacitor and the constant current built in the inverter control circuit 12 for controlling the inverter circuit 3. .

FIG. 3 shows another embodiment. The difference from FIG. 1 is that the input of the pilot arc power supply is
It is input from the output of the rectifier circuit 5 of the plasma arc power source, while the input is from the next winding _4c . There is no particular difference in operation.

Further, the switching element control circuit 19
Receives a signal from the plasma arc current detection circuit 25, and by opening the switching element 16 by this signal, the pilot arc can be extinguished without stopping the inverter circuit 3.

[0019]

As described above, according to the present invention, an excessive current does not flow when a plasma arc is generated and the main electrode is not damaged. Further, since the input power source is converted into high-frequency alternating current by the inverter, the response speed becomes faster, and highly accurate control can be performed. Further, in a large-capacity power supply device for a plasma processing machine, individual plasma arc power supplies can be made small in capacity by parallel operation of the plasma arc power supplies. This means that there are few high-capacity switching elements currently used in inverter circuits that perform high-frequency control, and it can be adapted to the current large-capacity plasma processing machine power supplies.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a power supply device for a plasma processing machine according to an embodiment of the present invention.

FIG. 2 is a diagram showing a time chart at the time of starting the power supply device for the plasma processing machine.

FIG. 3 is a diagram showing a circuit configuration of a power supply device for a plasma processing machine according to another embodiment of the present invention.

FIG. 4 is a diagram showing a circuit configuration of a conventional power supply device for a plasma processing machine.

[Explanation of symbols]

 1-input terminal 2/5/15 / 23-rectifier circuit 3.21 / inverter circuit 4.22 / transformer 6/17 / 24-smoothing reactor 7-workpiece 8-main electrode 9-nozzle electrode 11 / 18.25-Current detection circuit 12.26-Inverter control circuit 16-Switching element 19-Switching element control circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuro Ikeda 2-14-3 Awaji, Higashi-Yodogawa-ku, Osaka-shi Inside Sansha Electric Manufacturing Co., Ltd. (72) Inventor Kenzo Danjo 2-14-3, Awaji, Higashi-Yodogawa-ku, Osaka-shi No. 3 Sansha Electric Manufacturing Co., Ltd. (72) Inventor Masahiro Aoyama 2-14-3 Awaji, Higashiyodogawa-ku, Osaka

Claims (2)

(57) [Claims] 1. A rectifier circuit for rectifying an input AC power source, an inverter for converting an output of the rectifier circuit into an AC current, a transformer for converting an output of the inverter, and a rectified voltage thus converted. A rectifier, a plasma arc current detection circuit that detects the output of the rectifier, and two or more constant circuits having a control circuit that feedback-controls the inverter based on the detection amount of the plasma arc current detection circuit to make the plasma arc current a constant current. An output winding is added to one of the current plasma arc power supply and a transformer that transforms the output of the inverter of the constant current plasma arc power supply, and a rectifier circuit for rectifying the output of the winding and its output are provided. Equipped with a pilot arc current detection circuit and a high frequency generation circuit for generating pilot arc current, the detection amount of the pilot arc current detection circuit It is configured by a pilot arc power source for inputting to the control circuit of the constant current plasma arc power source on the side to which the output winding is added and feedback controlling the inverter to control the pilot arc current to a constant current. Power supply device for plasma processing machines. 2. The power supply device for a plasma processing machine according to claim 1, further comprising a switch means for interrupting the pilot arc current once the pilot arc is generated.