JPH079137A - Direct current arc welding machine and plasma cutter - Google Patents

Abstract

PURPOSE:To provide a direct current arc welding machine of long life electrode non-contact arc starting system or a plasma cutter which is noiseless and excellent in characteristic of cable extension. CONSTITUTION:The output of a 1st direct current power source 1 is supplied to a load through a switching element 11, a 2nd direct power source 10 impressed with direct current high voltage is also connected to the load, at the time of arc actuation, the direct current high voltage is impressed to the load from the 2nd direct current power source 10, a single directional rectifying device 11 is made conductive with the output of a discharge detector 12 to detect the discharge with the 2nd direct current power source 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct current arc welding machine which has a perfect arc start characteristic without generation of high frequency noise, and has a dramatically improved arc start characteristic without contact even when an extension cable is used. Plasma cutting machine

[0002]

2. Description of the Related Art FIG. 2 shows an example of a circuit configuration of a non-contact start circuit of a conventional welding machine or cutting machine for non-contact arc starting of an electrode and a base material. In FIG. 2, 1 is a first DC power supply device that is a welding or cutting DC power supply having a drooping characteristic or a quasi-constant voltage characteristic, 2 is an arc (welding load or cutting load), 3 is a base metal, 4 is an electrode, Reference numeral 5 is an arc generation detector, 6 is a start signal circuit, 7 is a contact point that closes after receiving the start signal until the arc is generated, 8 is a high frequency generator consisting of a high voltage transformer, an oscillating capacitor and a spark gap, 9 is a high frequency wave in the main circuit It is a coupling coil that overlaps.
Conventionally, the contact 7 is closed until the arc generation detection signal of the arc generation detector 5 is received after the activation signal of the activation signal circuit 6 is received, and the high frequency generated by the high frequency generator 8 during this period is the coupling coil 9 It is applied between the electrode 4 and the base material 3 via. That is, only when the arc is started, a high frequency is applied between the electrode 4 and the base material 3 to enable non-contact start.

[0003]

In the above-mentioned conventional example, a large amount of high frequency as shown in FIG. 6 is generated at the start. Further, when no load is applied, a radiation electric field strength of about 50 dBμV is generated as shown in FIG. Therefore, in addition to causing radio interference to nearby TVs, radios, and electronic devices, it may cause high-frequency malfunctions that lead to destruction. In addition, the high frequency power is too strong to roughen the electrode surface and impair the starting characteristics when the arc start is repeated. Further, since the center frequency is a high frequency of about 1 MHz, there was a problem to be solved such as a high frequency leaking during the extension of the secondary side cable, which did not reach the torch tip and arc start did not occur. As shown in Fig. 8, in the conventional model, the extension cable is 5
At 0 m or more, arc start was impossible.

The present invention solves the above problems, and an object thereof is to provide a non-contact arc start type DC arc welding machine or a plasma cutting machine which is excellent in noiseless and extension cable characteristics.

[0005]

In order to solve the above problems, a DC arc welding machine or a plasma cutting machine according to the present invention comprises:
A first DC power supply device that has a drooping characteristic or a quasi-constant voltage characteristic and supplies a DC voltage output to a welding load or a cutting load via a switching element, and a high DC voltage is applied to both ends of the welding load or the cutting load. A drooping characteristic type second DC power supply device and a discharge detecting means for detecting a discharge by the second DC power supply device. When an arc is started, a high DC voltage is applied to the load from the second DC power supply. The switching element is made conductive by a signal from the discharge detecting means.

[0006]

With the above structure, a high DC voltage of about 4 KV is applied between the electrode and the base material at the time of starting the arc. Therefore, even if the cable is extended, a non-contact start can be sufficiently performed. Moreover, since it is a DC high voltage, no noise is generated when there is no load. Further, since the surface of the electrode is not roughened by the high frequency, the life of the electrode can be improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram showing a configuration of a non-contact start circuit of a DC arc welding machine and a plasma cutting machine according to an embodiment of the present invention. In FIG. 1, a first DC power supply device 1 which is a welding or cutting DC power supply having a drooping characteristic or a quasi-constant voltage characteristic has an arc (welding load or cutting load) 2 via a unidirectional rectifying element 11 which is a switching element. Supply DC voltage to. 10 is a drooping characteristic type second DC power supply device for applying a DC high voltage, which is a DC high voltage generator of about 4 KV, and applies a DC high voltage between the electrode 4 and the base metal 3 at both ends of a welding load or a cutting load. To do. Reference numeral 12 is a discharge detector that detects a discharge between the electrode 4 and the base material 3 by the second DC power supply device 10, and operates to close the unidirectional rectifying element 11 by detecting the start of discharge immediately before the arc is generated. Therefore, the unidirectional rectifying element 11 makes the first direct-current rectifier 11 so that the high DC voltage of the second DC power supply device 10 is applied only between the electrode 4 and the base material 3.
Therefore, the high voltage application to the DC power supply device 1 is prevented. Since the contact 7 is closed after receiving the activation signal of the start signal circuit 6 to the arc generation detection arcing detector 5, as shown in FIG. 3, the second DC power supply unit 10 from time t ₁ to t ₂ An output is generated and a DC high voltage of about 4 KV as shown in FIG. 5 is applied between the electrode 4 and the base material 3. Further, as shown in FIG. 3, the discharge detector 12 starts from the time t ₁ ′ immediately before the arc occurrence time t _{2 to} the time t immediately after the arc occurrence.
_A signal is output up to 2'and the unidirectional rectifying element 11 is made conductive by this signal, and thereafter the conductive state is maintained.

In the present embodiment, the application of the high DC voltage to the both ends of the welding load or the cutting load by the second DC power supply device 10 is made between the times t _{1 and} t ₂ until the arc occurs. Alternatively, as shown in FIG. 4, a high voltage may be constantly applied during startup. The output static characteristic at this time is as shown in FIG. 7, and the second DC power supply output is applied between the electrode and the base material when no load is applied and the first DC power supply output is applied after the arc transition. Welding or cutting is possible by non-contact start between the electrode and the base material.

According to this embodiment, as shown in FIG.
According to the C test method, the noise electric field strength is about 30 compared to the conventional model.
It decreases by dBμV. Further, as shown in FIG. 8, the arc start rate is also significantly improved as the extension cable is loaded, compared with the conventional machine. In the conventional machine, the high frequency leaks on the way and the arc starts only up to 50 m, whereas in the present embodiment, even if it is extended by 100 m, the perfect arc start performance is exhibited. Here, the test was performed under the following conditions.

Test conditions-Electrode: tungsten containing thorium 2.4φ-Ar gas: 51 / min-Distance between electrode base materials: 3 mm-Current: 50 A-Torch switch ON / OFF cycle: 2 seconds ON / 13 seconds OFF-Test Number of times ... Repeat 100 times

[0011]

As described above, according to the present invention, since the high DC voltage of the second DC power supply device is applied between the electrode and the base material at the time of starting the arc, even if the cable is extended, it is sufficiently non-contact. It is possible to start. Moreover, since it is a high DC voltage, no noise is generated when there is no load, there is no radio interference to nearby TVs and electronic devices, and no high-frequency malfunction occurs by itself. Further, since the surface of the electrode is not roughened by the high frequency, the life of the electrode can be improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a non-contact start circuit of a current arc welding machine and a plasma cutting machine according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a non-contact start circuit according to a conventional machine.

FIG. 3 is a diagram showing a DC high voltage application timing according to the present invention.

FIG. 4 is a diagram showing another example of the DC high voltage application timing according to the present invention.

FIG. 5 is a voltage waveform diagram applied between an electrode and a base material according to the present invention.

FIG. 6 is a voltage waveform diagram applied between an electrode and a base material by a conventional machine.

FIG. 7 is a static output characteristic diagram according to the present invention.

FIG. 8 is a diagram showing test results of arc start performance according to the present invention and a conventional machine.

FIG. 9 is a diagram showing an example of data of radiation noise electrolytic strength according to the present invention and a conventional machine.

[Explanation of symbols]

1 1st DC power supply device which is a DC power supply for welding or cutting 2 Arc (welding load or cutting load) 3 Base material 4 Electrode 5 Arc generation detector 6 Start signal circuit 7 Contact that closes until arc is generated after receiving start signal 10 2nd DC power supply device which is a drooping characteristic type power supply for DC high voltage application 11 Unidirectional rectification element which is a switching element 12 Discharge detector

Claims (2)

[Claims] 1. A first DC power supply device having a drooping characteristic or a quasi-constant voltage characteristic, which supplies a DC voltage output to a welding load through a switching element, and a DC high voltage is applied to both ends of the welding load. A second drooping characteristic type direct current power supply device;
A discharge detecting means for detecting a discharge by the second DC power supply device, wherein a high DC voltage is applied to the load from the second DC power supply device when the arc is started, and the switching is performed by a signal from the discharge detecting means. A DC arc welding machine characterized by making elements conductive. 2. A first DC power supply device having a drooping characteristic or a quasi-constant voltage characteristic, which supplies a DC voltage output to a disconnecting load through a switching element, and a DC high voltage is applied across the disconnecting load. A second drooping characteristic type direct current power supply device;
A discharge detecting means for detecting a discharge by the second DC power supply device, wherein a high DC voltage is applied to the load from the second DC power supply device when the arc is started, and the switching is performed by a signal from the discharge detecting means. A plasma cutting machine characterized by making elements conductive.