JP3779780B2 - Power supply device for arc machining - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a power supply device for arc machining used for TIG welding, plasma cutting, or the like.
[0002]
[Prior art]
Conventionally, as a power supply device for arc processing for igniting an arc in this non-contact type, a spark gap type high-frequency generator using a firing circuit in series with a welding transformer is widely used. It has become. However, this method has drawbacks such as that it easily causes radio wave interference, and that if the cable from the power supply device to the arc generation point is long, the high frequency is attenuated and the ignition performance is deteriorated.
[0003]
As a system for improving these drawbacks, a system using a DC high voltage is proposed in Japanese Patent Publication No. 61-44394 and put into practical use. In this method, the output of the DC main power source for generating the main arc is supplied to the electrode and the workpiece through the high voltage rectifier, and the output of the DC high voltage power source for arc ignition is supplied to the high voltage rectifier. The + side is connected in parallel with the cathode side of the high voltage rectifier.
[0004]
FIG. 1 is a connection diagram showing an example of the prior art of this method. In FIG. 1, reference numeral 1 denotes a main power source for generating a main arc for processing, and includes a main switch 1a, a main transformer 1b, a rectifier 1c, and a DC reactor 1d that are closed during processing according to a command. 2 is a commercial power source, and 3 is an arc machining load composed of an electrode 3a and a workpiece 3b. 4 is a cable, 5 is a DC high-voltage power supply for arc ignition whose internal impedance is high and the output current is limited, 6 is a high voltage rectifier, 7 is an arc generation detection relay, and 8 is an auxiliary switch. 10a and 10b are output terminals, 11 is a start switch for an arc start command, and 12 is a logic circuit, which generates a high level signal only when the start switch 11 is closed and there is no output from the arc detection relay 7 to assist. A signal for closing the switch 8 is output. A power switch 13 is normally closed during operation.
[0005]
In the apparatus of FIG. 1, when the power switch 13 is closed and the start switch 11 is closed, the main switch 1a and the auxiliary switch 8 are closed, and the output of the DC main power supply 1 and the output of the arc ignition DC high voltage power supply 5 are These are added and supplied between the electrode 3a and the workpiece 3b. This high DC voltage ionizes the gas between the electrode 3a and the workpiece 3b, destroys the insulation between them, and generates a spark discharge. When this spark discharge grows and fills the space between the electrode 3a and the workpiece 3b, the discharge can be sufficiently sustained only by the output of the DC main power supply 1, and the main arc discharge starts. When the main arc discharge starts, the arc detection relay 7 operates, and the inverted output thereof inverts the output of the logic circuit 12, opens the auxiliary switch 8, and shuts off the input of the DC high voltage power source 5 for arc ignition.
[0006]
[Problems to be solved by the invention]
An arc machining device such as an arc welding machine or a plasma cutting machine is often used by a worker holding a torch for holding a tungsten electrode by hand, and the worker can easily touch the tungsten electrode. In the non-contact ignition method, both the high frequency method and the direct current high voltage application method are a method in which a high voltage of several kV is applied to the electrodes to cause discharge. Consideration of electric shock to workers due to these high voltages is required. Since the high-frequency system uses a high-frequency current of about 1 to 3 MHz, even if it flows to the human body, most of the current flows through the surface of the skin due to the skin effect, so the risk is low. However, in the DC high voltage application method, there is no skin effect as in the high frequency method, and the current rather flows in the body with a low DC resistance, so the danger when receiving electric shock is much higher than in the high frequency method.
[0007]
In the configuration of the prior art shown in FIG. 1, when the auxiliary switch 8 is welded due to a failure or the like, when the power switch 13 is turned on, the arc is always turned on even though the operator has not turned on the start switch 11. When there is an output of the DC high voltage power source 5 for ignition, when an operator touches the electrode for electrode replacement or the like, the operator receives an electric shock.
The present invention relates to a reduction in the risk of such electric shock.
[0008]
[Means for Solving the Problems]
In order to solve the problems of the conventional apparatus, the present invention supplies the output of a DC main power source for generating a working arc between an electrode and a workpiece via a high voltage rectifier. It has a non-contact arc ignition device using a DC high voltage application system in which the output of a DC high-voltage power supply for arc ignition is connected in parallel with the output of the DC high-voltage power supply for arc ignition connected in parallel with the cathode side of the high-voltage rectifier Power is supplied from the auxiliary winding to the DC high voltage power supply for arc ignition through an auxiliary contact that is closed directly from the output of the main power supply or through an auxiliary contact that is closed only when necessary, or provided in the transformer that constitutes the main DC power supply. A power supply device for arc machining is proposed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention is shown in FIG. In the figure, the DC high voltage power source for arc ignition is different from the conventional device of FIG. 1 only in that its input is obtained from the output of the DC main power source 1, and the other is the same as the conventional device of FIG. Functions having the same reference numerals will be omitted from description. In the figure, when the power switch 13 is turned on and the start switch 11 is closed, the main switch 1 a is closed and an output voltage appears in the DC main power supply 1. At the same time, the output of the DC main power source 1 is supplied to the input of the DC high voltage power source 5 for arc ignition, and the output voltage of the DC high voltage power source 5 for arc ignition also appears. As a result, the output voltage of the DC high voltage power supply 5 for arc ignition is added to the output voltage of the DC main power supply 1 and supplied to the arc load 3, and the gas between the electrode 3a and the workpiece 3b is ionized. A spark discharge occurs and grows, and the main arc discharge begins.
[0010]
In the apparatus of FIG. 2, since the output of the DC high voltage power source for arc ignition does not appear between the electrode and the workpiece unless the start switch is pushed, when the operator performs inspection and replacement of the electrode, etc. The risk of exposure to high voltages is eliminated.
[0011]
FIG. 3 is a connection diagram showing a second embodiment of the present invention. In the figure, a DC high voltage power supply 5 for arc ignition is connected to the output terminal of the DC main power supply 1 via an auxiliary switch 8 that is closed from when the start switch 11 is closed until the arc is generated. Yes. Others are the same as those of the apparatus shown in FIGS. 1 and 2, and the same functions are denoted by the same reference numerals and description thereof is omitted.
[0012]
In the apparatus shown in the figure, when the power switch 13 is turned on and the start switch 11 is closed, the main switch 1a is closed and an output voltage appears in the DC main power supply 1. At this time, since the arc has not yet occurred, the logic circuit 12 is at a high level, whereby the auxiliary switch 8 is also closed, and the output of the DC main power supply 1 is supplied as the input of the DC high voltage power supply 5 for arc ignition. The output voltage also appears in the DC high voltage power supply 5 for arc ignition. As a result, the output voltage of the DC main power supply 1 and the output voltage of the DC high voltage power supply 5 for arc ignition are added and applied to the electrode 3a and the workpiece 3b, and the gas between them is ionized to spark. The main arc discharge starts when a discharge is generated and grows and can be sustained even at the output voltage of the DC main power supply 1. When the main arc discharge starts, the arc occurrence detection relay 7 operates, the output reverses the output of the logic circuit 12, the auxiliary switch 8 is opened, and the input of the DC high voltage power source 5 for arc ignition is cut off. To stop the output.
[0013]
FIG. 4 is a connection diagram showing a third embodiment of the present invention. In the figure, 9 is an operation mode changeover switch, 14 is a power supply for always closing the main switch 1a when the operation mode changeover switch 9 is set to the b side, and the others are shown in FIG. Since it is the same as the apparatus, the same function is given the same reference numeral, and the description is omitted.
[0014]
In the apparatus shown in the figure, the operation mode change-over switch 9 is connected between the logic circuit 12 and the start switch 11 and between the start switch 11 and the main switch 1a, and is in a non-contact operation mode like TIG welding. When the change-over switch 9 is set to the a side, the output of the DC high-voltage power source 5 is applied to the electrode 3a and the workpiece 3b from when the start switch 11 is pressed until the main arc is generated, and also by manual welding. In the contact operation mode, when the changeover switch 9 is set to the b side, the DC high-voltage power supply 5 does not operate and the main switch 1a is always closed so that manual welding is possible.
[0015]
FIG. 5 is a connection diagram showing a fourth embodiment of the present invention. In the figure, a high voltage DC power source 5 for arc ignition is formed by winding an auxiliary winding 1b2 independent of an arc generating secondary winding 1b1 around a main transformer 1b that constitutes a DC main power source 1. The electric power of the DC high-voltage power source 5 for arc ignition is obtained from the winding 1b2. The rest of the configuration is the same as that shown in FIGS. The operation is also the same as that of the embodiment shown in FIG.
[0016]
[Effect of the present invention]
Since the power supply device for arc machining according to the present invention is as described above, the DC high-voltage power supply can be operated even when a failure of the auxiliary switch provided at the input of the DC high-voltage power supply for arc ignition or contact welding occurs. There is no longer any possibility of the output being released. That is, only when the operator turns on the start switch 11, the output of the DC high voltage power supply for arc ignition appears. Therefore, even if the operator touches the electrode for exchanging the electrode during the work pause. The danger of receiving an electric shock disappears.
[0017]
Further, in the invention of claim 2, when using in a contact start type operation mode that does not require a DC high-voltage power source for arc ignition, such as a dual-purpose welding machine for TIG welding and covering arc welding, switching is performed. Thus, the output of the DC high voltage power source for arc ignition can be stopped.
[0018]
Furthermore, in the invention of claim 3, in addition to the above, it is possible to insulate the input circuit of the DC high voltage power supply for arc ignition, which is effective for noise countermeasures.
[Brief description of the drawings]
FIG. 1 is a connection diagram illustrating an example of a conventional apparatus.
FIG. 2 is a connection diagram showing an embodiment of the apparatus of the present invention.
FIG. 3 is a connection diagram showing another embodiment of the apparatus of the present invention.
FIG. 4 is a connection diagram showing another embodiment of the apparatus of the present invention.
FIG. 5 is a connection diagram showing still another embodiment of the apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 DC main power source 1a Main switch 1b Main transformer 1b1 Secondary winding 1b2 Auxiliary winding 1c Main rectifier 1d Reactor 2 Commercial power source 3 Arc processing load 3a Electrode 3b Work piece 4 Cable 5 DC high voltage for arc ignition Power supply 6 High voltage rectifier 7 Arc generation detection relay 8 Auxiliary switch 9 Operation mode changeover switch 10a, 10b Output terminal 11 Start switch 12 Logic circuit 13 Power switch 14 Power supply

Claims (3)

An output of a DC main power source for generating a working arc is supplied between an electrode and a workpiece via a high voltage rectifier, and a positive output terminal is connected to the cathode side of the high voltage rectifier with respect to the high voltage rectifier. And a DC high voltage power supply for arc ignition connected in parallel, and an arc machining power supply apparatus in which an input terminal of the DC high voltage power supply for arc ignition is connected to an output terminal of the DC main power supply. An output of a DC main power source for generating a working arc is supplied between an electrode and a workpiece via a high voltage rectifier, and a positive output terminal is connected to the cathode side of the high voltage rectifier with respect to the high voltage rectifier. A DC high-voltage power supply for arc ignition connected in parallel with each other, and an arc in which an input terminal of the DC high-voltage power supply for arc ignition is connected to an output terminal of the DC main power supply via an auxiliary switch Power supply for processing. An output of a DC main power source for generating a working arc is supplied between an electrode and a workpiece via a high voltage rectifier, and a positive output terminal is connected to the cathode side of the high voltage rectifier with respect to the high voltage rectifier. A DC high voltage power source for arc ignition connected in parallel, and the input of the DC high voltage power source for arc ignition is input from an auxiliary winding wound around a main transformer constituting the DC main power source. A power supply device for arc machining that can be obtained.

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