JP3165230B2 - Inverter power supply for welding or cutting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter power supply for welding or cutting.

[0002]

2. Description of the Related Art JP-A-62-292273 discloses that
A commercial frequency AC input is converted into high-frequency AC by a primary rectifier and an inverter, supplies current to a main circuit via a transformer and a secondary rectifier, and is used as a power source of a pilot current circuit to be superimposed on the main circuit. A power supply for a plasma arc is disclosed which rectifies the output of a secondary winding of a transformer and uses an AC reactor instead of a conventional resistor as a means for limiting the rectified current.

[0003]

According to the above prior art, the power supply can be reduced in size and weight and energy can be saved. However, even if an AC reactor is adopted, there is a limit in reducing the size and weight of the power supply. Further, when an AC reactor is employed, if the output of the main circuit is changed, the value of the superimposed current also changes accordingly, and cannot be kept constant. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, to further reduce the size and weight of an inverter power supply for welding or cutting and to save energy, and to reduce the value of superimposed current even when the output of a main circuit is changed. It is to provide an inverter power supply for welding or cutting which can be kept constant.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to convert a commercial frequency AC input into a high frequency AC by a primary rectifier and an inverter, and to supply a current to a main circuit via a transformer and a secondary rectifier. An inverter power supply for welding or cutting wherein the tertiary or secondary winding of the transformer is used as a power supply for a superimposed current circuit or a pilot current circuit for superimposing a current on a main circuit. The problem is solved by connecting a capacitor in series to the tertiary winding or the secondary winding, and rectifying the output to produce a superimposed current or a pilot current. This is effectively solved by setting the output voltage of the superimposed current circuit obtained by rectifying the output of the tertiary winding or the secondary winding of the transformer to approximately twice the voltage of the superimposed current circuit power supply.

[0005]

The inverter is normally turned on and off at 8 to 20 kHz. That is, the output of the transformer is 8 to 20.
with a commercial frequency of 130 to 40 kHz
Since it is 0 times, a capacitor having a small capacity can be used as a current limiting means of the superimposed current circuit or the pilot current circuit. When a capacitor is used as the current limiting means, the size and weight are reduced to one third of that of the AC reactor.
Degree. Also, the heat generation is about 1/200 of that of the resistor, as in the case where the AC reactor is employed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the first to third embodiments will be described in the case where the present invention is applied to a pilot current circuit of a power supply for a plasma arc, and the fourth case in which the present invention is applied to a mag welding power supply. An example will be described with reference to the drawings. FIG. 1 is a connection diagram showing a first embodiment of the present invention, and shows a case where the present invention is applied to a pilot current circuit of a power supply for a plasma arc. In FIG. 1, reference numeral 1 denotes a primary-side rectifier for rectifying an AC input of a commercial frequency. 2 is an inverter connected to the primary rectifier 1
The DC is converted to an AC of 20 kHz. 3 is a smoothing capacitor. 4 is a transformer. 5 is a secondary winding of the transformer 4. A rectifier 6 converts the AC output of the secondary winding 5 into DC and supplies it to the output main circuit. 7 is a main circuit switching element. 8
Is a current detector. 9 is a work. 10 is an electrode. 11 is a coupling coil 1 for superimposing a high frequency at the time of arc start.
1.12 is a DC reactor. 15 is an output setting device. 1
6 is a comparator. Reference numeral 17 denotes a PWM control unit. The output-side main circuit includes a rectifier 6, a main circuit switching element 7, a current detector 8, a work 9, and an electrode 1 from both ends of the secondary winding 5.
0, the transformer 4 is provided via a coupling coil 11 for superimposing a high frequency at the time of arc start and a DC reactor 12. Further, in order for the current of the value set in advance by the output setting device 15 to flow to the output side main circuit, the signal from the current detector 8 and the value set to the value of the output setting device 15 are compared by the comparator 16. And compares the result with the PWM control unit 17
To operate the inverter 2. 30 is a tertiary winding. The voltage V generated at both ends of the tertiary winding 30
_pl is set to be higher than the voltage generated between both ends of the secondary winding 5 and the middle point. 31 is a capacitor current limiting, capacitance so that the value of the pilot current I _pl is 10~30A is selected. 32 is a full-wave rectifying diode.
De. 33 is a contact point of a relay 37 described later. 34 is a high frequency bypass capacitor. 35 is a nozzle. 36 is Rire-3
7 is a drive circuit. And the pilot current circuit is
The configuration is such that one end of the tertiary winding 30 reaches the other end of the tertiary winding 30 via the capacitor 31, the full-wave rectifying diode 32, the contact point 33, the nozzle 35, the coupling coil 11, and the DC reactor 12. Hereinafter, the operation will be described.

During the pause, there is no output from the inverter 2,
The main circuit switching element 7 is off, and the relay 37 is on. When a welding start signal is input by a start button (not shown), (1) a pilot arc is generated. That is, at the same time as the output of the inverter 2, a start high frequency generating circuit (not shown) operates to generate a high frequency in the coupling coil 11. Then, the high frequency is transmitted to the nozzle 35 through the condenser 4, so that a high frequency is applied between the electrode 10 and the nozzle 35, and the electrode 10 and the nozzle 3
5, a pilot arc is generated, a pilot current circuit is connected, and a pilot current _Ipl flows. When the occurrence of the pilot arc is confirmed, the start high frequency generating circuit (not shown) is turned off, and the preparation for welding is completed. (2) When a welding start signal is input, the main circuit switching element 7 is turned on, a main arc is generated between the work 9 and the electrode 10, and plasma welding is started. When the occurrence of the main arc is confirmed, the relay 37 is turned off, the contact 33 is turned off, and the pilot current circuit is turned off. In this embodiment, the pilot current circuit is turned off during the plasma welding, but the pilot current circuit may be kept on.

FIG. 2 is a connection diagram showing a second embodiment of the present invention, and shows a case where the present invention is applied to a pilot current circuit of a power supply for a plasma arc similarly to the first embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals. This second embodiment, the midpoint tertiary winding 38 provided by using two capacitors 31, full-wave rectifying diode - both ends of the terminal voltage V _D of the output side of the leads 32 is tertiary winding 38 The circuit is configured so as to be approximately twice the voltage V _T. In this embodiment, when the pilot current circuit is kept on even during plasma welding, the change in pilot current can be reduced as compared with the first embodiment or the prior art. That is, as shown in FIG. 5, output or inverter main circuit - when changing the data 2 output, because the change in the terminal voltage V _D as compared with the first embodiment or the prior art is small, The change in pilot current is small. If the load is large, the load voltage can be approximated to the no-load voltage, and the terminal voltage V _D and the terminal voltage V _{D in} FIG.
The average value V _Dav is described as a value when no load is applied.
It is a schematic one. In the figure, V is an inverter 2
Is the voltage output by D, D is the time when the inverter 2 is on,
T is the ON / OFF cycle of the inverter 2, and the sum of the ON time and the OFF time in one cycle is constant. In this embodiment, the diode 32 for full-wave rectification is used, but one diode may be used in combination. Also,
In the case where one diode is used in combination, the diodes 32c, 32c,
The circuit may be configured without the 32d and the capacitor 31b, but in that case, the reactance of the DC reactor 12 needs to be increased. Note that other operations are substantially the same as those of the first embodiment, and will not be described.

FIG. 3 is a connection diagram showing a third embodiment of the present invention, and shows a case where the present invention is applied to a pilot current circuit of a power supply for a plasma arc similarly to the first and second embodiments. In the third embodiment, the voltage of the pilot current circuit is twice the voltage of the main circuit, and the tertiary winding 38 in the second embodiment is omitted. In addition,
The operation is substantially the same as that of the second embodiment and will not be described.

Next, a case where the present invention is applied to a constant voltage type mag welding power source using a consumable electrode, that is, a wire, will be described as a fourth embodiment. By the way, in the case of the MAG welding power supply, the wire and the work are short-circuited at the time of the arc start. At this time, if the tip of the wire blows excessively, for example, the arc is cut off and the arc becomes unstable. There was a problem of becoming. The fourth embodiment is similar to the third embodiment.
Is applied to a current superimposing circuit of a mag welding power supply, and the same components as those in FIG. 1 are denoted by the same reference numerals. In the figure, reference numeral 40 denotes a DC reactor of a current superposition circuit. 41 is a DC reactor of the output side main circuit. 42 is a wire. 43 is a roller for feeding a pair of wires. 44 is an energizing chip. 45 is an arc load. The DC reactor 40
Is a large reactance for a small current, and the DC reactor 41 is set to a small reactance for a large current.

The output-side main circuit includes a rectifier 6, a DC reactor 41, a current-carrying chip 44,
Transformer 4 via wire 42, arc load 45, and work 9
It has a configuration leading to. In addition, the current superimposing circuit includes a capacitor 31, a full-wave rectifier diode 32, a DC reactor 40, a DC reactor 41, a conducting chip 44, a wire 42, an arc load 45, Through the loop 9 to the middle point of the secondary winding 5. Incidentally, the value of the current I _c flowing through the current superimposing circuit is smaller than the normal welding current A - are selected the capacitance of the capacitor 31 to be sized to maintain the click thoroughly. Hereinafter, the operation will be described.

For example, at the time of arc start, if the tip of the wire blows excessively and the arc voltage becomes high, the welding current becomes insufficient. However, in the case of this embodiment, the arc is not cut off as a result of the current being supplied from the current superposition circuit. In addition,
In the fourth embodiment, a MAG welding power supply of the constant voltage scheme described taking as an example, is applied to Parusumagu welding power source, base value of the current supplied from the superimposing circuit - scan current I _b to be slightly smaller than If set to a, for example, by wire feeding change in resistance during welding - so click is long, base - scan current I _b in a - even upcoming rise to click out, a - generate click breakage Can be prevented.

[0013]

As described above, according to the present invention,
For example, when applied to a pilot current circuit of a power supply for a plasma arc which is an inverter power supply for welding or cutting,
Almost the same energy saving can be achieved as in the case of using the conventional AC reactor, and further, the weight can be reduced as compared with the AC reactor. In addition, when applied to a constant voltage type mag welding power source using a wire, it is possible to prevent arcing at the time of arc start, and when using a pulse mag welding power source, arcing during welding is prevented. Therefore, there is an effect that work efficiency can be improved. Further the output of the transformer tertiary winding or secondary winding with two capacitors 31, full-wave rectifying diode - the voltage across V _T of the terminal voltage V _D of the output side of the leads 32 is tertiary winding 38 If the circuit is configured to be approximately twice as large as
There is an effect that a change in pilot current or superimposed current can be made substantially constant.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing a first embodiment of the present invention.

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

FIG. 3 is a connection diagram showing a third embodiment of the present invention.

FIG. 4 is a connection diagram showing a fourth embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation of the second exemplary embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary side rectifier 2 Inverter 4 Transformer 5 Secondary winding 6 Rectifier 30, 38 Tertiary winding 31 Capacitor

Claims (2)

(57) [Claims] An AC input of a commercial frequency is converted into a high-frequency AC by a primary rectifier and an inverter, and then a current is supplied to a main circuit through a transformer and a secondary rectifier, and a tertiary winding of the transformer is provided. Alternatively, in a welding or cutting inverter power supply in which the output of the secondary winding is rectified and used as a power supply for a superimposed current circuit or a pilot current circuit of the main circuit, the tertiary winding or the secondary winding of the transformer is used. A welding or cutting inverter characterized by connecting a capacitor in series and rectifying its output to produce a superimposed current or pilot current.
Power supply. 2. An output voltage of a superimposed current circuit obtained by performing PWM control of an inverter and rectifying an output of a tertiary winding or a secondary winding of a transformer is substantially twice the voltage of a superimposed current circuit power supply. The welding / cutting inverter power supply according to claim 1, characterized in that: