JP3704233B2 - DC arc welding power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DC arc welding power source.
[0002]
[Prior art]
FIG. 5 is an external connection diagram of a conventional consumable electrode type DC arc welding power source. Reference numeral 2 denotes a power source section of the welding power source 1. The voltage of the three-phase AC power source 4 is stepped down to a voltage suitable for welding by the transformer 3, rectified and smoothed by the diode 5 and the capacitor 6, and DC is connected between the terminals A and B. Supply output. 7 and 8 are switching elements, 9 and 10 are diodes, 11 and 12 are reactors, and 13 and 14 are external output terminals. Note that the inductance value of the reactor 12 is larger than the inductance value of the reactor 11. A positive output cable 15 connects the external output terminal 13 and the wire 16. 17 is a torch, 18 is a welding load, and 19 is a base material. A negative output cable 20 connects the external output terminal 14 and the base material 19. The external output characteristic of the welding power source 1 is a constant voltage characteristic.
[0003]
The operation will be described below. During the arc period Ta, the switching element 7 is turned on / off by PWM control. When the power is on, the DC current supplied from the power supply unit 2 causes the arc current Ia to be changed from terminal A → switching element 7 → reactor 11 → reactor 12 → external output terminal 13 → output cable 15 → wire 16 → welding load 18 → It flows through the circuit in the order of the base material 19 → the output cable 20 → the external output terminal 14 → the terminal B. Further, at the time of turning off, the arc current Ia is generated by the energy stored in the reactors 11 and 12, and the reactor 11 → the reactor 12 → the external output terminal 13 → the output cable 15 → the wire 16 → the welding load 18 → the base material 19 → the output cable 20 → Reflux in the order of external output terminal 14 → diode 9. Hereinafter, the external output terminal 13 to the external output terminal 14 in the above circuit is referred to as a load K.
[0004]
Further, during the short circuit period Ts, the switching element 8 is turned on / off by PWM control. When ON, the short-circuit current Is is generated in the order of terminal A → switching element 8 → reactor 12 → external output terminal 13 → load K → external output terminal 14 → terminal B by the DC output supplied from the power supply unit 2. Flowing into. Further, when it is off, the short circuit current Is recirculates in the order of the reactor 12 → the external output terminal 13 → the load K → the external output terminal 14 → the diode 10 due to the energy stored in the reactor 12.
[0005]
[Problems to be solved by the invention]
FIG. 6 is a diagram showing an output current waveform when welding is performed by the conventional DC arc welding power source. As is apparent from the figure, the current rise in the period Tu after the transition from the arc period Ta to the short-circuit period Ts and the current fall in the period Td after the transition from the short-circuit period Ts to the arc period Ta have a gentle slope. .
[0006]
When the short-circuit period Ts becomes longer, not only the wire 16 explosively blows and large spatters are generated, but the arc becomes unstable and the welding quality deteriorates. Further, in order to increase the magnitude of the short circuit current, it is necessary to increase the capacity of the semiconductor element.
[0007]
An object of the present invention is to provide a DC arc welding power source that solves the above-described problems and that can reliably control heat input by making the arc period Ta and the short-circuit period Ts constant, thereby improving welding quality. It is in.
[0008]
[Means for Solving the Problems]
In the DC arc welding power source having the constant voltage characteristic of the external output characteristic, the above-described problem is that the first wire constituting the reactor P and the second wire constituting the reactor B are wound around the same iron core, and the arc current period is The reactor P is connected to the output circuit and the reactor B is disconnected from the output circuit, and the reactor B is connected to the output circuit and the reactor P is disconnected from the output circuit during a short circuit period. The problem is solved by connecting to the output circuit so that the directions of magnetic fluxes formed in the reactor P and the reactor B are the same.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a connection diagram of a consumable electrode type DC arc welding power source according to the present invention. In addition, the same thing as FIG. 5 or the thing of the same function attaches | subjects the same code | symbol, and abbreviate | omits description.
Reference numeral 30 denotes a switch. When the contacts m and n are closed, the contacts r and s are opened, and when the contacts r and s are closed, the contacts m and n are opened. The contact m is connected to the output side of the switching element 7, and the contact r is connected to the output side of the switching element 8. A reactor 31 includes a winding p having a winding number Np, a winding b having a winding number Nb, and one iron core f, and is magnetically coupled by winding the winding p and the winding b around the iron core f. is there. The winding b and the iron core f constitute a reactor B, and the winding p and the iron core f constitute a reactor P. Further, one end of the winding b and the winding p is connected to the output circuit so that the directions of magnetic fluxes formed by the currents flowing through them are the same. Note that the self-inductance value of the reactor B is Lb, and the self-inductance value of the reactor P is Lp. Reference numeral 100 denotes a voltage detection device.
[0010]
The operation will be described below. In the arc period Ta, that is, when the input to the voltage detection device 100 is 0 V or a predetermined voltage (for example, 5 V) or more, the contacts m and n are closed. Then, the switching element 7 is chopper-controlled, and the arc current Ia is supplied to the external load via the reactor B (hereinafter, a circuit formed when the contacts m and n are closed is referred to as an arc current circuit). Further, in the short-circuit period Ts, that is, when the input to the voltage detection device 100 becomes 0 V or a predetermined voltage (for example, 5 V) or less, the contacts r and s are closed. Then, the switching element 8 is chopper-controlled, and the short-circuit current Is is supplied to the external load via the reactor P (hereinafter, a circuit formed when the contacts r and s are closed is referred to as a short-circuit current circuit).
[0011]
Next, the operation at the time of transition will be described with reference to FIG. 2 showing current waveforms in the present invention. The energy Es stored in the reactor P when the short-circuit current Is flows is 1/2 × Lp × Is ² , and the energy Ea stored in the reactor B when the arc current Ia flows is 1/2 × Lb × Ia ² . is there.
[0012]
When the short-circuit period Ts shifts to the arc period Ta, the short-circuit current circuit is cut off on the reactor P side with respect to the diode 10, so that no reflux circuit is formed, and all the energy Es stored in the reactor P shifts to the reactor B. To do. Similarly, when shifting from the arc period Ta to the short-circuit period Ts, all the energy Ea stored in the reactor B is transferred to the reactor P. Therefore, if the coupling coefficient between the reactor B and the reactor P is α (where α ≦ 1), the following formulas 1 and 2 are established. Equation 1 is a case where the short-circuit period Ts shifts to the arc period Ta, and Equation 2 is a case where the arc period Ta shifts to the short-circuit period Ts. Further, since the self-inductance is approximately proportional to the square of the number of turns, the following Expression 3 is established. Then, the following formula 4 is obtained from the formulas 1 and 3, and the following formula 5 is obtained from the formulas 2 and 3.
[0013]
α × 1/2 × Lp × (Is) ² = 1/2 × Lb × (Ia) ² ...... Formula 1
α × 1/2 × Lb × (Ia) ² = 1/2 × Lp × (Is) ² ...... Formula 2
Lp = Lb × (Np / Nb) ² ...... Equation 3
Ia = Np / Nb × Is × √α Equation 4
Is = Nb / Np × Ia × √α Equation 5
As apparent from Equation 5 above,
If the final current in the arc period Ta is Ia ₀ when the arc period Ta shifts to the short-circuit period Ts, the short-circuit current in the short-circuit period Ts immediately becomes Is ₀ (= Nb / Np × Ia ₀ × √α). To rise. Further, from the above formula 4, when the current in the short-circuit period Ts is Is ₁ when shifting from the short-circuit period Ts to the arc period Ta, the arc current is immediately equal to the current Ia ₁ substantially equal to the current Ia ₀ before the short-circuit. Go down.
[0014]
FIG. 3 is a diagram showing a second embodiment of the present invention. Components having the same or the same functions as those in FIG. 1 are denoted by the same reference numerals. 32 is a diode. In this example, the switching elements 7 and 8 and the diodes 9, 10 and 32 are combined to replace the switch 30 in the first embodiment. That is, during the arc period Ta, the chopper control of the switching element 7 is performed with the switching element 8 open. Further, during the short circuit period Ts, the switching element 7 is chopper-controlled while the switching element 8 is closed. During the short-circuit period Ts, the reverse bias is applied to the winding b due to the current flowing through the winding p. As a result, the voltage on the cathode side of the diode 32 becomes higher than the voltage on the anode side. That is, it becomes the same as the short-circuit current circuit in the first embodiment.
[0015]
It should be noted that the current fall at the time of transition from the short-circuit period Ts to the arc period Ta and the current rise at the time of transition from the arc period Ta to the short-circuit period Ts are exactly the same as in the first embodiment. Is omitted.
[0016]
FIG. 4 is a view showing a modification of the second embodiment of the present invention, and the same or the same functions as those in FIGS. 1 and 3 are given the same reference numerals. In the figure, 51 is an inverter, 52 is a transformer, and 53 is a diode. Here, the operation of the portion surrounded by the dotted line in FIG. 2 will be described. The DC voltage input by the inverter 51 is converted into an AC voltage, and the AC voltage is converted into a voltage suitable for welding by the transformer 52 to obtain a diode. Rectification is performed by a rectifier circuit including 9, 10, 31, and 53. As a result, the output output to the output terminals J and B is substantially the same as the switching element 7 in the second embodiment. Since the falling of the current when shifting from the short-circuit period Ts to the arc period Ta and the rising of the current when shifting from the base period Tb to the pulse period Tp are exactly the same as those in the first embodiment, description thereof is omitted. To do.
[0017]
In the case of this modification, the number of turns of the transformer 52 in the short circuit period Ts and the arc period Ta is changed, so that the current waveforms of the short circuit current Is and the arc current Ia are both flat waveforms with small ripples. can do. Further, the terminals a and e may not be provided among the terminals of the transformer 52, and only the terminals b, B, and d may be provided, and the connection point J in the figure may be connected to the connection point K. Then, it becomes almost the same as the second embodiment.
[0018]
【The invention's effect】
As described above, according to the present invention, in the DC arc welding power source having a constant voltage characteristic in the external output characteristic, the first wire constituting the reactor P and the second wire constituting the reactor B are connected to the same iron core. In the arc current period, the reactor P is connected to the output circuit and the reactor B is disconnected from the output circuit. In the short circuit period, the reactor B is connected to the output circuit and the reactor P is output. Since it is configured to be disconnected from the circuit and connected to the output circuit so that the directions of magnetic fluxes formed in the reactor P and the reactor B are the same, when the transition is made from the short-circuit period Ts to the arc period Ta, the arc When shifting from the period Ta to the short-circuit period Ts, the welding current can be immediately set to the arc current Ia or the short-circuit current Is. Therefore, heat input control can be performed reliably and welding quality can be improved by proper droplet transfer.
[Brief description of the drawings]
FIG. 1 is a connection diagram of a consumable electrode type DC arc welding power source according to the present invention.
FIG. 2 is a diagram showing an output current waveform in the present invention.
FIG. 3 is a diagram showing a second embodiment of the present invention.
FIG. 4 is a diagram showing a modification of the second embodiment of the present invention.
FIG. 5 is a connection diagram of a conventional consumable electrode type DC arc welding power source.
FIG. 6 is a diagram showing a conventional output current waveform.
[Explanation of symbols]
31 Reactor B Reactor P Reactor b Second line p First line f Iron core

Claims (2)

In a direct current arc welding power source having an external output characteristic of a constant voltage characteristic, the first wire constituting the reactor P and the second wire constituting the reactor B are wound around the same iron core, and the reactor P is wound during the arc current period. The reactor B is connected to the output circuit and disconnected from the output circuit, and during the short circuit period, the reactor B is connected to the output circuit and the reactor P is disconnected from the output circuit. And a DC arc welding power source connected to the output circuit so that the directions of magnetic fluxes formed in the reactor B are the same. A plurality of sets of reactors P and reactors B formed of the first wire and the second wire wound around the same iron core are provided by changing the winding number ratio of the first wire and the second wire, and welding conditions The direct current arc welding power supply according to claim 1, wherein one of the plurality of sets of reactors P and reactors B is connected in accordance with the above.

Images