JPH0331501Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field This invention relates to an AC arc welding power supply device that includes a start switch that turns on and off the operation of a control section such as a high frequency conversion circuit control section.

(b) Summary of the invention The AC arc welding power supply device according to this invention is
This is a device that converts power to a high frequency and then transforms it to a low frequency.It is a device that converts power to a high frequency, transforms it, and converts it to a low frequency. Prevent damage to electrical elements connected to the reactor.

(c) Prior art and its drawbacks Figure 2 shows a circuit diagram of a general AC arc welding power supply device.

A rectifier circuit 2 that full-wave rectifies the three-phase AC power supply 1, a smoothing capacitor 3 that smoothes the rectified output, a high frequency conversion circuit 4 that converts the smoothed DC to high frequency, and a transformer 5 that transforms the high frequency output of the high frequency conversion circuit 4. The primary winding 5a constitutes a primary side circuit. Secondary windings 5b and 5c are wound around the transformer 5, and each of the secondary windings is provided with an intermediate tap. The output of the secondary winding 5b is rectified by the rectifier 6,
The positive electrode (output terminal of the rectifier 6) is connected to the base material 12 via the switching transistor 8, and the negative electrode (intermediate tap) is connected to the electrode 11 via the current detector 13 and reactor 10. The output of the secondary winding 5c is rectified by a rectifier 7, the positive electrode (output terminal of the rectifier 7) is connected to an electrode 11 via a current detector 13 and a reactor 10, and the negative electrode (intermediate tap) is connected to a switching transistor 9. It is connected to the base material 12 via. With the above configuration, voltage is applied with positive polarity when switching transistor 8 is on, and with reverse polarity when switching transistor 9 is on. The switching transistors 8 and 9 are turned on and off by a switching transistor control section 14. The on/off frequency is several tens of Hz. This switching transistor control section 14 corresponds to the switching circuit of the present invention.
The high frequency conversion circuit 4 is controlled by a high frequency conversion circuit control section 15. In this control, the conversion frequency is increased or decreased so that a welding current corresponding to the setting value of the output setting device 16 connected to the high frequency conversion circuit control section 15 flows. The detected value of the welding current is input from the current detector 13. Power for the switching transistor control section 14 and the high frequency conversion circuit control section 15 is supplied from a DC power supply 18;
is turned on and off by the start switch 17.
That is, when the start switch 17 is closed, power is supplied to the switching transistor control section 14 and the high frequency conversion circuit control section 15, and the circuits operate, and when the start switch 17 is opened, the switching transistor control section 14 and the high frequency conversion circuit control section 15 are operated. The section 14 and the high frequency conversion circuit control section 15 are not supplied with power and do not operate.

In the AC arc welding power supply device configured as described above, when the welding work is completed and the start switch 17 is turned off, the switching transistor control section 14 and the high frequency conversion circuit control section 15 simultaneously stop operating. When the high frequency conversion circuit control section 15 stops operating, the high frequency is no longer input to the transformer 5, so power is no longer supplied to the secondary side. Therefore, the welding current also stops, but a polar spike-like induced voltage is generated in the reactor 10 that prevents the current from stopping. At this time, since the arc between the electrode 11 and the base material 12 has not yet been completely extinguished, this voltage attempts to cause current to flow through the switching transistors 8 and 9; is off, so switching transistors 8 and 9 are both off. Therefore,
The spike-like induced voltage is applied between the collectors and emitters of the switching transistors 8 and 9,
If the induced voltage is higher than the withstand voltage of the switching transistors 8 and 9 when they are off, there is a risk that the switching transistors will be destroyed.

(d) Purpose of the invention In view of the above drawbacks, the object of this invention is to provide a power supply device for AC arc welding that does not destroy other elements due to spike-like induced voltage when the circuit stops operating.

(e) Structure and Effects of the Invention This invention is characterized in that it includes a timer that maintains the on-state of the switching circuit control section for a certain period of time after the starting switch is turned off.

With the above configuration, according to this invention, even after the high frequency conversion circuit control section stops operating and power is no longer supplied to the secondary side, the switching transistor remains conductive for a certain period of time, so the reactor The induced voltage generated in this case is quickly short-circuited and discharged. This has the advantage that switching transistors and the like are not destroyed by the application of this voltage, and the welding operation can be turned on and off with peace of mind.

(f) Embodiment FIG. 1 shows a circuit diagram of an AC arc welding power supply device which is an embodiment of this invention.

The configuration of this embodiment differs from the configuration of the AC arc welding power supply device shown in FIG. This point is that the DC power supply 18 and the switching transistor control section 14 are directly connected via 19a. The timer 19 is a relay with a delay device, and the contact 19a is a normally open contact that is closed when the relay is on. Therefore, the contact 19a is closed when current is flowing through the timer 19, and the contact 19a is opened after a certain period of time has passed after the current no longer flows through the timer 19.

With the above configuration, when the start switch 17 is closed to start welding work, power is supplied to both the high frequency conversion circuit control section 15 and the switching transistor control section 14, and this AC arc welding power supply device starts working. When the welding work is completed and the start switch 17 is turned off, the high frequency conversion circuit control section 15 immediately stops, and high frequency output is no longer supplied to the transformer 5. Therefore, power is no longer supplied to the secondary side, and an induced voltage is generated in the reactor 10. However, the contact 19a continues to be closed for a certain period of time due to the operation of the timer 19, and since power is supplied to the switching transistor control unit 14, the switching transistors 8 and 9 are turned on. The current due to the induced voltage generated in the reactor 10 through the switching transistors 8 and 9 is quickly short-circuited and discharged, and the welding current can be stopped without damaging the switching transistors 8 and 9 and other elements. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a power supply device for AC arc welding which is an embodiment of this invention, and FIG. 2 is a circuit diagram of a conventional power supply device for AC arc welding. 19...Timer, 19a...Contact.

Claims (1)

[Claims for Utility Model Registration] A rectifier circuit that converts an alternating current power source into direct current, a high frequency conversion circuit that converts the DC voltage to high frequency, and two secondary windings each having an intermediate tap on both sides. a transformer for transforming the high-frequency voltage; a fully parallel rectifier circuit including diodes connected to terminals at both ends of the two secondary windings, and these two;
It consists of an open/close circuit that applies the rectified outputs of the two rectifier circuits to the base metal and the welding electrode alternately with positive polarity and reverse polarity, respectively, and converts the transformed high frequency into a low frequency and applies it to the base metal and the welding electrode. A low frequency conversion circuit, a high frequency conversion circuit control section that controls the high frequency conversion circuit, a switching circuit control section that controls the switching circuit, and turning on/off the operation of the high frequency conversion circuit control section and the switching circuit control section. What is claimed is: 1. A power supply device for AC arc welding comprising a starting switch, comprising: a timer that maintains the on-state of the switching circuit control section for a certain period of time after the starting switch is turned off.