JPS61135480A - DC arc welding machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an inverter type and series chopper type DC arc welding machine using a switching element having a predetermined constant voltage characteristic for welding by feeding a consumable electrode at a constant rate. It is related to.

Conventional configuration and its problems This type of DC arc welding machine has constant voltage characteristics as shown in Figure 2, so if there is a short circuit between the power supply tip 5 and the base material 8 shown in Figure 1, the A large current exceeding that of the human body flows through the output circuit, causing the welding transformer 2 and output rectifier diode 3 to
, the switching elements inside the DC reactor 4 switching unit 1 may be completely deteriorated or destroyed. Therefore, in an inverter-type DC arc welding machine using a conventional switching element, a shunt 9 is provided to detect the output current It as shown in FIG. Output current limit value I
The drive circuit 1 of the switching element is transmitted via the control signal R8f output control circuit 11 so that Iw does not exceed MAX.
2. Then, the output current is limited as shown by the broken line in FIG. 2, and control is performed so that the output current does not exceed IM xf under any output short-circuit condition. 6 is a wire, and 7 is a torch nozzle.

However, if you compare the magnitude of the load at the rated load point of the DC arc welding machine on the rated load line in Figure 2 and the output current limit point)B, the output current limit point)B is much larger.
Since the load of 0 is larger, the switching element needs to fully satisfy the electrical rating at the output current limit point ()H. However, at the output current limit point ()B, the switching loss of the switching element becomes very large. 1.5 compared to a switching element that satisfies the rated load
It was necessary to use switching elements with ~2 times the electrical rating. As described above, the conventional DC arc welding machine using a switching element has the disadvantage that an unnecessarily large switching element must be used to provide output short-circuit protection.

Purpose of the Invention The present invention was made for the purpose of eliminating the drawbacks of the conventional DC arc welding machine that uses a switching element equipped with an output short-circuit protection circuit of an output current limiting type, and uses a switching element that is larger than necessary. It is an object of the present invention to provide a DC arc welding machine that can reliably protect a switching element in the event of an output short circuit without causing any damage.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides a frequency switching circuit that reduces the switching frequency or chopper frequency of the switching element to the lowest level during normal operation to reduce the switching loss of the switching element. This is one way to suppress the heat generation of the switching element as much as possible. That is, by reducing the switching loss of the switching element, it is possible to obtain a DC arc welding machine that can ensure reliability in the event of an output short circuit even with a small-capacity switching element.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the invention will now be described in detail with reference to FIG. Third
As shown in the figure, the device of the present invention includes a switching unit 1
, welding transformer 2, output rectifier diode 3, DC reactor 4, power supply chip 5, wire 6, torch nozzle 7, base material 8, shunt 9, output current limiting circuit 10, output control circuit 11. The drive circuit 12 is connected in substantially the same arrangement as in the conventional example shown in FIG. A frequency switching circuit 13 receives a signal from the output current limiting circuit and outputs a switching signal for switching frequency of the switching element to the output control circuit 11.

The operation of the DC arc welding machine of the present invention will be explained with reference to FIG. 4 as follows. Figure 4 (IL) shows the output current It and the output current limit value IMAI over time of the DC arc welding machine, and Figure 4 (b) shows the output current limit signals R, S,
FIG. 2C shows frequency switching signals F and Si for switching the switching frequency of the switching element. The output current limit signals R and S are output when the welding current 1w reaches the IM value X due to the output short circuit at time t1, and the output control circuit 11
The output current is lm1x through the drive circuit 12.
The output of the switching unit 1 is controlled so as not to exceed . At the same time, the output current limit signal R-8 is transmitted to the frequency switching circuit 13, and a frequency switching signal y-st- is outputted to the output control circuit 11 so that the switching frequency of the switching unit 1 becomes the low frequency of μ in steady state. . In other words, when the output is short-circuited, the output current is limited and the switching loss of the switching element is greatly reduced.

Here, in order to further reduce the watt loss (steady state loss + switching loss) of the switching element in the event of an output short circuit and to provide sufficient margin for the rating of the switching element, a start/stop switch 16 and its start/stop switch are installed as shown in FIG. Output start/stop circuit 14t-provides 0 to switch 16
When an output short-circuit occurs, if the power continues in the output short-circuit state for 0.1 seconds to 0.2 seconds, the output will be reduced to 0. It is stopped for 6 seconds to 1 second, and then the above operation is continued until the output short-circuit condition is canceled, and when the short-circuit condition is canceled, the original output condition is restored.Then, the duty of energization of the switching element is low. Therefore, even if the electrical rating of the switching element is even lower, reliability can be ensured sufficiently.

Effects of the Invention As mentioned above, the present invention reduces switching loss during output short circuit. Since it can be greatly reduced compared to the conventional one, the switching element used can be reduced to ~μ compared to the conventional one. In addition, by reducing the capacity of the switching element, the capacity of the drive circuit of the surrounding switching elements is reduced, making it possible to make the drive circuit smaller and the switching element cooling fin smaller, as well as saving materials and making the welding power source smaller. I can measure it.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of an inverter-type DC arc welding machine using conventional switching elements, Fig. 2 is an output static characteristic diagram of a DC arc welding machine with constant voltage characteristics, and Fig. 3 is an embodiment of the present invention. Electrical circuit diagram of an inverter-type DC arc welding machine according to Figure 4 shows the characteristics of the Iw, R, S, F, and S signals in Figure 3 and the operation status of the start/stop switch in No. 6 (2) over time. 6 are electrical circuit diagrams of an inverter type DC arc welding machine according to another embodiment of the present invention. 1...Switching unit, 2...
Welding transformer, 6... Power supply tip, 6...
... Wire, 8 ... Base material, 9 ... Shunt, 10 ... Output current limiting circuit, 11 ...
...Output control circuit, 12...Drive circuit,
13... Frequency switching circuit, 14... Output start/stop circuit, 16... Start/stop switch. Name of agent: Patent attorney Toshio Nakao and 1 other person/2
tt t. Figure 2

Claims (2)

[Claims] (1) Has constant voltage characteristics of an inverter type or series chopper type using a switching element, and when an output short circuit other than normal welding occurs, the switching frequency or chopper frequency of the switching element is changed to that of normal welding. A DC arc welding machine equipped with a frequency switching circuit that lowers the frequency. (2) If an inverter type or series chopper type constant voltage characteristic using a switching element occurs, and an output short circuit other than normal welding occurs, the switching frequency or chopper frequency of the switching element is changed to the normal welding time. and an output start/stop circuit that alternately starts and stops the output at a set cycle when an output short circuit occurs, and turns the output into a start state when the output short circuit is released. A DC arc welding machine characterized by: