JPS59137177A - Power source for welding - Google Patents

Abstract

PURPOSE:To increase the max. rated output value in the stage of CO2 and MAG welding by increasing the one period time which is increased in the period of a reference period signal and is constituted of the on-off time of a power transistor for controlling welding output. CONSTITUTION:This power source for welding transforms the input with a voltage transformer 1 and conducts welding current between output terminals 6 and 6 via a rectifier 2, a smoothing capacitor 3, a transistor (TR) 4 for controlling welding output and a reactor 5. The TR4 is turned on and off at a prescribed period by the signal from a driving circuit 8. An instruction digital signal (n) is outputted from an arithmetic/storage circuit 11 by the set value of an output setter 12 and an output characteristic selector 13 to a frequency dividing counter circuit 9. The circuit 9 is inputted simultaneously with the reference clock signal from a reference frequency signal generating circuit 10, divides down the reference clock signal of frequency N by n and outputs the same to the circuit 8. As a result, the TR4 makes switching operation at the frequency N/n so that the increase in the one period time constituted by the on-off time is made possible together with an increase in the output set value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a transistor chopper type welding power source that performs welding while automatically feeding a welding wire, which is a consumable electrode.

Conventional configuration and its problems One cycle time, which consists of the transistor on time and off time of a transistor chopper type welding power source, traditionally decreases as the wire feed rate increases in pulsed MAG welding of spray transfer arc welding. In short-circuit transfer, R-drop transfer arc MAG, and CO2 welding, it was usual to keep the value constant regardless of the wire feed rate. This cycle time is set to 3 to achieve a smooth spray transition arc in pulsed MAG welding.
In mag and C02 welding, it was set to a constant value of around 0.5 m5ec to reduce the output ripple and realize a stable short-circuit transfer two-ball drop transfer arc. FIG. 1 shows an example of the characteristic of one cycle time, which is made up of transistor on/off, with respect to the wire feed amount of a conventional transistor chopper type welding electric current i.

In the same figure, a is the characteristic during pulsed mag welding, b
is the characteristic during C02, MAG welding.

The problem with the conventional example shown in FIG. 1 is the maximum rating of one device due to transistor loss. Transistor im loss p
is the sum of the losses when the transistors are turned on.Pt is the sum of the losses when the transistors are turned on. PtoFF1 is the sum of the losses when the transistors are turned on.

If the sum of losses due to the base current of the N1 transistor is Pb, then the sum of these losses becomes Pb. That is, P=Ptol■+PtoFF+PoN+Pb11 (
1). The value of Pb is small compared to the others, and the value of PoN is a substantially constant value regardless of the synchronization time if the average output value is the same. However, PtoN and PtoFF become larger as one cycle time becomes smaller. Moreover, especially P
The value of toFF has a fairly large ratio to the total loss P. Therefore, the characteristics during CO2 and MAG welding shown in FIG. 1 can be said to be disadvantageous in terms of heat loss of the transistor. Therefore, the conventional welding power source having both characteristics is C0
2. A workaround was achieved by specifying the maximum rated output value for MAG welding to a value smaller than the maximum rated output value for pulsed MAG welding.

OBJECTS OF THE INVENTION An object of the present invention is to provide a welding power source that can increase the maximum rated output value of equipment during CO2 and MAG welding without increasing the capacity of the transistor.

Composition of the Invention This invention increases the above-mentioned period time and uses low-frequency transistor switching in a high output range (a range where the wire feed rate is large) where CO2 and welding output ripple of MAG welding do not significantly affect welding performance, P in the above formula (1)
It is characterized by reducing loss P by reducing toH and PtoFF.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows a circuit diagram of a transistor chopper type welding power source according to an embodiment of the present invention. In Figure 2, 1
is a welding transformer, 2 is a rectifier, 3 is a smoothing capacitor,
4 is a welding output control transistor, 5 is a reactor, 6 is a welding machine output terminal, 7 is a welding machine input terminal, 8 is a transistor drive circuit, 9 is a frequency division circuit, 10 is a reference frequency signal generation circuit, and 11 is a micro Computing and
12 is a welding output setting device; 13 is an output characteristic switcher for switching output characteristics between pulsed MAG welding, CO2, and MAG welding; and 14 is a resistor 1. ．． 15 is a thyristor.

This transistor chopper type welding power supply has a welding machine input terminal 7 to is connected to the welding machine output terminal 6 through the welding output control transistor 4 and the reactor 5.
Welding current is applied between 6 and 6. Welding output control transistor 4
is turned on and off at a predetermined period by a drive signal from the transistor drive circuit 8.

Further, by using the set value I of the output setter 12 and the output characteristic switch 13, the arithmetic/storage circuit 11 outputs the command digital signal n to the frequency divider circuit 9. In this case, the command digital signal Jijn increases as the set value l of the output projector 12 increases by the arithmetic/memory circuit 11.

The branch divider circuit simultaneously inputs the reference clock signal of the reference frequency signal generation circuit 10, divides the reference tally signal of frequency N by n, and outputs the divided signal to the transistor drive circuit 8. As a result, the welding output control transistor 4 performs a switching operation with a circuit of -N-. In the embodiment shown in FIG. 2, the explanation regarding the control of the on-time and off-time of the transistor within the - period time is omitted.

With the above configuration, one cycle time made up of the on time and off time of the transistor can be increased as the output setting value increases (wire feeding amount increases). Incidentally, as described in the conventional example section, when the -synchronization time is increased in CO2 and MAG welding, the ripple in the welding output increases. However, over a large range of welding power this ripple has little effect on welding performance.

Specifically, 8192 Hz was used as the reference tarok signal. Also, for the welding output setting value 1 (A), calculation and
Data n to be output from the storage circuit 11 to the frequency divider circuit 9 was calculated using the following equation.

n=4 (1<256A)
”(2) n=2Ll−3(1≧256
A)---(3)2 The calculations of equations (2) and (3) are performed using the calculations and calculations in Figure 2.
Memory episode W! It is executed by the program stored in the Y microcomputer of r11 and the storage element. Of course, the characteristics of equations (2) and (3) can be easily changed by a program.

C02 according to formula (2) and formula (3). Figure 3 shows the characteristics during MAG welding. In Fig. 3, a' shows the characteristics during pulsed MAG welding similar to the conventional example, and b' shows the C02
, shows the characteristics during MAG welding. In addition, referring to FIG. 3, in order to calculate the execution of equation (3) by integer, -T-T-
The number after the decimal point in the calculation result of 1 is programmed to be rounded down.

As a result of this configuration, it is possible to reduce the loss of the welding output control transistor 4 without impairing the welding performance at the same output for CO2 and MAG welding. Therefore, without increasing the capacity of the welding output control transistor 4, 002. It is possible to provide a transistor Chiro 72 type welding power source with a large maximum rated output value during MAG welding, and the contribution to the industry is significant.

In addition, the output characteristics during pulsed mag welding are calculated and
This can be realized by gradually decreasing the command digital signal n from the memory circuit 11 to the set value I of the output setter 12 according to a program. Further, in the embodiment, a case has been described in which the welding output control transistor 4 is provided on the secondary side of the welding transformer, but it can be similarly applied even if it is provided on the negative side.

Effects of the Invention According to the welding power source of the present invention, the maximum rated output value of the equipment during CO2 and MAG welding can be increased without increasing the capacity of the transistor.

[Brief explanation of drawings]

Figure 1 shows the conventional example of pulsed mag welding and CO2
, Wire feed M in one cycle time during MAG welding! FIG. 2 is a circuit diagram of an embodiment of the present invention, and FIG. 3 is a characteristic diagram of welding output at one synchronous time during pulsed mag welding and CO2, MAG welding in the embodiment. 1... Welding transformer, 2... Rectifier, 3... Smoothing capacitor, 4... Welding output control transistor,
5...Reactor, 6...Welding machine output terminal, 7...
Welding machine input terminal, 8...transistor drive circuit, 9.
...Frequency division kakunta circuit, 10 units...$1! ￥+i number signal generation circuit, et... calculation/memory circuit, 12... welding output setting device, 13... output characteristic switcher Fig. 1 Fig. 2

Claims (4)

[Claims] (1) Automatically feeds the welding wire, which is a consumable electrode,
A welding power source comprising a welding output control power transistor for controlling welding output on the primary side or secondary side of a welding transformer, the welding output setting device for setting the welding output;
A reference period generation circuit that calculates a setting value of the welding output setting device to generate a reference period signal, and a reference period signal outputted from the reference period generation circuit on the primary or secondary side of the welding transformer. and a drive circuit that controls on/off of the power transistor for controlling the welding output provided in the welding output setting device, and increases the period of the reference period signal as the set value of the welding output setting device increases. A welding power source, characterized in that one cycle time consisting of an on time and an off time of the power transistor for controlling welding output is increased. (2) The reference period generating circuit is a logical operation element. The welding power source according to claim 1, further comprising a storage element, a tarlock signal generator, and a division element that divides and outputs the frequency of the clock signal based on the digital output of the logic operation element. (3) Automatically feeds the welding wire, which is a consumable electrode,
A welding power source comprising a welding output control power transistor for controlling welding output on the primary side or secondary side of a welding transformer, the welding output setting device for setting the welding output;
a reference period generation circuit that generates a reference period signal by calculating the set value of the welding output setting device and the output of a switching device that switches the welding output characteristics; Or the said melt provided on the secondary side! and a drive circuit that controls on/off of a power transistor for output control, and the power for controlling welding output is increased by increasing the period of the reference period signal as the set value of the output setting device increases. (by decreasing the period of the basic IP period signal as the setting value of the welding output setting device increases) A welding power source characterized in that a characteristic that reduces the time can be selected using the switch. (4) The reference period generating circuit is a logic operation element. This feature includes a dividing element that divides and outputs the frequency of the clock signal based on the digital output of the storage element, the tarlock signal generator, and the logic operation element! F @ desired range (3)
) Welding power source listed in item 2.