JPH0341892Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a power supply device for an arc welding machine that uses an inverter to adjust the output. related to things.

[Conventional technology]

Conventionally, a power supply device for an arc welding machine whose output is adjusted using an inverter has a configuration as shown in FIG.

That is, in the same figure, 1 is a switch that inputs a three-phase AC power supply, 2 is an input side rectifier that performs full-wave rectification of the three-phase AC from the switch 1, and six diodes 2a, 2b, 2c. , 2d, 2e, and 2f. 3 is a capacitor that smoothes the rectified output of the rectifier 2; 4 is a capacitor that suppresses the rush current that flows into the capacitor 3 when the power is turned on;
This resistor is inserted between the positive output terminal of the rectifier 2 and the positive terminal of the capacitor 3.

5 is an inverter that converts the DC rectified and smoothed by the rectifier 2 and the capacitor 3 into AC, and is composed of four NPN type switching transistors 5a, 5b, 5c, and 5d. , 5d and 5~
AC output can be obtained by alternately turning on and off at 30KHz.

6 is an output transformer into which the AC output of the inverter 6 is input to the primary winding 6a; 7 is an output side rectifier that rectifies the output of the transformer 6; 2 with anode connected to each
It consists of diodes 7a and 7b. A DC reactor 8 has one end connected to the cathodes of both diodes 7a and 7b, and smoothes the rectified output of the rectifier 7.

9 is a welding electrode of a DC arc welding machine connected to the other end of the DC reactor 8; 10 is a base material that constitutes a welding load together with the electrode 9;
is connected to the tap terminal ta of the secondary winding 6b.

When the three-phase AC power is input by the closing operation of the switch 1, this is full-wave rectified by the input rectifier 2 and smoothed by the capacitor 3. The output is converted to alternating current by an inverter 5, and is input to an output rectifier 7 via a transformer 6, where it is rectified, and then smoothed by a direct current reactor 8.
DC power is supplied to the welding load of the electrode 9 and the base metal 10 to promote the generation of an arc between them.

Here, by varying the on/off switching frequency of the transistors 5a to 5d constituting the inverter 5, the DC output to the electrode 9 and the base material 10 can be adjusted.

[Problem that the invention attempts to solve]

However, in the conventional device, current flows through the resistor 4 provided to suppress the inrush current when the power is turned on, even during arc welding when power is supplied to the welding load. It is necessary to use a resistor with a large capacity, and the power loss caused by the resistor 4 has the disadvantage of lowering efficiency.

[Means for solving problems]

This invention was made in order to eliminate the conventional drawbacks, and includes an input rectifier that rectifies the AC power input through the switch, a capacitor that smoothes the rectified output of the rectifier, and the switch. an inverter that converts the DC rectified and smoothed by the rectifier and the capacitor into AC, and an inverter that rectifies the output of the inverter and arcs the rectified output. In a power supply device for an arc welding machine, which is equipped with an output side rectifier that supplies a welding load consisting of an electrode of a welding machine and a base metal, a thyristor is provided in parallel with the resistor, and a gate circuit of the thyristor is connected to a gate circuit of the thyristor after the power is turned on. The device is provided with an opening/closing element that closes after a delay time of , outputs a gate signal, and opens when the power is cut off to prohibit output of the gate signal.

[Effect]

Therefore, according to this invention having the above-mentioned configuration, when the power is turned on by the switch, the switching element opens and the thyristor is turned off, that is, into a non-conducting state, so that the inrush current generated at this time flows through the resistor. When the delay time elapses, the switching element closes and a gate signal is output to the thyristor, so the thyristor becomes conductive and the current from the input rectifier during arc welding flows through the resistor. The current flows through the thyristor.

Then, when the arc welding is finished by shutting off the power by the switch, the switching element opens and prohibits the output of the gate signal to the thyristor when the power is cut off, so the thyristor becomes non-conductive and returns to its initial state.

〔Example〕

Next, this invention will be explained in detail with reference to FIGS. 1 to 3 showing one embodiment thereof.

In FIG. 1, the same symbols as those in FIG. 4 indicate the same things. A gate circuit is constructed by connecting a series circuit of a resistor 12, a relay contact (a contact) 13 serving as a switching element, and a diode 14 between the gate and the gate.

FIG. 2 shows a control circuit for the relay contact 13, in which 15 is an auxiliary transformer in which both ends of the primary winding 15a are connected between, for example, two arbitrary phases on the output side of the switch 1; The first relay 17 connected between both ends of the secondary winding 15b of the transformer 15 is a rectifier that rectifies the output of the auxiliary transformer 15 whose input side is connected between both ends of the secondary winding 15b.

18 is a resistor whose one end is connected to the positive output terminal of the rectifier 17, and 19 is the a contact 16a of the first relay 16.
This is a capacitor connected between the other end of the resistor 18 and the negative output terminal of the rectifier 17 via the resistor 1.
Together with 8, it constitutes an integrating circuit.

A second relay 20 is connected in parallel to the capacitor 19, and its a contact is the relay contact 13. 21 is a discharge resistor, and the first relay 16
A series circuit of the b contact 16b and the resistor 21 is connected in parallel to the capacitor 19.

Next, the operation of the embodiment will be explained.

When the switch 1 is turned on, three-phase alternating current is input to the input rectifier 2, and at the same time, single-phase alternating current is input to the auxiliary transformer 15.

Then, the first relay 16 is excited by the output from the transformer 15, and the a contact 16a and the b contact 1
6b turns on and off, respectively, and
After the output from the transformer 15 is rectified by a rectifier 17, it is supplied to a capacitor 19 via a resistor 18 and an a contact 16a to charge the capacitor 19.

Here, until the charging voltage of the capacitor 19 reaches the excitation voltage of the second relay 20, the second relay 20
does not operate, and the relay contact 13, which is its a contact, remains off, the output of the gate signal is prohibited, and the thyristor 11 is in a non-conducting state.

After that, when the charging voltage of the capacitor 19 becomes equal to the excitation voltage of the second relay 20, the second relay 20 operates and the relay contact 13 is turned on, and the rectified output from the input rectifier 2 is transferred to the resistor 12, the contact 13, and the diode 14. Thyristor 1 as gate signal through
1, and the thyristor 11 becomes conductive.

Therefore, as shown in FIG.
After the closing operation at t, relay contact 1 at t ₁ after a delay time T determined by resistor 18 and capacitor 19.
3 turns on and the thyristor 11 becomes conductive, so the inrush current flowing into the capacitor 3 when the power is turned on is suppressed by the resistor 4, and after that, the thyristor 11 becomes conductive and the rectified output from the rectifier 2 flows through the resistor. It flows to the thyristor 11 without passing through 4.

Note that the DC output smoothed by the capacitor 3 is converted into AC by the inverter 5, then passed through the output transformer 6, rectified by the output rectifier 7, and converted to DC, as described in the conventional example. The DC output thus obtained is smoothed by the reactor 8 and is supplied to the welding load between the electrode 9 and the base material 10.

Next, as shown in Figure 3, at t ₂ , switch 1
When the power is cut off, the input to the auxiliary transformer 15 is also cut off, so the first relay 16 becomes de-energized, the A contact 16a turns off, the B contact 16b turns on, and the capacitor 19 is charged. The charge is discharged through the b contact 16b and the resistor 21, and the second relay 20 is also de-energized and the relay contact 13 is turned off.

Therefore, the gate signal of the thyristor 11 does not flow, and the thyristor 11 becomes non-conductive and returns to its initial state.

Note that the switching element provided in the gate circuit of the thyristor 11 is not limited to the relay contact 13 of the above embodiment, but it closes after a delay time after the power is turned on to output a gate signal, and opens when the power is cut off to output the gate signal. Any device that prohibits signal output may be used.

[Effect of idea]

As described above, according to the power supply device for an arc welding machine of this invention, the inrush current flowing into the capacitor when the power is turned on can be reliably suppressed by the resistor, and after the delay time, the thyristor in parallel with the resistor is brought into conduction to perform arc welding. In some cases, it is possible to prevent current from flowing through the resistor, allowing the use of a small-capacity resistor, and greatly reducing power loss through the resistor, allowing for efficient power supply to the welding load, especially when input voltage is effective for high input circuits such as 400V systems.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the power supply device for an arc welding machine of this invention, and Figure 1 is a wiring diagram;
FIG. 2 is a wiring diagram of a control circuit for a relay contact, FIG. 3 is a time chart for explaining the operation of a switch and a relay contact, and FIG. 4 is a wiring diagram of a conventional power supply device for an arc welding machine. 1... Switch, 2... Input side rectifier, 3... Capacitor, 4... Resistor, 5... Inverter, 7...
... Output side rectifier, 9 ... Electrode, 10 ... Base material, 1
1...Thyristor, 13...Relay contact.

Claims (1)

[Claims for Utility Model Registration] An input rectifier that rectifies AC power input through a switch, a capacitor that smoothes the rectified output of the rectifier, and an inrush that flows into the capacitor when power is turned on by the switch. It consists of a resistor that suppresses the current, an inverter that converts the DC rectified and smoothed by the rectifier and the capacitor into AC, and an electrode of an arc welding machine and a base material that rectifies the output of the inverter and converts the rectified output into AC. In a power supply device for an arc welding machine equipped with an output side rectifier that supplies a welding load, a thyristor is provided in parallel with the resistor, and a gate circuit of the thyristor is closed after a delay time after the power is turned on to output a gate signal. A power supply device for an arc welding machine equipped with an opening/closing element that outputs a gate signal and opens when the power is cut off to prohibit the output of a gate signal.