JPH03230869A - Condenser type multiple inverter welding machine - Google Patents

Abstract

PURPOSE:To widen a welding range by subjecting the energy charged in a condenser to a high-frequency conversion with an inverter, impressing this energy to the primary winding of the inverter corresponding number of the single voltage transformer and connecting the single secondary winding of the same voltage transformer to a welding electrode. CONSTITUTION:The energy charged in the condenser 6 is subjected to the high- frequency conversion by the inverter 7 consisting of field-effect transistors 701 to 704 and is then impressed to the primary winding 801 corresponding to the inverter 7 of the single voltage transformer 8. The single secondary winding 803 of the same voltage transformer 8 is connected to the welding electrode 9. The control of waveforms of various welding currents is possible in this way and the welding with which welding conditions are hardly obtd. is executed. Since the magnetic core of the welding voltage transformer can be formed to a smaller size and weight, the field of utilizing the welding machine is widened.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a capacitor type multiple inverter welding machine.

[Conventional technology]

An example of a conventional capacitor type spot welding machine is the one shown in FIG. In the figure, an AC power source 1 is connected to the primary winding of a transformer 11, and its secondary winding is connected to a bridge-connected rectifier 2. The rectified output of the rectifier 2 is connected to the capacitor 6 via a thyristor 30 and a resistor 300. The thyristor 30 has an AC power supply 1
synced to. A control pulse is applied to its gate electrode to control the charging current to the capacitor 6 to the desired value. Capacitor 6 is further fed via thyristor 70 to the primary winding of transformer 8 . A large current multiplied by the inverse ratio of the turns ratio between the primary winding and the secondary winding of the transformer 8 flows from the secondary winding to the welding electrode 9. The object to be welded sandwiched between the welding electrodes 9 is welded. In this welding machine, the current flowing through the welding electrode 9 is 1
2 is a capacitor discharge waveform as shown in the figure, and the current flow period t and its waveform are almost fixed.

[Problem to be solved by the invention]

In the discharge control of such a conventional capacitor-type spot welder, the discharge is performed as a unidirectional current via a welding transformer. This discharge current is unidirectional, and as shown in Figure 6, it is a single pulse with a conduction period of about t = 0.1 seconds, and the thyristor 70 cannot be turned off until the current drops below its holding current, causing a change in the discharge waveform. The back part is long. During this period,
There is also the problem that when the welding electrode is opened and separated from the workpiece, spatter is generated due to the arc generated between the welding electrode and the workpiece. And since the welding current waveform is determined only by the charging voltage of the capacitor and the number of turns of the welding transformer, the welding current waveform is limited.

It has not been possible to deliver waveforms with the versatility to suit materials with different resistivities.

An object of the present invention is to obtain a wide range of shaping possibilities for discharge waveforms and to expand the welding conditions of a welding machine.

[Means to solve the problem]

The present invention aims to solve such problems.

[11 After the energy charged in the capacitor is converted into high frequency by multiple inverters, it is applied to a number of primary windings corresponding to the number of inverters in a single transformer, and the energy is converted into a single secondary winding of the transformer. A capacitor-type multiple inverter welding machine, which is characterized by connecting a welding electrode to a welding electrode.

(2) After the energy charged in the capacitor is converted into high frequency by a plurality of inverters, it is connected to the primary windings of a number of transformers corresponding to the number of inverters.

The present invention proposes a capacitor-type multiple inverter welding machine characterized in that the secondary windings of the transformer are connected in series and connected to a welding electrode.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention. First, the configuration will be explained. A three-phase AC power supply l is connected to a controlled rectifier 300 consisting of bridge-connected thyristors 301 to 303 and diodes 304 to 306.

The rectified output of controlled rectifier 300 is connected to capacitor 6 . Although not shown, the thyristors 301 to 303 are synchronized with the three-phase AC power supply 1. Control pulses are applied to their gate electrodes to control the charging current to the capacitor 6 to the desired value. Capacitor 6 is further connected to an inverter consisting of field effect transistors 701-704. The field effect transistors 701 to 704 are switched and driven at approximately 20 kHz by a control circuit 709 and sent to the primary winding 801 of the transformer 8 .

Similarly, the three-phase AC power supply l is connected to a controlled rectifier 320 consisting of bridge-connected thyristors 321 to 323 and diodes 324 to 326. The rectified output of controlled rectifier 320 is connected to capacitor 62 .

Although not shown, the thyristors 321 to 323 are synchronized with the three-phase AC power supply 1. Control pulses are provided to their gate electrodes to control the charging current to capacitor 62 to a desired value. Capacitor 62 is further connected to inverter 72 consisting of field effect transistors 721-724. The field effect transistors 721 - 724 are driven by a control circuit 729 to switch at approximately 20 kHz and are fed to the second primary winding 802 of the transformer 8 . In this way, the magnetic energy of the transformer excited by the two secondary windings 801 and 802 of the transformer 8 is combined, and an output current io is obtained from the secondary winding 803. The turn ratio between the primary winding and the secondary winding of the transformer 8 is selected to be approximately 60=1, and a large current multiplied by this inverse ratio flows from the secondary winding to the welding electrode 9. The object to be welded sandwiched between the welding electrodes 9 is welded.

Here, the control circuit 709 and the control circuit 729 are each
They are controlled in a relational manner by general control circuit 770 to generate a predetermined output current waveform as described below. That is, the inverter 7 causes a current having a waveform as shown in FIG. Then, these are combined in the secondary winding 803 (C
A waveform as shown in 1 is obtained. In this way (dl
A waveform as shown in , or a waveform with only one polarity as shown in tel can also be obtained.

In the embodiment shown in FIG. 1, by configuring the secondary winding of the transformer 8 as shown in FIG. 3 (even with the output waveform shown in dl, the current flowing through the welding electrode 9 The wave is rectified and becomes a waveform similar to (e).

In this case, the utilization rate of the transformer 8 is improved.

FIG. 4 shows another embodiment of the invention. This example is the first
In the embodiment shown in the figure, the capacitor 6 is charged via a converter 3 operating at a high frequency, and the energy from the capacitor 6 is transferred to an inverter (7, 72) and a welding transformer (8, 82). It is supplied to the workpiece through the system. To explain the configuration, an AC power source 1 is rectified by a rectifier 2 made up of diodes 21 to 24, and charges capacitors 31 and 32 to the same potential. Field effect transistors 33, 34 connected in series are connected to both ends of this capacitor 31, 32. Junction of capacitor 31° and field effect transistor 33.3
4, a capacitor 38 and an inductor 37 are connected in series. A primary winding of a transformer 4 is connected to both ends of the capacitor 38, and a secondary winding thereof is connected to a rectifier 5 comprising diodes 51-54.

The field effect transistors 33 and 34 are turned on and off at high frequency by a control circuit 39 to form the converter 3.

That is, the 50 to 60 Hz waveform of the AC power supply I is converted to a frequency several hundred to thousand times higher than that, and the capacitor 6 is charged in a controlled manner. The charging energy of the capacitor 6 is fed in parallel to the inverter 7.72, and the output current direction is obtained by combining the respective secondary windings 803.802 of the series connected transformer 8.82.

Although not shown, the embodiment of FIG. 4 can be extended to provide an arbitrary number of n inverters and connect the secondary side of the welding transformer in series. Further, it is also possible to provide an arbitrary number of n converters and connect them to an arbitrary number of n converters, so that the secondary side of the welding transformer is connected in series. Furthermore, by connecting a rectifier in series to the secondary circuit formed by connecting the secondary windings 803 and 823 of the welding transformer 8.82 in series, a unidirectional discharge current can be applied to the workpiece. Can be supplied.

〔Effect of the invention〕

The present invention has the features described above.

It produces the following effects.

(1) It is possible to control various welding current waveforms.

Welding that was previously difficult or difficult to obtain under welding conditions is now possible with the welding current waveform of the multiple inverter system.

(2) Depending on the work to be welded, the welding current waveform and current size can be instantly adapted to the purpose by simply setting the conduction time and overlap width of the inverter's switching elements without making any connection changes.

(3) Depending on the work to be welded, the welding current direction can be instantly changed from bidirectional to unidirectional, or vice versa, simply by setting the control mode without any connection changes. Therefore, the nugget (penetration portion) can be adapted to the properties of the workpiece.

(4) By preparing a plurality of inverters with the same standard capacity, a desired large-capacity welding machine can be manufactured using a limited number of standard inverters, which is excellent in mass productivity.

(5) Since a high frequency inverter is used, the magnetic core of the welding transformer can be made smaller and lighter, or the magnetic core can be eliminated and an air core can be used, expanding the fields of use of the welding machine. For example, it becomes possible to mount it on a robot or the like.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of a capacitor type multiple inverter welding machine according to the present invention, FIG. 2 shows waveforms for explaining its characteristics, and FIG. 3 shows a partial diagram of another embodiment. Further, FIG. 4 shows another embodiment of the capacitor type multiple inverter welding machine according to the present invention. FIG. 5 shows an example of a conventional capacitor type spot welding machine, and FIG. 6 shows waveforms for explaining its characteristics. 0 ■... AC power supply, 11... Transformer, 2... Rectifier. 21.22.23,24...Diode 3...Converter 30...Thyristor, 390...-Resistor 3
1.32... Capacitor, 33.34... Field effect transistor, 35.3B... Diode 37... Inductor, 38... Capacitor. 39... Control circuit, 4... Transformer, 5... Rectifier. 51.52, 53.54...Diode 6...Capacitor 7.72...Inverter 701, 702.703.704...Field effect transistor 705, 706.707.708...-Diode 721.702 , 723, 724--... Field effect transistor 725, 726. 727, 728... Diode 709, 729... Control circuit

Claims (2)

[Claims] (1) After the energy charged in the capacitor is converted into high frequency by multiple inverters, it is applied to the primary windings of the number corresponding to the number of inverters in a single transformer, and the energy is applied to the primary windings of the single transformer. A capacitor-type multiple inverter welding machine that connects a wire to a welding electrode. (2) After the energy charged in the capacitor is converted into high frequency by multiple inverters, it is connected to the primary windings of transformers whose number corresponds to the number of inverters, and the secondary windings of the transformers are connected in series. A capacitor-type multiple inverter welding machine characterized by being connected to a welding electrode.