JPH04133662A - Power supply equipment - Google Patents

Abstract

PURPOSE:To convert three-phase AC into single-phase AC efficiently by equipping it with a transforming part, wherein the secondary outputs of three single-phase transformers are connected in common, and the three-phase outputs of a six-phase/ three-phase conversion circuit to the primary side of each of the above-mentioned single-phase transformers through a phase control circuit. CONSTITUTION:The power from three-phase AC power sources 1-3 in converted into the AC power of six phases with the conversion circuit 51 of a six-phase/three-phase conversion circuit 50, and is output to a phase selection circuit 52. The phase selection circuit 52 selects the first phase, the second phase, and the third phase out of each output of the six phases of the conversion circuit. And the current application from the phase conversion circuit 52 to each single-phase transformer 71-73 of a transforming part 70 is controlled with a phase control circuit 60, and current application is performed to the first, the second, and the third single-phase transformer 71-73, only within the range of 120 deg.-180 deg. in the phase angles of the AC sine waveforms X, Y, and Z of each phase. By repeating current application to three single-phase transformers 71-73 in order this way, a saw-shaped AC current, which has the dropping properties of triple cycles, is output to the secondary common output 101.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power supply device that converts three-phase alternating current to single-phase alternating current, and is particularly applicable to welding equipment such as alternating current arc welding, spot welding, seam welding, etc. The present invention relates to a single-phase AC power supply device that is highly efficient and can be used as a power source for arc welding or submerging for low-hot loading, or as a power source for lighting equipment, vibrators, electric motors, electric heaters, etc.

[Conventional technology]

Generally, single-phase alternating current is usually used as a power source for spot welding equipment, lighting equipment, electric motors, electric heaters, etc. In order to obtain this single-phase alternating current, devices that convert three-phase alternating current to single-phase alternating current include Scott wiring, three coarse frequency method,
One-sided inverter systems are also known, but in these cases, the higher the current, the more three-phase unbalance occurs, and there is also the problem of poor power efficiency.

In other words, the above-mentioned scott wiring etc. has a complicated circuit configuration, makes the device large as a power supply, and only one of the three phases
It was difficult to extract stable current, such as twice the excessive current flowing through the phases, and there were problems with reliability as a power supply.

In addition, the above-mentioned three-phase similar frequency system is used as a power source for spot welding equipment, and the equipment is large, expensive, and frequently breaks down.

In addition, since arc welding equipment generally requires a large current, two types of power supply systems are adopted: magnetic leakage type and reactor type. The former uses a magnetic leakage transformer as a transformer, and the latter uses a transformer. A saturable reactor is inserted in series with a discharge circuit composed of a secondary side and an arc electrode. All of these are designed to obtain output characteristics that match the drooping characteristics during arc welding, in which the voltage rises sharply to a high voltage and then drops rapidly, and in these cases, losses due to electromagnetic leakage and acdle in the transformer section are avoided. There was a problem that it was too big.

Furthermore, recently a one-sided inverter type has been widely adopted, and this method involves rectifying the alternating current, increasing the frequency to about several hundred cycles to 1,200 cycles, making the transformer smaller and lighter, and converting the secondary side to direct current. This was also extremely expensive, inefficient, and frequently broken down. Therefore, there was a need for a small, lightweight, and efficient power supply device.

[Invention or problem to be solved]

The present invention was made in view of the above circumstances, and an object of the present invention is to provide an efficient power supply device that uses an existing single-phase transformer to convert three-phase alternating current to single-phase alternating current.

[Means to solve the problem]

The power supply device according to the present invention is connected to a three-phase AC power supply,
A 6-phase/3-phase conversion circuit that can generate 6-phase AC, select and output three desired phases from among them, and supply output power from the 6-phase/3-phase conversion circuit, for example, for each phase. Approximately 120
A phase control circuit that controls the operation only in the range of 180° to 180° is commonly connected to the secondary outputs of the three single-phase transformers, and the 6-phase /A transformer section formed by connecting the three-phase outputs of the three-phase conversion circuit, and outputs single-phase alternating current to the common output of the single-phase transformer.

[Effect]

In this invention, since the above configuration is adopted, the ignition control by the phase control circuit ensures that the primary side of each single-phase transformer is energized only in the range of about 120° to about 180° of the AC sine waveform of each phase. A sawtooth alternating current waveform having a frequency three times that of the three-phase alternating current is generated at the common output on the secondary side of the single-phase transformer. In other words, a triple-frequency single-phase alternating current having a drooping characteristic in which the voltage level rises steeply and then rapidly drops is induced in the secondary side common output. As a result, an efficient power supply device using an existing single-phase transformer without the problem of three-phase unbalance can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1(a) is an overall configuration diagram showing an arc welding apparatus using a power supply device according to an embodiment of the present invention, and FIG. 1(b) is a diagram showing the configuration of its 6-phase/3-phase conversion circuit. .

In the figure, 1. 2. 3 is 3-phase AC power supply, 5° is 3
This is a 6-phase/3-phase conversion circuit that is connected to a phase AC power supply, generates 6-phase AC, and can select and output the desired 3 phases from among them. AC power is supplied to the first to third phases of the power supply and the first phase which is opposite to these.
A conversion circuit 51 that converts into 6-phase AC power consisting of reverse phase to 3rd reverse phase, and a phase selection circuit 52 that can select desired three outputs from each of the six phase outputs of the conversion circuit 51. Here, the second phase selection circuit 52 is set to select the first to third phases.

60 is connected to the latter stage of the phase selection circuit 52, and supplies three-phase AC power that is the output of the circuit to 120° to 180° of each phase.
This is a phase control circuit that controls the operation only within the range of 100°. Further, 70 is a transformer connected to the latter stage of the phase control circuit 60, which combines three existing single-phase transformers 71 to 73, that is, connects the secondary side outputs of each single-phase transformer in common.
The above 6 phases/3 are connected to each primary side via the above phase control circuit.
It is constructed by connecting the three-phase outputs of the phase conversion circuit 50.

Further, 300 is a welding part for performing arc welding, and this is the welding electrode 1 connected to the secondary output 101 of the common connection.
0 and a material to be welded 11 connected to a ground end 12, and 13 is an arc.

FIG. 1(C) shows details of the phase control circuit 60, in which 20a, 20b, and 20c are thyristors, and 21 is a zero-crossing point detector for detecting the zero-crossing point of the sine wave of each phase of the three-phase alternating current. , 22a, 22b, 22c are the zero cross point detectors 2
Thyristors 20a, 20 of each phase receive the output of
b, 20 This is a phase adjuster that adjusts the firing angle of c.

Next, the operation will be explained.

The power from the three-phase AC power sources 1, 2.3 is converted into the first phase to third phase of the power source and the first reverse phase to third phase of the power source by the conversion circuit 51 of the six-phase/three-phase conversion circuit 50. 6 consisting of the third reverse phase and
It is converted into phase AC power and output to the phase selection circuit 52. The phase selection circuit 52 selects one of the first phase, second phase, and third phase from among the six-phase outputs of the conversion circuit.

The energization from the phase selection circuit 52 to each of the single-phase transformers 71 to 73 of the transformer section 70 is controlled by the phase control circuit 60, and as shown in FIG. The third single-phase transformers 71 to 73 have AC sine waveforms X of each phase,
Current is applied only within the phase angle range of 120 degrees to 180 degrees for Y and Z (C and f for X, b and e for Y, a,...!:d for Z), and at other times. , each single-phase transformer is open.

When the three single-phase transformers 71 to 73 are sequentially energized in this way, the secondary side common output 101 has a sawtooth shape with triple frequency drooping characteristics, as shown in FIG. 2(b). An alternating current will be output.

Then, this sawtooth triple frequency current is applied to the welding electrode 10 of the welding part 300 to generate an arc 13 between the welding material 11 and the welding material 11, thereby performing arc welding. At this time, the following effects can be obtained.

■ In this example, three phases are converted to single phase, so three
No phase imbalance problems arise. In addition, as for the single-phase output on the secondary side, as mentioned above, the frequency is three times higher than that of three-phase AC, that is, 180 cycles compared to 60 cycles, so it is necessary to use a welding speed or a conventional three-phase/single-phase converter. It will be 3 times more than the case.

At the same speed, the welding beat is three times finer as shown in FIG. 3(b) than the conventional welding beat shown in FIG. 3(a). In this way, the quality of welding can be improved.

■ With conventional three-phase/single-phase conversion power supplies, the single-phase output obtained is a sine wave, or with the present invention, the power output value is a sawtooth wave that rises sharply to a high voltage and then drops to zero. Therefore, it is possible to easily generate an arc during final welding and to obtain a stable arc.

In other words, this power supply device essentially has a drooping characteristic, which is extremely convenient for welding.

■ Since the power supply of the present invention has a drooping characteristic as described above, in order to obtain this drooping characteristic, a leakage flux type device commonly used in the past or a saturable reactor as shown in Fig. 4 is used. There is no need to use L, etc., and there is no accompanying loss or reduction in power factor.

■ Also, since the frequency obtained is tripled, the transformer is smaller and the weight is only 1/3 of the conventional one, making it extremely small and lightweight. Furthermore, since the structure is simple, small and lightweight, manufacturing costs can be significantly reduced.

■ Also, in conventional equipment, the no-load voltage is 60V to 100V.
In the present invention, the no-load voltage required is quite small, and it is safe, easy to handle, does not require technical skill, and is easy to automate.

(2) By appropriately adjusting the firing angle of the one-phase AC sinusoidal waveform back and forth around 120 degrees, the strength of the arc can be greatly adjusted.

In other words, the adjustment range can be made wider than before,
By performing automatic control using a computer, it is possible to weld in areas that were previously impossible, and welding stability can be achieved.

■ Also, since the arc is stable, it is possible to arc weld large thick plates by mounting it on a robot. In other words, it is possible to demonstrate three times the welding capacity of the conventional method.

Next, other embodiments of the invention will be described.

FIG. 5 (al indicates a power supply device according to a second embodiment of the present invention; in this embodiment, the phase selection circuit 52 in the first embodiment is replaced with a phase selection circuit 52 having a phase opposite to that of the third phase). In this embodiment, as in the first embodiment, when each phase is fired between about 1.20° and about 180°, the obtained waveform is set to select the 5th phase. Figure (b)
The waveform becomes as follows, and in the - period, three sawtooth waves are obtained on the + side and three sawtooth waves are obtained on the side. For a three-phase, 60-cycle power input, 360 sawtooth waves can be obtained per second even though it is a single-phase, 6° cycle.

In this way, each of the three phases is approximately 120
If the phase is controlled between 180° and 180°, a 60-cycle sawtooth wave as described above can be obtained on the secondary side, so if this is used as a heating power source for spot welding or forging, 1
This is advantageous because it has less reactance loss than the 80-cycle sawtooth wave, and the heating energy increases accordingly. Specifically, it becomes possible to perform deep welding, that is, welding at a location quite far from the transformer.

FIG. 6(a) shows a third embodiment of the present invention, in which the three phases are reversed as in the second embodiment, and the first
The phase is about 120° to about 180°, the second phase is about 0° to about 18
0°, the third reverse phase is ignited at about 60° to about 180°, and in this case, as shown in Fig. 6(b),
A 60-cycle sawtooth wave with a large wave height is obtained, which is further advantageous for spot welding.

In addition, in the above explanation, the ignition start time of the first phase is about 120°.
6(b), but if the ignition start timing is set to about 100 degrees, the welding current waveform will be more forward than the rising position, and the rising waveform will be A rounded sawtooth wave can be obtained from the upper end of the welding current (see FIG. 6(C)), and a welding current with such a waveform is effective depending on the welding application.

FIG. 7(a) shows a fourth embodiment of the present invention, which differs from the first embodiment in that the phase control circuit 60 is configured such that the third phase is always open and the first and second phases are from about 120°
It is configured to ignite at an angle of about 180°. In this case, as shown in FIG. 7(b), in the - period, the + side and -
Two sawtooth waves are obtained at a predetermined interval on each side, and a waveform with a middle rest period on the + side and - side is obtained. Convenient for welding.

Also, here, as shown in FIG. 7(C), the first phase is
If the second phase is fired at 0° to 180°, the energy of both phases will be combined, and a pseudo-sawtooth wave will be generated at the beginning of the waveform that becomes strong and gradually weakens (see Figure 7 (d).
) can be obtained.

FIG. 8 shows a fifth embodiment of the present invention, in which:
The phase selection circuit 52 is set to select the first phase, the second phase, and the third reverse phase, and the phase control circuit 6° is set to select the first phase from 60° to
The configuration is such that the ignition occurs at 180°, the third reverse phase is ignited at 06 to 180°, and the second phase is always open. A large waveform as shown in FIG. 8(C) is obtained.

In this case, the energy at the beginning of the rise of the waveform is large,
Also, since it rises steeply, it is advantageous for spot welding, arc welding, etc. Furthermore, in this case, the strength of the weld increases, making it possible to increase the welding speed and to weld thick materials. Furthermore, by changing the ignition range of each phase, the output energy can be adjusted to any value.

In the above explanation, ignition is performed by conducting current until the voltage of each phase becomes zero, that is, until the phase reaches 180 degrees, but ignition control using transistors, etc. Therefore, for example, in the third embodiment shown in Fig. 6, if the second phase is energized from 0° to 120°, the ignition stop timing can be set arbitrarily. ) waveform, the energizing time is shorter and the drooping characteristic is steeper. This also applies to the fifth section shown in Figure 8.
In the embodiment described above, the same effect can be obtained even if the reverse phase of the third phase is energized from 0° to 120°.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a 6-phase/3-phase conversion circuit that is connected to a 3-phase AC power supply, generates 6-phase AC, and is capable of selecting and outputting desired 3 phases from among the 6-phase AC, and Phase/3
For example, the output power from the phase conversion circuit is
A phase control circuit that controls the operation only in the range of 20° to 180° is commonly connected to the secondary outputs of the three single-phase transformers, and the above 6. It is equipped with a transformer section that connects the three-phase outputs of the phase/three-phase conversion circuit, and outputs single-phase AC to the common output of the single-phase transformer, so the output is a triple-frequency sawtooth waveform. This has the effect of providing an efficient power supply device without the problem of three-phase unbalance.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a power supply device used in an arc welding machine according to an embodiment of the present invention, FIG. 2 is a diagram showing the output waveform of the power supply device, and FIG. 3 is a diagram showing the operation of the arc welding machine. FIG. 4 is a diagram showing an arc welding machine using a conventional saturable reactor, FIG. 5 is a diagram showing a power supply device according to a second embodiment of the present invention, and FIG. A diagram showing a power supply device according to a third embodiment, FIG. 7 is a diagram showing a power supply device according to a fourth embodiment of the present invention.
FIG. 8 is a diagram showing a power supply device according to a fifth embodiment of the present invention. In the figure, 1. 2. 3 is a three-phase AC power supply terminal, 10
1 is a welding electrode, 11 is a material to be welded, 12 is a ground, 13 is an arc, 50 is a 6-phase/3-phase conversion circuit, 51 is a conversion circuit, 5
2 is a phase selection circuit, 60 is a phase control circuit, 70 is a transformer,
71 to 73 are first to third single-phase transformers, 100 is a power supply device, 101 is an output terminal, and 300 is a welding part. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (9)

[Claims] (1) Connected to a 3-phase AC power supply, generates 6-phase AC, and can output 6-phase AC by selecting the desired 3 phases.
A three-phase conversion circuit, a phase control circuit that controls the firing of the output of the six-phase/three-phase conversion circuit for each phase, and the secondary outputs of three single-phase transformers are commonly connected, and each single-phase transformer A transformer is provided on the primary side by connecting the 3-phase output of the 6-phase/3-phase conversion circuit through the phase control circuit, and outputs single-phase alternating current to the common output of the single-phase transformer. Features a power supply device. (2) In the power supply device according to claim 1, the 6-phase/3-phase conversion circuit is connected to a 3-phase AC power source and converts the 3-phase AC power into a first
A conversion circuit that converts into six-phase AC power consisting of phase to third phase and first negative phase to third negative phase that are opposite to these, and a desired one from among the outputs of the six phases of the conversion circuit. A power supply device comprising a phase selection circuit that selects three outputs. (3) The power supply device according to claim 2, wherein the phase selection circuit selects the first to third phases from among the six phase outputs of the conversion circuit. (4) The power supply device according to claim 2, wherein the phase selection circuit selects a first phase, a second phase, and a third reverse phase of the three-phase AC power supply. . (5) In the power supply device according to claim 3 or 4, the phase control circuit comprises approximately 120% of each phase selected by the phase selection circuit.
A power supply device characterized in that it ignites only in a range of 0° to about 180°. (6) In the power supply device according to claim 3 or 4, the phase control circuit controls the first phase and the second phase by approximately 120 degrees.
A power supply device characterized in that it fires in a range of about 180° and does not fire a third phase. (7) In the power supply device according to claim 3 or 4, the phase control circuit fires the first phase at approximately 120° to 180°, fires the second phase at approximately 0° to 180°, and fires the third phase at approximately 0° to 180°. A power supply device characterized by not igniting a phase. (8) The power supply device according to claim 4, wherein the phase control circuit fires the first phase at about 120° to about 180°, fires the second phase at about 0° to about 180°, and fires the second phase at about 0° to about 180°. 3. A power supply device characterized in that it ignites a reverse phase at about 60° to about 180°. (9) The power supply device according to claim 4, wherein the phase control circuit fires the first phase at about 60° to about 180°, and fires the third negative phase at about 0° to about 180°; A power supply device characterized in that the second phase is not ignited.