JPH0315259Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a welding/cutting power supply device that can perform both arc welding (welding) and plasma welding (cutting) by switching the secondary side tap of a transformer.

As shown in Fig. 1, a conventional welding/cutting type power supply device is provided with a cutting tap and a welding tap on the secondary side of a transformer 1 whose primary side is supplied with input voltage, and the secondary side is connected via a changeover switch. The output is rectified by a controlled rectifier 3, and is further rectified by a smoothing reactor 4.
I was trying to get the output through . In addition, a pilot supply winding 6, its switch 7, and a rectifier 8 are provided for forming a pilot arc during cutting (plasma welding), and the rectified output obtained thereby is transferred to a pilot smoothing reactor 9 and a pilot current limiting resistor 5. The pilot voltage for arc starting was created through the However, in the conventional device described above, the commercial voltage is directly transformed by the transformer 1 to obtain the power output, so there is a drawback that the transformer becomes very large. In addition, when cutting, the arc voltage fluctuates very widely and the changes are steep, so if the power supply ripple is large in that state, the nozzle of the plasma cutting tome has a small diameter, so the nozzle wears out rapidly, and the so-called series failure occurs. It becomes easier to cause an arc (double arc).
Therefore, it is necessary to use a large-capacity reactor 4 in order to reduce the power ripple and to be able to supply arc current even in sudden changes in load. It had the disadvantage of being expensive, large, and extremely heavy. Furthermore, it is necessary to provide a separate pilot circuit, and the voltage drop across the current limiting resistor 5 also increases, resulting in the problem of increased heat generation.

The purpose of this invention is to eliminate the above-mentioned drawbacks and provide a welding and cutting welding device that is small, lightweight, and has excellent responsiveness.

FIG. 2 is a circuit diagram of a welding/cutting type power supply device which is an embodiment of this invention.

The commercial voltage is rectified by a rectifier 10 and further smoothed by a capacitor 11. The smoothed voltage is applied to the switching element 12. This switching element repeatedly turns on and off alternately in response to high frequency (several kilometres or more) switching pulses from the switching control circuit 13, and supplies its output to the inverter transformer 14. In this embodiment, a capacitor 11 and a switching element 12 constitute a half-bridge circuit. Inverter transformer 1
When the primary winding receives the voltage switched by the switching element 12, the voltage is transformed into a predetermined voltage, and then a voltage is induced in the secondary winding. The secondary winding of the inverter transformer 14 is provided with a cutting tap a having a large number of windings and a welding tap b having a small number of windings. Disconnect tap a increases the output voltage,
Weld tap b lowers the output voltage. The welding tap b, which has a small number of windings, is connected to a rectifier 15, and the cutting tap a, which has a large number of windings, is connected to a rectifier 16. The center tap c of the inverter transformer 14 is connected to the contact c1 of the changeover switch 17, the contact c2 of this changeover switch 17 is connected to the anode side of the diode 16, and the common terminal c0 is connected to the negative output terminal of the power supply. There is. Furthermore, a smoothing reactor 18 of the main circuit, a reactor 19 of the pilot circuit, and a current limiting resistor 20 are connected to the cathode of the rectifier 15.
Further, the rectified output of the inverter transformer 14 is detected by the detector 21, and its magnitude and reference voltage E
The error from the set output given by 0 is amplified by the error amplifier 22 and fed back to the switching control circuit 13. The detector 21, the error amplifier 22, and the switching control circuit 13 constitute a feedback circuit. This circuit performs switching control so that the power supply output becomes a constant current.

In the above configuration, when the power is turned on, the switching element 12 performs rectification and smoothing output by several K.
Switching is performed at the above frequency to induce a switching voltage in the secondary winding of the inverter transformer 1 according to the winding ratio. If the changeover switch 17 is now set to the terminal c1 side, a low voltage output is supplied to the positive output terminal. Further, when the changeover switch 17 is switched to the terminal c2 side, a high voltage output is supplied to the positive output terminal. As a result, one power supply device can be used for both welding and cutting by simply switching the changeover switch 17. When disconnecting, set the switching output to the maximum and light the pilot at that voltage. In this case, even when switching from the pilot to the main arc, the response of the power supply is extremely good due to the interaction between the feedback circuit and the switching circuit, so the switching element is immediately controlled to provide the optimum load current. Ru. Therefore, no excessive current flows through the load. Also, the pilot circuit is connected in parallel with the main arc circuit, but this can be easily done without configuring a separate circuit as in the past, since the switching frequency is sufficiently high compared to the commercial 50 or 60 This is because the control response of the device is very fast.

FIG. 3 shows another embodiment of this invention. The difference between this embodiment and the embodiment shown in FIG. 2 is that switch switches 17a and 17b are provided for the upper and lower welding taps and cutting taps of the secondary winding of the inverter transformer 14, respectively, to switch the taps to the cutting taps. In some cases, a full-wave rectifier circuit is constructed on the highest tap side of the secondary winding.
By doing so, the efficiency of the secondary winding can be increased.

As described above, according to this invention, the rectified and smoothed output of the input voltage is supplied to the primary side of the transformer as high frequency switching, and the secondary output of the transformer is used as the cutting output or welding output by switching the taps. A switching control circuit is installed that sets the optimal voltage, detects the error between the output of the secondary rectifier circuit and the set output, and controls the switching circuit to eliminate that error, improving the responsiveness of the power supply. It is possible to reduce the wear of the electrode during cutting, and to suppress the occurrence of series arcs.
Furthermore, since the responsiveness is very good, the capacity of the reactor for the main arc circuit can be reduced, and the transformer can also be made smaller, so that the arc power supply itself can be significantly reduced in size and weight.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional welding/cutting power supply device. FIG. 2 is a circuit diagram of a welding/cutting power supply device according to an embodiment of this invention, and FIG. 3 is a circuit diagram of a main part of another embodiment. 12... Switching element (switching circuit), 13... Switching control circuit, 14...
Inverter transformer (trans), 15, 16...
... Rectifier (secondary side rectifier circuit), 17... Changeover switch.

Claims (1)

[Scope of utility model registration request] A primary rectifier circuit that rectifies and smoothes the input voltage,
A transformer is provided with a switching circuit that switches the rectified output at high frequency, a switching output that is supplied to the primary winding, and a secondary winding that is provided with a disconnect tap that increases the output voltage and a weld tap that decreases the output voltage. a secondary rectifier circuit that rectifies the output of the transformer; a switch that switches the output terminal of the transformer to either the cut tap or the weld tap; A switching control circuit that detects an error and controls the switching circuit to eliminate the error.