JPH05111244A - Power source for arc welding machine - Google Patents

Abstract

PURPOSE:To provide a power source for an arc welding machine which can easily code with various input voltages and has a small size, a light weight and high performance characteristics. CONSTITUTION:A reactor 21 connected in series with an input current path, a step-up switching element 22 connected between the path and an input current feedback path and a steep switching controller 23 which controls ON, OFF of the element 21 and has ON/OFF time regulating means are connected to input sides of smoothing capacitors 5, 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for an arc welding machine which can easily cope with a change in input AC power supply voltage.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional example of a power supply device for an arc welding machine of this type. Reference numeral 1 is an input terminal for receiving a commercial AC power supply voltage, and as a commercial power supply voltage, a 200V power supply of Japan or a 400V power supply of Europe is connected. Reference numeral 2 is an input transformer, which is provided with a plurality of taps so that one standard arc power supply device can support it according to the commercial power supply voltage. The switch 3 provided on the input side of the input transformer 2 is switched so as to obtain a desired arc output with respect to an arbitrary commercial power supply voltage. 4 is a rectifier for rectifying commercial power supply voltage, 5, 6
Is a smoothing capacitor, and 7 and 8 are switching elements, which are on / off controlled at high frequency by a high frequency switching circuit 9. Reference numeral 10 is an output transformer, 11 and 12 are output rectifiers for rectifying the output of the output transformer 10, and 13 is a smoothing reactor. Further, 14 is an arc load and is constituted by a torch 15 and a base material 16. The arc load is used for welding and cutting the base metal.

[0003]

In the conventional power supply device shown in FIG. 4, (1) it is necessary to provide many taps on the input transformer 2, and the operation of the switch 3 becomes complicated.

(2) By providing the input transformer 2, the whole becomes large and heavy.

(3) The loss increases due to the excitation of the input transformer 2.

(4) Since the capacitor input type rectifier is constructed, the power factor is poor and the waveform distortion rate is large.

[0007] There are drawbacks such as.

An object of the present invention is to provide a power supply device that solves the above-mentioned drawbacks by connecting a boost converter instead of an input transformer having a plurality of taps.

[0009]

The present invention is directed to a rectifier for converting an AC power supply voltage into a DC, a smoothing capacitor for smoothing a rectified output, and a high frequency switching for converting the smoothed output into a high frequency AC by turning on / off a switching element. In the arc welding machine power supply device comprising a circuit, and supplying high-frequency alternating current as an alternating current or as a direct current to an arc load, on the input side of the smoothing capacitor, a reactor connected in series to an input current path, A step-up switching element connected between the input current inflow path and the input current feedback path, and a step-up switching control circuit that controls ON / OFF of the switching element and includes an operating means for adjusting the ON / OFF time. Is characterized by.

[0010]

[Operation] Since the boost switching element is connected to the reactor connected to the input side of the smoothing capacitor,
The magnitude of the input current to the capacitor can be controlled by on / off controlling the boosting switching element. That is, when the boosting switching element is turned on, an exciting current flows in the reactor to accumulate energy, but when the switching element is turned off, the accumulated energy is released. That is, the smoothing capacitor is charged. Therefore, the charging time of the smoothing capacitor, that is, the magnitude of the input voltage of the smoothing capacitor can be controlled by adjusting the on / off time of the boosting switching element by the adjusting operation means. Therefore, by appropriately adjusting the adjusting operation means, the input voltage of the capacitor can be set to substantially the same level even if the size of the commercial power supply voltage changes.

[0011]

1 is a circuit diagram of a first embodiment of the present invention.

1 is an input terminal for receiving a commercial AC power supply voltage,
Reference numeral 20 is a thyristor-controlled input rectifier that rectifies a commercial AC power supply voltage, 21 is an energy storage reactor, 22 is a boosting switching transistor, and 23 is an adjusting operator 2.
It is a boosting switching control circuit provided with 3a. Further, 24 is a backflow prevention diode, 5 and 6 are smoothing capacitors, 7 and 8 are switching transistors, 9 is a high-frequency switching circuit for on / off controlling the switching transistors 7 and 8, 10 is an output transformer, and 11 and 12 are outputs. Rectifier, 13 is smoothing reactor, 14 is torch 15
And the arc load including the base material 16.

The diode 25 and the resistor 26 connected between the input terminal 1 and the input rectifier 20 are circuits for charging the capacitors 5 and 6 at the time of starting.

As shown in FIG. 1, on the input side of the smoothing capacitors 5 and 6, the reactor 21 connected in series to the input current path and the boosting switching connected between the input current inflow path and the input current feedback path. A transistor 22 and
Controlling ON / OFF of the switching transistor 22;
A step-up switching control circuit 23 including an operator 23a for adjusting the on / off time is provided. Also,
In this embodiment, in order to prevent the inrush current to the smoothing capacitors 5 and 6, a series circuit for reducing current of a diode 25 and a resistor 26 is connected between the input terminal 1 and the rectifier 20, and the rectifier 20 is controlled by a thyristor. As the input rectifier, the input rectifier 20 is turned off for a short time and the smoothing capacitors 5 and 6 are supplied with an appropriate current through the diode 25 and the resistor 26 to be charged when the power is turned on. When a certain time has elapsed, the thyristor is turned on and the power supply voltage is rectified by the input rectifier 20.

Next, the operation of the above power supply device will be described.

First, when the power is turned on as described above, the input current is smoothed through the diode 25 and the resistor 26 before the thyristor-controlled input rectifier 20 starts operating (before the thyristor is turned on). It flows to 5,6. Since the current at this time is limited by the resistor 26, a large inrush current does not flow. When the smoothing capacitors 5 and 6 are appropriately charged, the thyristor of the input rectifier 20 is turned on, and a large charging current flows to the smoothing capacitors 5 and 6. At this time, the step-up switching control circuit 23 generates an on / off signal based on the value set by the adjustment operator 23a and supplies it to the base side of the step-up switching transistor 22. Now, if the boosting switching transistor 22 is turned on within a half cycle of a certain power supply voltage, a current i _L flows through the reactor 21 and energy is accumulated. Then, when the switching transistor 22 is turned off, the stored energy is discharged to the smoothing capacitors 5 and 6 via the diode 24 and charging is performed. This operation is repeated, and the input voltage V ₀ of the smoothing capacitors 5 and 6 gradually increases. Changes in the input current i _L are shown in FIG. By controlling the switching transistor 22 to be turned on and off in this manner, energy storage due to the input current is stopped before magnetic saturation due to the input current, and the energy storage and release are repeated, so that the reactor is It is possible to reduce the distortion of the exciting current (input current) caused by the non-linear magnetization characteristic and the hysteresis characteristic of 21.

FIG. 2 shows the input current i _L to the reactor 21.
And the input power supply voltage V _IN (absolute value) and the input voltage V ₀ of the smoothing capacitor. The envelope of the input current i _L becomes the input current (charging current) of the smoothing capacitors 5 and 6. As shown in the figure, the power factor is improved by reducing the distortion of the input current to the smoothing capacitors 5 and 6, and the input voltage V ₀ of the smoothing capacitor is thereby changed to the input power supply voltage V _IN.
Can be larger than. Where input current i _L
ON / OFF time of switching (duty or cycle)
By changing, the magnitude of the input current (charging current) to the smoothing capacitors 5 and 6 can be easily changed. The current waveform of the solid line shown in FIG. 2 shows a current that is approximately half the current shown by the broken line. That is, the charging voltage (input voltage) of the smoothing capacitors 7 and 8 can be controlled by adjusting the adjusting operator 23a.

Therefore, the reactor 21, the boosting switching element 22, and the boosting switching control circuit 2
3 constitutes a boost converter.

The above boost converter will be further described below. The relationship between the rectified output voltage V ₁ and the input voltage V ₀ of the smoothing capacitors 5 and 6 is (V ₀ / V ₁ ) = 1 / (1-γ) where γ is the flow rate, and the flow rate is The conduction ratio = (ON time of the boosting switching transistor 22) / (ON / OFF cycle of the boosting switching transistor).

Therefore, if the above-mentioned flow rate γ is changed,
The input voltage V ₀ of the smoothing capacitors 5 and 6 can be set to any value. The flow rate can be changed by the adjusting operator 23a including a volume.
A circuit for varying the ON time and ON / OFF cycle of the boosting switching transistor 22 is well known because it has the same circuit configuration as that of the switching control circuit 9 even if the circuit configuration is not shown.

In the above circuit, the smoothing capacitors 5,
6, the input voltage V ₀ of the switching transistors 7, 8
The boosting switching control circuit 23 is adjusted so that the voltage does not break. If the voltage detection circuit 40 that detects the capacitor input voltage V ₀ and sends a control signal to the boosting switching transistor control circuit 23 based on the change in the voltage is provided, the input voltage V ₀ is automatically made constant. Can be held.

FIG. 3 shows a circuit diagram of another embodiment of the present invention. In this embodiment, the reactor 21 for energy storage in FIG. 1 is not provided in the input current path on the DC side, but is provided in the input current path on the AC side, and the boosting switching transistor is provided in parallel with the rectifying diodes 33 and 34. 35 and 36 are provided.

In the embodiment, in the half wave in which the potential of one terminal 1a of the input terminal 1 is higher than the potential of the other terminal 1b, the energy of the reactor 30 is accumulated and released by the on / off control of the switching element 35. .. In the opposite half-wave (half-wave in which the potential of the input terminal 1b is higher than the potential of the input terminal 1a), the switching element 36 is turned on / off to store and release the energy of the reactor 30. In this way, by providing two boosting switching transistors and storing and releasing energy for the reactor by each switching transistor for each half wave, the input voltage V ₀ to the capacitors 5 and 6 is independent of the input power supply voltage. It can be adjusted to be constant by the volume 37a or the like. The boost switching control circuit 37 is the boost switching control circuit 23 shown in FIG.
However, the step-up switching control circuit 37 of the present embodiment alternately switches the step-up switching transistors 35 and 36 at high frequency for each half wave.

Further, in the above embodiments, a single-phase circuit configuration is shown for easy understanding, but the same configuration can be adopted even when the input power source is a three-phase power source. Figure 3
In order to make the embodiment shown in FIG.
It is sufficient to insert 0 into each of the three wires and insert a backflow prevention diode between the input rectifier and the capacitor.

[0025]

The effect of the conventional input transformer is not required,
Compact and lightweight. There is also no loss of exciting current. Further, there is no need for a tap operation as in the past. Further, the distortion of the input current is reduced, and thereby the power factor of the input can be made approximately 1.

[Brief description of drawings]

FIG. 1 shows a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing current and voltage waveforms of the above embodiment.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional example.

[Explanation of symbols]

 5, 6-Smoothing capacitor 7, 8-High-frequency switching transistor 14-Arc load 20-Thyristor-controlled input rectifier 21-Reactor 22-Boosting switching transistor 23-Boosting switching control circuit 23a-Adjusting operator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H02M 9/00 B 8325-5H (72) Inventor Haruo Moriguchi 2-14-3 Awaji, Higashiyodogawa-ku, Osaka Sansha Denki Seisakusho Co., Ltd. (72) Inventor Kunio Kano 2-14-3 Awaji, Higashiyodogawa-ku, Osaka City Sansha Denki Seisakusho Co., Ltd.

Claims (1)

[Claims] 1. A rectifier for converting an AC power supply voltage into a DC current,
An arc that is provided with a smoothing capacitor that smoothes the rectified output and a high-frequency switching circuit that converts the smoothed output into high-frequency alternating current by turning on and off a switching element. In a welding machine power supply device, on the input side of the smoothing capacitor, a reactor connected in series with an input current path, a boosting switching element connected between an input current inflow path and an input current feedback path, and a switching element of the switching element. A power supply device for an arc welding machine, which is connected to a step-up switching control circuit which controls on / off and has an operating means for adjusting the on / off time.