JPH0713906Y2 - Input synchronization circuit of three-phase input thyristor arc welder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an input synchronizing circuit of an arc welding machine which is used with a three-phase input and whose output is controlled by a thyristor.

Conventional technology Conventionally, in order to control the output of a three-phase input thyristor arc welding machine, the thyristor must always be controlled in synchronization with the phase of the phase on the input side to control the ignition phase. A synchronization circuit is required.

FIG. 3 shows an input synchronizing circuit 12 as a conventional example. In this circuit, three step-down transformers 13, 14 and 15 are connected in delta. First, the step-down transformers 13, 14, and 15 insulate and step down the line voltage on the input side of the welding machine, the diodes 16 to 21 perform full-wave rectification, and the transistors 25 to 27 are connected via resistors 22 to 24.
Had been added to the base. The relationship between the voltage waveform that is full-wave rectified by the diode of this circuit and the operating state of the transistor is
This is as shown in FIG.

However, in the conventional input synchronization circuit as described above, the step-down transformers 13 to 15 are large in size, and it is difficult to mount them on the printed circuit board, resulting in high cost. .

When the input voltage of the arc welder changes, the input synchronization circuit 12
It was necessary to change the primary side voltage of the step-down transformers 13 to 15 corresponding to the input voltage of the welding machine, which made it difficult to support the arc welding machine of different voltage input.

The purpose of the present invention is to reduce the size of the input synchronization circuit so that it can be mounted on a printed circuit board, reduce the cost, and facilitate the handling of different voltage inputs. The input synchronization circuit of a three-phase input thyristor arc welder. Is to provide.

Means for Solving the Problems In order to achieve the above object, the present invention provides an anti-parallel input synchronization circuit that provides a synchronization signal to a thyristor firing circuit for each half-wave of an AC waveform of a three-phase input thyristor arc welding machine. The photodiode connected to the input side is connected to the input side, the photo coupler with the transistor on the output side and the resistor connected in series are connected in a delta connection, and the connection points of this delta connection circuit are connected to the three-phase input power supply line, respectively. Then, the output of the photocoupler of each phase is used as a synchronizing signal of the thyristor firing circuit section to form an input synchronizing circuit of a three-phase input thyristor arc welding machine.

Action The present invention is configured as described above, so when the input side AC voltage is close to zero V, the current flowing in the phototransistor of the photocoupler disappears, the output side transistor of the photocoupler is turned off, and the power input line It electrically insulates the thyristor firing circuit from the thyristor and makes it possible to extract the synchronization signal.

Embodiment An input synchronizing circuit according to an embodiment of the present invention will be described with reference to FIG.

Reference numeral 1 is a main transformer portion, 2 is a thyristor portion, 3 is a thyristor ignition circuit portion, 4 is an output setting portion, 5 is an input synchronizing circuit portion, and these constitute a three-phase input thyristor arc welding machine. . The input synchronization circuit unit 5 can synchronize the thyristor unit 2 with the phase of each phase on the input side by supplying a synchronization signal to the thyristor firing circuit unit 3 for each half wave of the AC waveform of the arc welding machine. This input synchronizing circuit diagram is composed of resistors 6, 7, and 8 and photocouplers 9, 10, and 11, which are each composed of a photodiode and a transistor connected in antiparallel. When the input side AC voltage is close to zero V, the current flowing through the photodiode disappears and the output side transistors of the photocouplers 9, 10 and 11 are turned off to achieve synchronization. At this time, the waveform of the AC input voltage waveform of only one phase and the operation of the phototransistor on the output side of the photocoupler can be represented by the waveforms as shown in FIGS.

Effect of the Invention Since the input synchronization circuit of the present invention has the above-mentioned configuration,
The output from the photocoupler changes as the input AC voltage changes, and a synchronization signal is supplied to the thyristor firing circuit to synchronize. By using a photocoupler in this way, the input synchronization circuit can be mounted on a printed circuit board in a small size, which can reduce the cost and can cope with different voltage inputs without any change. The practical effect is great.

[Brief description of drawings]

FIG. 1 is an input synchronizing circuit diagram of the three-phase input thyristor type arc welding machine of the present invention, and FIG. 2 is a time chart diagram showing the AC input voltage waveform and the operation of the photocoupler output of the input synchronizing circuit part of the present invention. FIG. 3 is an input synchronization circuit diagram of a conventional three-phase input thyristor arc welding machine, and FIG. 4 is a time chart diagram showing a full-wave rectified voltage waveform of the input synchronization circuit unit of the conventional example and operating states of transistors. 3 ... Thyristor firing circuit section 5 ... Input synchronization circuit section, 6, 7, 8 ... Resistor 9, 10, 11 ... Photo coupler

Claims (1)

[Scope of utility model registration request] 1. An input synchronizing circuit for supplying a synchronizing signal to a thyristor firing circuit for each half-wave of an AC waveform of a three-phase input thyristor arc welding machine, having a photodiode connected in antiparallel on the input side. , Delta connection is made by connecting a photo coupler equipped with a transistor on the output side and a resistor in series, and the connection points of this delta connection circuit are connected to the three-phase input power supply line, and the output of the photo coupler of each phase is connected. An input synchronizing circuit for a three-phase input thyristor arc welding machine, which is characterized by using a synchronizing signal for a thyristor firing circuit section.