SU1690989A1 - Device for automatically on/off switching of welding source - Google Patents

Abstract

The invention relates to the welding industry and can be used in mechanical engineering. The purpose of the invention is to expand the scope of application, smoothly adjust the welding mode, reduce power consumption, increase speed, reliability and durability. The device consists of a power supply unit, a time delay circuit, a control circuit, a high frequency generator, a NOT circuit, and an electronic switch. When the electrode comes into contact with the part, the signal of the high-frequency generator goes through a low contact resistance, without creating a significant voltage drop. A voltage is NOT input to the circuit, which means that a voltage including the control circuit appears at its "care". The pulses developed by the control circuit open up the power thyristors of the electronic switch and the mains voltage is applied to the welding power source, including it. The invention can be used to automatically turn on and off welding sources of both AC and DC current. 1 il. (Ls

Description

The invention relates to the welding industry and can be used in mechanical engineering.

The purpose of the invention is the expansion of the field of application, smooth adjustment of the welding mode, reduction of power consumption, increase in speed, reliability and durability,

The drawing shows a device for automatically turning on and off a welding power source (functional block diagram).

The device for automatic switching on and off of the welding power source consists of a power supply unit 1, a time delay circuit 2, a control circuit 3, an electronic switch 4, terminals 5, 6, 7. an NOT circuit (logical negation, inversion) 8 and a high-frequency generator 9.

The input of the power supply unit 1 and the input of the electronic switch 4 are connected in parallel with the terminals 6 of the power electrical network. The output of the power supply unit 1 is connected to the power terminals of the time delay circuit 2, the control circuit 3, the HE 8 circuit and the high frequency generator 9. The output of the electronic switch 4 is connected to the terminals 7. The time delay circuit 2 is connected to the output stage of the control circuit 3. The control circuit 3 input connected to the output of the NOT circuit 8. The output of the control circuit 3 is connected to the control electrodes of the electronic switch 4. The input of the HE circuit 8 and the output of the high-frequency generator 9 are connected in parallel

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through isolating capacitors with terminal 5.

The power supply unit 1 is a step-down transformer and bridge rectifier circuit and is designed to power all the circuits and blocks of the device.

The time delay circuit 2 consists of a capacitor and an adjustable resistance and is connected to the output transformer of the last stage of control circuit 3. The values of the resistance and capacitance of the capacitor determine the required delay time for switching off the welding source.

The control circuit 3 is a thyristor phase control circuit and provides the formation of pulses of the required size and the possibility of controlling their phase to control the power thyristors of the electronic switch 4,

The electronic switch 4 is assembled on the power thyristors according to the scheme of counter-parallel connection and is intended for connecting and disconnecting from the mains a welding power source. If the welding power source is single phase, then two oppositely connected thyristors of the electronic switch are included in the phase, which are read by passing the maximum current under load and the effective mains voltage. If the welding power source has a three-phase power supply, then another same pair of thyristors is connected to the second phase, and the third phase wire is connected directly to the welding power source.

Terminals 5 are used to connect the input of the HE 8 circuit and the output of the high-frequency generator 9 to the output terminals of the power supply, and hence to the welding electrode and the workpiece to be welded.

Terminals 6 are used to connect a 1 h electronic switch 4 device to the power supply unit.

Terminals 7 are designed to supply the mains voltage from the output of the electronic switch 4 to the input of the welding power source.

A HE 8 circuit assembled on a single transistor ensures the correct functioning of the device depending on the presence or absence of a control signal — a sawtooth high-frequency voltage at the output terminals of the welding power source. The input of the circuit NOT 8 is protected from welding voltage from the output of the power source by isolating

capacitors transmitting only the high frequency control signal.

The high frequency generator 9 is a sawtooth generator

voltages producing pulses with a frequency of 30–150 kHz. The use of a high-frequency generator of a sawtooth voltage is due only to the simplicity of its design, stability

0 and reliable operation. The lower limit in frequency is due to the magnitude of the inductive resistance of the welding power source, and the upper limit is due to the need to exclude the generator in the range

5 radio frequencies and radio interference. The amplitude of the sawtooth voltage was selected ii3 for calculating the creation of a voltage drop on the inductive resistance of the welding power source (and therefore on its output terminals) sufficient for the NOT 8 circuit to operate. A separation capacitor designed to pass only high-frequency pulses protects the generator output from the low-frequency

5 voltages from the output terminals of the welding power source.

The device works as follows.

When the mains is turned on, the network voltage is set to the electronic switch and power supply unit. Since the power thyristors of the electronic switch are in the locked state (voltage is not supplied to the control electrodes), the welding

5, the power supply remains off, the voltage from the power supply unit is supplied to all circuits and blocks of the device. The high-frequency generator produces sawtooth pulses that create

0 inductive resistance of the welding power source voltage drop. It is fed to the input of the circuit NOT, the output of which will not have voltage, and therefore the control circuit connected to it is not

5 will produce control pulses and therefore the power thyristors of the electronic switch will be locked. The capacitor of the time delay circuit is almost instantly charged when the device is turned on due to the low resistance of its charging circuit, the time delay circuit will be ready for operation,

When the electrode contacts the component, the high-frequency generator signal goes through a low contact resistance, without creating a significant voltage drop. A voltage is NOT input to the circuit, which means that a voltage appears on its output, including the control circuit. The pulses developed by the control circuit open the power thyristors of the electronic switch and the mains voltage is supplied to the welding power source, including it. When the electrode is withdrawn from the part, a welding arc is excited, through which the output of the high-frequency generator still closes and the welding power source remains switched on. If, when the electrode is removed from the part, the arc is not energized or energized and interrupted, the discharge of the capacitor of the time delay circuit will ensure the operation of the control circuit, and therefore keep the welding power source on for a specified time and you can re-energize the arc and continue welding. The power-off delay time can be adjusted by changing the resistance value in the capacitor discharge circuit of the time-delay circuit. Since the control circuit allows (using a potentiometer) to control the phase of the pulse supply, and thereby change the phase of switching on the power thyristors, it is possible to smoothly adjust the welding mode.

At the end of welding or a long break, the electrode is retracted from the part and the welding arc is cut off. The pulses of the high-frequency generator (as when switching on the mains voltage at the beginning of operation) create a voltage drop on the inductive resistance of the power source, which is fed to the input of the NOT circuit. At the output of the circuit, the voltage does NOT disappear and after a predetermined time delay the control circuit ceases to supply control pulses to the power thyristors of the electronic switch. The thyristors are closed and the welding power source is disconnected from the mains. The device will return to its original state. If it is necessary to resume work, it is necessary, as before, to close the electrode to the product, the welding power source will be turned on, and the removal of the electrode can initiate a welding arc.

Compared with the known, this device has a wide range of applications, since it can be used for automatic switching on and off of welding sources of both alternating and direct current (welding transformers, rectifiers, generators), since the high-frequency generator when switched on the welding power source is closed through the low-resistance circuit of the electrode component or the electrode-arc-component, and when it is turned off, it creates a voltage drop (which is a control signal) at a high inductive resistance ivlenii which have all welding power sources and their nature is not critical current (variable or constant low frequency welding current and voltage dividing capacitors are passed and not in creating a control signal is not involved in the scheme of the device),

The use of an electronic switch on the thyristors in the device makes it possible to smoothly control the welding mode by changing the phase of the supply of control pulses with a change in the value of the adjustable resistance in the control circuit. In addition, the use of an electronic switch determines its high speed, reliability, durability. The speed of the device is also increased due to the instantaneous operation of the device at the first contact of the electrode with the part. The high speed and lack of time at switching on reduces the power consumed by the welding power source at idle.

Claims (1)

Claims for automatically switching on and off a welding power source consisting of a power supply unit, a time delay circuit, an electronic switch control circuit and a high-frequency generator, the power supply input and the electronic switching input connected in parallel with the power electrical network terminals, the power supply output connected to the power terminals, control circuit and high-frequency generator, the output of the electronic switch is connected to the input of the welding power source, The output of the control circuit is connected to the control electrodes of the electronic switch, characterized in that, in order to expand the scope of application, smooth adjustment of the welding mode, reduction of power consumption, increase in speed, reliability and durability, it is equipped with a NOT circuit, the output of the power supply unit is additionally connected with the power terminals of the time delay circuit and the NOT circuit, the time delay circuit is connected to the control circuit, the control circuit input is connected to the output of the NOT circuit, and the circuit input is NOT and the high-frequency output A generator is connected in parallel with the output of the welding power source. five