SU1719167A1 - Device to excite and stabilize alternating current welding arc - Google Patents

Abstract

The invention relates to welding equipment and can be used in power sources of an AC arc for energizing and stabilizing it. The purpose of the invention is to improve the quality of the welded joint by improving the excitation and stability of the arc. To do this, a multiplication circuit was introduced into the device for exciting and stabilizing the AC welding arc, which contains a welding and pulse transformer, a switching thyristor and a threshold element, and a pulse transformer with additional winding, using a multiplying circuit in a storage capacitor and switching capacitor the threshold element allows an increase in the air gap breakdown voltage of the electrode product. 1 il ..

Description

The invention relates to arc welding technology and can be used in power sources of an AC arc for its excitation and stabilization.

A device for driving an arc comprises a step-up transformer, a storage capacitor, a switching element with a control circuit, a capacitor, and a limiting element. The circuit is single-stage, there is no impulse, saturating transformer and high-voltage transformer, which reduces the level of electrical disturbance, size and weight, and ensures the constant amplitude of the voltage of the output high-voltage pulses.

The disadvantage of this circuit is power supply from a separate input of the network, and not from a welding transformer. The circuit does not provide for the regulation of the arc excitation pulse depending on the brand or diameter of the electrode, the type of protective medium.

A device for stabilizing an AC welding arc is known, comprising a transformer, a half-wave charging circuit, a choke, a discharge thyristor and a control circuit with a peak transformer and a current transformer, an adjustable DC source. The use of a peak transformer / made with the auxiliary bias winding and the introduction of an adjustable DC source allows changing and adjusting the moment of supply of a stabilizing pulse, improving the arc stabilization.

The drawback of the circuit is also its power supply from a separate input of the network in the absence of feedback to the power source, the range of the supply voltage is limited.

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Closest to the proposed device is a device for stabilizing AC curdles, fed from a cooking transformer, contains two heating capacitors, a current-limiting element, an auxiliary transformer, a switch, a threshold element, and two diodes. This device is designed as a remote unit, feeding the welding transformer and welder located at the workplace due to the inclusion of capacitors in the shoulders of the bridge, the voltage doubled across the primary winding of the auxiliary transformer is doubled. Such a circuit solution allows the pulse amplitude to double, resulting in an improved arc stability.

The disadvantage of this solution is the impossibility in this circuit of serial connection to the auxiliary transformer of a large number of capacitors for the case when the voltage supplied to the primary circuit is insufficient to initiate the arc. The switching device does not allow for the regulation of the supply voltage, limiting the range of use of a particular stabilizer for different types of electrodes or protective environment.

The purpose of the invention is to improve the quality of the welded joint by improving the excitation and stability of the arc.

The goal is achieved by the fact that a multiplying circuit is additionally introduced into the device containing a welding pulse transformer, a switching thyristor and a threshold element, and the winding of the pulse transformer is connected parallel to the secondary winding of the welding transformer, a. The cathode of the switching thyristor, the anode of which is connected to the output of the secondary winding of the transformer, is connected to one end of the secondary winding of the pulse transformer, the threshold element is connected to the control electrode of the thyristor. In addition, the pulse transformer is provided with an additional winding and a multiplication circuit in the form of a diode-capacitor circuit, the inputs of the multiplication circuit are connected to the secondary windings of the welding transformer, and the output end of the secondary winding of the pulse transformer. The additional winding of the impulse transformer is shunted by a capacitor, one end of which is connected to the cathode of the switching thyristor, and the other end is connected to the control electrode of the thyristor through a threshold element. An increase in the discharge voltage from storage capacitors to the low-voltage winding of a pulse transformer gives the voltage on the high-voltage winding 2 times higher than in similar devices. The threshold element, having an adjusting resistance, allows

expose the voltage to open the switch thyristor over a wide range depending on the required welding modes. All this increases the stability of the welding arc and improves the quality

weld seam.

The drawing shows a diagram of a device for exciting and stabilizing an AC arc.

The device contains a welding transformer 1, a pulse transformer 2, a switch consisting of a thyristor 3, a threshold element consisting of a diode 4, a limiting 5 and an adjusting resistors / storage capacitors 7,

included in the capacitor-diode circuit 8 according to the multiplication scheme. The additional winding of the pulse transformer 2 is connected to the cathode of the switching thyristor 3 and to the threshold element consisting of a diode 4, a limiting 5 and a variable 6 resistors. The voltage multiplier 8 is connected to the secondary winding of the welding transformer 1. Connecting the circuit to the low-voltage source of the welding source reduces the electrical safety of the device and takes it directly to the welding torch.

At the time of turning on the welding

the voltage source is applied to the electrode 9 and the product 10 and is supplied to the capacitor-diode chain 8, while the storage capacitors 7 are charged before the voltage

K Uxx

U0

0.85

where K is the number of cascades of multiplication;

Uxx is the no-load voltage of the welding arc.

In the above scheme, U0 4UXx, and the time to reach this voltage is achieved in two periods of the mains supply.

The no-load voltage flows through the pulse transformer 2 to the additional winding, and from it to the anode of diode 4, from the cathode of diode 4 through the limiting 5 and adjusting resistors to the control electrode of the switching thyristor.

If the voltage on the control electrode of the thyristor 3 exceeds the opening voltage, the anode-cathode transition of the thyristor 3 opens and the storage capacitors 7 are discharged to the winding of the pulse transformer, at the output of which a high-voltage pulse is generated. When the arc is energized, the voltage on the secondary winding decreases, which leads to a decrease in the voltage between the cathode and the control electrode of the thyristor 3 and it closes. The storage capacitors 7 are charged to a voltage lower than idle. This pre-voltage reduces the output time of the storage capacitors 7 to the required voltage. The device operates at the time of initiation of the arc and turns on automatically at the time of ignition and stabilization (at the breakage) of the arc. By supplying a higher voltage pulse transformer 2 to the input, stability of the arc on the low voltage arc is ensured.

The use of a multiplication circuit in the storage capacitor circuit and the switch that controls the threshold element allows a significant increase in the air gap breakdown voltage - product. This increases the likelihood of arcing the arc. A threshold element with an adjustable voltage to open the thyristor switch allows you to adjust the supply voltage of the stabilizing high-voltage pulse.sec. As a result, the arc stability is improved, and hence the quality of the seam is improved.

Claims (1)

Claims. A device for excitation and stabilization. alternating current arc welding system, containing a welding transformer, in parallel with the secondary winding of which includes a pulse winding of the transformer, to one end of the secondary winding the cathode of the switching thyristor, the anode of which is connected to the output of the secondary winding of the welding transformer, is connected to the control electrode of the switching thyristor, a pore element, characterized in that a multiplication circuit is introduced, and the pulse transformer is made with an additional winding, while the inputs of the multiplication circuit are connected to the terminals of the secondary winding of the welding transformer, and you the course of the multiplication circuit is connected to the other end of the secondary winding of the pulse transformer, one end of the additional winding is connected to the threshold element, and the other end of the additional winding is connected to the cathode of the switching thyristor.