Improving the performance of welding machines. Scheme, description

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Improving the performance of welding machines. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / welding equipment

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Several schemes of home-made welding machines have been published on the pages of the magazine. The changes proposed by the author are aimed at improving their input and output characteristics. The main elements of welding machines are single-phase transformers and valves, with the help of which one-sided current flow in the load circuit is ensured, as a result of which the alternating voltage is converted into a pulsating one.

The operation of such rectifiers shows that DC welding electrodes do not ensure the quality of the weld and it is difficult to form an arc. To smooth out the ripples of the rectified current, a smoothing filter is connected to the output terminals of the rectifier, which reduces the ripples to the level required by the operating conditions of the welding electrodes.

Smoothing filters are made on reactive elements in the form of chokes and capacitors. The inductive filter is used in rectifiers of medium and high power, as it allows to ensure the continuity of the current in the load circuit and a favorable operation of the rectifier. In powerful rectifier installations, the use of filters with a capacitive input link worsens the shape of currents in valves and transformer windings, which leads to an increase in losses in them and an increase in installed power, and a deterioration in the harmonic composition of the supply network [1]. In addition, the capacitive input link leads to oscillatory phenomena in the load circuit, and at resonance - to a sharp drop in the current consumed from the network [2], the variable component of the current increases in the load circuit, which reduces the quality of filtering. Shunting the inductor with a valve [3] leads to the fact that the energy accumulated by the inductance at the moment the valves are closed is discharged on it, i.e. wasted uselessly.

These shortcomings can be eliminated by eliminating the capacitor bank and turning on the auxiliary valve VD, as shown in the figure, which significantly improves the properties of the welding rectifiers.

Improving the performance of welding machines

Due to the presence of the VD valve, the welding arc during the period of time when the main valves are closed is fed by the energy stored by the inductance of the choke. Thus, the auxiliary valve works as a regenerative valve, transferring energy to the load. This reduces the reactive power consumed from the network, and consequently improves the power factor of the welding machine. Resistor R, connected in parallel with the welding arc, reduces the overvoltage at the output terminals of the device, if necessary, to interrupt the arc. The operation of welding machines according to this scheme showed stable ignition and burning of the arc when using electrodes for DC welding, including stainless steels.

References:

Chizhenko I.M., Rudenko Z.S., Senko V.I. Fundamentals of converting technology. - M.: Higher. school, 1974. - 440 p.
Bogaditsa D. Household welding machine//Radioamator. - 2003. - No. 5. - S.2021.
Bogoslavets L. Voltage regulator of the welding machine//Radioamator. 2003. - No. 9. - P.20-21.

Author: A.N. Baskakov

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