SU55641A1 - Three Phase Welding Transformer - Google Patents

Description

When working on a welding transformer, to maintain the correct operating mode, it is necessary to obtain a stable electric arc. Arc stability depends on a number of factors. One of the factors that ensure continuous and stable arc burning is an increase in inductance in the arc circuit, which leads to a strong increase in phase angle. Experiments show that for the continuous arc burning, cos should be no more than 0.35-0.45.

As is known, after passing a voltage curve through a zero value, the current between the electrode and the workpiece is not established immediately, but after a certain period of time. During this time, the voltage from zero increases to the arc ignition voltage. In order to obtain a stable welding arc and a stable thermal welding process, it is necessary to strive to reduce the recovery time of arc ignition voltage. This can be achieved by non-sectoral methods: an increase in the no-load voltage of the welding transformer, an increase in the frequency of the welding current, or the imposition of a third harmonic wave on the fundamental wave.

The increase in the no-load voltage of the welding transformer has a number of significant drawbacks: the power consumption increases significantly; the power factor decreases sharply; It is difficult, according to safety regulations, the work of the attendants.

The method of high-frequency current welding is not yet widely used in practice due to the absence of structurally simple and cheap equipment.

The present invention aims to reduce the ignition voltage recovery time by using the third of the above methods, i.e., by leaning on the main wave of the secondary voltage of the third harmonic.

The invention consists in the specific form of the implementation of a three-phase transformer, which allows to obtain the resulting voltage at the arc terminals, the curve of which has a saddle in the middle part of the half-wave and an increased value but edges.

In the drawing fng. 1 shows a curve, 1c of the voltage of the proposed transformer, and FIG. 2nd scheme.

As can be seen from the FNG. 1 of the drawing, the curve of the resultant voltage of the traEuformer when going through a zero value has a steeper rise than a usual sinusoid of the same non-periodicity.

This circumstance leads to a decrease in the recovery time of the arc ignition voltage and to a stabilization of the welding mode. The value of the no-load voltage is under normal conditions, which is the positive side of the proposed method.

The author notes that his studies of this method showed that the most optimal mode is obtained when the amplitude of the third harmonic is 40-

50,

from the amplitude of the main sinusoid. To obtain the same effect with the method of increasing the idle speed, the latter would need to be increased 2-2.5 times, as the calculations show, which is extremely uneconomical.

To obtain indicated on the fng. 1, the shape of the resulting voltage curve, the author uses a three-phase 111 .1Y transformer with a four-core magnetic circuit {Fig. 2). On the fourth additional core of the transformer there are two single-phase windings in which a triple frequency voltage is induced; These windings are connected in series with the two phases of the main secondary winding, which are connected to the electrodes. Phase, going directly to the metal, has no additional winding.

Since triple frequency electromotive forces are induced in additional windings, this three-phase transformer circuit ensures the fulfillment of the above conditions, i.e., it reduces the recovery time of arc ignition only in working arcs between the electrodes and the metal, because the arc has only one place electrodes, plays a secondary role. The time for the recovery of voltage on this arc to be left ordinary without any damage to welding; O process.

The subject is invented and.

A three-phase welding transformer for welding with two electrodes, with a secondary voltage containing, in addition to the main wave, a harmonic wave, characterized in that, in order to increase arc stability, two single windings on the fourth terminal of the transformer are: the triple frequency voltage is connected in series with two: the phases of the main secondary winding: so that the shape of the resulting voltage at the arc arc has a saddle in the middle part of the half-wave and is equal to Niemi tzo edges.

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