RU2103760C1 - Welding transformer - Google Patents

Abstract

FIELD: electrical engineering, equipment for AC arc welding. SUBSTANCE: welding transformer has bar magnetic core, primary winding put on first bar and secondary winding arranged on second bar which has section amounting to 0.5-0.8 section of first bar. Secondary winding is saturated when transformer operates under no-load condition. Capacitor compensating reactive component of current consumed by transformer may be placed between leads of primary winding. EFFECT: reduced mass of welding transformer. 2 cl, 1 dwg

Description

 The invention relates to electrical engineering, in particular to equipment for arc welding with alternating current.

 The prior art welding transformer containing a magnetic circuit with cores on which the primary and secondary windings are located, and the secondary winding consists of two parts, one of which is located on the movable core, and the other on the stationary [1].

 The fixed core, on which part of the secondary winding is located, is made saturable and has a smaller cross section. This allows you to increase the steepness of the front of the voltage rise in the arc gap and, accordingly, increase the stability of the arc. However, the transformer has large mass and dimensional indicators, since the total cross section of the steel covered by the parts of the secondary winding remains equal to (or large) the cross section of the steel covered by the primary winding.

 To reduce the mass-dimensional characteristics of the welding transformer, the entire magnetic circuit, on which the primary and secondary windings are located, can be made saturated [2].

 In this case, a choke should be included in the primary circuit of the transformer, limiting the no-load current. The aforementioned inductor is located on a separate magnetic circuit and is an additional structural unit, which also has significant mass and dimensional characteristics.

 Currently, welding transformers having rod magnetic circuits with spaced windings [3] are most widely used. This is due to the fact that rod-type transformers have greater efficiency, lower consumption of active materials and are technologically advanced to manufacture. A transformer of this design is taken as a prototype. However, currently commercially available transformers, as a rule, have large dimensions and weight and are not intended to be connected to a household AC network.

 The aim of the invention is the creation of a welding transformer having a small weight and dimensions and not creating a large load on the network.

 The goal is achieved in that in a welding transformer containing a core magnetic circuit, a primary winding located on the unsaturated first core of the magnetic circuit, and a secondary winding completely placed on the second rod, the second core of the magnetic circuit is made saturated and has a cross section of 0.5-0.8 section of the first rod. This ratio of the cross sections of the rods is optimal and follows from the ratio of the voltage of stable burning of the arc to the voltage necessary for its ignition. That is, the cross section of the second rod is sufficient to ensure the normal operation of the transformer in welding mode, and the cross section of the first rod is sufficient to limit the idle current of the transformer at the required level.

 To reduce the reactive current consumed by the transformer from the network, a capacitor can be connected in parallel with the primary winding. With the transformer described above, the capacitance of the capacitor can be selected based on the compensation condition of the inductive component of the current both in welding mode and in idle mode. That is, both in the welding mode and in the idle mode, the capacitor and the primary winding covering the unsaturated portion of the magnetic circuit connected in parallel have a large complex resistance. This makes it possible to connect the capacitor directly to the terminals of the primary winding (and not through any protective switching device that disconnects it when the transformer is idling). It is advisable to choose the capacitor capacity from the condition that the current flowing through it is 0.3-0.8 of the current flowing in the primary winding of the transformer in the short circuit mode. This is because the reactive current during the welding process is 0.3-0.8 short-circuit current. The indicated choice of capacitor capacitance makes it possible to almost completely compensate for the reactive component of the current flowing through the primary winding in welding mode.

 The current flowing through the transformer in idle mode depends on the cross sections of the sections of the magnetic circuit. The cross section of the second rod and the sections connecting the first and second rods should be such that the current flowing through the capacitor is 0.3-0.8 current flowing in the primary winding of the transformer in idle mode. In this case, the capacitive current consumed by the capacitor selected on the basis of the condition specified in paragraph 2 of the formula is compensated by the first harmonic of the inductive current flowing in the primary winding in idle mode and is 0.3-0.8 of the current value of the open circuit current .

 Thus, the distinguishing features of the invention can reduce the mass of the transformer, the current consumed by it and increase the power factor.

 The drawing shows the proposed welding transformer.

 The transformer comprises a core magnetic core 1, a primary winding 2 located on the first rod 3 having a cross section S1, and a secondary winding 4 located on the second rod 5 having a cross section S2. From a technological point of view, it is advisable to use a split tape magnetic circuit, which must be performed in such a way that the ratio S2 / S1 is 0.5-0.8. It is possible to reduce the cross section of both the second core of the magnetic circuit and the sections connecting the first and second rods (shown in dashed lines in the drawing). Between the terminals of the primary winding 2, a capacitor 6 can be included.

 The transformer operates as follows.

 In idle mode, the current flowing in the primary winding 3 creates a magnetic flux in the magnetic circuit 1, the magnitude of which is sufficient to saturate a section having a section S2, and insufficient to saturate a section having a section S1. Since part of the magnetic circuit 1 is not saturated, the primary winding has an inductive resistance sufficient to limit the current consumed by the transformer from the network at a given level. In welding mode, the current flowing in the secondary winding of the transformer creates a magnetic flux in the magnetic circuit 1, compensating for the magnetic flux generated by the primary winding. In this case, the portion of the magnetic circuit having a smaller cross section leaves the saturation state. The capacitor 6 allows you to reduce the reactive component of the current consumption and increase the power factor of the transformer.

Claims (3)

 1. A welding transformer containing a core magnetic circuit, a primary winding located on the unsaturated first core of the magnetic circuit, and a secondary winding completely placed on the second rod, characterized in that the second core of the magnetic circuit is made saturated and has a cross section of 0.5 to 0.8 sections first rod.  2. The transformer according to claim 1, characterized in that a capacitor is connected directly between the terminals of the primary winding, the capacitance of which is selected from the condition that the current flowing through it is 0.3 0.8 of the current flowing in the primary winding of the transformer in the short-circuit mode short circuits.  3. The transformer according to claim 2, characterized in that the cross section of the second rod of the magnetic circuit and the sections connecting the first and second rods are selected from the condition that the current flowing through the capacitor is 0.3 to 0.8 of the current flowing through the primary winding of the transformer in idle mode.