RU2306212C2 - Power supply source for mechanized welding - Google Patents

Abstract

FIELD: units of electric equipment, namely transformers and rectifiers for power supplying to welding electric arc at mechanized and automatic gas-shield welding and at automatic welding under flux layer.

SUBSTANCE: power source includes power transformer with constant outer characteristics and saturation choke whose windings are connected in series with windings of power transformer. A part of magnetic circuit of saturation choke is made with possibility of motion relative to its remaining stationary part without cutting off magnetic circuit of choke and without forming air gap. Mutual displacement of parts of magnetic circuit changes working cross section of magnetic circuit and therefore saturation phase of magnetic circuit.

EFFECT: simple and reliable process for regulating outlet voltage of power source.

2 dwg

Description

The invention relates to elements of electrical equipment, in particular to transformers and rectifiers for powering the welding arc during mechanized and automatic welding in a protective gas environment, as well as in automatic submerged arc welding. The claimed invention may also find application as a power source with hard (sloping) external characteristics in electrotechnological installations or in an electric drive, etc.

A known transformer with dipping external characteristics for automatic submerged arc welding (Arc welding equipment. A reference manual edited by V.V.Smirnov. - L .: Energoatomizdat, 1986, p.375), consisting of a power transformer and two counter - parallel connected thyristors included in the circuit of its primary winding. The voltage at the output terminals of the transformer is regulated by changing the phase of turning on the thyristors. The use of such transformers and other thyristor arc power sources with relatively expensive electronic equipment is justified under increased requirements for the stability of the welding process and its controllability.

Known rectifier with dipping external characteristics during mechanized welding in a protective gas environment, consisting of a three-phase power transformer, rectifier bridge and smoothing inductor. To regulate the operating voltage, the power transformer is configured to change the number of turns of the primary winding using switches. A greater number of turns of the primary winding corresponds to a lower value of the operating voltage of the rectifier.

Such a rectifier is cheap and reliable enough, but has several disadvantages. When operating at maximum power, at the highest voltage of the rectifier load, a significant part of the turns of the primary winding is not used, sectioning of the winding is associated with an increase in the rated power of the transformer (Paton B.E., Lebedev V.K. Electrical equipment for electric arc and slag welding. - M .: Engineering, 1966, p. 317), with unproductive losses of winding copper and transformer steel. Another significant drawback of the rectifier with a change in the number of turns of the primary winding of the transformer is the inability to smoothly control the operating voltage. The number of taps from the primary winding is limited by the volume of switching equipment and the technological complexity of the taps.

Smooth (stepless) regulation of the operating voltage is achieved in the rectifier for welding in protective gases of the VDG series (Zaks MI Welding rectifiers. - L .: Energoatomizdat, 1983, p.39 and p.70.), Equipped with a saturation inductor and adopted as a prototype.

Like the rectifier with a partitioned primary winding discussed above, it contains a three-phase power transformer, a rectifier bridge, and a smoothing inductor, however, in the prototype, a working winding of the saturation inductor is connected in series with each of the six rectifier bridge diodes. Each working winding has its own closed magnetic circuit; all six magnetic circuits are covered by a single control winding. It is known that in a three-phase rectifier with a bridge rectification circuit, each of the bridge diodes conducts current for 1/3 of the mains voltage period. During this time, called the working interval of the saturation inductor, the magnetic circuit, the working winding of which is connected to a conductive diode, is saturated with the load current passing through the winding. In the absence of a control winding current, all six saturable inductor magnetic cores will be in a short time after the transformer is turned on to the load in a saturated state, the reactance of the working windings will be close to zero, and all the voltage of the transformer secondary windings rectified by the bridge will be on the load. If, however, a current is passed through the control winding, the direction of which will be opposite to the direction of the current of the working winding, then at the time intervals corresponding to the closed state of the bridge diodes (control intervals), the saturation inductor magnetic circuits will be magnetized and the more intense, the greater the value of the control winding current.

With an increase in the control current, an increasing part of the working range of the inductor will be spent on magnetization reversal of the magnetic circuit steel and, accordingly, a smaller part of the voltage of the windings of the power transformer will be applied to the load. We can say that the current of the control winding of the inductor sets the moment or phase of saturation of each of the six magnetic circuits of the saturation inductor, determining the value of the operating voltage of the rectifier.

The disadvantage of the prototype is the complexity of manufacturing a saturation inductor, its bulkiness. For symmetrical control of two half-periods of each phase of the supply voltage, the saturation inductor, like any magnetic amplifier, must have two magnetic cores and two working windings for each phase.

Thus, we see that in the known designs of welding power supplies with damping external characteristics, the operating voltage is regulated either stepwise, by mechanical switching of the number of turns of the windings of the power transformer, or smoothly, by controlling the phase of switching on (saturation) of the electronic or electromagnetic key elements.

The basis of the invention is the task of creating a welding power source with dipping external characteristics, in which the smooth regulation of the operating voltage is provided by simple and reliable mechanical means.

The problem is solved due to the fact that the proposed power source for mechanized welding, as well as the known one, contains a power transformer with a rigid external characteristic, and a saturation inductor, the windings of which are connected in series with the windings of the power transformer. But in contrast to the known in the proposed power source, at least one part of the saturation inductor magnetic circuit is made with the possibility of mechanical movement relative to the rest, stationary part of the magnetic circuit, without breaking the magnetic circuit of the inductor by an air gap.

This design of the inductor allows you to mechanically change the cross section of the section of the magnetic circuit of the inductor and thus control the moment (phase) of saturation of the magnetic circuit.

The set of features set forth in paragraph 2 of the claims characterizes a power source in which the moving part of the magnetic circuit of the saturation inductor is moved using a screw mechanism, the running nut of which, for example, is rigidly connected to the moving yoke of the magnetic circuit, and the screw is connected to fixed rods on which throttle working windings are located.

The set of features set forth in paragraph 3 of the claims characterizes a device in which the moving part of the magnetic circuit of the saturation reactor is made of material with a rectangular hysteresis loop.

The invention is illustrated by drawings, on which:

Figure 1 is an external view of a single-phase saturation inductor, load voltage diagrams for three positions of the moving part of the inductor magnetic circuit and a simplified circuit diagram of a welding transformer with a saturation inductor.

Figure 2 is a simplified schematic diagram of a three-phase welding rectifier with a saturation inductor and the appearance of a three-phase saturation inductor.

The throttle with mechanical regulation has a winding 1 mounted on a fixed part of the magnetic circuit 2 (figure 1). The upper yoke of the magnetic circuit 3 is movable, with one degree of freedom - along the axis of the thrust 4.

The design of the magnetic circuit ensures the movement of its moving part relatively stationary without the formation of air gaps that can affect the parameters of the magnetic circuit of the inductor. This result can be obtained through the use of stamped U-shaped plates in the fixed part of the magnetic circuit and grinding of the end surfaces of its moving part.

In figure 1, d, the winding of the inductor 1 is connected in series with the secondary winding of the power transformer 5, but it can be connected in series with its primary winding. The number of turns of the winding should be increased n times, where n is the transformation coefficient; accordingly, the required cross-section of the winding wire is reduced n times.

Figure 2, a shows the appearance of the saturation inductor of a three-phase rectifier. The fixed part 2 of the magnetic circuit is made in the form of a package of stamped W-shaped plates, three phase windings of the inductor W _a , W _b , W _{c are} installed on the rods of the package. The upper yoke of the magnetic circuit is made in the form of two moving parts 3 connected by a common rod 4, with the possibility of moving along the axis of the rod without the formation of air gaps between the fixed 2 and the moving 3 parts of the magnetic circuit. The inductor windings are included in the secondary winding circuit of the power transformer 5, as shown in the circuit diagram (Fig. 2, b).

The power source operates as follows. When connecting the output terminals of the source to the load, the voltage of the secondary windings of the power transformer is distributed between the load and the windings (winding) of the saturation inductor in proportion to their resistances. The reactance of the inductor winding until its magnetic core is saturated is large, and only a small magnetization current of the inductor flows in the load. At the time of saturation of the magnetic circuit, indicated in Fig. 1 as the switching phase φ, the magnetic permeability of the steel of the magnetic circuit drops sharply, the reactance of the winding jumps to a value close to the value of the active resistance of the winding. All voltage of the secondary winding of the transformer is supplied to the load.

The flux in the magnetic circuit of the inductor, given by the voltage applied to the winding and the number of its turns, is constant in all parts of the magnetic circuit, and the flux density, magnetic induction is inversely proportional to the steel cross section in the magnetic flux path. Consequently, the saturation of the steel of the magnetic circuit occurs in that section where the cross section is minimal. Extending a part of the magnetic circuit and thereby reducing the real cross section on the magnetic flux path, it is possible to control the saturation moment, i.e. the moment of "break" of the magnetic circuit and a sudden drop in reactance of the inductor (figure 1). The speed of switching the voltage of the winding of the power transformer from the inductor winding to the load at the time φ of saturation of the moving section of the magnetic circuit is determined by the degree of rectangularity of the hysteresis loop of the material from which this section is made. With a rectangular hysteresis loop, the magnetic permeability of the saturated magnetic core is close to air permeability, voltage switching occurs almost instantly (dashed line in figure 1). This result can be achieved by performing movable sections of the magnetic core from permalloy or very thin electrical steel. Quite satisfactory results are also obtained by electrical steel of general application.

A saturation inductor with control of the moving part of the magnetic circuit, which does not need a DC winding (control winding), is absolutely symmetrical in AC circuits, the processes in it do not depend on the direction of the current in the working winding.

Power supplies with a saturation reactor controlled by the moving part of the magnetic circuit are simple to manufacture and reliable in operation. The welding properties of the experimental power source for a rated current of 300 A, in which the proposed invention is implemented, are not inferior to the welding properties of the VDG-313 power source, adopted as an analog.

Claims (1)

A power source for mechanized welding, comprising a power transformer with a rigid external characteristic and a saturation inductor, the windings of which are connected in series with the windings of the power transformer, characterized in that at least one part of the saturation inductor magnetic circuit is made with the possibility of mechanical movement relative to the rest of the fixed part of the magnetic circuit without breaking the magnetic circuit of the throttle.

Images