JPS59103317A - Large current 3-phase electric circuit - Google Patents

Abstract

1. An arrangement for the transmission of large electrical outputs comprising large currents with small voltage differences from a transformer to an adjacent load, for example a steel melting furnace or an electrolytic bath, by means of a three-phase power line comprising conductors which have a wide cross-section in relation to their thickness, characterised in that all the conductors (10, 15, 17, 18) of the three-phase power line from the transformer windings (5, 6, 7) to the load In the region of the winding output lines (10 to 15) and also in the region of an outlet (16) through the transformer casing (9) and also in a subsequent conductor section have their broader faces respectively opposite one another with adjacent conductors (10, 15, 17, 18) mutually overlapping over their full width, and in that the width of the conductors (10, 17, 18, 15) approximately equals the height of the winding in the transformer.

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] This invention relates to the application of large currents from a transformer to an adjacent load, such as a steel melting furnace or an electrolytic cell, through a conductor that is very wide in cross section compared to its thickness. It is concerned with high-current three-phase circuits for conducting low-voltage high-power.

[Prior art and its problems]

Electrical circuits for such applications are, for example) w-on (Tranaformato)
Trafo-Brief 7, published in April 1978 by Ren Union AG
829, page 2, the individual conductors are usually constructed so as to form approximately the edges of a triangular prism. In this case, a rotating leakage field is generated on the outside of the plate or tube conductor. Therefore, surrounding the entire circuit with metallic or conductive sheaths should be avoided. This is because the braking sheath is considered to be a short-circuited rotor with an externally fixed current carrying a constant starting current.

Generally, in consideration of the large converted power, transformers that supply power to a steel melting furnace or the like are oil-cooled. The functional parts of such a transformer are therefore assembled in an oil-filled tank, and the winding lead-out conductors have to be led out through the side walls thereof. Also in this bushing portion, the conductor has a very wide width compared to its thickness. The wide sides of the conductor are parallel to each other since the winding axes themselves are parallel), and at the same time the center of gravity of the conductor cross section forms the vertex of an approximately equilateral triangle, so that the narrow side of the conductor in the bushing area is practically They are facing each other. This inevitably results in a highly non-uniform distribution of current over the existing conductor cross-section, resulting in severe thermal problems even at relatively small powers for such circuits. Due to the very high current densities on the opposite narrow sides of the conductors, particularly in the bushing area, strong localized temperature increases occur.

[Purpose of the invention]

This invention aims to configure an electric circuit for guiding a large current from a large voltage transformer to an adjacent large load so that the current load on all cross sections of the incorporated conductor is approximately equal while keeping the inductance of the electric path small. With the goal.

[Means for achieving the objective] This objective is such that all conductors of the electrical path from the transformer windings to the load are connected to the bushing section both at the section of the winding outlet conductor and at the section of the bushing penetrating the transformer tank wall. Also in the conductor parts, the wide sides of these conductors are positioned so that they face each other and overlap,
This is achieved by making the width of these conductors approximately equal to the height of the winding.

[Embodiments of the invention]

In an advantageous embodiment of the invention, the winding lead conductor of the low-voltage winding on the end core leg, which is close to the central core leg, is connected to the lead conductor of the low-voltage winding on the central core leg located on this conductor side. At the same time, the lead conductors on the transformer end side of each low-voltage winding on the end core leg are individually led out through the transformer tank wall, and are conductively coupled to each other near the load circuit of the load device to form a triangular shape. By forming the third apex of the connection, the low voltage windings that feed the three-phase circuit are triangularly connected. In this case, the ratio of the width to the thickness of the conductors is preferably between 50 and 150, in particular 100, and the mutual spacing of the conductors is preferably greater than the thickness of these conductors.

In a further advantageous embodiment of the invention, in which no external magnetic field is generated, the two external conductors are connected to each other on the upper and lower sides by means of a conical closure strip and the other two A tube is formed surrounding the two conductors, through which a cooling medium flows.

In another advantageous embodiment of the invention, the individual conductors are assembled by a plurality of tubes through which the cooling medium flows in electrically parallel and spatially parallel traps, and each of the two spatially adjacent The voltage between the two conductors is made individually adjustable.

In a further advantageous embodiment of the invention, the high-current conductor is connected to a transition piece in which the four conductors are connected to three conductors with a figure-7 cross-section. The two lead conductors on the transformer end side of the windings on the end core legs are connected to the same V-shaped conductor. The ends of each V-shaped conductor are respectively coupled to a triangular plate, and the triangular plate is coupled to the connection pole of the load via a flexible conductor bundle or a series-connected tube and flexible conductor bundle. It is better.

[Embodiments of the invention]

Next, the present invention will be explained in detail with reference to drawings showing embodiments of a high current three-phase electric circuit based on the present invention.

In FIG. 1, which shows a horizontal cross-section of a transformer, the core has a central leg 1 and end legs 2, 3, with a high-voltage winding 4 located on the radially inner side and a low-voltage winding located on the radially outer side. 5.6
．． It supports 7. Low voltage side winding 5, 6.77-1. It consists of a strip plate each consisting of one turn, the width of which is equal to the length of the winding between the lower yoke 8 and the upper yoke (not shown). A yoke 8 connects the ends of the end legs 2.3 with the ends of the central leg i in a reciprocal manner. The iron core has high voltage side winding 4 and low voltage side winding a
5°6.7 is assembled in a tank with tank side walls 9 filled with oil. Winding lead conductor 10. n.

12, 13, 14 and 15 are each low voltage side winding 5. '6.7
is made by opening the extension of the winding conductor, so that the winding is formed in the same direction as the winding 5.6.7 in the axial direction.

The winding lead conductors lo to 15 pass through the tank side wall 9 via the composite bushing 16 and are led out of the tank.

At that time, the low voltage side winding 5.6. To form a triangular connection of r, the winding lead conductors 11 and 12 and 13 and 14 are respectively interconnected and further guided by a common thick conductor 17 and 18.

Outside the tank, conductors 17, 18 and winding lead conductor 1
The 0.15 extensions run parallel in space, their full widths overlapping each other. To fix this position, the conductor 17.18 and the winding lead conductor 10.15 are
Auxiliary means, not shown, press against the spacing piece 20 made of insulating material.

The winding lead conductor is captured outside the tank in a conical closure 21 to form a tube 19, which carries the voltage at the third vertex of the triangular connection, as shown in FIG. The tube 19 is also used to conduct the cooling liquid, and this circuit cooling structure further increases the operational safety of the high current circuit. If the negative first connection to be supplied is of suitable construction, the tube 19 is led together with the conductor 17.18 directly to the load.

However, since load connection devices often have a center of gravity of their connection terminals forming an equilateral triangle, a transition from the electrical circuit according to the invention to a triangular electrical circuit is necessary. For this purpose, the transition piece shown in FIG. 3.4.5 is used. After this transition piece, the semiconductor 17.18 and the tube 19, which has returned to the two bands, are each rotated by half 120', so that the conductor 17.18 and the tube 19 form a figure 7-shaped conductor 2 in cross section.
2, 23 and 24. The conductors 22, 23124 having a figure 7 cross section formed at this time are assembled into a three-light star shape.

A pulsating magnetic flux primarily occurs between the opposite legs of the conductors 22, 23, 24, while a rotating leakage field occurs outside the star and its turns. However, the star-shaped conductors 22, 23, 24 can be connected to a predetermined load via a flexible intermediate conductor without any problem. In order to connect the free ends of the conductors 22, 23, 24 to the flexible intermediate conductor, it is advantageous to provide a plate which is attached to the conductor with a figure 7 cross-section at right angles to the long axis of the high-current circuit.

〔Effect of the invention〕

In the present invention, as described above, large power with a large current and small voltage difference is transmitted from the transformer to an adjacent load, such as a steel melting furnace or an electrolytic cell, through a conductor whose cross section is very wide compared to its thickness. In high-current three-phase circuits, all conductors of the circuit from the transformer windings to the load are connected both at the winding lead-out conductor section, at the bushing section penetrating the transformer tank wall, and at the bushing section connecting to the bushing section. In this case, the wide sides of these conductors are placed opposite each other and overlapped, and the width of these conductors is made approximately equal to the height of the winding, so that the three-phase conductors are placed on their narrow sides as before. This basically eliminates the problem of non-uniform distribution of current in the conductor when the conductors are placed opposite each other. In other words, while in the past non-uniform distribution of current occurred in the width direction of the conductor, in the case of the conductor arrangement of the present invention, non-uniform distribution of current occurs only in the thickness direction of the conductor. This is because the non-uniformity of the current is reduced to a practically negligible level since the width is smaller than the width direction dimension by at least one order of magnitude.

Furthermore, in the high current three-phase circuit constructed based on the present invention, there is virtually no magnetomotive force caused by these conductors outside the space surrounded by these conductors.
Very advantageous. The magnetomotive forces in the three intermediate spaces between the conductors are then symmetrical. There is virtually no leakage outside the conductor, since the magnetic flux between the chihiro bodies with wide cross-sectional sides facing each other is well guided due to the easily generated eddy currents.

Furthermore, since there are no conductors that are mutually shifted by 120 degrees on the circumference, no rotating magnetic field is generated. As a result, in bushings constructed according to the invention in which the conductor bundle penetrates the transformer tank wall, difficulties due to stray magnetic flux do not arise up to arbitrarily high currents. Due to the symmetrical magnetic flux, symmetrical voltage drops also occur, so that the voltage drops due to the inductance in the individual conductors are also equal in absolute value. The voltage drop due to resistance in the conductor occurs in the phase of the current, supporting the symmetry of the voltage drop.

Due to such magnetic flux distribution, in this high-current three-phase circuit, the current load on all cross-sectional portions of the conductor is approximately equal to tl, especially in the bushing portion, and therefore the temperature rise is uniform and low.

The voltage drop across the inductance of the circuit according to the invention is also very small. This is because the width of a conductor is very large (as compared to its thickness), and at the same time, although the spacing between conductors is larger than the thickness of the conductors, it is extremely small when considered in absolute value. Therefore, insofar as the conductors require only a small driving voltage, the advantages of the high current circuit according to the invention arise even further, and for a given load power the rated capacity of the transformer is small compared to conventional conductor arrangements. Ru.

[Brief explanation of the drawing]

Fig. 1 is a horizontal sectional view of a transformer showing one embodiment of a high current three-phase circuit based on the present invention, Fig. 2 is a cross sectional view of the electric circuit shown in Fig. 1, and Fig. 3 is an embodiment of a transition piece. Example plan, 4th
The figure is a cross-sectional view of the transition piece shown in FIG. 3, and FIG. 5 is a side view of the transition piece shown in FIG. 3. In the drawing, 1.2.3 is the core leg, 5.6.7 is the low voltage side winding, 9 is the transformer tank wall, 10.11.12.13
14 and 15 are low-voltage side windings, 17 and 18 are conductors, 19 is a tube, 21 is a closing band, and 22, 23, and 24 are V-shaped conductors. FIG 4 FIG 5

Claims (1)

[Claims] 1) A high-current three-phase circuit for transmitting large power with a large current and small voltage difference from a transformer to an adjacent load through a conductor that is very wide in cross section compared to its thickness. , all conductors of the electrical path from the transformer windings to the load are connected, both at the winding lead-out conductor, at the bushing that penetrates the transformer tank wall, and at the conductor that connects to the bushing. A high-current three-phase electric circuit characterized in that the wide sides of the conductors are positioned so as to face each other and overlap each other, and the width of these conductors is made approximately equal to the height of the winding. 2. In the electric circuit according to claim 1, the conductor portion, which is connected to a bushing penetrating the transformer tank wall and is located such that its wide sides overlap each other, extends directly to the load. A high current three-phase circuit characterized by: 3) In the electric circuit according to claim 1 or 2, the winding lead conductor close to the center core leg of the low voltage winding on the end core leg is connected to the low voltage winding on the center core leg on the side of this conductor. At the same time, the lead conductor of the transformer end of each low voltage winding on the end core leg is connected to the lead conductor of the high-voltage winding wire, and is led out independently through the transformer tank wall, near the load circuit of the load device. are conductively coupled to each other to form the third vertex of the triangular connection,
A high-current three-phase circuit characterized by triangular connection of low-voltage windings that feed power to the three-phase circuit. 4)' A high-current three-phase electrical circuit according to any one of claims 1 to 3, characterized in that the conductor has a width to thickness ratio of 50 to 150, particularly 100. circuit. 5) A high current three-phase electric circuit according to any one of claims 1 to 4, characterized in that the mutual spacing between the conductors is greater than the thickness of these conductors. 6) In the electric circuit according to any one of claims 1 to 5, both outer conductors are connected to each other at the upper and lower sides by a closing band having a sickle-shaped cross section. A high-current three-phase electric circuit characterized by forming a tube surrounding two conductors, through which a cooling medium flows. 7) In the electrical circuit according to any one of claims 1 to 5, the individual conductors are formed by a number of electrically parallel and spatially parallel tubes through which a cooling medium flows. A high-current three-phase circuit characterized by being integrated. 8) In the electric circuit according to any one of claims 1 to 7, a large current characterized in that the voltage between six spatially adjacent conductors can be individually adjusted. Three-phase electrical circuit. 9) In the electric circuit according to any one of claims 1 to 8, the four conductors (10°17, 1
8.15) is guided by three conductors (22, 23, 24) with a V-shaped cross section in the transition piece of the high current circuit to the load connection conductor part assembled in a star shape, and the end A high current three-phase electric circuit characterized in that two lead conductors on the transformer end side of the winding on the core leg are connected to one ■-shaped groove body (24). 10)% Allowance In the electric circuit according to any one of claims 1 to 9, each of the V-shaped conductors (22°23
．． 24), the ends of which are respectively coupled to triangular plates, and the triangular plates are coupled to connection poles of the load via a flexible conductor bundle or a series-connected tube and flexible conductor bundle. Phase circuit.