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INVENTION
Patent of the Russian Federation RU2027240
CURRENT REACTOR
The name of the inventor: Seryakov K.I.
The name of the patent holder: All-Russian Electrotechnical Institute named after VILenin
Address for correspondence:
The effective date of the patent: 1992.01.13
Use: in electrical engineering, namely in devices for limiting the short-circuit current in an electrical circuit. SUMMARY OF THE INVENTION: The device comprises a dielectric frame 1 onto which the winding 2 is wound from a conventional conductor material. On the winding 2 is wound a winding 3 made of a superconducting material and having a direction opposite to the winding of the winding 2. The windings 2 and 3 are connected in parallel. On the winding 3, a winding 4 is wound, made of a conventional conductor material. This winding is connected in series with the windings 2 and 3. The device provides savings for the superconductor material.
DESCRIPTION OF THE INVENTION
The invention relates to electrical engineering, namely to devices for limiting the short-circuit current in an electrical circuit.
A current-limiting device [1] is known, comprising two windings wound together on the carcass, which are connected in parallel, one of the parallel branches comprising a resistive element. Such a device serves as a current-limiting reactor in transient processes when the switching device is switched on, or by a damping resistor when the apparatus is disconnected. It can be used as a shunt switching device to limit current surges and overvoltages that occur when switching current by switches or disconnectors. However, it can not be used to limit the current in a circuit with short circuits in it.
The closest to the proposed is a current-limiting device [2] containing two windings that are identical in number of turns, connected in parallel, counter-wound on one frame and made of superconductors. When a working current flows that is less than the critical current of superconductors, such a device has practically no active or reactive resistance. With an increase in the current in the event of a short circuit due to the excess of the critical current, the superconductor goes into a resistive state and the resulting active resistance limits further growth of the short-circuit current. The disadvantage of such a device is the need for a relatively large number of superconductors, since their total cross section must be calculated for the flow of operating current.
The purpose of the invention is to reduce the amount of superconductor materials used in the current limiting device.
The aim is achieved in that in a current-limiting reactor containing two nested and parallel wound windings connected in parallel, and at least one winding is made of a material having the superconductivity property with respect to the electric current at operating temperature, there are at least three Windings, and at least one of the windings is made of a material that does not have the superconductivity property at operating temperature, and the adjacent windings are made of materials with different properties with respect to superconductivity.
These characteristics are not available in the known technical solutions.
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In Fig. 1 shows a proposed device with a series-parallel connection of windings; 2 shows a variant with a parallel connection of the windings and with a magnetic circuit.
The device (Figure 1) comprises a dielectric frame 1 on which the winding 2 is wound from a conventional conductor material. On the winding 2, a winding 3 is made, made of a superconducting material and having a winding direction opposite to the winding of the winding 2. The windings 2 and 3 are connected in parallel. On the winding 3, a winding 4 is wound, made of a conventional conductor material. This winding is connected in series with the windings 2 and 3 and has a winding direction identical to that of the winding 3. It is advisable that the winding 2 has a number of turns greater than the number of turns in the winding 3.
The device works as follows
When the working current flows after its transition from winding 4 to windings 2 and 3, it is redistributed between the latter so that the total magnetic field inside the device is practically zero, i.e. The inductive resistance of the device has a zero value. With current growth in the event of a short circuit in the network and exceeding its limiting value, the superconducting winding transforms into a resistive state, as a result of which the current through it practically ceases to grow. This means that for short-circuit currents, the inductive resistance of the device is determined only by the series-connected windings 2 and 4. The resulting inductive resistance limits the growth of the short-circuit current.
The advantage of placing the third winding 4 from a conventional conductor that is separated from the other such winding 2 by the winding 3 of superconducting material is that the superconductor in the winding 3 has less magnetic fields than the prototype variant (i.e., Having the same inductance of the nonsuperconducting winding as co-winding 2 and 4 of the proposed device). Since the critical current density of modern ceramic high-temperature superconductors depends strongly on the magnetic field, this makes it possible to use in the device a superconducting winding with a smaller cross section and a smaller length of the superconductor, i.e. To achieve savings of superconducting materials.
Further reduction of the magnetic field acting on the superconductor is possible by further increasing the number of coils wrapped in one another, including superconducting windings. In Fig. 2 shows a variant with two superconductor windings and two windings made of a conventional material. The device has a cylindrical frame 1, on which windings 2 of a common material and windings 3 of a superconductor material are wound in an alternating order. In this case, all the windings are connected in parallel, and the adjacent windings have a counter winding direction. To increase the inductive resistance in the current-limiting mode, the device is provided with a magnetic core 4, which can have, as in the presented case, or do not have an air gap. For a more even distribution of currents, equalizing inductors 5 or other inductive elements can be used.
The device of FIG. 2 works as follows
In the operating mode of the electrical circuit, the flowing current is less than the critical current for superconducting windings, so the current through the windings is distributed inversely with the number of turns in the windings, as a result of which the magnetic field inside the frame is almost completely compensated and the current-limiting device has negligible active and reactive resistance. When the current exceeds the critical value, the superconductor windings become a resistive state, the current increase occurs mainly in windings made of a conventional conductor, and since they have the same winding direction, this leads to the appearance of an inductive resistance.
The use of several pairs of windings in the device of FIG. 2 allows a corresponding number of times to increase the rated current in comparison with a device having one pair of windings of the same dimensions. To make these two devices equal in nominal current, it is not sufficient to increase proportionally the conductor cross-sections in the conventional and superconductor windings, since in this case the magnetic field acting on the superconducting winding would increase correspondingly, which leads to a decrease in the rated current. To compensate for this negative effect, the cross section of the superconductor will have to be increased. Simultaneously, it is necessary to increase its length in order to obtain the same resistance value of the winding in the resistive state. Thus, an increase in the number of windings, and in this variant of their connection, leads to a saving of the superconducting material.
When the critical magnetic fields of the superconductors used are small (less than the induction of saturation of ferromagnets), which is characteristic of ceramic high-temperature superconductors, the efficiency of the device can be improved by using magnetic wires with an air gap (as depicted in Figure 2) or without it. The efficiency of the device can also be increased by using superconductor windings with a significantly larger number of turns than in windings made from conventional materials (for example, by a factor of 10 or more), since in this case the cross section of a superconductor can be reduced by an appropriate number of times, and some of the superconducting The winding is replaced by a winding made of a conventional non-superconductor material.
CLAIM
1. A TO-CURRENT REACTOR containing two main windings, one of which is made of a superconductor, characterized in that it is provided with an additional winding, the main windings are wound opposite and are connected in parallel, the adjacent windings having different superconducting properties.
2. Reactor according to claim 1, characterized in that the main windings are connected in series with the additional one.
3. Reactor according to claim 1, characterized in that it is provided with a fourth winding, all windings are in parallel connected to each other.
print version
Date of publication 05.04.2007gg
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