RU2217830C2 - Saturable reactor - Google Patents

Abstract

FIELD: electrical engineering; reactive power correction in power lines. SUBSTANCE: saturable reactor is mounted in tank and has magnetic system with intermediate legs, yokes, and two side yokes. Intermediate legs carry control windings connected to regulated dc voltage supply. Each phase of three-phase power winding encloses two adjacent intermediate legs mounting differentially connected control windings. Newly introduced is delta- connected three-phase compensating winding. Each of its phases is disposed concentrically to power winding phase. Additional three-phase reactor is disposed in mentioned tank. Some of reactor leads are connected to vortices of delta-connected compensating windings and other leads, to bushings on tank cover. Short-circuit inductance of power and compensating windings L_c+L = (0,5-1,2)L_r, where L is inductance of additional reactor reduced to turn number of power winding; L_r is rated inductance of saturable reactor. Filter capacitors or reactive-power correcting condensers may be connected to compensating winding leads. This winding may be used as auxiliary power winding of substation to feed regulated voltage supply and the like. EFFECT: reduced higher harmonic level in supply current; enlarged functional capabilities of saturable reactor. 1 cl, 5 dwg

Description

 The invention relates to the field of electrical engineering and can be used for magnetically controlled reactors installed, for example, in an electrical network to compensate for reactive power.

 Known electric reactor with magnetization [1], containing a magnetic system with middle rods, two yokes, with two side yokes. On the middle rods are placed control windings. On the middle rods there are also network windings covering the control windings. To increase reliability and increase speed between network windings of one phase, there are complex electrical reconnections. In addition to the complexity of the design, a drawback [1] is the increased consumption of basic materials - the conductive material of the network windings and the electrical steel of the magnetic system. In the analog reactor [1] there are current distortions due to higher harmonics.

 Partially, the disadvantages [1] are eliminated in the known device [2], which is the closest in technical essence to the proposed invention. As in the analogue [1], in this prototype device there is a magnetic system with rods, yokes, two side yokes. On the rods are placed control windings connected to an adjustable constant voltage source, and network windings covering two adjacent rods with control windings. The reactor is located in the tank, on the cover of which the inlets are located. Unlike the analogue [1], there is not two, but one network winding, covering two adjacent rods with control windings, which allows to simplify the design and reduce material consumption. However, the known reactor [2] has current distortions due to higher harmonics, has limited functional capabilities, since when operating in a network, it can only consume reactive power from the network.

 The aim of the invention is to reduce the distortion current by higher harmonics, expanding the functionality of the reactor, increasing the electrodynamic resistance at short circuit

This goal is achieved by the fact that an electric reactor with magnetization, located in the tank, on the cover of which there are bushings, and containing a magnetic system with middle rods, yokes, two side yokes, control windings connected to an adjustable constant voltage source are placed on the middle rods, and each phase of the three-phase network winding covers two adjacent middle rods with the control windings turned on in turn, equipped with a three-phase compensation winding connected in a triangle the waiting phase of which is located concentrically with the phase of the network winding, and an additional three-phase reactor located in the said tank, the windings of which at one end are connected to the vertices of the compensation windings triangle, and at the other ends with the said inputs on the tank cover,
L _to + L = (0.5-1.2) L _n ,
where L _to - short-circuit inductance of the network and compensation windings,
L is the inductance of the additional reactor, reduced to the number of turns of the network winding,
L _n - nominal inductance of an electric reactor with magnetization.

 The proposed electric reactor with magnetization is illustrated by drawings.

 In FIG. 1 shows the design of the magnetic system of the reactor with windings in section along the main axis, FIG. 2 shows a section of the reactor with windings in plan view, and FIG. 3 - additional reactor, figure 4 shows the installation location of the additional reactor in the tank and figure 5 - connection diagram of the windings of the main reactor and the additional reactor.

 The magnetic system of the reactor contains rods 1-6, two yokes (horizontal) - upper 7 and lower 8, two side yokes 9 and 10. On all the rods are placed control windings 11-16. In the reactor there are three (according to the number of phases A, B and C) network windings 17, 18 and 19. Each network winding covers two adjacent phase terminals with control windings. Compensationally with the network windings, compensation windings 20, 21 and 22 are installed on each phase. The reactor is placed in a tank 23, on the cover 24 of which the inputs are installed. An additional three-phase reactor 25 is placed in the tank together with the reactor, which is, for example, three inductors 26, 27 and 28 located one above the other on the insulating cylinder.

 The network windings 17-19 are connected in a three-phase circuit (for example, to a star with a neutral) and are brought to the tank cover by inputs A, B, C and 0. Located on the adjacent rods of each of the three phases of the control winding (11 and 12, 13 and 14, 15 and 16) are paired in series with each other, these pairs are interconnected in parallel and connected to the inputs "+" and "-" on the tank lid. Another connection of control windings is also possible, for example, serial, parallel, mixed.

 Compensation windings 20, 21 and 22 are connected in a triangle. The windings of the additional three-phase reactor 26, 27 and 28 are connected at one end to the vertices of the compensation winding triangle, and at the other ends to the bushings “a”, “b” and “c”.

 An electric magnetization reactor, made in accordance with the claims of the invention, operates as follows.

When a three-phase alternating current network is connected to the inputs of the network windings A, B, and C and the regulated constant current source is disconnected, in each two adjacent rods, for example 1 and 2, the same magnitude and direction alternating magnetic fluxes with an amplitude Φ _m closing through yokes 7, 8 and side yokes 9, 10. The amplitude of the fluxes Ф _{m is} approximately equal to the saturation flux of the rods Ф _s (this corresponds to the most rational use of steel rods), and there is no constant magnetic flux. In all sections of the magnetic system, the flux does not exceed the saturation flux Ф _s (equal to the saturation induction of steel multiplied by the steel cross-sectional area); therefore, the reactor current is almost very small. This mode of operation of the reactor is called idle.

The reactor power control is carried out by connecting to the inputs "+" and "-" of the control windings of an adjustable constant voltage source, for example, an adjustable converter (rectifier). When the rectifier is connected to the control windings, a current arises in them, which leads to the appearance and increase of the bias flux Φ ₀ (constant component in the flow curve). In adjacent rods, this flow Φ _{0 is} directed in different directions (due to the on-off switching of the control windings). Since a variable flux Ф _{s is} superimposed on the magnetization flux Ф ₀ , the resulting flux begins to shift to the steel saturation region, i.e. the rods are saturated for some part of the period. In turn, saturation of the rods leads to an increase in current in the network windings. This reactor current consists of sinusoid parts, i.e. it contains both the main first harmonic of the network and the unwanted higher harmonics.

 The main function of the compensation windings introduced into the reactor is to reduce the higher harmonics distorting the network current of the reactor. The inclusion of compensation windings in a triangle leads to the fact that all currents of higher harmonics, multiples of 3, are closed in this triangle and do not go into the network. Capacitors or reactor-condenser filters can be connected to the inputs on the tank cap "a", "b" and "c", which short-circuit the higher harmonics currents, reducing them in the current of the network windings. One of the functions of the introduced additional reactors is their fulfillment of the role of higher harmonic filter reactors.

 The second function of the compensation windings is their fulfillment of the function of transformer windings in the reactor, i.e. transformation of the prototype reactor into a transformer reactor. This means that a load can be connected to inputs a, b and c, for example, an adjustable rectifier for a reactor or a load of auxiliary needs of a substation. It is also possible to connect a capacitor bank. In this case, the reactor turns into a regulated source and consumer of reactive power (without such capacitors, the reactor is only a consumer of reactive power).

 When connected to the inputs "a", "b" and "c" of a high-speed switch (short-circuit), the reactor instantly reaches the boost power. Thus, inertia is compensated - one of the disadvantages of bias-controlled reactors.

 As a result, the introduction of a compensation winding significantly expands the functionality of the bias reactor.

Compensation windings that perform the function of reducing the current in higher harmonics have a small power, i.e. small cross-section of wires. But in the event of a short circuit at the inputs "a", "b" and "c", the short circuit current determined by the inductance of the short circuit between the mains and compensation windings can be large, dangerous for the electrodynamic resistance of the compensation winding. An important function of the introduced additional reactors is to limit the short circuit current. It is important that the additional reactors are located in the same tank with the main reactor. In this case, the shortest circuit for the windings directly on the compensation winding becomes impossible. The performance of two functions by the additional reactor — limiting the short circuit current and ensuring the boost mode — is possible only when the nominal parameters and geometric dimensions of the reactor windings and the additional reactor are related by the ratio:
L _to + L = (0.5-1.2) L _n ,
where L _to - the inductance of the short circuit of the windings of the network and compensation,
L is the inductance of the additional reactor, reduced to the number of turns of the network winding,
L _n - rated inductance of a controlled reactor.

 The boundaries of this ratio are determined by the coefficients of 0.5 and 1.2. With a coefficient of 0.5, the short circuit current in the network winding becomes equal to its double rated current. However, the nominal power of the compensation winding is usually small to save active materials (for example, 20% with respect to the rated power of the reactor, i.e. the network winding). Therefore, the multiplicity of the short circuit current in the compensation winding will be large (in our example, with a coefficient of 0.5, the short circuit current of the compensation winding will be 10 times). According to additional calculations, the coefficient 0.5 is the lower limit, while it is possible to ensure the electrodynamic stability of the reactor without the use of serious and expensive measures. Computational studies have shown that a coefficient of 1.2 is the upper limit. If this coefficient is greater, then the efficiency of the reactor function decreases sharply with high-speed power gain, and the effect of additional reactors as elements of an inductive-capacitive filter of higher harmonics decreases.

 The performance of the proposed bias-controlled electric reactor and its high technical and economic indicators are confirmed by calculations and physical modeling. Compared with the analogue and prototype, the present invention has a clear advantage - improving the shape of the current curve, reducing losses, as well as the consumption of materials.

Literature
1. An electric reactor with magnetization. RF patent 1762322. H 01 F 29/14. Bulletin of inventions 34, 1992

 2. Core for electrical apparatus. Paul A. Vanse. U.S. Patent 2,267,382. Application Juli 23, 1940, Serial N 346904. Patendet Dec. 23, 1941.

Claims (1)

An electric magnetization reactor located in the tank, on the cover of which there are bushings, and containing a magnetic system with middle rods, yokes, two side yokes, control windings connected to an adjustable constant voltage source are placed on the middle rods, and each phase of the three-phase network winding covers two adjacent middle reactor rods with control windings included in the opposite direction, characterized in that it is equipped with a three-phase compensation winding connected in a triangle, each aza which is concentric with the phase of the power windings, and an additional three-phase reactor, placed in said tank, the windings of which one ends are connected to the vertices of the triangle of compensation coils, and the other ends - with said inputs of the tank cover, wherein L _to + L = (0.5-1.2) L _n , where L _to - the inductance of the short circuit of the network and compensation windings; L is the inductance of the additional reactor, reduced to the number of turns of the network winding, L _n - nominal inductance of an electric reactor with magnetization.

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