RU2310940C1 - Electrical saturable reactor - Google Patents

Abstract

FIELD: electrical engineering; saturation-controlled reactors installed, for instance, in electric mains for reactive power correction.

SUBSTANCE: proposed electrical reactor has top, bottom, and two side yokes, as well as intermediate cores mounting control windings connected to controllable DC supply. Power winding of each phase encloses two adjacent intermediate cores carrying differentially-connected control windings and compensating winding. Novelty is that compensating winding of each phase is built of two parts. Each part is disposed on each intermediate core. Two adjacent parts of compensating winding enclosed by power winding of each phase are cumulatively connected. Electrodynamic stability of reactor rises by 2.25 to 4 times due to enhancing short-circuit resistance between power winding and compensating winding which makes it possible to dispense with additional measures such as installation of additional current-limiting reactors within tank adding complexity to reactor mechanical design and reducing its reliability. Reactor current distortions are reduced by 30 - 50%.

EFFECT: enhanced reliability, resistance to short-circuits due to reduced short-circuit current and higher-harmonic distorted currents.

1 cl, 3 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 two yokes, with two side rods and middle rods on which control windings are placed. The network winding of each phase covers two middle rods with control windings included in the opposite direction. A disadvantage of the known device is the reduced reliability due to the complexity of the electrical circuit of the regulation system, because To ensure autonomous operation of the reactor, the control windings are used not only to magnetize steel of the middle rods, but also to power the control system converter.

Partially, the disadvantages [1] are eliminated in the known device [2], which is the closest in technical essence to the invention. As in the analogue [1], in this prototype device there is a magnetic system with two yokes, with two side rods and middle rods, on which control windings are connected, connected in opposite, which are connected to a constant current source. In contrast to the prototype [1], in addition to the network winding covering two rods with control windings of each phase, each phase also has a compensation winding, as well as the network winding covering two rods with control windings. This compensation winding serves to eliminate the higher harmonics in multiples of three in the reactor current and to power the converter of the control system. However, such a compensation winding has a large short circuit current, therefore, to ensure its electrodynamic resistance during short circuit, it is necessary to take measures, for example, by installing additional current-limiting reactors inside the reactor tank, complicating the design of the device and reducing its reliability. In addition, the design of the prototype reactor [2] has an increased level of higher harmonics (especially the 5th and 7th) in the network current of the reactor.

The aim of the invention is to increase the reliability of a controlled magnetization of the reactor, increase its resistance to short circuit by reducing the short circuit current and reducing the distortion current by higher harmonics due to the introduction of compensation windings mounted on the middle rods.

This goal is achieved by the fact that in an electric reactor containing upper, lower and two side yokes, middle rods on which control windings are connected, connected to an adjustable constant current source, a network winding of each phase, covering two adjacent middle rods with control windings included counter, and the compensation winding, the compensation winding of each phase is made of two parts, each part is located on each middle rod, and two adjacent parts of the compensation winding, about vachennye network winding of each phase included under.

The proposed electric reactor with magnetization is illustrated by drawings.

Figure 1 shows the design of the magnetic system of the reactor with windings (in section along the main axis) in relation to a single-phase reactor, figure 2 - section of a single-phase reactor in plan, figure 3 shows the design of a three-phase reactor (in plan).

The magnetic system of the reactor contains two horizontal yokes - upper 1 and lower 2, two lateral vertical yokes 3 and 4, and middle rods 5-10. On each middle rod 5-10 there are control windings 11-16 and parts of the compensation windings 17-22. The network windings 23-25 of each phase cover two adjacent rods with control windings and parts of the compensation windings. Parts of the compensation windings 17-22 can be placed both on top of and inside the control windings 11-16 (between the control windings 11-16 and the middle rods 5-10).

The control windings, by means of which the reactor is controlled (current controlled) by magnetizing the steel of the magnetic circuit, are connected to a converter or a direct current source, while various options for connecting control windings are possible. For example, two control windings 11 and 12, covered by the network winding 23, can be connected in series in the opposite direction or parallel to the opposite direction. The control windings of the three phases of a three-phase reactor can be connected in parallel or in series.

Each two parts of the phase compensation windings (17 and 18, 19 and 20, 21 and 22) covered by the network winding (23, 24 and 25) can be connected in series according to or parallel according to. The compensation windings of the three phases are connected in a triangle. Parts of the compensation windings 17-22 can be placed inside the control windings, as shown in Fig. 1 (between the control windings and the middle rods), or on top of the control windings 11-16, for example, directly wound on them, as on a powerful frame, fig. .2-3.

In a three-phase network, three-phase reactors (FIG. 3) or three-phase groups of reactors can be used. In a three-phase group of single-phase reactors (3 reactors of FIGS. 1-2), the network windings 23, 24 and 25 can be connected to a star with a neutral ground (dead or through the reactor) or into a triangle.

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

Consider first the operation of a single-phase reactor in figure 1-2. The description of the operation of a single-phase reactor fully applies to each phase of a three-phase reactor, i.e. entirely to a three-phase reactor controlled by magnetization or to a three-phase group of single-phase reactors.

When the winding 23 is connected to an alternating current electric network and an uncontrolled direct current source (for example, a converter controlled by a rectifier) in the middle rods 5 and 6, alternating magnetic fluxes of the same magnitude and direction with an amplitude Φ _m occur, which are closed through the yokes of the magnetic system horizontal 1 and 2 and lateral vertical 3 and 4. The amplitude of the flows Ф _{m is} slightly less than the saturation flux Ф _{s of the} rods 5 and 6 (this corresponds to the most rational use of steel rods with induction in steel about 1.7-1.8 T at saturation induction of about 2 T), and there is no constant magnetic flux. In the idle mode of the reactor without magnetization in all sections of the magnetic system, the variable flux does not exceed the saturation flux Ф _s (equal to the saturation induction of steel multiplied by the steel section), therefore, the reactor current is close to zero.

Regulation of reactor power is carried out by connecting to the control windings an adjustable direct current 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 magnetization flux Ф 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), therefore it closes mainly along the shortest path through a part of the lower and upper yoke 1 and 2 located between the rods 5 and 6. Since the flow of magnetization Φ _{0, an} alternating stream Φ _{s is} superimposed, the resulting stream is shifted 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 the appearance and increase of current in the network winding 23. With an increase in the constant voltage on the control winding, the bias flux increases, the time intervals inside each period when one of the rods is in a saturated state (i.e., when the flux this rod is larger than the saturation flux Ф _s ), in accordance with this, the mains current also increases. Thus, the power is controlled by magnetization reversal of the reactor.

After reaching such a state, when the magnetic flux of the rod for the whole period is equal to or greater than the saturation flux, the mains current reaches the maximum possible value and does not increase further, differential magnetic permeability of saturated steel becomes close to vacuum permeability. This mode of operation of the reactor is called the full-cycle saturation mode.

A special intermediate mode, in which the magnetization flux Ф ₀ becomes equal to the amplitude of the variable magnetic flux Ф _m , is characterized by the fact that the saturated state of the rods is the same and equal to half the sinusoid period, and due to the different directions of the variable flux Ф _m and the constant flux Ф ₀ in the rods covered by the network winding, one half of the period is saturated with one rod, and the other with the other. The mode under consideration is called the half-period saturation mode, and reactors usually controlled by magnetization at rated power operate in this half-period saturation mode.

In the half-period (practically nominal) mode and in the full-period saturation mode, there are practically no higher harmonics in the reactor current and the current has a purely sinusoidal shape. In intermediate modes, the middle rods are generally saturated in part of the half-wave of a sinusoid, the reactor current is distorted, and higher odd harmonics are present in it.

To eliminate the higher harmonics in multiples of three (3rd, 9th, ...) in the reactor current, each two parts of the compensation windings of the three phases, connected according to (17 and 18, 19 and 20, 21 and 22), are included in triangle pattern. Since the compensation windings also serve to power the converter of the control system, a short circuit at its inputs and damage to the winding by electrodynamic forces is possible. The magnitude of the short circuit current depends on the resistance of the short circuit between the mains and compensation windings. This resistance is the smaller, the smaller the area of the scattering channel between the network and compensation windings, therefore, it increases significantly (1.5-2 times) when the compensation winding is removed from the network. That is why the compensation windings 17-22 are located on the middle rods, and do not simultaneously cover two rods, as in the prototype. Due to the decrease in the short-circuit current by 1.5-2 times, the electrodynamic short-circuit forces decrease by 2.25-4 times, the reliability of the reactor increases. The electrodynamic resistance is further enhanced if parts of the compensation windings 17-22 are placed on top of the control windings 11-16 - they are wound directly on them, as on a powerful frame. If parts of the compensation windings 17-22 are located inside the control windings 11-16, then the electrodynamic resistance is enhanced by increasing the short circuit resistance (due to an increase in the area of the scattering channel) and a corresponding decrease in current and electrodynamic forces.

Due to the nonlinear magnetic characteristics of steel, middle rods are sources (generators) of higher harmonics in the reactor. Compared with the prototype, the compensation winding is located significantly closer to the middle rods. The proximity of the compensation winding (connected in a triangle) to the middle rods can significantly (up to 30-50%) reduce the higher harmonic components in the mains current (first of all, the distortions of the 5th and 7th harmonic reactors most affecting the current).

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 prototype, the electrodynamic resistance of the reactor is increased 2.25-4 times, therefore, no additional measures have to be taken, for example, installing (as in the prototype) additional current-limiting reactors inside the tank, complicating the design of the device and reducing its reliability. The distortion current in the reactor current in comparison with the prototype is reduced (up to 30-50%). The effect of reducing the level of the 5th and 7th harmonics of the current when the compensation winding approaches the middle rods is confirmed by the results of additional computational studies on mathematical models that take into account all the main influencing factors, including the nonlinearity of the magnetic characteristics of steel. Additional materials may be submitted if necessary.

Literature

1. An electric reactor with magnetization. RF patent №2217831. H01F 29/14. Invention Bulletin No. 33 of 2003

2. An electric reactor with magnetization. RF patent №2217830. H01F 29/14. Invention Bulletin No. 33 of 2003

Claims (1)

An electric magnetization reactor containing upper, lower and two side yokes, middle rods, on which control windings are connected, connected to an adjustable constant current source, a network winding of each phase, covering two adjacent middle rods with opposite control windings, and a compensation winding , characterized in that the compensation winding of each phase is made of two parts, each part is placed on each middle rod, and two adjacent parts of the compensation winding, oh wired by the network winding of each phase are included according to.

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