Magnetic core with controllable inductance and choke comprising such a magnetic core

Abstract

The invention relates to a magnetic core (1) for a coil (15) of a high-voltage device, in particular for a choke (17), wherein the magnetic core (1) has at least one core leg (3) composed of several core leg segments (23) arranged successively along a longitudinal direction (19) of the core leg (3). In order to be able to regulate the inductance of the magnetic core (1) in a simple manner over a large range and with a linear characteristic, at least one of the core leg segments (23) is a control element (27) for controlling the inductance of the core leg (3). The control element (27) comprises a disk (29), the two opposite flat sides (33, 35) of which are arranged transversely to the longitudinal direction (19) of the core leg (3), and at least one electrically controllable winding (31) designed to generate a magnetic flux (45) in the disk (29).

Description

[0001] The invention relates to a magnetic core for a coil of a high-voltage device, in particular for a choke. The magnetic core has at least one core leg extending along a longitudinal direction. The longitudinal direction defines a main magnetic flux direction for the core leg. A high-voltage winding can be arranged around the core leg. The magnetic core and high-voltage winding together form a coil. The core leg in the high-voltage winding influences the inductance of the coil.

[0002] Chokes are used to compensate for reactive power in power transmission lines and thus improve the transmission capacity of existing lines. The inductance of a choke should be adjustable over a certain range. However, an adjustable inductance can also be useful for other high-voltage devices, such as transformers.

[0003] It is known to saturate a magnetic core by applying a direct current to the high-voltage winding or an additional winding. However, this solution is nonlinear.

[0004] Alternatively, it is known to assemble the core leg from several core leg segments that are arranged successively along the longitudinal direction.

[0005] Adjacent core leg segments can be spaced apart by spacers, particularly made of ceramic. The air gap in the magnetic core caused by the spacers increases the magnetic resistance of the choke circuit and thus also the inductance of the high-voltage device.

[0006] Furthermore, it is known, also in combination with a core composed of core leg segments, to change the inductance within a certain range by changing the number of turns of the high-voltage winding via a load switch.

[0007] However, the number of setting options with this solution depends on the number of switching levels.

[0008] It is therefore the object of the invention to overcome at least one of the above-mentioned problems and to provide a solution with which the inductance of a coil, in particular a choke, can be controlled in a simple manner over the largest possible range and preferably linearly.

[0009] This object is achieved by a magnetic core according to the invention according to the teaching of claim 1. Advantageous embodiments are the subject of the subclaims.

[0010] According to the invention, a magnetic core is provided which has at least one core leg which is composed of a plurality of core leg segments which are arranged successively along a longitudinal direction of the core leg, wherein at least one core leg segment is a control element for controlling the inductance of the core leg, and wherein the control element has a disk whose two opposite flat sides are arranged transversely to the longitudinal direction of the core leg, and at least one electrically controllable winding designed to generate a magnetic field in the disk.

[0011] By energizing the winding of a control element, the disc of this control element is brought into saturation and thus acts as an air gap in the core leg.

[0012] If the disc is saturated, the magnetic resistance of the magnetic circuit in the magnetic core increases and the inductance increases.

[0013] Since the alternating flux of the choke does not generate any voltage in the control element's winding, the current can be supplied to the control element's winding with low power. Only the ohmic resistance needs to be overcome.

[0014] The overall behavior of a choke fitted with a magnetic core is linear, meaning that no distorted currents are caused.

[0015] The control of the current supply to the winding of the control element is easy to implement.

[0016] Depending on how many of the control element disks are saturated, the effective magnetic resistance of the iron circuit and thus the inductance of the choke can be changed without having to change the number of turns of the high-voltage winding. The inductance can be varied over a relatively wide range. The range depends primarily on the proportion of the control elements in the core leg segments.

[0017] The solution according to the invention can be further improved by various, individually advantageous, and combinable embodiments. These embodiments and their associated advantages are discussed below.

[0018] According to a first advantageous embodiment of the magnetic core according to the invention, the at least one winding, in particular at least one turn thereof, can overlap the flat sides of the disk at least in sections. The turns of the winding can therefore run essentially parallel to the flat sides. The magnetic flux induced by the winding in the disk then runs parallel to the flat sides.

[0019] The disk is preferably a circular disk. Since a circular disk itself has very low magnetic resistance in the circumferential direction, only a few turns of the control element winding are required to saturate the disk.

[0020] It is particularly advantageous if the disc is an annular disc with a central opening. The central opening can extend longitudinally through the control element. A magnetic flux generated by the winding can then, for example, run along the circumferential direction of the annular disc, i.e., the annular direction.

[0021] Efficient generation of a magnetic flux through the ring of a disc shaped as an annular disc can be achieved by at least one turn of the winding extending through the central opening and being wound at least partially around at least one ring section of the annular disc.

[0022] Preferably, the winding of the control element has a plurality of turns which are arranged equidistant from one another along a circumferential direction of the disc, in particular the annular direction of an annular disc.

[0023] The turns can extend radially outward from the central opening. Preferably, one turn each runs from the circumference of the annular disc along one of the flat sides to the central opening, penetrates the central opening, and runs along the opposite flat side back to the circumference.

[0024] The disk of the control element is preferably made of electrical steel. Electrical steel is a silicon-containing iron alloy, known as electrical sheet.

[0025] To obtain a disc that is easy to manufacture, it can be made from a wound strip of electrical steel.

[0026] According to a further advantageous embodiment, the core leg is provided with a plurality of control elements according to one of the preceding claims. These control elements can preferably be controlled independently of one another. Control is understood to mean the supply of current to the windings.

[0027] Depending on how many of the discs are saturated, the effective magnetic resistance of the magnetic circuit and thus the inductance of the coil can be changed without having to change the number of turns of the high-voltage winding. A tap changer is therefore unnecessary.

[0028] To prevent the turns of one or more windings between two core leg segments from being damaged, at least one spacer can be provided between the two core leg segments. The at least one spacer can be made, in particular, of a ceramic material.

[0029] As an alternative to spacers, other measures for protecting the windings are also conceivable. For example, the disks can be provided with grooves to accommodate the windings, windings made of flat material can be used, or the passive core leg segments can be provided with recesses, particularly trench-shaped recesses, to accommodate the windings in the assembled state.

[0030] The invention also relates to a choke with at least one magnetic core according to the invention and with a high-voltage winding wound around a core leg of the magnetic core. Preferably, the core leg has a plurality of the control elements according to the invention, which can be controlled independently of one another.

[0031] To further explain the invention, reference is made to the figures in the following part of the description, from which further advantageous details and possible areas of application of the invention can be seen. The figures are to be understood as examples and are intended to illustrate the nature of the invention, but in no way restrict or exhaustively represent it. The same reference numerals are used for elements with the same structure and / or the same function.

[0032] They show: Fig. 1 shows an advantageous embodiment of a magnetic core according to the invention in a side view; and Fig. 2 shows an advantageous embodiment of a control element according to the invention in a plan view.

[0033] Figure 1 shows a schematic diagram of a magnetic core 1 for a coil of a high-voltage device. The magnetic core 1 has a core leg 3, which is connected to two additional core legs 9, 11 via yokes 5, 7.

[0034] A high-voltage winding 13 can be arranged around the core leg 3, which Figure 1 is only indicated by the dotted lines. The magnetic core 1 and the high-voltage winding 13 together form a coil 15, in particular a choke 17.

[0035] The core leg 3 extends along a longitudinal direction 19, which corresponds to the main magnetic flux direction 21 of the magnetic flux induced in the core leg 3 by the high-voltage winding 13. The magnetic core 1, in particular the yokes 5, 7 and the other core legs 9, 11, can be constructed from electrical steel sheet.

[0036] The core leg 3 is composed of core leg segments 23. Some of the core leg segments 23 may be passive core leg segments 25. These, like the yokes 5, 7 and the other core legs 9, 11, may be constructed of electrical steel.

[0037] In addition, the core leg 3 has core leg segments 23, which are control elements 27. The control elements 27 can alternatively be referred to as active core leg segments 27.

[0038] Preferably, the core leg 3 is constructed from alternately arranged passive core leg segments 23 and control elements 27. The different segments 25 and 27 are arranged alternately along the longitudinal direction 19.

[0039] Each control element 27 has a disk 29 and an electrically controllable winding 31. The disk 29 has two opposing flat sides 33, 35.

[0040] In the core leg 3, the control elements 27 are arranged such that their flat sides 33, 35 are aligned perpendicular to the longitudinal direction 19.

[0041] The passive core leg segments 23 are preferably shaped as cylindrical sections, including a disc shape. The control elements 27 can therefore be stacked with the passive core leg segments 23 to form the core leg 3.

[0042] In the following, a single control element 27 is described with reference to the Figure 2 described in more detail. Preferably, all control elements 27 in the core leg 3 are constructed identically.

[0043] The disc 29 of the control element 27 preferably has the shape of a circular disc, particularly preferably the shape of an annular disc 36.

[0044] Preferably, the annular disc 36 has a circular circumference 37 and a central opening 39, which is preferably also circular. This forms a ring 41 that extends along a ring direction 46. In the assembled state of the core leg 3, the ring direction 46 extends around the longitudinal direction 19. In other words, the core leg 3 and the ring 41 extend coaxially with one another. This is shown in Figure 2 indicated.

[0045] The disc 29 is preferably made of electrical steel, i.e., a silicon-containing iron alloy. Particularly preferably, the disc 29 is made of a rolled strip of electrical steel sheet. This allows the desired material properties to be achieved. Furthermore, the annular disc shape can be easily achieved by rolling a sheet metal strip.

[0046] The winding 31 of the control element 27 consists of turns 43. The turns 43 preferably extend radially between the central opening 39 and the circumference 37 of the ring 41 and penetrate the central opening 39.

[0047] The windings 43 are wound around the ring 41. They sweep over the flat sides 33, 35 of the disc 29. The windings can be arranged equidistant from one another along the circumference 37.

[0048] The above-described arrangement of the winding 31 with respect to the disc 29 results in a magnetic flux 45 being induced in the ring 41 along a ring direction 46 of the ring 41 when a current flows through the winding 31. The magnetic flux 45 is in Figure 2 indicated by the arrow.

[0049] If the magnetic flux 45 is strong enough to saturate the disk 29, the disk acts as an air gap in the core leg 3. Because the control elements 27 of the core leg 3 can be controlled individually, the inductance of the coil 15 can be adjusted via the number of disks 29 that are saturated.

[0050] Only hinted at in Figure 2 are spacers 47 which are intended to prevent the windings 43 from being damaged by contact with the adjacent passive core leg segment 25.

[0051] As an alternative to spacers 47, other measures for protecting the windings 43 are also conceivable. Reference symbol

[0052] 1Magnetic core 3Core limbs 5, 7Yokes 9, 11Additional core limbs 13High-voltage winding 15Coil 17Inductor 19Longitudinal direction 21Main magnetic flux direction 23Core limb segment 25Passive core limb segment 27Control element 29Disk 31Winding 33, 35Flat sides 36Annular disc 37Circumference 39Central opening 41Ring 43Turning 45Magnetic flux 46Ring direction 47Spacer

Claims

1. A magnetic core (1) for a coil (15) of a high-voltage device, in particular for a choke (17), wherein the magnetic core (1) has at least one core leg (3) composed of a plurality of core leg segments (23) arranged successively along a longitudinal direction (19) of the core leg (3), wherein at least one of the core leg segments (23) is a control element (27) for controlling the inductance of the core leg (3), and wherein the control element (27) has a disk (29), the two opposite flat sides (33, 35) of which are arranged transversely to the longitudinal direction (19) of the core leg (3), and at least one electrically controllable winding (31) designed to generate a magnetic flux (45) in the disk (29).

2. Magnetic core (1) according to claim 1, wherein the at least one winding (31) overlaps the flat sides (33, 35) of the at least one disc (29) at least in sections. ​3. Magnetic core (1) according to claim 1 or 2, wherein the at least one disc (29) is an annular disc (36) with a central opening (39).

4. Magnetic core (1) according to claim 3, wherein at least one turn (43) of the winding (31) extends through the central opening (39) and is wound at least partially around at least one portion of the annular disc (36).

5. Magnetic core (1) according to one of claims 1 to 4, wherein the winding (31) has a plurality of turns (43) arranged equidistant from one another along a circumference (37) of the disk (29).

6. Magnetic core (1) according to one of claims 1 to 5, wherein the at least one disc (29) is made of electrical steel.

7. Magnetic core (1) according to claim 6, wherein the at least one disc (29) is made of a wound strip of electrical steel. ​8. Magnetic core (1) according to one of claims 1 to 7, wherein the core leg (3) is provided with a plurality of control elements (27) according to one of the preceding claims.

9. Magnetic core (1) according to one of claims 1 to 8, wherein at least one spacer (47) is provided between two adjacent core leg segments (23), at least one of which is a control element (27).

10. Choke (17) with a magnetic core (1) according to one of the preceding claims and a high-voltage winding (13) wound around the magnetic core (1).

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