Reactor Core

Abstract

A reactor core capable of reducing reactor noise is provided. [Solution] In order to solve the above problem, according to one aspect of the present invention, there is provided a reactor core comprising: a plurality of legs made of laminated electromagnetic steel sheets, each having one or more gaps formed in a magnetic path; a gap maintaining member made of a non-magnetic material that fills the gap; and a compression mechanism capable of compressing the legs in a direction parallel to the legs, wherein the compression force P (MPa) (P≧0) applied by the compression mechanism satisfies the following formula (1). (3 / 40)×Ng-0.1≦P≦(3 / 40)×Ng+0.1 (1) Here, Ng is the maximum number of gaps between the legs around which the wire is wound, and is an integer equal to or greater than 1.

Description

[Technical Field]

[0001] The present invention relates to a reactor core. [Background technology]

[0002] For example, as disclosed in Patent Documents 1 to 4, a reactor is known. This reactor has a reactor core with multiple legs, and an electric wire (i.e., a coil) wound in a coil shape around one of the legs. The legs are made of laminated electromagnetic steel sheets. One or more gaps are formed in the legs to increase magnetic resistance. The gaps may be filled with a filler made of a non-magnetic material. The legs are connected to each other by connecting parts. The connecting parts are also made of laminated electromagnetic steel sheets.

[0003] Reactors have a variety of uses. For example, they can be used as a lagging reactance source. Specifically, when AC current is supplied to a device with a capacitor (such as a motor), the current phase leads the voltage phase. If the voltage phase is out of phase with the current, the voltage may rise excessively. Therefore, a reactor is connected to the device with a capacitor. A reactor can delay the current phase, aligning the current phase with the voltage phase. Alternatively, when power is supplied to various facilities via transmission lines, a capacitor may form between the transmission line and the ground, causing the current phase to lead the voltage phase. Therefore, before using the power, each facility passes current through a reactor to delay the current phase and align the voltage phase with the current phase.

[0004] Reactors also have the function of preventing capacitor burnout by cutting high-frequency currents, and by connecting a reactor in series with a DC power supply, they also have the function of suppressing current pulsation (current pulsation). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-025830 [Patent Document 2] Patent No. 3628370 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-15924 [Patent Document 4] Special Publication No. 50-25608 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, reactors are extremely useful devices because they are used for a variety of purposes. However, reactors have the problem of generating noise when they are in operation. This noise can be classified into two types: noise caused by magnetic attraction and noise caused by magnetostriction. As described above, one or more gaps are formed in the legs. The electromagnetic steel sheets around the gaps are isolated by these gaps. Therefore, when current flows through the coil, the separated electromagnetic steel sheets are attracted to each other by magnetism and vibrate. This vibration causes air vibrations, generating noise. This is noise caused by magnetic attraction. Meanwhile, the electromagnetic steel sheets are deformed by magnetism (so-called magnetostriction), and this magnetostriction causes air vibrations, generating noise. This is noise caused by magnetostriction.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a reactor core that can reduce reactor noise. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a reactor core comprising: a plurality of legs made of laminated electromagnetic steel sheets, each having one or more gaps formed in a magnetic path; a gap maintaining member made of a non-magnetic material that maintains the gap; and a compression mechanism that can compress the legs in a direction parallel to the longitudinal direction of the legs, wherein an electric wire is wound around at least one or more of the plurality of legs, and the compression force P (MPa) (P≧0) applied to the legs by the compression mechanism satisfies the following formula (1). (3 / 40)×Ng-0.1≦P≦(3 / 40)×Ng+0.1 (1) Here, Ng is the maximum number of gaps that can be provided in the leg, and is an integer of 1 or greater.

[0009] According to another aspect of the present invention, there is provided a reactor core comprising: a plurality of legs made of laminated electromagnetic steel sheets, each having one or more gaps formed in a magnetic path; gap maintenance members made of a non-magnetic material for maintaining the gap; and a compression force adjustment mechanism for adjusting the compression force applied by at least one gap maintenance member to one and the other core blocks adjacent to the gap maintenance member, wherein the compression force adjustment mechanism causes the compression force P (MPa) (P≧0) in a direction parallel to the longitudinal direction of the leg to satisfy the following formula (1) at any position in the longitudinal direction of the leg: (3 / 40)×Ng-0.1≦P≦(3 / 40)×Ng+0.1 (1) Here, Ng is the maximum number of gaps that can be provided in the leg, and is an integer of 1 or greater. [Effects of the Invention]

[0010] According to the above-described aspects of the present invention, reactor noise can be reduced. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a front view showing the appearance of the reactor core. [Figure 2] 1 is a graph showing the correlation between the compressive force (MPa) acting on the legs of the reactor core and noise (dB). [Figure 3] FIG. 4 is an explanatory diagram showing a second embodiment of a reactor core. DETAILED DESCRIPTION OF THE INVENTION

[0012] <1. Reactor core configuration> Next, the reactor core according to this embodiment will be described in detail with reference to the drawings. As shown in Fig. 1, the reactor core 10 includes a pair of legs 20 and 30, leg connecting portions 40 and 50, a ceiling portion 70, a bottom portion 71, and compression mechanisms 80 and 90. When the reactor core 10 is used as a reactor, an electric wire is wound in a coil shape around the leg 20 or the leg 30 (or both the legs 20 and 30), and a current flows through the electric wire.

[0013] The leg portion 20 includes a plurality of core blocks 21 (three in the example of Figure 1) formed by stacking a plurality of electromagnetic steel plates, gaps 22a formed between the core blocks 21 and between the leg portion 20 and the leg connecting portions 40, 50, and gap maintaining members 22 that maintain the gaps 22a.

[0014] The core block 21 is a laminate of electromagnetic steel sheets, and is the part that generates a magnetic field when an electric wire is wound in a coil shape around the leg portion 20 and a current is passed through the electric wire. The electromagnetic steel sheets are laminated in a direction perpendicular to the plane of the paper in FIG. 1. The manner in which the electromagnetic steel sheets are laminated is not limited to this example. The same applies to the core block 31 and leg connectors 40 and 50 described below. In other words, when an electric wire is wound in a coil shape around the leg portion 20 and a current is passed through the electric wire, a magnetic field is formed that circulates around the leg portion 20, the leg connector 40, the leg 30, and the leg connector 50.

[0015] Gaps 22a are formed between the core blocks 21 and between the leg portions 20 and the leg connecting portions 40, 50. That is, gaps 22a are formed in the magnetic path of the magnetic field formed in reactor core 10. This can increase the magnetic resistance of reactor core 10. The length of gap 22a (the length in the direction parallel to the length of leg portion 20) is not particularly limited, but may be, for example, about 1 to 2 mm.

[0016] The gap maintaining member 22 is a member made of a non-magnetic material and serves to maintain the gap 22a. As will be described in detail later, in this embodiment, the legs 20, 30 are compressed in a direction parallel to the longitudinal direction of the legs 20, 30 to reduce noise from the reactor core 10. Therefore, if nothing is filled in the gap 22a, the gap 22a disappears. In this case, the reactor core 10 cannot perform its function. In other words, the reactor core 10 cannot be used as a reactor. Therefore, in this embodiment, the gap maintaining member 22 is provided in the gap 22a. This maintains the gap 22a even when the legs 20, 30 are compressed. The gap maintaining member 22 is, for example, a bakelite plate. The gap maintaining member 22 may be a hollow member or a solid member.

[0017] The leg portion 30 is a member having the same function as the leg portion 20. That is, the leg portion 30 includes a plurality of core blocks 31 (three in the example of FIG. 1) formed by stacking a plurality of electromagnetic steel plates, gaps 32a formed between the core blocks 31 and between the leg portion 30 and the leg connecting portions 40, 50, and gap maintaining members 32 that maintain the gaps 32a.

[0018] The core block 31 is a part in which an electric wire is wound in a coil shape around the leg portion 30, and generates a magnetic field when a current is passed through the electric wire. Gaps 32a are formed between the core blocks 31 and between the leg portion 30 and the leg connecting portions 40, 50. That is, the gaps 32a are formed in the magnetic path of the magnetic field formed in the reactor core 10. This increases the magnetic resistance of the reactor core 10. The gap maintaining member 32 is a member made of a non-magnetic material and serves to maintain the gap 32a. The gap maintaining member 32 is, for example, a bakelite plate. The gap maintaining member 32 may be a hollow member or a solid member.

[0019] Although the present embodiment has two legs, the number of legs is not limited to this example and may be, for example, three or more.

[0020] The leg connecting parts 40, 50 are made of laminated electromagnetic steel sheets. The leg connecting part 40 connects the upper ends of the legs 20, 30, and the leg connecting part 50 connects the lower ends of the legs 20, 30. The leg connecting parts 40, 50 are parts where magnetic flux flows when an electric wire is wound in a coil shape around the leg 20 or the leg 30 and a current is passed through the electric wire.

[0021] The ceiling portion 70 and the bottom portion 71 are members disposed at the upper and lower ends of the reactor core 10, and when nuts 82, 92 of the compression mechanisms 80, 90 are tightened, they compress the legs 20, 30 in a direction parallel to the length of the legs 20, 30. Details of the compression mechanisms 80, 90 will be described later.

[0022] The compression mechanism 80 includes a bolt 81 and a pair of nuts 82. The bolt 81 is disposed on the left end side of the reactor core 10 and passes through the ceiling portion 70 and the bottom surface portion 71. The pair of nuts 82 are fastened to the protruding portion of the bolt 81 (the portion protruding from the ceiling portion 70 and the bottom surface portion 71).

[0023] The compression mechanism 90 includes a bolt 91 and a pair of nuts 92. The bolt 91 is disposed on the right end side of the reactor core 10 and passes through the ceiling portion 70 and the bottom portion 71. The pair of nuts 92 are fastened to the protruding portion of the bolt 91 (the portion protruding from the ceiling portion 70 and the bottom portion 71).

[0024] The compression mechanisms 80, 90 apply pressure to the reactor core 10 from above and below by tightening the nuts 82, 92. This causes the ceiling portion 70 and the bottom portion 71 to compress the legs 20, 30 in a direction parallel to the longitudinal direction of the legs 20, 30. Note that in this embodiment, the compression mechanisms are configured with bolts and nuts, but the compression mechanism is not limited to this example and may be any mechanism that can compress the reactor core 10 from above and below.

[0025] Here, the compressive force P (MPa) (P≧0) by the compression mechanisms 80 and 90 satisfies the following formula (1). (3 / 40)×Ng-0.1≦P≦(3 / 40)×Ng+0.1 (1) Here, Ng is the maximum number of gaps that can be provided in the leg, and is an integer of 1 or greater. For example, in Fig. 1, the number of gaps in the leg 20 (or leg 30) is the maximum value of 4, so Ng = 4. By compressing the reactor core 10 under these conditions, noise can be reduced. The reactor noise increases as Ng increases, and the effect of the applied compressive force also weakens, so it is thought that the maximum number of gaps becomes the controlling factor.

[0026] FIG. 2 is a graph showing the correlation between leg-direction compressive force (compressive force parallel to the length direction of legs 20, 30) (MPa) and noise (dB) for each value of Ng. Specific experimental conditions will be explained in the examples. The horizontal axis shows leg-direction compressive force (MPa), and the vertical axis shows noise (dB). Graph L1 is a graph showing the correlation between leg-direction compressive force (MPa) and noise (dB) when Ng=4. Point P1 indicates the minimum point of graph L1.

[0027] Graph L2 is a graph showing the correlation between leg-direction compressive force (MPa) and noise (dB) when Ng = 2. Point P2 indicates the minimum point of graph L2. Graph L3 is a graph showing the correlation between leg-direction compressive force (MPa) and noise (dB) when all gaps in reactor core 10 are eliminated (i.e., when Ng = 0). In this case, reactor core 10 essentially becomes the core of the transformer.

[0028] When Ng=2 or 4, noise (dB) decreases as the compressive force increases while the compressive force is low. In this case, it is assumed that the noise is caused by magnetic attraction. This is because it is believed that the higher the compressive force, the more the vibration of the electromagnetic steel sheet is suppressed. When the compressive force is further increased, the noise begins to increase at the boundary of the minimum point. It is assumed that the noise at this time is noise caused by magnetostriction. Therefore, in this embodiment, the range of 0.1 MPa around the minimum point is defined as the range with a low noise level, and Equation (1) is set. According to Equation (1), when Ng=4, the noise level is reduced by setting the compressive force to 0.2 to 0.4 MPa, and when Ng=2, the noise level is reduced by setting the compressive force to 0.05 to 0.25 MPa.

[0029] On the other hand, when Ng = 0, that is, when compressive force is applied to the transformer core, it can be seen that the higher the compressive force, the higher the noise level. In other words, it is thought that the stronger the compressive force, the stronger the noise caused by magnetostriction.

[0030] A second embodiment of the present invention will now be described. FIG. 3 is a diagram illustrating only the leg 110 of the reactor core 100 according to the second embodiment. In the example of FIG. 3, the leg 110 is divided into six core blocks 130 by seven gap maintainers 120. Each gap maintainer 120 includes a bolt 140 and a nut 150 (compression force adjustment mechanism) that penetrate the gap maintainer 120, allowing the compression force applied to each core block 130 to be adjusted. The compression force applied to each core block 130 may be adjusted in advance using a test model. That is, in the test model (e.g., a test model consisting of the core block 130, the gap maintainers 120 arranged above and below the core block 130, the above-mentioned bolt 140, and the above-mentioned nut 150), for example, a pressure sensor is inserted between the core block 130 and the gap maintainer 120, and the tightening of the nut 150 is adjusted so that the compression force P (P≧0) falls within the range of Equation (1). The position of the nut 150 at that time may be measured and recorded, and the position of the nut 150 of a product having the same dimensions and shape as the test model may be set to match the position of the nut 150 on the test model.

[0031] As described above, according to this embodiment, the noise of the reactor can be reduced. [Example]

[0032] Next, an example of this embodiment will be described. In this example, the reactor core 10 shown in FIG. 1 was fabricated. The gaps 22a and 32a were both 1 mm long. The gap maintainers 22 and 32 were made of bakelite boards. Next, an electric wire was wound around the leg 20. A microphone was installed 300 mm away from the center of the reactor core 10. Next, an AC current of 1 to 8 A and a frequency of 50 Hz was passed through the electric wire to generate a magnetic field. The current value was adjusted so that the magnetic flux density was always 1.4 T for each gap number and compression force condition. Next, the leg-direction compression force was changed by adjusting the torque applied to the bolts 82 and 92. The leg-direction compression force was measured by measuring the bolt tightening pressure with a torque wrench and converting it. At each leg-direction compression force, a current was passed through the electric wire, and the noise was measured with a microphone to determine the correlation between the leg-direction compression force and the noise.

[0033] Graph L1 was obtained when the number of gaps in leg 20 was 4 and the number of gaps in leg 30 was 2. The same electric wire as that in leg 20 was wound around leg 30, and the same current as above was passed through it to measure the noise, resulting in a graph similar to L1. Next, the number of gaps in leg 20 was changed to 2, and the number of gaps in leg 30 was changed to 2, and the same test as above was performed. As a result, graph L2 shown in Figure 2 was obtained.

[0034] Furthermore, when all gaps 22a, 32a were eliminated from reactor core 10 (i.e., Ng=0) and the electric wire was wound around leg portion 20, a test similar to the above was carried out, and the graph L3 shown in FIG. 2 was obtained.

[0035] From the above results, it is clear that noise can be reduced by pressurizing reactor core 10 so as to satisfy formula (1).

[0036] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0037] 10 Reactor Core 20, 30 legs 22a, 32a gap 22, 32 Gap maintaining member 40, 50 Leg connection part 70 Ceiling 71 Bottom part 80, 90 compression mechanism

Claims

1. a plurality of legs formed of laminated electromagnetic steel sheets, each having one or more gaps formed in a magnetic path; a gap maintaining member made of a non-magnetic material that maintains the gap; a compression mechanism capable of compressing the leg portion in a direction parallel to the length direction of the leg portion, An electric wire is wound around at least one of the plurality of leg portions, A reactor core, characterized in that a compressive force P (MPa) (P≧0) applied to the leg portion by the compression mechanism satisfies the following formula (1). (3 / 40) × Ng − 0.1≦P≦(3 / 40) × Ng + 0.1 (1) Here, Ng is the maximum number of gaps that can be provided in the leg portion, and is an integer of 1 or greater.

2. a plurality of legs formed of laminated electromagnetic steel sheets, each having one or more gaps formed in a magnetic path; a gap maintaining member made of a non-magnetic material that maintains the gap; At least one of the gap maintaining members has a compression force adjusting mechanism that adjusts the compression force applied to one and the other core blocks adjacent to the gap maintaining member, A reactor core characterized in that the compression force adjustment mechanism causes the compression force P (MPa) (P≧0) in a direction parallel to the longitudinal direction of the leg to satisfy the following formula (1) at any position in the longitudinal direction of the leg. (3 / 40) × Ng − 0.1≦P≦(3 / 40) × Ng + 0.1 (1) Here, Ng is the maximum number of gaps that can be provided in the leg portion, and is an integer of 1 or greater.

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