Arc extinguishing structure of disconnecting switch
By using the first and second grid sets of different arrangement of track lines and the inclined arc extinguishing grid plates in the rotary isolation switch, the problem of low utilization rate of arc extinguishing grids in the prior art is solved, and a better arc extinguishing effect is achieved.
Patent Information
- Application Number
- CN202422411937.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-09-30
AI Technical Summary
In the existing rotary isolation switch, the grids of the arc extinguishing chamber are arranged in a single arc, resulting in low utilization of arc extinguishing gates and difficult to effectively extinguish the arc.
The arc extinguishing chamber structure including the first grid set and the second grid set is adopted. The two imaginary arrangement trajectories are different. The first arc extinguishing gate of the first grid set is close to the static contact. The curvature of the imaginary arrangement trajectory of the first grid set is greater than that of the second grid set. Combined with the inclined arc extinguishing gate and the gas-producing member, the arc extinguishing effect is enhanced.
The utilization rate of the arc extinguishing gate is improved, the extinguishing effect of the arc is enhanced, and the arc extinguishing performance is improved.
Smart Images
Figure CN223155902U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a rotary disconnecting switch, in particular to an arc extinguishing structure of a disconnecting switch. Background Art
[0002] Arc extinguishing chambers are often used in some switches to extinguish the arcs generated when the moving and static contacts are separated. Arc extinguishing technology is also applied in rotary disconnecting switches.
[0003] In the existing disconnecting switch, the grid plates of the arc extinguishing chamber are generally arranged in a single arc shape, that is, all the arc extinguishing grids are arranged according to an imaginary line of an arc, and the curvature of this imaginary line of the arc is basically the same everywhere. The utilization rate of such an arc extinguishing grid arrangement is not high. Summary of the Invention
[0004] In view of this, the purpose of the utility model is to overcome the deficiencies in the prior art, and aims to provide an arc extinguishing structure of a disconnecting switch with a better arc extinguishing effect.
[0005] The utility model provides an arc extinguishing structure of a disconnecting switch, which includes a static contact, a moving contact and an arc extinguishing chamber; the moving contact rotates relative to the static contact to enable the moving contact to switch between a first position and a second position; the first position is the position in contact with the static contact, and the second position is the breaking position; the arc extinguishing chamber is arranged on the path where the moving contact breaks; wherein, the second position is within the range covered by the arc extinguishing chamber, the arc extinguishing chamber includes a first grid plate group and a second grid plate group, the imaginary arrangement trajectory line of the second grid plate group is arc-shaped, and the imaginary arrangement trajectory line of the first grid plate group is different from that of the second grid plate group; the first arc extinguishing grid of the first grid plate group is in contact with or adjacent to the static contact.
[0006] In some embodiments of the present application, the minimum distance between the first arc extinguishing grid and the static contact is not greater than 3 times the thickness of the first arc extinguishing grid, so as to enable the first arc extinguishing grid of the first grid plate group to be adjacent to the static contact.
[0007] In some embodiments of the present application, the imaginary arrangement trajectory line of the first grid plate group is also arc-shaped, and the second position is within the range covered by the second grid plate group; the curvature of the imaginary arrangement trajectory line of the first grid plate group is greater than that of the imaginary arrangement trajectory line of the second grid plate group; the connection line between the first arc extinguishing grid of the first grid plate group and the imaginary rotation center of the moving contact is a first imaginary connection line, and the connection line between the last arc extinguishing grid of the first grid plate group and the imaginary rotation center of the moving contact is a second imaginary connection line, and the included angle between the first imaginary connection line and the second imaginary connection line is α, 30° < α < 90°.
[0008] In some embodiments of the present application, the closest distance from each arc extinguishing grid in the first grid group to the imaginary rotation center of the moving contact is d, the order from the first arc extinguishing grid to the last arc extinguishing grid in the first grid group is X, and d increases as the order X increases.
[0009] In some embodiments of the present application, it further includes a unit housing, an installation cavity is provided in the unit housing, the installation cavity includes a dimension F in the length direction and a dimension f in the width direction, and F > f; the length center line P2 in the length direction passes through the static contact; with the width center line P1 in the width direction as the boundary, the first grid group and the second grid group are respectively arranged on both sides of the width center line P1.
[0010] In some embodiments of the present application, it further includes a unit housing, an installation cavity is provided in the unit housing, the installation cavity includes a dimension F in the length direction and a dimension f in the width direction, and F > f; the first grid group is closer to the length center line P2 in the length direction than the second grid group, and the length center line P2 in the length direction passes through the static contact.
[0011] In some embodiments of the present application, the imaginary arrangement trajectory line in the first grid group is a straight line, and each arc extinguishing grid in the first grid group is inclined, and the inclined angles are all different; the first static contact includes a first inclined surface, the first arc extinguishing grid at the head of the first grid group is in contact with or adjacent to the first inclined surface, and the included angle between each arc extinguishing grid in the first grid group and the first inclined surface increases as the distance from it to the first inclined surface increases.
[0012] In some embodiments of the present application, the arc extinguishing chamber further includes a third grid group, the third grid group is connected to the second grid group, the imaginary arrangement trajectory line of the third grid group is a straight line, and each arc extinguishing grid of the third grid group is inclined.
[0013] In some embodiments of the present application, the arc extinguishing chamber includes two side plates and at least one gas generating part, all arc extinguishing grids are fixed to the side plates; the end of the arc extinguishing grid close to the moving contact is the first end, and the end of the arc extinguishing chamber far from the moving contact is the second end; the gas generating part is arranged on the side plate and at least near the first end of some arc extinguishing grids, and some of these arc extinguishing grids come from the first grid group and the second grid group.
[0014] In some embodiments of the present application, a blocking part is arranged near the last arc extinguishing grid of the arc extinguishing chamber.
[0015] Such a design of the blocking part can effectively guide the internal airflow to move backward in the arc extinguishing chamber, which is beneficial to improving the exhaust effect and the arc extinguishing performance.
[0016] In some embodiments of the present application, it further includes a unit housing, and an installation cavity is provided in the unit housing. The installation cavity includes a dimension F in the length direction and a dimension f in the width direction, and F > f; the length center line P2 in the length direction passes through the static contact.
[0017] Advantages of the present application compared with the prior art:
[0018] By adopting such a form of at least two sets of grid pieces, and the imaginary arrangement trajectory lines of the two sections are different, and the first grid piece of the first section is in contact with or adjacent to the static contact, all the arc extinguishing grids can be utilized more fully (because in the prior art, in the arc extinguishing chamber with a single-section circular arc structure, the first grid piece and the arc extinguishing grids near the first grid piece are difficult to be fully utilized). BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.
[0020] Figure 1 Shows a schematic diagram of the disconnector of the embodiment of the present invention;
[0021] Figure 2 Shows a schematic diagram of the switch unit layer in the embodiment of the present invention;
[0022] Figure 3 Shows a schematic diagram of the first embodiment of the arc extinguishing chamber in the embodiment of the present invention;
[0023] Figure 4 Shows a schematic diagram of the arc extinguishing grids of the first embodiment of the arc extinguishing chamber in the embodiment of the present invention;
[0024] Figure 5 Shows a perspective view of the first embodiment of the arc extinguishing chamber in the embodiment of the present invention;
[0025] Figure 6 Shows a schematic diagram of removing one side plate of the first embodiment of the arc extinguishing chamber in the embodiment of the present invention;
[0026] Figure 7 Shows a schematic diagram of the second embodiment of the arc extinguishing chamber in the embodiment of the present invention;
[0027] Figure 8 Shows a schematic diagram of the arc extinguishing grids of the second embodiment of the arc extinguishing chamber in the embodiment of the present invention and the static contact. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0028] Embodiments of the present utility model will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present utility model and should not be construed as a limitation of the present utility model.
[0029] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present utility model.
[0030] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, the meaning of "a plurality" is two or more unless otherwise specifically defined.
[0031] In the present utility model, unless otherwise clearly defined and limited, terms such as "mounted", "connected", "connected to", "fixed" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.
[0032] In the present utility model, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be the direct contact between the first and second features, or the indirect contact between the first and second features through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature. Embodiment
[0033] As shown Figure 1-8 in the figure, an embodiment of the present utility model is a rotary disconnect switch. This rotary disconnect switch includes an operating unit layer K1 and a switch unit layer K2. An operating mechanism is provided in the operating unit layer K1, and a moving contact disk, a static contact 100, and an arc extinguishing structure are provided in the switch unit layer K2. The rotation of the moving contact disk can be realized through the operating mechanism, so as to realize the connection and disconnection of the switch unit layer K2, and the arc extinguishing structure is used to achieve an arc extinguishing effect during disconnection.
[0034] Since the structures inside each switch unit layer are basically the same, the following takes one group of switch unit layers as an example:
[0035] Each switch unit layer has a unit housing 400. Two static contacts 100 are arranged in the unit housing 400, and the two ends of the moving contact 200 on the moving contact disk correspond to the two static contacts 100 respectively. Since the moving contact disk is rotatably arranged on the unit housing 400 and the static contact 100 is fixed on the unit housing 400, the moving contact 200 rotates relative to the static contact 100. When the moving contact 200 rotates to the position where it contacts the static contact 100 (the first position), the connection is completed; when the moving contact 200 rotates to the maximum disconnection position (the second position), the moving and static contacts 100 are completely disconnected.
[0036] The arc extinguishing structure adopts an arc extinguishing chamber 300. The number of arc extinguishing chambers 300 here corresponds to the number of moving and static contacts 100. One pair of moving and static contacts 100 corresponds to one arc extinguishing chamber 300. In this way, the arc extinguishing chamber 300 can be arranged on their disconnection path to eliminate the arc generated when the moving and static contacts 100 are separated.
[0037] Here, the second position is within the range covered by the arc extinguishing chamber 300, specifically referring to that the final disconnection position of the arc extinguishing chamber 300 is still within the arc extinguishing chamber 300. The reason for realizing such a method is mainly that the range of the arc extinguishing chamber 300 is larger than the disconnection movement stroke of the moving contact 200. In this way, when the moving contact 200 disconnects and enters the arc extinguishing chamber 300 until the second position, it is within the range covered by the arc extinguishing chamber 300.
[0038] The arrangement of the arc extinguishing grids inside the arc extinguishing chamber 300 here at least includes a first grid sheet group 310 and a second grid sheet group 320. The first grid sheet group 310 is closer to the static contact 100 than the second grid sheet group 320. Specifically, the imaginary arrangement trajectory line of the arc extinguishing grids in the second grid sheet group 320 is arc-shaped, and the imaginary arrangement trajectory line of the arc extinguishing grids in the first grid sheet group 310 is different from that of the arc extinguishing grids in the second grid sheet group 320. The first arc extinguishing grid of the first grid sheet group 310 is in contact with or adjacent to the static contact 100. Here, being in contact means that the two are fitted together, and being adjacent means that the two are very close to each other (specifically, the minimum distance between the first arc extinguishing grid and the static contact 100 is not greater than 3 times the thickness of the first arc extinguishing grid). Through such a design, the first grid sheet group 310 is closer to the static contact 100, making full use of the arc extinguishing grids in the first grid sheet group 310, and making it easier for the interrupted arc to enter the arc extinguishing chamber 300.
[0039] Here, there are many ways to set the imaginary arrangement trajectory line of the first grid sheet group 310. The following are two examples:
[0040] First, the imaginary arrangement trajectory line of the first grid sheet group 310 is also arc-shaped, as Figure 3-5 shown. The curvature of this arc is greater than the curvature of the imaginary arrangement trajectory line of the arc extinguishing grids in the second grid sheet group 320, that is, the arrangement of the first grid sheet group 310 is more curved than that of the second grid sheet group 320. Here, the second position is within the range covered by the second grid sheet group 320. Based on the imaginary rotation center O of the moving contact 200, the range covered by the first grid sheet group 310 is described. Specifically, the connection line between the first arc extinguishing grid of the first grid sheet group 310 and the imaginary rotation center O of the moving contact 200 is the first imaginary connection line A, and the connection line between the last arc extinguishing grid of the first grid sheet group 310 and the imaginary rotation center O of the moving contact 200 is the second imaginary connection line B. The included angle α between the first imaginary connection line A and the second imaginary connection line B is about 65°. This is not limited to 65° here. As long as the included angle α satisfies 30° < α < 90°, it is worth mentioning that the larger the angle α here, the larger the first grid sheet group 310 (the more arc extinguishing grids it contains), and the smaller the angle α, the smaller the first grid sheet group 310 (the fewer arc extinguishing grids it contains). The setting of these angles fully considers the space inside the unit housing 400, and the arc-shaped first grid sheet group 310 fits the movement trajectory of the moving contact 200 better, making the arc extinguishing performance more excellent.
[0041] Here, the closest distance from each arc extinguishing grid in the first grid group 310 to the imaginary rotation center of the moving contact 200 is d. The order of the first arc extinguishing grid to the last arc extinguishing grid in the first grid group 310 is X, and as the order X increases, d also increases. That is to say, with the imaginary rotation center O as the reference, the closest distance from each grid in the first grid group 310 to the imaginary rotation center O is d, which are d1 for the first piece, d2 for the second piece... and dn for the last piece in sequence. The order of the first arc extinguishing grid to the last arc extinguishing grid in the first grid group 310 means that the order of the first static contact piece close to the static contact 100 is X1, the next one is X2... and the last one (close to the second grid group 320) is Xn. As X increases, D also increases. For example, d2 corresponding to X2 is greater than d1 corresponding to X1. Such a setting is more conducive to forming the arc-shaped arrangement trajectory of the first grid group 310, making its curvature greater than the imaginary arrangement trajectory line of the second grid group 320.
[0042] For the unit housing 400, the interior of the unit housing 400 is an installation cavity 401, and the installation cavity 401 here is used to arrange components such as the static contact 100, the arc extinguishing structure, and the moving contact disc. Here, the installation cavity 401 includes the dimension F in the length direction (the maximum distance between the inner walls in the length direction) and the dimension f in the width direction (the maximum distance between the inner walls in the width direction), and F > f. Here, the static contact 100 is arranged at the middle position in the length direction of the installation cavity 401, that is, the length center line P2 passes through the static contact 100. Taking the width center line P1 in the width direction as the boundary, the first grid group 310 and the second grid group 320 are arranged on both sides of the width center line P1. Such an arrangement is a fully reasonable arrangement of the first grid group 310 and the second grid group 320 with appropriate sizes, considering the overall arc extinguishing performance, making the formed arc extinguishing structure more suitable for the rotation trajectory of the moving contact 200.
[0043] At the same time, the first grid group 310 here is closer to the length center line P2 in the length direction than the second grid group 320. Such a design is also to ensure that the grids in the first grid group 310 can be utilized more fully.
[0044] Of course, in this case, a static arc ignition piece 350 can also be added at the end of the second grid group 320.
[0045] Second, the imaginary arrangement trajectory line of the first grid group 310 is linear, as Figure 7-8As shown, each arc extinguishing grid in the first grid group 310 is inclined and arranged along a straight line, and the inclination angle of each first grid is different here. Taking the first inclined surface 101 on the first static contact 100 as a reference, the first arc extinguishing grid of the first grid group 310 is in contact with or adjacent to the first inclined surface 101 (the above has explained the meaning of adjacent, so it will not be elaborated here). The included angle β between each arc extinguishing grid in the first grid group 310 and the first inclined surface 101 increases as the distance from it to the first inclined surface 101 increases. That is to say, the included angle β1 between the first arc extinguishing grid and the first inclined surface 101 in the first grid group 310 is smaller than the included angle β2 between the second arc extinguishing grid and the first inclined surface 101 in the first grid group 310.
[0046] In this way, the length center line P2 in the length direction of the installation cavity 401 of the unit housing 400 also passes through the static contact 100.
[0047] For this situation, a third grid group 330 is also provided. Here, the third grid group 330 is connected to the second grid group 320. The imaginary arrangement track line of the third grid group 330 is also a straight line, and each arc extinguishing grid of the third grid group 330 is inclined.
[0048] Regardless of the above-mentioned situation, the arc extinguishing chamber 300 includes two side plates 301 and two gas generating parts 302. All arc extinguishing grids are fixed to the side plates 301, and the fixing methods include clamping, plugging, riveting and other methods. The end of the arc extinguishing grid close to the moving contact 200 is the first end. The gas generating parts 302 are arranged between the two side plates 301 and are located near the first end. Here, the gas generating parts 302 are fixed to the side plates 301 by hot riveting, clamping and other methods. The material of the gas generating parts 302 here is selected to be an insulating material that can generate gas under the high temperature of arc gas, such as PA66, polyamide, etc. The specific setting of the gas generating parts 302 here is that they are located near the first end of a part of the arc extinguishing grids. Some of these arc extinguishing grids come from the first grid group 310, and some come from the second grid group 320 (for the second method, some also come from the third grid group 330).
[0049] There is also a sealing part 304 between the two side plates 301 of the arc extinguishing chamber 300. The sealing part 304 is located near the last arc extinguishing grid, which is beneficial to the movement of arc gas into the arc extinguishing chamber 300, effectively guiding the internal air flow to the rear of the arc extinguishing chamber, which is beneficial to improving the exhaust effect and the arc extinguishing performance.
[0050] In the above-mentioned embodiments, the lines with the word "imaginary" are not visible to the naked eye and exist on the product, but are virtual reference lines.
[0051] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.
[0052] Although the embodiments of the present utility model have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present utility model. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present utility model.
Claims
1. An arc extinguishing structure of a disconnector, which comprises a static contact, a moving contact and an arc extinguishing chamber; the moving contact is rotatable relative to the static contact so as to enable the moving contact to switch between a first position and a second position; the first position is the position in contact with the static contact, and the second position is the breaking position; the arc extinguishing chamber is arranged on the path where the moving contact breaks; and it is characterized in that: The second position is within the range covered by the arc extinguishing chamber. The arc extinguishing chamber includes a first grid group and a second grid group. The imaginary arrangement trajectory line of the second grid group is arc-shaped, and the imaginary arrangement trajectory line of the first grid group is different from that of the second grid group; the first arc extinguishing grid of the first grid group is in contact with or adjacent to the static contact.
2. The arc extinguishing structure of a disconnector according to claim 1, characterized in that: The minimum distance between the first arc extinguishing grid and the static contact is not greater than 3 times the thickness of the first arc extinguishing grid, so as to make the first arc extinguishing grid of the first grid group adjacent to the static contact.
3. The arc extinguishing structure of a disconnector according to claim 1, characterized in that: The imaginary arrangement trajectory line of the first grid group is also arc-shaped, and the second position is within the range covered by the second grid group; the curvature of the imaginary arrangement trajectory line of the first grid group is greater than that of the imaginary arrangement trajectory line of the second grid group; the connection line between the first arc extinguishing grid of the first grid group and the imaginary rotation center of the moving contact is the first imaginary connection line, and the connection line between the last arc extinguishing grid of the first grid group and the imaginary rotation center of the moving contact is the second imaginary connection line. The included angle between the first imaginary connection line and the second imaginary connection line is α, and 30° < α < 90°.
4. The arc extinguishing structure of a disconnector according to claim 3, characterized in that: The nearest distance from each arc extinguishing grid in the first grid group to the imaginary rotation center of the moving contact is d. The order from the first arc extinguishing grid to the last arc extinguishing grid in the first grid group is X, and d increases as the order X increases.
5. An arc extinguishing structure of a disconnector according to claim 3, characterized in that: It further includes a unit housing. An installation cavity is provided in the unit housing. The installation cavity includes a dimension F in the length direction and a dimension f in the width direction, and F > f; the length center line P2 in the length direction passes through the static contact; with the width center line P1 in the width direction as the boundary, the first grid group and the second grid group are arranged on both sides of the width center line P1.
6. The arc extinguishing structure of a disconnector according to claim 3, characterized in that: It further includes a unit housing. An installation cavity is provided in the unit housing. The installation cavity includes a dimension F in the length direction and a dimension f in the width direction, and F > f; the first grid group is closer to the length center line P2 in the length direction than the second grid group, and the length center line P2 in the length direction passes through the static contact.
7. The arc extinguishing structure of a disconnector according to claim 1, characterized in that: The imaginary arrangement trajectory line in the first grid group is a straight line, and each arc extinguishing grid in the first grid group is inclined, and the inclination angles are all different; the first static contact includes a first inclined surface. The first arc extinguishing grid of the first grid group is in contact with or adjacent to the first inclined surface, and the included angle between each arc extinguishing grid in the first grid group and the first inclined surface increases as the distance from it to the first inclined surface increases.
8. The arc extinguishing structure of a disconnector according to claim 7, characterized in that: The arc extinguishing chamber further includes a third grid group. The third grid group is connected to the second grid group. The imaginary arrangement trajectory line of the third grid group is a straight line, and each arc extinguishing grid of the third grid group is inclined.
9. An arc extinguishing structure of a disconnector according to any one of claims 1-8, characterized in that: The arc extinguishing chamber includes two side plates and at least one gas generating component. All arc extinguishing grids are fixed to the side plates; the end of the arc extinguishing grid close to the moving contact is the first end, and the end of the arc extinguishing chamber far from the moving contact is the second end; The gas generating component is arranged on the side plate; at least near the first end of some arc extinguishing grids, and some of these arc extinguishing grids come from the first grid group and the second grid group; Or / and, a sealing component is arranged near the last arc extinguishing grid of the arc extinguishing chamber.
10. An arc extinguishing structure of a disconnector according to any one of claims 1-4, 7-8, characterized in that: It further includes a unit housing. An installation cavity is provided in the unit housing. The installation cavity includes a dimension F in the length direction and a dimension f in the width direction, and F > f; the length center line P2 in the length direction passes through the static contact.