Magnetic holding system for a contactor
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN ELECTRICAL & POWER
- Filing Date
- 2024-06-27
- Publication Date
- 2026-05-13
AI Technical Summary
Existing power contactors face damage and welding issues during short circuits due to levitation of the moving part, leading to increased contact resistance and local heating, with existing solutions being either bulky, complex, or not space-saving and fast enough to prevent re-closure.
A magnetic holding system for contactors, featuring a movable part with two contact points, a spring, an actuator, and a magnetic circuit surrounding the movable part, where a plate comes into contact with the magnetic circuit during a short circuit to create a holding force that surpasses the spring's pressure, preventing re-closure and reducing short-circuit current.
The magnetic holding system effectively limits short-circuit current and prevents damage by maintaining a safe distance between the contact points, reducing the risk of welding and heating, and ensuring the contactor remains open during a short circuit.
Smart Images
Figure FR2024050849_09012025_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title of the invention: Magnetic holding system for contactor
[0003] Technical Field
[0004] The present invention relates to the general field of electrical protection devices, such as electromechanical contactors and electrical contactors, more particularly to the protection of these protection devices during a short circuit.
[0005] Prior art
[0006] Power contactors are electrical protection devices generally made up of a fixed part and a moving part which may or may not be in contact with the fixed part.
[0007] To close a contactor, and therefore put the moving part in contact with the fixed part so that an electric current can flow between the two parts, the contactor motor is powered which will allow a force to be applied to the moving part via a spring, and thus allow the flow of an electric current between the two parts.
[0008] When the current flowing between the two parts exceeds a predefined threshold, for example in the event of a short circuit, electromagnetic repulsion forces will be applied to the moving part and compensate for, or even exceed, the force applied by the spring on the moving part. This causes levitation of the contacts of the moving part, i.e. an unwanted opening of the contactor between the fixed and moving parts. In addition, during this phase, i.e. during levitation, the contact resistance between the fixed part and the moving part of the contactor increases and creates local heating (proportional to the contact resistance multiplied by the current squared) which can lead to the destruction of the moving part, irreversible damage to the contactor and / or welding of the moving part to the fixed part when the moving part falls back onto the fixed part after levitation.Currently, to avoid damage to contactors in the event of a short circuit, i.e. to prevent the two parts of the contactor from welding together, several solutions exist:
[0009] - The pressure force on the moving part is increased, but this requires a more cumbersome actuator, which is not compatible with aeronautics;
[0010] - The contact points between the fixed part and the moving part can be multiplied, but this involves managing a large number of moving parts, which is difficult to implement on double-break contactors for linear motor actuation;
[0011] - An expulsion circuit associated with a disconnection system can be used to open the moving part by magnetic repulsion and cut the circuit.
[0012] There are therefore no compact and sufficiently rapid means of preventing the contactor from closing after levitation.
[0013] It is therefore desirable to have a new contactor with a reduced risk of damage in the event of a short circuit.
[0014] Statement of the invention
[0015] The invention relates to a power contactor comprising:
[0016] - a fixed part;
[0017] - a movable part capable of coming into contact with the fixed part and of moving between an open position and a closed position of the contactor, the movable part comprising two points of contact with the fixed part;
[0018] - a first spring placed on the movable part and configured to apply a pressure force on the movable part in the direction of the fixed part;
[0019] - an actuator configured to actuate the moving part and bring it into contact with the fixed part; and
[0020] - an insulating support containing the fixed part, the moving part and the first spring, characterized in that the contactor also comprises:
[0021] - a magnetic circuit surrounding at least a portion of the moving part; and
[0022] - a plate fixed to the moving part and configured to come into contact with the magnetic circuit so as to form a closed magnetic circuit surrounding the moving part when the contactor is in the closed position, the insulating support also containing the plate and the magnetic circuit and the distance between the plate and the magnetic circuit being strictly greater than the distance between the two contact points and the fixed part.
[0023] So when the contactor is in the closed position, during a short circuit, for example for a current flowing between the fixed part and the moving part of 1500 A, the contactor will levitate, so at least one of the contact points of the moving part will no longer be in contact with the fixed part, and the plate will move closer and come into contact with the magnetic circuit. The current still flowing in the moving part will therefore create its own magnetic field which will be channeled by the magnetic circuit and the plate; and a holding force is then created between the plate and the magnetic circuit which exceeds the pressure forces exerted by the spring on the moving part. The distance between the fixed part and the moving part is then of the order of 1 mm to 2 mm. This distance promotes the creation of higher electric arc voltages and therefore a limitation of the current. Thus, the short-circuit current is reduced.
[0024] After a certain time related to the type of actuator, the distance between the fixed part and the moving part increases to a distance of 2 mm to 3 mm. The contactor is fully open. The electric arcs leave the area of the contact points of the moving part to be cut in a dedicated device not described in this invention.
[0025] According to one embodiment of the invention, the power contactor also comprises a second spring configured to apply a pressure force on the movable part towards the fixed part, the first and second springs being placed opposite the two contact points of the fixed part. By having two springs each placed opposite a contact point with the fixed part, it can be ensured that the contactor closes well and that the pressure forces are well balanced between the two contact points. In addition, having two springs makes it possible to avoid opening the contactor at a single contact point.
[0026] According to another embodiment of the invention, the magnetic circuit comprises two portions located on either side of the first spring, and the plate is configured to form two closed magnetic circuits, with the two portions of the magnetic circuit surrounding the moving part when the contactor is in the closed position.
[0027] According to a particular characteristic of the invention, the magnetic circuit and the plate are made of ferromagnetic steel.
[0028] According to another particular characteristic of the invention, the distance between the plate and the magnetic circuit is between 2 mm and 4 mm, and the distance between the two contact points and the fixed part is between 1 mm and 2.5 mm.
[0029] Another object of the invention relates to a method of closing a power contactor in the open position according to the invention, comprising bringing the two contact points of the moving part into contact with the fixed part, the plate remaining at a distance from the magnetic circuit.
[0030] Yet another subject of the invention relates to a method for opening a power contactor in the closed position, during a short circuit, according to the invention, comprising bringing the plate into contact with the magnetic circuit, then opening the contact between the two contact points and the fixed part and finally opening the contact between the plate and the magnetic circuit.
[0031] Thus, during a short circuit, thanks to the force of holding the plate on the magnetic circuit created by the contact between the plate and the magnetic circuit, the moving part does not fall back onto the fixed part, which prevents damage to the power contactor.
[0032] Brief description of the drawings Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate exemplary embodiments thereof which are not limiting in nature.
[0033] [Fig. IA] Figure IA shows, schematically and partially, a power contactor according to an embodiment of the invention in the open position.
[0034] [Fig. IB] Figure IB represents a three-dimensional view of the power contactor of Figure IA.
[0035] [Fig. 2] Figure 2 shows, schematically and partially, a power contactor according to the embodiment of Figure 1 in the closed position.
[0036] [Fig. 3] Figure 3 shows, schematically and partially, a power contactor according to the embodiment of Figure 1 during a short circuit.
[0037] [Fig. 4] Figure 4 schematically represents the evolution of the short-circuit current in a power contactor of the prior art and in that of Figure 1.
[0038] [Fig. 5] Figure 5 shows, schematically and partially, a power contactor according to another embodiment.
[0039] Description of the embodiments
[0040] Figures 1A, 1B, 2 and 3 schematically and partially represent a power contactor 100 according to an embodiment of the invention in several positions: Figures 1A and 1B represent the contactor 100 in the open position, Figure 2 represents the contactor 200 in the closed position and Figure 3 represents the contactor 300 during a short circuit.
[0041] The contactor 100, 200 comprises a fixed part 120, 220 and a movable part 110, 210 capable of coming into contact with the fixed part 120, 220 at two contact points (111, 112), (211, 212). When the movable part 210 is in contact with the fixed part 220, the contactor 200 is in the closed position as shown in FIG. 2. When the movable part 120 is not in contact with the fixed part 120, the contactor 100 is open as shown in FIGS. 1A and 1B.
[0042] The contactor 100, 200 also comprises a plate 102, 202 fixed on the movable part 120, 220 and a magnetic circuit 103, 203 which at least partially surrounds the movable part 110, 210. In this embodiment, the magnetic circuit 103, 203 is U-shaped and surrounds the movable part 110, 210. The magnetic circuit 103, 203 is able to come into contact with the plate 102, 202 to form a closed magnetic circuit in the event of a short circuit as will be described below with reference to FIG. 3.
[0043] Ideally, the magnetic circuit 103, 203 has a shape complementary to the moving part 110, 210 in order to limit the size and facilitate the integration of the magnetic circuit within the contactor 100, 200.
[0044] The contactor 100, 200 also comprises two springs 141, 142, 241, 242 configured to apply a pressure force to the movable part 110, 210 when the contactor 100, 200 is closed; as well as an actuator 150, 250 for actuating the movable part 110, 210 towards the fixed part 120, 220 to close or open the contactor 100, 200 and an insulating support 101, 201.
[0045] The insulating support 101, 201 comprises the fixed part 120, 220, the movable part 110, 210, the two springs 141, 142, 241, 242, the magnetic circuit 103, 203 and the plate 102, 202. This support makes it possible to isolate the magnetic circuit 103, 203 from all electromagnetic disturbances and to protect the contactor 100, 200.
[0046] The distance dl between the plate 102, 202 and the magnetic circuit 103, 203 is strictly greater than the distance d2 between the fixed part 120, 220 and the movable part 110, 210. This ensures that in the closed position, the plate 102, 202 is not in contact with the magnetic circuit 103, 203.
[0047] The operation of the contactor 100, 200 during a short circuit is now described with reference to FIG. 3 and with reference to FIG. 4 which represents the short-circuit current in a conventional contactor (curve 401) and in the contactor 300 of the invention (curve 402). During a short circuit, for example for a current flowing in the contactor 300 greater than 1500 A corresponding to the current Iccl of FIG. 4, the contactor 300 will open on at least one of the contact points 311, 312 and enter into levitation. The threshold for which the contactor 300 levitates is determined by the force of the spring(s) 341, 342 applying the pressure force on the movable part 310.
[0048] The plate 302 will then move closer to the magnetic circuit 303, and the current still flowing in the moving part 310 will create its own magnetic field which is channeled through the magnetic circuit 303 and the plate 302. In the nominal position (closed or open), the air gap between the plate 302 and the magnetic circuit 303 is not sufficient to create a force allowing them to be brought together.
[0049] If the current continues to increase and reaches the current Icc2 of Figure 4, which is for example 2000 A, the plate 302 continues to move closer to the magnetic circuit 303 until it is in contact with it. A magnetic holding force is then created between the plate 302 and the magnetic circuit 303 which overcomes the pressure forces exerted by the springs 341, 342 on the moving part 310. This makes it possible to prevent the contactor from closing again and therefore the moving part 310 from sticking to the fixed part 320. The distance between the fixed part 320 and the moving part 310 is then of the order of 1 mm to 2 mm, which promotes the creation of higher electric arc voltages and therefore a limitation of the current which corresponds to the current Icc3 of Figure 4. Indeed, the electric arcs created are seen as resistances by the contactor 300.Thus, the short-circuit current in the contactor 300 (curve 402 of Figure 4) is reduced compared to the short-circuit current in a conventional contactor (curve 401 of Figure 4). This reduction in the short-circuit current thus makes it possible to limit heating at the contact points 311, 312 and therefore to limit possible damage to the contactor 300.
[0050] Then, after a certain time defined by the opening mode of the contactor and therefore the type of actuator, the moving part 310 is definitively separated from the fixed part 320 and the distance between the two is of the order of 2 mm to 3 mm. The electric arcs leave the contact zone and are cut in a dedicated cutting device not described here. The cutting device can for example be a block of ionization fins.
[0051] Figure 5 shows, schematically and partially, a power contactor 500 according to another embodiment of the invention in the open position only.
[0052] This contactor 500 comprises, like the contactor 100 of FIG. 1, a fixed part 520, a movable part 510 comprising two contact points 511, 512 which can be in contact with the fixed part 520 when the contactor 500 is closed, a magnetic circuit 503, 504 and a plate 502 as described previously. However, this contactor 500 comprises a single spring 540 and the magnetic circuit is formed of two portions 503 and 504 surrounding the spring 540. In other words, the two portions 503 and 504 of the magnetic circuit are located on either side of the spring 540. The spring 540 therefore exerts the pressure force at the center of the movable part 510 and not at the two contact points 511 and 512. The two portions 503 and 504 of the magnetic circuit are capable of forming two closed magnetic circuits with the plate 502 during a short circuit in the same way as the contactor of FIGS. 1 to 3.
[0053] The contactor 500 can, like the contactor 100 described with reference to FIG. 1, be in a closed position, as described with reference to FIG. 2 and its operation, during a short circuit, will be the same as that described with reference to FIG. 3.
[0054] Whatever the embodiment, the plate and the magnetic circuit can be made of ferromagnetic steel, and more particularly of pure iron type ferromagnetic steel.
[0055] Regardless of the embodiment, the distance dl between the plate and the magnetic circuit is between 2 mm and 4 mm, and the distance d2 between the fixed part and the moving part is between 1 mm and 2.5 mm. The distances dl and d2 are chosen within these ranges of values while retaining the fact that dl is strictly greater than d2. Regardless of the embodiment, the actuator may be a pyrotechnic or electromagnetic actuator. In the case of high short-circuit currents, for example for short-circuit currents greater than 3000 A, the actuator will preferably be a pyrotechnic actuator because it is faster to trigger than an electromagnetic actuator. For short-circuit currents less than 3000 A, an electromagnetic actuator is preferred.
Claims
Claims
1. Power contactor (100, 200, 300, 500) comprising: - a fixed part (120, 220, 320, 520); - a movable part (110, 210, 310, 510) capable of coming into contact with the fixed part and of moving between an open position and a closed position of the contactor, the movable part comprising two points of contact (111, 112, 211, 212, 311, 312, 511, 512) with the fixed part; - a first spring (141, 241, 341, 540) placed on the movable part and configured to apply a pressure force on the movable part towards the fixed part; - an actuator (150, 250, 350) configured to actuate the movable part and bring it into contact with the fixed part; - an insulating support (101, 201, 301, 501) containing the fixed part, the movable part and the first spring, characterized in that the power contactor also comprises: - a magnetic circuit (103, 203, 303, 503) surrounding at least a portion of the moving part; and - a plate (102, 202, 302, 502) fixed on the moving part and configured to come into contact with the magnetic circuit so as to form a closed magnetic circuit surrounding the moving part when the contactor is in the closed position, the insulating support also containing the plate and the magnetic circuit and the distance (dl) between the plate and the magnetic circuit being strictly greater than the distance (d2) between the two contact points and the fixed part when the contactor is in the open position or crossed by a nominal current.
2. Power contactor (100, 200, 300) according to claim 1, comprising a second spring (142, 242, 342) configured to apply a pressure force on the movable part towards the fixed part, the first (141, 241, 341) and the second (142, 242, 342) springs being placed opposite the two contact points of the fixed part.
3. Power contactor (500) according to claim 1, wherein the magnetic circuit comprises two portions (503, 504) located on either side of the first spring (540), and the plate (502) is configured to form two closed magnetic circuits, with the two portions (503, 504) of the magnetic circuit, surrounding the movable part when the contactor is in the closed position.
4. A power contactor according to any one of claims 1 to 3, wherein the magnetic circuit and the plate are made of ferromagnetic steel.
5. A power contactor according to any one of claims 1 to 4, wherein the distance between the plate and the magnetic circuit is between 2 mm and 4 mm, and the distance between the two contact points and the fixed part is between 1 mm and 2.5 mm.
6. Method for closing a power contactor in the open position according to any one of claims 1 to 5, comprising bringing the two contact points of the movable part into contact with the fixed part, the plate remaining at a distance from the magnetic circuit.
7. Method for opening a power contactor in the closed position, during a short circuit, according to any one of claims 1 to 5, comprising bringing the plate into contact with the magnetic circuit, then opening the contact between the two contact points and the fixed part and finally opening the contact between the plate and the magnetic circuit.