Switching device

Abstract

An electromechanical switching device for breaking an electric current, the switching device including a stationary main contact; a movable main contact; a stationary arcing contact; a movable arcing contact, the stationary arcing contact and the movable arcing contact being arranged in parallel with the stationary main contact and the movable main contact; an actuating arrangement configured to move the movable main contact and the movable arcing contact; and a magnetic member arranged to generate a magnetic holding force in response to an electric current flow through the movable arcing contact when the movable arcing contact is in the closed position, the magnetic holding force acting on the movable arcing contact in a direction against the stationary arcing contact.

Claims

1. An electromechanical switching device for breaking an electric current, the switching device comprising: a stationary main contact; a movable main contact; a stationary arcing contact; a movable arcing contact, the stationary arcing contact and the movable arcing contact being arranged in parallel with the stationary main contact and the movable main contact; an actuating arrangement configured to move the movable main contact relative to the stationary main contact between a closed position, in contact with the stationary main contact, and an open position, separated from the stationary main contact, and configured to move the movable arcing contact linearly relative to the stationary arcing contact between a closed position, in contact with the stationary arcing contact, and an open position, separated from the stationary arcing contact; and a magnetic member arranged to generate a magnetic holding force in response to an electric current flow through the movable arcing contact when the movable arcing contact is in the closed position, the magnetic holding force acting on the movable arcing contact in a direction against the stationary arcing contact.

2. The switching device according to claim 1, wherein the magnetic member is of a material having positive magnetic susceptibility.

3. The switching device according to claim 1, wherein the magnetic member is stationary.

4. The switching device according to claim 1, wherein the magnetic member is a rigid piece.

5. The switching device according to claim 1, further comprising an arcing contact carrier carrying the movable arcing contact.

6. The switching device according to claim 5, wherein the arcing contact carrier is an arm.

7. The switching device according to claim 1, wherein the magnetic member is U-shaped or V-shaped.

8. The switching device according to claim 6, wherein the magnetic member partly encloses the arcing contact carrier when the movable arcing contact is in the closed position.

9. The switching device according to claim 1, wherein the actuating arrangement comprises an actuator and a transmission, wherein the movable main contact is driven by the actuator, and wherein the movable arcing contact is driven by the actuator via the transmission.

10. The switching device according to claim 9, wherein the movable main contact is driven directly by the actuator.

11. The switching device according to claim 9, wherein the transmission is a speed increasing transmission.

12. The switching device according to claim 1, wherein the actuating arrangement is arranged to move the movable main contact linearly relative to the stationary main contact between the closed position and the open position.

13. The switching device according to claim 1, wherein the switching device is configured to break an electric current with two contact pairs in series.

14. The switching device according to claim 1, wherein the switching device is a contactor.

15. The switching device according to claim 1, wherein the actuating arrangement is configured to move the movable arcing contact away from the stationary arcing contact at a first speed, and configured to move the movable main contact away from the stationary main contact at a second speed, lower than the first speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

(2) FIG. 1: schematically represents a perspective view of an electromechanical switching device;

(3) FIG. 2: schematically represents a partial perspective view of the switching device;

(4) FIG. 3: schematically represents a movable main contact in a closed position and a movable arcing contact in a closed position;

(5) FIG. 4: schematically represents the movable main contact in an open position and the movable arcing contact in the closed position; and

(6) FIG. 5: schematically represents the movable main contact in the open position and the movable arcing contact in an open position.

DETAILED DESCRIPTION

(7) In the following, an electromechanical switching device for breaking an electric current, which switching device comprises a magnetic member, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

(8) FIG. 1 schematically represents a partial perspective view of an electromechanical switching device 10. The switching device 10 is configured to break an electric current. In this example, the switching device 10 is a contactor. In FIG. 1, some parts of the switching device 10 are removed to increase visibility.

(9) FIG. 2 schematically represents a partial perspective view of the switching device 10. Also in FIG. 2, some parts of the switching device 10 are removed to increase visibility. With collective reference to FIGS. 1 and 2, the switching device 10 comprises a stationary main contact 12, a movable main contact 14, a stationary arcing contact 16 and a movable arcing contact 18. The switching device 10 further comprises switching bars 20 for connection of the switching device 10 to an external main electric circuit (not shown).

(10) The stationary main contact 12 and the movable main contact 14 form a main contact pair. The stationary arcing contact 16 and the movable arcing contact 18 form an arcing contact pair. The main contact pair is arranged in parallel with the arcing contact pair.

(11) The switching device 10 further comprises an actuating arrangement 22. The actuating arrangement 22 is configured to move the movable main contact 14 relative to the stationary main contact 12 between a closed position and an open position. In the closed position, the movable main contact 14 is in mechanical and electrical contact with the stationary main contact 12. In the open position, the movable main contact 14 is separated from the stationary main contact 12. In FIGS. 1 and 2, the movable main contact 14 is in the open position.

(12) The actuating arrangement 22 is further configured to move the movable arcing contact 18 linearly relative to the stationary arcing contact 16 between a closed position and an open position. In this example, the movable arcing contact 18 is arranged to move linearly in a vertical direction. In the closed position, the movable arcing contact 18 is in mechanical and electrical contact with the stationary arcing contact 16. In the open position, the movable arcing contact 18 is separated from the stationary arcing contact 16. In FIGS. 1 and 2, the movable arcing contact 18 is in the open position.

(13) In the example in FIGS. 1 and 2, the switching device 10 comprises four main contact pairs and four arcing contact pairs. In the illustration in FIGS. 1 and 2, three of the arcing contact pairs are covered by a respective stack of splitter plates 24.

(14) The switching device 10 of this example further comprises two main contact carriers 26 and two arcing contact carriers 28. Each of the main contact carriers 26 and the arcing contact carriers 28 is here exemplified as an arm. On each main contact carrier 26, a movable main contact 14 is fixedly attached on each side of the actuating arrangement 22. On each arcing contact carrier 28, a movable arcing contact 18 is fixedly attached on each side of the actuating arrangement 22.

(15) Thus, two arcing contact pairs are provided on a front side of the actuating arrangement 22 and two arcing contact pairs are provided on a rear side of the actuating arrangement 22. Moreover, two main contact pairs are provided on the front side of the actuating arrangement 22, between the two front arcing contact pairs, and two-front main contact pairs are provided on the rear side of the actuating arrangement 22, between the two rear arcing contact pairs. The switching device 10 thus comprises a first set of two main contact pairs in series, a second set of two main contact pairs in series, a third set of two arcing contact pairs in series, and a fourth set of two arcing contact pairs in series.

(16) Each main contact pair is responsible for carrying/conducting a current. Each arcing contact pair is responsible for experiencing arcs occurring during a switching operation that may be either a closing or an opening operation.

(17) The switching device 10 further comprises a magnetic member 30. The magnetic member 30 is stationary and of a material having positive magnetic susceptibility, such as magnetic iron. The magnetic member 30 is thus a magnetic core. In this example, each arcing contact carrier 28 is magnetically effected by the magnetic member 30.

(18) As shown in FIGS. 1 and 2, the magnetic member 30 of this example is a rigid U-shaped piece formed from a single piece of material. When the movable arcing contact 18 adopts the closed position, the magnetic member 30 is arranged to generate a magnetic holding force in response to a current flow through the movable arcing contact 18, as detailed below.

(19) In the example in FIGS. 1 and 2, the switching device 10 comprises four magnetic members 30. Each magnetic member 30 is associated with a movable arcing contact 18. Two magnetic members 30 are arranged on the front side of the actuating arrangement 22 and two magnetic members 30 are arranged on the rear side of the actuating arrangement 22. Each magnetic member 30 is positioned below one of the arcing contact carriers 28.

(20) FIG. 3 represent a more schematic illustration of the switching device 10. In FIG. 3, the movable main contact 14 is in the closed position and the movable arcing contact 18 is in the closed position. In the closed position of the movable main contact 14, the movable main contact 14 is in mechanical and electrical connection with the associated stationary main contact 12. In the closed position of the movable arcing contact 18, the movable arcing contact 18 is in mechanical and electrical connection with the stationary arcing contact 16.

(21) Moreover, in the closed position of the movable arcing contact 18 according to FIG. 3, the arcing contact carrier 28 is snugly received in the U-shaped magnetic member 30. The magnetic member 30 thereby partly encloses the arcing contact carrier 28.

(22) The switching device 10 further comprises a first support member 32 and a second support member 34. The first support member 32 is fixed to the main contact carrier 26. The second support member 34 is fixed to the arcing contact carrier 28.

(23) As shown in FIG. 3, the actuating arrangement 22 comprises an actuator 36 and a transmission 38. The first support member 32 is arranged to be driven directly by the actuator 36, i.e. without any intermediate transmission. The second support member 34 is arranged to be driven by the actuator 36 via the transmission 38. The transmission 38 of this example is a speed increasing transmission having a ratio of 1:4.

(24) The transmission 38 of this specific example comprises a first gear rack 40, a second gear rack 42, a first gear wheel 44 and a second gear wheel 46. The first gear rack 40 is fixed to the first support member 32. The second gear rack 42 is fixed to the second support member 34. Each of the first gear rack 40 and the second gear rack 42 is vertically oriented. The first gear wheel 44 is smaller than the second gear wheel 46. The first gear wheel 44 is fixed to the second gear wheel 46 for common rotation about a horizontal rotation axis (not denoted).

(25) In the following, a current breaking operation of the switching device 10 will be described. Although the description is given for two contact pairs, it should be understood that the described breaking operation also takes place for each of the remaining contact pairs.

(26) FIG. 4 schematically represents the movable main contact 14 in an open position and the movable arcing contact 18 in the closed position. During a breaking operation, the actuator 36 drives the first support member 32 vertically upwards. Thereby, the main contact carrier 26 is moved vertically upwards such that the movable main contact 14 moves linearly away from the closed position and separates from the stationary main contact 12.

(27) Only at the very end of this initial movement of the first support member 32, the first gear rack 40 moves into meshing engagement with the first gear wheel 44. Therefore, this initial movement of the first support member 32 is not transmitted to any movement of the second support member 34.

(28) In FIG. 4, instead of flowing through the main contact pair, the current now flows through the arcing contact pair. The current flow through the arcing contact pair generates a separation force. The separation force acts to separate the movable arcing contact 18 from the stationary arcing contact 16. The magnitude of this separation force is dependent on the magnitude of the current.

(29) However, at the same time, the magnetic member 30 generates a magnetic holding force in response to the current flow through the movable arcing contact 18. Since the magnetic member 30 is stationary, the magnetic holding force is generated independently of the kinematics of the actuating arrangement 22. In this example, when the current passes through the movable arcing contact 18, a magnetic circuit comprising the magnetic member 30 and the arcing contact carrier 28 is magnetized, whereby the magnetic holding force arises between the magnetic member 30 and the arcing contact carrier 28. This magnetic holding force acts on the movable arcing contact 18 in a direction against the stationary arcing contact 16, i.e. pressing downwards in FIG. 4. Also the magnitude of the magnetic holding force is dependent on the magnitude of the current.

(30) The magnetic holding force thus reduces or eliminates the effect of the separation force. A balancing effect is thereby generated. The magnetic holding force is particularly advantageous for this particular switching device 10 in the state in FIG. 4 since the actuating arrangement 22 can only provide a reduced downward pressing force of the movable arcing contact 18 against the stationary arcing contact 16 due to the transmission 38.

(31) FIG. 5 schematically represents the movable main contact 14 in a further open position and the movable arcing contact 18 in an open position. As the first support member 32 is driven further (from the FIG. 4 position) by means of the actuator 36, the meshing between the first gear rack 40 and the first gear wheel 44 causes the first gear wheel 44 and the second gear wheel 46 to rotate in common, as illustrated by arrow 48. Since the second gear wheel 46 meshes with the second gear rack 42, the second support member 34 and the arcing contact carrier 28 are driven vertically upwards. The movable arcing contact 18 thereby moves linearly from the closed position in FIG. 4 to the open position in FIG. 5. The electric arc between the movable arcing contact 18 and the stationary arcing contact 16 is extinguished by the splitter plates 24.

(32) As can be gathered from FIGS. 4 and 5, the movable arcing contact 18 moves faster than the movable main contact 14. In the state of the switching device 10 in FIG. 5, the distance between the movable arcing contact 18 and the stationary arcing contact 16 is larger than the distance between the movable main contact 14 and the stationary main contact 12.

(33) While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.