EP4246546A1

EP4246546A1 - Automatic transfer switch and contact system for automatic transfer switch

Info

Publication number: EP4246546A1
Application number: EP23305361.0A
Authority: EP
Inventors: Xiangyu GENG; Zhenzhong Liu; Gang Yu; Xiaojing ZENG; Bin Zhou; Haitao Sun
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2022-03-17
Filing date: 2023-03-16
Publication date: 2023-09-20
Also published as: CN216980376U; AU2023201673A1; AU2023201673B2

Abstract

An automatic transfer switch (10) and a contact system (100) for automatic transfer switch are disclosed. The contact system includes a first stationary contact (150), a second stationary contact (180) and a movable contact (120). The movable contact is movable between a first contact position and a second contact position, in the first contact position of the movable contact, the movable contact is in contact with the stationary contact engagement part of the first stationary contact, and, in the second contact position of the movable contact, the movable contact is in contact with the stationary contact engagement part of the second stationary contact. At least one stationary contact of the first stationary contact and the second stationary contact includes: a first part (162), extending in a vertical direction and including a first vertical end and a second vertical end; and a second part (164), extending in a horizontal direction and including a first horizontal end and a second horizontal end, the first vertical end of the first part meets the first horizontal end of the second part, and a chamfered corner is formed at a joint position of the first part and the second part of the at least one stationary contact. The automatic transfer switch includes one or more contact systems.

Description

TECHNICAL FIELD

The present disclosure relates to a contact system for automatic transfer switch and an automatic transfer switch including the contact system.

BACKGROUND

The electrical performance index Icm/Icw of an automatic transfer switch (ATS) is an index that considers the ability of the product to withstand high currents in the circuit. At present, there are two main types of failures for this index: fusion welding and contact burnout.
The automatic transfer switch with a clamping contact system usually has excellent performance in short-term current withstand index because of an electric clamping force formed between clamping contacts. However, there is still room for further improvement in the short-term current withstand index of the clamping contact system.
There are also some automatic transfer switches may fail in the short-term current withstand test and thus results in a greatly reduced short-term current withstand index of the automatic transfer switches due to the form of its contact structure.
Therefore, there is a need for a contact system for automatic transfer switch, such as a clamping contact system, which has improved short-term current withstand index, can reduce the failure under short-term current withstand working condition, and improve the stability and reliability of the contact system.

SUMMARY

The present disclosure aims to overcome at least some of the abovementioned problems in the prior art.
According to an aspect of the present disclosure, a contact system for automatic transfer switch is provided. The contact system includes a first stationary contact, a second stationary contact and a movable contact, the first stationary contact and the second stationary contact each include a stationary contact engagement part and a conductive connection part suitable to be electrically connected with a wire connection terminal of the automatic transfer switch, the movable contact is movable between a first contact position and a second contact position, in the first contact position of the movable contact, the movable contact is in contact with the stationary contact engagement part of the first stationary contact, and, in the second contact position of the movable contact, the movable contact is in contact with the stationary contact engagement part of the second stationary contact, at least one stationary contact of the first stationary contact and the second stationary contact includes: a first part, extending in a vertical direction and including a first vertical end and a second vertical end; and a second part, extending in a horizontal direction and including a first horizontal end and a second horizontal end, the first vertical end of the first part meets the first horizontal end of the second part, the stationary contact engagement part of the at least one stationary contact is at or close to the second vertical end of the first part, the conductive connection part of the at least one stationary contact is at or close to the second horizontal end of the second part, and a chamfered corner is formed at a joint position of the first part and the second part of the at least one stationary contact.
According to one or more embodiments of the present disclosure, a dimension of the chamfered corner in the horizontal direction is 80%-130% of a dimension of the first part in the horizontal direction.
According to one or more embodiments of the present disclosure, a dimension of the chamfered corner in the vertical direction is 80%-130% of a dimension of the second part in the vertical direction.
According to one or more embodiments of the present disclosure, the at least one stationary contact further includes a magnetically conductive block connected to the chamfered corner, and the magnetically conductive block is formed of a magnetically conductive material.
According to one or more embodiments of the present disclosure, a thickness of the magnetically conductive block is greater than a thickness of the at least one stationary contact.
According to one or more embodiments of the present disclosure, the at least one stationary contact further includes an arc striking corner extending in the horizontal direction from the second vertical end of the first part, and an extending direction of the arc striking corner is the same as an extending direction of the second part.
According to one or more embodiments of the present disclosure, the movable contact includes a pair of movable contact pieces which are parallel to each other and spaced apart from each other, in the first contact position of the movable contact, the movable contact pieces clamp the stationary contact engagement part of the first stationary contact therebetween, and, in the second contact position of the movable contact, the movable contact pieces clamp the stationary contact engagement part of the second stationary contact therebetween.
According to one or more embodiments of the present disclosure, each of the pair of movable contact pieces includes a front surface facing the other one of the movable contact pieces and a back surface opposite to the front surface, and at least one of the movable contact pieces includes a magnet enhancement piece, and the magnet enhancement piece is formed of a magnetically conductive material.
According to one or more embodiments of the present disclosure, the magnet enhancement piece is a flat plate structure and is arranged on the back surface of at least one of the movable contact pieces.
According to one or more embodiments of the present disclosure, the magnet enhancement piece includes a U-shaped structure, a bottom of the U-shaped structure of the magnet enhancement piece is arranged on the back surface of at least one of the movable contact pieces, and two arms of the U-shaped structure of the magnet enhancement piece are arranged on respective lateral surface of the at least one of the movable contact pieces.
According to one or more embodiments of the present disclosure, the at least one stationary contact includes the first stationary contact and the second stationary contact.
According to an aspect of the present disclosure, an automatic transfer switch is provided. The automatic transfer switch includes one or more contact systems for the automatic transfer switch as described above.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 shows a perspective view of an automatic transfer switch according to one or more embodiments of the present disclosure;
Fig. 2 shows a perspective view of a contact system according to one or more embodiments of the present disclosure;
Figs. 3A and 3B show front views of a contact system according to one or more embodiments of the present disclosure, wherein Fig. 3A shows a double separation position where a movable contact assembly is not in contact with a first stationary contact assembly and a second stationary contact assembly, and Fig. 3B shows a first contact position where the movable contact assembly is in contact with the first stationary contact assembly;
Figs. 4A and 4B show front views of a first stationary contact assembly according to one or more embodiments of the present disclosure;
Fig. 5A shows a front view of a first stationary contact assembly of an automatic transfer switch, and Fig. 5B is a front view of a first stationary contact, showing current in the first stationary contact when the movable contact assembly of the automatic transfer switch is in contact with the first stationary contact assembly;
Fig. 6A is a partial front view of a contact system according to one or more embodiments of the present disclosure, showing current in the contact system at a first contact position of the movable contact assembly;
Fig. 6B shows a schematic diagram of an electromagnetic force (Lorentz force) on the movable contact assembly in Fig. 6A;
Figs. 7A-7B show a movable contact piece according to one or more embodiments of the present disclosure; and
Figs. 8A-8B show another movable contact piece according to one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described in detail below, examples of which are shown in the accompanying drawings, wherein same or similar reference numerals indicate same or similar elements or elements with the same or similar functions. The embodiments described below by reference to the accompanying drawings are exemplary and are intended only to explain the present disclosure, and cannot be understood as limitations of the present disclosure.
Unless otherwise defined, technical terms or scientific terms used here shall have their ordinary meanings as understood by skilled person in the field to which the present disclosure belongs. In the description of the present disclosure, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate or imply that the referred device or element must have the specific orientation, and be constructed and operated in the specific orientation, so it cannot be understood as a limitation to the present disclosure. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.
The present disclosure provides a contact system for automatic transfer switch, which includes a first stationary contact, a second stationary contact and a movable contact. The first stationary contact and/or the second stationary contact includes a first part extending in a vertical direction and a second part extending in a horizontal direction, and the first part and the second part meet each other end to end. A chamfered corner is formed at a joint position of the first part and the second part. The inventor(s) of the present disclosure found that the current in the first part of the stationary contact extending in the vertical direction generates an electromagnetic field, which applies an electromagnetic force (Lorentz force) on the current in the movable contact assembly. This electromagnetic force tends to separate the movable contact assembly from the stationary contact. In the present disclosure, by forming the chamfered corner at the joint position of the first part and the second part, the length of the current section in the first part of the stationary contact is significantly reduced, thereby significantly reducing the electromagnetic force (Lorentz force) that tends to separate the movable contact assembly from the stationary contact. Therefore, the short-term current withstand index of the contact system is improved.
Furthermore, in some embodiments, the stationary contact assembly includes a magnetically conductive block connected to the chamfered corner of the stationary contact. The magnetically conductive block can guide the electromagnetic field or magnetic flux, so that the magnetic flux is better concentrated in the magnetically conductive block, thereby reducing the magnetic flux in the movable contact assembly, thus reducing the electromagnetic force (Lorentz force) that tends to separate the movable contact assembly from the stationary contact. Therefore, the magnetically conductive block can further improve the short-term current withstand index of the contact system.
In addition, in some embodiments, a magnet enhancement piece formed of a magnetically conductive material is provided on the movable contact. Due to the presence of the magnet enhancement piece, the electromagnetic field generated by the movable contact pieces is guided to be better concentrated, so that a pair of movable contact pieces of the clamping contact system form a greater clamping force on the stationary contact assembly between the pair of movable contact pieces when there is current on the clamping contact system. Therefore, the magnet enhancement piece can further improve the short-term current withstand index of the contact system.
Fig. 1 shows a perspective view of an automatic transfer switch 10 according to one or more embodiments of the present disclosure. The automatic transfer switch 10 includes a plurality of first power input terminals 12a, a plurality of second power input terminals 12b and a plurality of output terminals 14. The automatic transfer switch 10 also includes a plurality of contact systems 100 (only one contact system is shown in the figure). The contact system 100 includes a movable contact assembly 110, a first stationary contact assembly 140 and a second stationary contact assembly 170. The first stationary contact assembly 140 is electrically connected to a corresponding one of the first power input terminals 12a, the second stationary contact assembly 170 is electrically connected to a corresponding one of the second power input terminals 12b, and the movable contact assembly 110 is electrically connected to a corresponding one of the output terminals 14. The movable contact assembly 110 is movable between a first contact position in contact with the first stationary contact assembly 140 and a second contact position in contact with the second stationary contact assembly 170, so that the automatic transfer switch 10 switches between a first power supply (not shown) electrically connected to the first power input terminal 12a and a second power supply (not shown) electrically connected to the second power input terminal 12b. In the embodiment shown in Fig. 1, the automatic transfer switch 10 has four first power input terminals, four second power input terminals and four output terminals, and four contact systems (only one contact system is shown in the figure). In other embodiments according to the present disclosure, the automatic transfer switch can have any suitable numbers of first power input terminals, second power input terminals, output terminals and contact systems. In still other embodiments according to the present disclosure, the automatic transfer switch can have any suitable form and number of terminals, and is not limited to the form and number of terminals shown in Fig. 1 (the first power input terminals, the second power input terminal and the output terminal), as long as these terminals of the automatic transfer switch can be properly connected to the stationary contacts and the movable contact of the contact system.
Fig. 2 shows a perspective view of the contact system 100. The movable contact assembly 110 of the contact system 100 includes a pair of movable contact pieces 120, a movable contact actuating device 112 and a movable contact conductive member 114. The movable contact actuating device 112 drives the pair of movable contact pieces 120 to move. The movable contact conductive member 114 is electrically connected to the pair of movable contact pieces 120 of the movable contact assembly 110, for electrically connecting the pair of movable contact pieces 120 to the output terminals of the automatic transfer switch 10. The pair of movable contact pieces 120 are parallel to each other and spaced apart from each other, and define a receiving space therebetween. Upon the movable contact assembly being in contact with the first stationary contact assembly or the second stationary contact assembly, the pair of movable contact pieces 120 of the movable contact assembly clamp the corresponding stationary contact therebetween. The first stationary contact assembly 140 includes a first stationary contact 150 and a first stationary contact conductive member 142. The first stationary contact conductive member 142 is electrically connected to the first stationary contact 150, for electrically connecting the first stationary contact 150 to the corresponding power input terminal. The second stationary contact assembly 170 includes a second stationary contact 180 and a second stationary contact conductive member 172. The second stationary contact conductive member 172 is electrically connected with the second stationary contact 180, for electrically connecting the second stationary contact 180 to the corresponding power input terminal.
Figs. 3A and 3B show front views of the contact system 100, wherein Fig. 3A shows a double separation position where the movable contact assembly 110 is not in contact with both the first stationary contact assembly 140 and the second stationary contact assembly 170, and Fig. 3B shows a first contact position where the movable contact assembly 110 is in contact with the first stationary contact assembly 140. The contact assembly system 100 also includes a second contact position (not shown) where the movable contact assembly 110 is in contact with the second stationary contact assembly 170.
Figs. 4A and 4B show front views of the first stationary contact assembly 140 according to one or more embodiments of the present disclosure. As shown in the figures, the first stationary contact 150 includes a first part (vertical extension part) 162 extending in a vertical direction and a second part (horizontal extension part) 164 extending in a horizontal direction. A lower end (a first vertical end) of the first part 162 meets a right end (a first horizontal end) of the second part 164 to form a generally L-shape. The second part 164 includes a conductive connection part 154 arranged at or close to a left end (a second horizontal end) of the second part 164. The conductive connection part 154 is connected with the first stationary contact conductive member 142 for electrically connecting the first stationary contact 150 to the corresponding power input terminal of the automatic transfer switch 10.
At the first contact position where the movable contact assembly 110 is in contact with the first stationary contact assembly 140, a first stationary contact engagement part 152 of the first stationary contact 150 is in contact with and electrically connected with the pair of movable contact pieces 120 of the movable contact assembly 110. The first stationary contact engagement part 152 is at or close to an upper end (a second vertical end) of the first part 162 of the first stationary contact 150. At the first contact position, the current flows from the corresponding power input terminal of the automatic transfer switch 10 to the first stationary contact conductive member 142, through the conductive connection part 154 of the first stationary contact 150 and the body of the first stationary contact 150 to the first stationary contact engagement part 152, and then to the output terminal of the automatic transfer switch 10 through the movable contact assembly 110.
As shown in the figure, a chamfered corner 166 is formed at a joint position of the first part 162 and the second part 164 of the first stationary contact 150. The chamfered corner 166 has a horizontal dimension D1 and a vertical dimension D2. The first part 162 has a horizontal dimension D3 and the second part 164 has a vertical dimension D4. In the illustrated embodiment, D1>D3 and D2>D4. In some other embodiments according to the present disclosure, D1 is 80%-130% of D3, and D2 is 80%-130% of D4.
As shown, the first stationary contact 150 further includes an arc striking corner 156 extending in a substantially horizontal direction from the upper end (second vertical end) of the first part 162. An extending direction of the arc striking corner 156 is the same as an extending direction of the second part 164, so that the first part 162, the second part 164 and the arc striking corner 156 of the first stationary contact 150 together form a substantially U-shape. The arc striking corner 156 has a generally conical shape, and the vertical dimension of the arc striking corner 156 gradually decreases with the distance from the first part 162.
Fig. 5A shows a front view of the first stationary contact assembly 240 of the automatic transfer switch according to a comparative embodiment, and Fig. 5B is a front view of the first stationary contact 250, showing the current in the first stationary contact 250 when the movable contact assembly of the automatic transfer switch is in contact with the first stationary contact assembly 240. As shown, the first stationary contact assembly 240 includes a first stationary contact 250 and a first stationary contact conductive member 242. The first stationary contact 250 includes a first part 262 extending in the vertical direction and a second part 264 extending in the horizontal direction. The second part 264 has a conductive connection part 254 at or close to the left end of the second part 264, and the conductive connection part 254 is connected with the first stationary contact conductive member 242. The first stationary contact 250 also includes an arc striking corner 256. The main difference between the first stationary contact assembly 240 and the first stationary contact assembly 140 is that the first stationary contact 250 does not include the chamfered corner. Other aspects of the first stationary contact assembly 240 are similar to those of the first stationary contact assembly 140, and detailed description thereof is omitted herein.
As shown in Fig. 5B, the current in the first stationary contact 250 includes a current section p24 in the first part 262 and a current section p28 in the second part 264. The inventor(s) of the present disclosure found that the electromagnetic field generated by the current section in the first part 262 of the first stationary contact 250 generates an electromagnetic force on the movable contact in contact with the first stationary contact 250, which tend to make the movable contact to be separated from the first stationary contact 250. when the current in the contact system is large, the movable contact may be separated from the first stationary contact 250, which results in a reduced short-term current withstand index of the contact system.
Fig. 6A is a front view of a part of the contact system 100 according to one or more embodiments of the present disclosure, showing the current in the contact system 100 at the first contact position of the movable contact assembly 110. As shown in Fig. 6A, the current in the contact system 100 includes a current section p12 in the movable contact assembly 110, a current section p14 in the first part 162 of the first stationary contact 150, a current section p16 in a transition part between the first part 162 and the second part 164 of the first stationary contact 150, and a current section p18 in the second part 164 of the first stationary contact 150. Compared with the case shown in Fig. 5B, because the first stationary contact 150 includes the chamfered corner 166 at the joint position of the first part 162 and the second part 164, the length of the current section p14 in the first part 162 of the first stationary contact 150 is shortened (compared with the current section p24 in Fig. 5B), and the current section p16 in the transition part is added between the current section p14 in the first part 162 and the current section p18 in the second part 164, the current section p16 is inclined to the current section p14.
In Figs. 5B and 6A, black line segments p24, p28, p12, p14, p16 and p18 are used to represent the current passing through the first stationary contact 250 and the first stationary contact 150. This representation is schematic, and the actual current is not limited to the position shown by the black line segments. For example, the current sections p14 and p 16 in Fig. 6A roughly correspond to the currents in the regions indicated by dotted lines p14 and p16 in Fig. 4B, respectively.
Fig. 6B shows a schematic diagram of the electromagnetic force (Lorentz force) applied upon the current section p12 (movable contact assembly 110) in Fig. 6A. As shown, the current section p14 in the first part 162 of the first stationary contact 150 generates an electromagnetic field M14, which generates a clockwise electromagnetic force (Lorentz force) F upon the current section p12 in the movable contact assembly 110. This clockwise electromagnetic force F tends to separate the movable contact assembly 110 from the first stationary contact 150. Because the first stationary contact 150 includes the chamfered corner 166, the length of the current section p14 in the first part 162 of the first stationary contact 150 is significantly shortened compared with the current section p24 shown in Fig. 5B. Therefore, compared with the comparative embodiment of Fig. 5B, under the same current, the electromagnetic force of the current section p14 in the first part 162 of the first stationary contact 150 upon the movable contact assembly is significantly reduced. This improves the short-term current withstand index of the contact system 100.
In addition, the current section p16 of the first stationary contact 150 also generates an electromagnetic field (not shown). The electromagnetic field generated by the current section p16 generates a counterclockwise electromagnetic force (Lorentz force, not shown) upon the current section p12 in the movable contact assembly 110. Therefore, the current section p16 can partially counteract or cancel the clockwise electromagnetic force F generated by the current section p14. This further improves the short-term current withstand index of the contact system 100. Those skilled in the art can understand that the electromagnetic force of p16 to the movable contact assembly 110 is much smaller than the electromagnetic force of p14 to the movable contact assembly 110 due to the relatively large distance between p16 and the movable contact assembly 110.
In one or more embodiments according to the present disclosure, the first stationary contact assembly 140 includes a magnetically conductive block 168 connected to the chamfered corner 166. The magnetically conductive block 168 is made of a magnetically conductive material, which may be, for example, low carbon steel, silicon steel sheet, etc. Due to the existence of the magnetically conductive block 168, the electromagnetic field or magnetic flux generated by the first stationary contact 150, for example, the current section p14 therein, is guided, so as to be more intensively distributed in the magnetically conductive block 168. Therefore, the electromagnetic field intensity of the electromagnetic field M14 generated by the current section p14 at the movable contact assembly 110 decreases, and the electromagnetic force F of the current section p14 to the movable contact assembly 110 decreases. Because the electromagnetic force F tends to separate the movable contact assembly 110 from the first stationary contact 150, the contact system 100 can withstand greater current due to the reduction of the electromagnetic force F, which further improves the short-term current withstand index of the contact system 100. As shown in the figure, the shape of the magnetically conductive block 168 basically corresponds to the shape of the chamfered corner 166, so the magnetically conductive block 168 does not occupy extra space. In one or more embodiments according to the present disclosure, the magnetically conductive block 168 has an increased thickness, that is, the thickness of the magnetically conductive block 168 is greater than the thickness of the first stationary contact 150, so that the electromagnetic field or magnetic flux generated by the current section p14 is more guided and concentrated in the magnetically conductive block 168. This can further improve the short-term current withstand index of the contact system 100. As used herein, the thickness direction of the magnetically conductive block and the stationary contact refers to the direction of into and out of the paper of Figs. 3A-3B, 4A-4B and 6A.
The above describes the contact system 100 of the present disclosure in connection to the first stationary contact assembly 140 and the movable contact assembly 110. As shown, the second stationary contact assembly 170 has a structure and operation similar to that of the first stationary contact assembly 140, and detailed description thereof is omitted herein.
In the embodiment shown, the first stationary contact 150 and the second stationary contact 180 have similar structures, that is, both the first stationary contact 150 and the second stationary contact 180 have chamfered corners and magnetically conductive blocks connected to the chamfered corners. In other embodiments according to the present disclosure, only one stationary contact of a pair of stationary contacts of the contact system may include a chamfered corner and a magnetically conductive block connected to the chamfered corner. In other embodiments according to the present disclosure, one or both of the pair of stationary contacts of the contact system may only include the chamfered corner and not include the magnetically conductive block connected to the chamfered corner.
In the illustrated embodiment, the first stationary contact 150 includes a recess 162a in the first part 162. In other embodiments according to the present disclosure, the recess 162a of the first stationary contact 150 may be omitted, that is, the first stationary contact 150 may not include a recess 162a.
The contact system of the embodiment shown in the accompanying drawings is a clamping contact system, and its movable contact assembly includes a pair of movable contact pieces. The pair of movable contact pieces are parallel to each other and spaced apart from each other, and define a receiving space therebetween. When the movable contact assembly is in contact with the first stationary contact assembly or the second stationary contact assembly, the pair of movable contact pieces 120 of the movable contact assembly clamp the corresponding stationary contact therebetween. When there is current in the clamping contact system, the current flows in the same direction along the pair of movable contact pieces that are parallel to each other. The current on each movable contact piece in the pair of movable contact pieces generates an electromagnetic field, which acts upon the current of the other one of the movable contact pieces, and generates an electromagnetic force (Lorentz force) that pulls the movable contact pieces toward each other, so that the movable contact pieces form a greater clamping force on the stationary contact assembly therebetween. This improves the short-term current withstand index of the clamping contact system.
Figs. 7A-7B show a movable contact piece 120 according to one or more embodiments of the present disclosure. The movable contact piece 120 includes a movable contact piece body 122 and a magnet enhancement piece 124 disposed on the movable contact piece body 122. The magnet enhancement piece 124 is made of a magnetically conductive material, which may be, for example, low carbon steel, silicon steel sheet, etc. Due to the presence of the magnet enhancement piece 124, when there is current in the clamping contact system, the electromagnetic field generated by the movable contact piece 120 is guided to be more concentrated. Therefore, the pair of movable contact pieces forms a greater clamping force on the stationary contact assembly between the pair of movable contact pieces. The clamping contact system with the magnet enhancement piece can increase the contact pressure or force at the moment of closing, avoiding contact bouncing and pulling arcs that may cause product fusion welding, and further improve the short-term current withstand index of the clamping contact system. As shown, the magnet enhancement piece 124 is a flat plate structure, which is arranged on the back surface of the movable contact piece body 122, that is, the magnet enhancement piece 124 is on a surface of the movable contact piece 120 facing away from the other movable contact piece.
Figs. 8A-8B show a movable contact piece 120' according to another embodiment or embodiments of the present disclosure. The movable contact piece 120' includes a movable contact piece body 122' and a magnet enhancement piece 124' arranged on the movable contact piece body 122'. The difference between the movable contact piece 120' and the movable contact piece 120 is that the magnet enhancement piece 124 has a flat structure, while the magnet enhancement piece 124' has a U-shaped structure. The bottom of the U-shaped structure of the magnet enhancement piece 124' is arranged on the back surface of the movable contact piece body 122', and the two arms of the U-shaped structure of the magnet enhancement piece 124' are arranged on the two lateral surfaces of the movable contact piece body 122'. The U-shaped magnetized plate 124' can better guide and concentrate the electromagnetic field, so the U-shaped magnetized plate 124' can effectively improve the short-term current withstand index of the clamping contact system.

The inventor(s) of the present disclosure performed a short-term current withstand index experiment for the contact system of the Comparative embodiment and the contact system of the Experimental embodiment. The contact system of the Comparative embodiment in this experiment includes the stationary contact assembly as shown in Fig. 5A, while the contact system of the Experimental embodiment includes the stationary contact assembly as shown in Fig. 6A. The experimental results are provided as follows.

	Comparative embodiment	Experimental embodiment
Experiment projects	20kA short-term current withstand experiment	30 kA short-term current withstand experiment
Experiment times	2 times	3 times
Experiment results	Failed twice	Succeeded three times

As seen from the above experimental results, the 20kA short-term current withstand experiment of the Comparative embodiment (the contact system with the stationary contact assembly shown in Fig. 5A) failed twice, so its short-term current withstand index was below 20kA, while the 30kA short-term current withstand experiment of the Experimental embodiment (the contact system with the stationary contact assembly shown in Fig. 6A) succeeded three times, so its short-term current withstand index was above 30 kA. Therefore, compared with the Comparative embodiment, the short-term current withstand index of the Experimental embodiment is improved by more than 50%.
As used herein, the terms indicating directions such as "vertical" and "horizontal" of the first part and the second part of the stationary contact are based on the orientation shown in the accompanying drawings (for example, Figs. 3A-3B, 4A-4B and 6A). These terms are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the first part and the second part of the stationary contact must have a specific orientation, be constructed and operated in a specific orientation. As shown in Figs. 3A-3B, 4A-4B and 6A, the first part and the second part of the stationary contact basically extend in the vertical direction and the horizontal direction, that is, the first part and the second part are perpendicular to each other. The "vertical" and "horizontal" of the present disclosure are not limited to absolute "vertical" and "horizontal" situations. For example, the extending directions of the first part and the second part of the stationary contact may be within the range of +/-5 degrees of mutually perpendicular directions. According to other embodiments of the present disclosure, the extending directions of the first part and the second part of the stationary contact can be within the range of +/-10 degrees, +/-15 degrees, or +/-20 degrees of mutually perpendicular directions.
What has been described above is only exemplary embodiments adopted to illustrate the principle of the present disclosure, and is not used to limit the protection scope of the present disclosure. For ordinary skilled in this art, various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also within the protection scope of the present disclosure.

Claims

A contact system for automatic transfer switch, the contact system comprising a first stationary contact, a second stationary contact and a movable contact, wherein
the first stationary contact and the second stationary contact each comprise a stationary contact engagement part and a conductive connection part suitable to be electrically connected to a wire connection terminal of the automatic transfer switch,

wherein the movable contact is movable between a first contact position and a second contact position, the movable contact being in contact with the stationary contact engagement part of the first stationary contact in the first contact position of the movable contact, and the movable contact being in contact with the stationary contact engagement part of the second stationary contact in the second contact position of the movable contact,

wherein at least one stationary contact of the first stationary contact and the second stationary contact comprises:
a first part extending in a vertical direction and comprising a first vertical end and a second vertical end; and

a second part extending in a horizontal direction and comprising a first horizontal end and a second horizontal end,

wherein the first vertical end of the first part meets the first horizontal end of the second part, the stationary contact engagement part of the at least one stationary contact is at or close to the second vertical end of the first part, the conductive connection part of the at least one stationary contact is at or close to the second horizontal end of the second part, and a chamfered corner is formed at a joint position of the first part and the second part of the at least one stationary contact.
The contact system for automatic transfer switch according to claim 1, wherein a horizontal dimension of the chamfered corner is 80%-130% of a horizontal dimension of the first part.
The contact system for automatic transfer switch according to claim 1, wherein a vertical dimension of the chamfered corner is 80%-130% of a vertical dimension of the second part.
The contact system for automatic transfer switch according to claim 1, wherein the at least one stationary contact further comprises a magnetically conductive block connected to the chamfered corner, and the magnetically conductive block is formed of a magnetically conductive material.
The contact system for automatic transfer switch according to claim 4, wherein a thickness of the magnetically conductive block is greater than a thickness of the at least one stationary contact.
The contact system for automatic transfer switch according to claim 1, wherein the at least one stationary contact further comprises an arc striking corner extending in the horizontal direction from the second vertical end of the first part, and an extending direction of the arc striking corner is the same as an extending direction of the second part.
The contact system for automatic transfer switch according to any one of claims 1 to 6, wherein the movable contact comprises a pair of movable contact pieces which are parallel to each other and spaced apart from each other, in the first contact position of the movable contact, the movable contact pieces clamp the stationary contact engagement part of the first stationary contact therebetween, and, in the second contact position of the movable contact, the movable contact pieces clamp the stationary contact engagement part of the second stationary contact therebetween.
The contact system for automatic transfer switch according to claim 7, wherein each of the pair of movable contact pieces comprises a front surface facing the other one of the movable contact pieces and a back surface opposite to the front surface, and at least one of the movable contact pieces comprises a magnet enhancement piece, and the magnet enhancement piece is formed of a magnetically conductive material.
The contact system for automatic transfer switch according to claim 8, wherein the magnet enhancement piece is a flat plate structure and is arranged on the back surface of the at least one of the movable contact pieces.
The contact system for automatic transfer switch according to claim 8, wherein the magnet enhancement piece comprises a U-shaped structure, the magnet enhancement piece includes a bottom arranged on the back surface of at least one of the movable contact pieces, and two arms each arranged on one respective lateral surface of the at least one of the movable contact pieces.
The contact system for automatic transfer switch according to any one of claims 1 to 6, wherein the at least one stationary contact comprises the first stationary contact and the second stationary contact.
An automatic transfer switch, wherein the automatic transfer switch comprises one or more contact systems for the automatic transfer switch according to any one of claims 1 to 11.