CN105679597B - There is the contact and vacuum interrupter of short circuit current connecting-disconnecting function with fixed fracture - Google Patents

Abstract

A contact with a fixed fracture and a short-circuit current breaking capability and a vacuum interrupter. The contact includes a set of fixed fracture contacts and a set of movable fracture contacts. The movable fracture contacts are in the fixed fracture state in the opening state. The inside of the contact; the vacuum interrupter includes a contact with a fixed fracture and a short-circuit current breaking capability, a housing and a shield; the invention solves the problem of the existing composite magnetic field contact structure and other designs for capacitive current breaking The complex structure of the vacuum interrupter and the lack of magnetic field control of the vacuum arc; the invention realizes the electric field shielding and protection of the movable fracture contact by the fixed fracture contact, and avoids the movable fracture contact The impact of the defects formed on the surface of the head on the breakdown; the invention separates the breaking function and the insulating function, realizes the breaking function with the composite magnetic field contact, and realizes the insulating function with the fixed contact, which can not only break the short-circuit current, but also be used for Switching capacitive current, such as reactive power compensation fields such as capacitor bank switching.

Description

Contacts and vacuum interrupter with fixed fracture and short-circuit current breaking capacity

technical field

The invention belongs to the technical field of high-current vacuum circuit breakers, and in particular relates to a contact with a fixed fracture and capable of breaking short-circuit currents and a vacuum interrupter, which can be used for capacitor bank switching and has short-circuit current breaking capabilities.

Background technique

The application of vacuum circuit breakers in the entire power system develops rapidly, but with the development of power systems, the requirements for vacuum circuit breakers are also constantly increasing, especially the switching of capacitor banks. In the medium-voltage power distribution system, a high-frequency inrush current of 4250 Hz and 20 kA will be generated during switching of the capacitor bank, and its pre-breakdown arc will locally ablate the surface of the contact and cause the contact to weld. When breaking the capacitor bank, the breaking current can reach hundreds of amperes. At this time, the welded area is pulled apart, and a protrusion will be formed on the contact surface. After the breaking current crosses zero, both ends of the vacuum interrupter contacts will bear the DC recovery voltage, and the peak value of breaking the single-phase capacitor bank or three-phase load neutral point grounding capacitor bank will reach 2 times the system voltage Um, breaking the three-phase The peak value of the ungrounded capacitor bank at the load neutral point will reach 2.5 times the system voltage Um. This makes the vacuum circuit breaker may have a re-breakdown phenomenon after breaking the capacitive current, and even a delayed re-breakdown phenomenon will occur after the breaking current crosses zero for a few seconds. The overvoltage generated by heavy breakdown will seriously damage the switch itself and other power system equipment, and even cause casualties. The research found that the cause of heavy breakdown is closely related to the high-frequency inrush current generated during switching. The ring contact surface structure increases the field emission coefficient of the contact surface. In this case, it has important practical significance and huge economic value to develop vacuum breaking equipment suitable for capacitor bank switching.

The magnetic field control technology of vacuum arc mainly includes transverse magnetic field control technology and longitudinal magnetic field control technology. Among them, the transverse magnetic field technology uses a specific contact structure so that the current path formed during the arcing process forms a transverse magnetic field perpendicular to the arc current flow in the contact and its contact gap area. The transverse magnetic field acts on the vacuum arc to drive it to rotate on the surface of the contact, avoiding excessive ablation of the contact by the arc and improving the breaking capacity of the switch. The longitudinal magnetic field technology also forms a magnetic field parallel to the arc current flow through the contact structure. The longitudinal magnetic field technology makes the vacuum arc more uniform, reduces the accumulation of the vacuum arc, reduces the ablation of the arc on the contact surface, and improves the breaking capacity of the switch. The longitudinal magnetic contact structures are mainly cup-shaped longitudinal magnetic contact structures and coil type longitudinal magnetic contact structures. The transverse magnetic contact structures are mainly cup-shaped transverse magnetic contact structures, swastika-shaped and other slotted transverse magnetic contact structures. The existing transverse and longitudinal magnetic field structure contacts have their own advantages and disadvantages in the application of circuit breakers, and their structures are constantly being improved and perfected. In addition, a new design idea is to combine the transverse magnetic field and the longitudinal magnetic field to form a composite magnetic field and give full play to the respective advantages and characteristics of the transverse magnetic field and the longitudinal magnetic field.

At present, the high-voltage vacuum switch invented by General Electric Company in 1975 is shown in Fig. 1. By designing a pair of movable contacts inside the vacuum interrupter to be located inside the other pair of shielding contacts in the fully open position, vacuum arc extinguishing is realized. The high withstand voltage characteristics of the chamber (HIGH-VOLTAGE VACUUM SWITCH, Appl. No: 499,740). Wang Jianhua and Liu Zhiyuan of Xi'an Jiaotong University proposed a composite contact structure vacuum interrupter ("a new type of composite contact vacuum interrupter", patent number: ZL201310534332.3), and proposed a vacuum interrupter with a fixed fracture ("a vacuum interrupter with a fixed fracture", public number: CN104145318A), the structure of a vacuum interrupter with a fixed fracture is shown in Figure 2.

However, in practical applications, the structural design of the contact part of the composite magnetic field contact proposed by Wang Jianhua and Liu Zhiyuan of Xi'an Jiaotong University is relatively complicated, which will inevitably increase the resistance of the contact part and the processing cost of the contact. , In addition, the structural design of the fixed fracture interrupter of Xi'an Jiaotong University and General Motors only realizes the purpose of achieving multiple positions of the vacuum interrupter, and its fixed fracture does not have the breaking ability of the current.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the object of the present invention is to provide a contact with a fixed fracture and a short-circuit current breaking capability and a vacuum interrupter, which solves the problems of the existing composite magnetic field contact structure and other problems for capacitors. The structure of the vacuum interrupter designed for permanent current breaking is too complicated, and there are problems such as the lack of composite magnetic field control of the vacuum arc. The invention separates the breaking function and the insulating function, realizes the breaking function with the movable contact, and realizes the insulating function with the fixed contact, and can be used for breaking capacitive loads, such as back-to-back capacitor banks, single capacitor banks and other power systems. field of compensation.

To achieve the above object, the present invention adopts the following technical solutions:

A contact with a fixed fracture and short-circuit current breaking capability, including a static side structure part and a moving side structure part, the static side structure part includes a static side conductive rod 101, and the static side large part welded to the lower end of the static side conductive rod 101 Diameter magnetic field contact 104, static side large diameter contact material 105 welded on the lower end of static side large diameter magnetic field contact 104, static side small diameter magnetic field contact 102 welded on the inner bottom surface of static side large diameter magnetic field contact 104, static side The lower end of the side small-diameter magnetic field contact 102 is welded with a static-side small-diameter contact material 103; the static-side small-diameter magnetic field contact 102 and the welded static-side small-diameter contact material 103 are placed on the static-side large-diameter magnetic field contact Inside 104, the surface of the small-diameter contact material 103 on the static side is 2-7 mm lower than the surface of the large-diameter contact material 105 on the static side; the large-diameter contact material 105 on the static side bends toward the large-diameter magnetic field contact 104 internal contraction;

The moving side structure part includes a movable end movable conductive rod 110, a movable end movable magnetic field contact 108 welded on the upper end of the movable end movable conductive rod 110, and a movable end small welded on the upper end of the movable end movable magnetic field contact 108. Diameter contact material 106; the movable conductive rod 110 at the movable end is connected with the lower side cover plate 128 of the arc extinguishing chamber through a bellows 126; The bottom of the end-fixed conductive rod 111 is welded on the lower side cover 128 of the arc extinguishing chamber; the upper end of the movable-end fixed conductive rod 111 is welded with a movable-end fixed large-diameter magnetic field contact 109, and the movable-end fixed large-diameter magnetic field contact The upper end of 109 is welded with a moving end fixed large-diameter contact material 107;

During the arcing process, the movable magnetic field contact 108 at the movable end moves down with the movable conductive rod 110, and the arc burns between the small-diameter contact material 103 on the static side and the small-diameter contact material 106 at the movable end, and the dynamic The movement stop position of the small-diameter contact material 106 at the moving end is placed inside the fixed large-diameter contact material 107 at the moving end, and the surface of the small-diameter contact material 106 at the moving end is 2-7 mm lower than the surface of the fixed large-diameter contact material 107 at the moving end;

The movable fracture contact formed by the static side small diameter magnetic field contact 102 and the welded static side small diameter contact material 103 and the movable end movable magnetic field contact 108 and the welded movable end small diameter contact material 106 is separated. The brake state is in the fixed fracture contact formed by the large-diameter magnetic field contact 104 on the static side and the welded large-diameter contact material 105 on the static side, and the fixed large-diameter magnetic field contact 109 on the moving end and the fixed large-diameter contact material 107 on the moving end Internally, the electric field shielding and protection of the movable fracture contact by the fixed fracture contact is realized, and the influence of the defects formed on the surface of the movable fracture contact during the capacitive closing process on the breakdown is avoided.

The interior of the large-diameter magnetic field contact 104 on the static side and the welded large-diameter contact material 105 on the static side, the fixed large-diameter magnetic field contact 109 at the moving end, and the fixed large-diameter contact material 107 at the moving end are " Cup-shaped field contact structure or "coil" field contact structure;

The small-diameter magnetic field contact 102 on the static side and the small-diameter contact material 103 welded on the static side and the movable magnetic field contact 108 on the moving end and the small-diameter contact material 106 on the moving end are "cup-shaped" that match the static and dynamic sides. "magnetic field contact structure, "coil" magnetic field contact structure, "swastika" magnetic field contact structure or "spiral groove" magnetic field contact structure.

The "cup-shaped" magnetic field contact structure is a "cup-shaped" transverse magnetic contact structure or a "cup-shaped" longitudinal magnetic contact structure. The "coil" magnetic field contact structure is a "coil" transverse magnetic contact structure or a "coil" longitudinal magnetic contact structure.

The "swastika" magnetic field contact structure and the "spiral groove" magnetic field contact structure are transverse magnetic contact structures.

A vacuum interrupter with a fixed fracture, comprising the above-mentioned contact with a fixed fracture and capable of breaking short-circuit current, a housing and a shield.

The invention provides a vacuum interrupter with a fixed fracture. The interrupter is equipped with a movable fracture composed of small-diameter contacts and a fixed fracture composed of large-diameter contacts. The movable fracture is composed of a pair of small-diameter moving and static contacts, which are used to carry the rated current and cut off the capacitive load to complete the breaking performance of the vacuum interrupter; the fixed fracture is composed of a pair of large-diameter contacts, which not only It has the capability of breaking current. At the same time, when the moving and static contacts forming the movable fracture reach the full opening position, they enter into the pair of large-diameter contacts forming the fixed fracture. At this time, the DC property of the capacitive current is restored after breaking. The voltage is borne by the fixed fracture, so as to realize the insulation performance of the vacuum interrupter. Therefore, only the surface of the movable small-diameter moving and static contact that completes the current breaking function is broken by the inrush current, and the insulation withstand voltage capacity of the vacuum interrupter is determined by the fixed large-diameter contact fracture. In addition, the small-diameter contacts of the movable fracture and the large-diameter contacts of the fixed fracture are both magnetic field contact structures, and during the arcing process, the arc can be pulled by the small-diameter contact of the movable fracture to start the arc, and then burn To the surface of the large-diameter contact with a fixed fracture, the composite magnetic field formed by the combination of the large-diameter contact and the small-diameter contact realizes effective control of the short-circuit breaking current. This design fully considers the characteristics of the control characteristics of the transverse magnetic field and the longitudinal magnetic field on the arc, and also makes full use of the excellent performance of the combined design of the fixed fracture and the movable fracture in the capacitive current breaking process.

Compared with prior art, the present invention has following advantage:

1) The combination structure of moving and static contacts is designed according to the breaking characteristics of capacitive loads; the combination structure of moving and static contacts is proposed, the breaking function and the insulation function are separated, and the breaking function of the movable contact is realized, and the fixed The insulating function of the contacts, which can be used to break capacitive loads.

2) The combined structure of contacts with different diameters is used to form a composite magnetic field; the design of the magnetic field structure is added to the combined design of the dynamic and static contact structures. , the composite magnetic field contact structure can realize the different characteristics of the transverse and longitudinal magnetic fields in the composite contact structure, which is not only beneficial to the control of the arc, but also helpful to the transfer of the arc between the fixed fracture contact and the movable contact .

3) The traditional interrupter with fixed fracture is improved and optimized; in the design of the traditional fixed fracture structure contact vacuum interrupter, although the combined structure of dynamic and static contacts is also proposed to realize the breaking function The function is separate from the insulation function, but due to the simple structure of the contact and the lack of control over the arc, it is often difficult to meet the design expectations. Therefore, on this basis, a new contact design structure is proposed.

Description of drawings

Fig. 1 is a schematic diagram of a conventional high-voltage vacuum switch with a pair of movable contacts and a pair of shielding contacts.

Fig. 2 is a schematic structural diagram of an existing vacuum interrupter with fixed fractures.

Fig. 3 is a schematic diagram of an axial section of a vacuum interrupter with a movable contact of a cup-shaped magnetic field structure in an open state according to the present invention.

Fig. 4 is a schematic diagram of an axial section of the vacuum interrupter with a movable contact of a cup-shaped magnetic field structure in a closed state according to the present invention.

Fig. 5 is a schematic diagram of the axial section of the vacuum interrupter with the movable contact of the "swastika" magnetic field structure in the closed state of the present invention.

Fig. 6 is a schematic diagram of the axial section of the vacuum interrupter with the movable contact of the "swastika" magnetic field structure in the closed state of the present invention.

Fig. 7a is a structural schematic diagram of a composite contact with a movable contact with a cup-shaped magnetic field structure according to the present invention.

Fig. 7b is a structural schematic diagram of a compound contact with a movable contact of a "swastika" magnetic field structure according to the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

The present invention has a contact with a fixed fracture and short-circuit current breaking capability, including a static side structure part and a moving side structure part. The static side structure part includes a static side conductive rod 101, and a static The side large-diameter magnetic field contact 104, the static-side large-diameter contact material 105 welded to the lower end of the static-side large-diameter magnetic field contact 104, the static-side small-diameter magnetic field contact 102 welded to the inner bottom surface of the static-side large-diameter magnetic field contact 104 The lower end of the static-side small-diameter magnetic field contact 102 is welded with a static-side small-diameter contact material 103; the static-side small-diameter magnetic field contact 102 and the welded static-side small-diameter contact material 103 are all placed in the static-side large-diameter magnetic field Inside the contact 104, the surface of the small-diameter contact material 103 on the static side is lower than the surface of the large-diameter contact material 105 on the static side by 2-7 mm; The internal contraction of the contact 104;

The moving side structure part includes a movable end movable conductive rod 110, a movable end movable magnetic field contact 108 welded on the upper end of the movable end movable conductive rod 110, and a movable end small welded on the upper end of the movable end movable magnetic field contact 108. Diameter contact material 106; the movable conductive rod 110 at the movable end is connected with the lower side cover plate 128 of the arc extinguishing chamber through a bellows 126; The bottom of the end-fixed conductive rod 111 is welded on the lower side cover 128 of the arc extinguishing chamber; the upper end of the movable-end fixed conductive rod 111 is welded with a movable-end fixed large-diameter magnetic field contact 109, and the movable-end fixed large-diameter magnetic field contact The upper end of 109 is welded with a moving end fixed large-diameter contact material 107;

During the arcing process, the movable magnetic field contact 108 at the movable end moves down with the movable conductive rod 110, and the arc burns between the small-diameter contact material 103 on the static side and the small-diameter contact material 106 at the movable end, and the dynamic The movement stop position of the small-diameter contact material 106 at the movable end is placed inside the fixed large-diameter contact material 107 at the movable end, and the surface of the small-diameter contact material 106 at the movable end is 2-7mm lower than the surface of the fixed large-diameter contact material 107 at the movable end.

The static-side small-diameter magnetic field contact (102) and the welded static-side small-diameter contact material (103) and the moving-end movable magnetic field contact (108) and the welded moving-end small-diameter contact material (106) are formed The movable fracture contact is in the static side large-diameter magnetic field contact (104) and welded static side large-diameter contact material (105) and the moving end fixed large-diameter magnetic field contact (109) and welded dynamic The inside of the fixed fracture contact formed by the fixed large-diameter contact material (107) realizes the electric field shielding and protection of the fixed fracture contact for the movable fracture contact, and avoids the surface of the movable fracture contact during the capacitive closing process. The effect of formed defects on breakdown;

The small-diameter magnetic field contact 102 on the static side and the small-diameter contact material 103 welded on the static side and the movable magnetic field contact 108 on the moving end and the small-diameter contact material 106 on the moving end are "cup-shaped" that match the static and dynamic sides. "magnetic field contact structure, "coil" magnetic field contact structure, "swastika" magnetic field contact structure or "spiral groove" magnetic field contact structure.

The interior of the static side large-diameter magnetic field contact (104) and the welded static side large-diameter contact material (105) and the moving end fixed large-diameter magnetic field contact (109) and the welded moving end fixed large-diameter contact material ( 107) It is a "cup-shaped" magnetic field contact structure and a "coil" magnetic field contact structure that are matched on the static and dynamic sides.

As shown in FIG. 3 , it is a schematic diagram of an axial section of a vacuum interrupter with a movable contact of a cup-shaped magnetic field structure in an open state according to the present invention. The vacuum interrupter includes a static side structure part, a moving side structure part and a shell structure. The shell structure includes the static side shell 123 of the arc extinguishing chamber and the moving side shell 124 of the arc extinguishing chamber, and the upper cover plates of the arc extinguishing chamber are respectively arranged on the upper end of the static side shell 123 of the arc extinguishing chamber and the lower end of the moving side shell 124 of the arc extinguishing chamber 121 and the lower side cover plate 128 of the arc extinguishing chamber; the upper side cover plate 121 of the arc extinguishing chamber and the lower side cover plate 128 of the arc extinguishing chamber are respectively connected to the static end end shield 122 and the moving end end shielding Cover 127. A central main shield 125 of the arc extinguishing chamber is installed at the central position of the arc extinguishing chamber.

The static side large-diameter magnetic field contact 104 is combined with the movable end fixed large-diameter magnetic field contact 109 to form a longitudinal magnetic field during the arcing process. The small-diameter magnetic field contact 102 on the static side is combined with the movable magnetic field contact 108 on the moving end to form a transverse magnetic field during the arcing process. As shown in Fig. 3, the vacuum interrupter of the present invention is in the open state, the static side large diameter contact material 105 welded by the static side large diameter magnetic field contact 104 is welded with the movable end fixed large diameter magnetic field contact 109 welded A fixed fracture is formed between the fixed large-diameter contact materials 107; the ring-shaped static-side small-diameter contact material 103 welded by the cup-shaped static-side small-diameter magnetic field contact 102 and the cup-shaped movable end movable magnetic field contact 108 A movable fracture is formed between the welded annular small-diameter contact material 106 at the movable end. The distance of the movable fracture is 4-14mm greater than that of the fixed fracture, and the movable fracture is placed inside the fixed fracture. The surface of the small-diameter contact material at the moving end and the static end is placed 2-7mm inside the surface of the fixed large-diameter contact material at the moving end and the static end. Cup-shaped static side small-diameter magnetic field contact 102 and welded ring-shaped static-side small-diameter contact material 103 and cup-shaped moving end movable magnetic field contact 108 and welded ring-shaped moving end small-diameter contact material The combination of 106 forms a cup-shaped transverse magnetic field; according to the needs of the design, it can also be replaced with a "spiral groove" transverse magnetic field contact structure that matches the dynamic and static sides. The cup-shaped static-side small-diameter magnetic contact 102 and the cup-shaped moving-end movable magnetic field contact 108 can be a cup-shaped longitudinal magnetic contact structure that matches each other, or a cup-shaped transverse magnetic contact structure. The static-side large-diameter magnetic contact 104 and the moving-end fixed large-diameter magnetic contact 109 can be a cup-shaped longitudinal magnetic contact structure that matches each other, or a cup-shaped transverse magnetic contact structure.

As shown in Figure 4, it is a schematic diagram of the axial section of the vacuum interrupter with a cup-shaped magnetic field structure movable contact in the closed state of the present invention, the surface of the ring-shaped static side small-diameter contact material 103 and the cup The small-diameter contact material 106 of the movable end welded on the upper end of the movable end movable magnetic field contact 108 is in contact with. Then, the movable conductive rod 110 at the movable end welded at the bottom of the cup-shaped movable magnetic field contact 108 forms a current path when the arc extinguishing chamber is turned on. When the vacuum interrupter is in the closed state, the fixed fracture contact parts of the static end and the moving end do not participate in the conduction of the current.

As shown in Figure 5, it is a schematic diagram of the axial section of the vacuum interrupter with the movable contact of the "swastika" magnetic field structure in the opening state of the present invention. The vacuum interrupter includes a static side structure part, a dynamic Side structure parts and shell structure. The static side structure part includes the static side conductive rod 101, the static side large diameter magnetic field contact 104 is welded on the lower side of the static side conductive rod 101, and the static side large diameter magnetic field contact 104 is welded with the static side large diameter contact material 105. The static-side large-diameter magnetic field contact 104 is welded to the lower end of the static-side conductive rod 101 with a “swastika” static-side small-diameter magnetic field contact 102 . The surface of the "swastika" static-side small-diameter magnetic field contact 102 is 2-7 mm lower than the surface of the static-side large-diameter contact material 105 . The structural part of the movable side includes a movable conductive rod 110 at the movable end, and a "swastika" movable magnetic field contact 108 at the movable end welded on the upper end of the movable conductive rod 110 . The movable conductive rod 110 at the movable end is connected to the lower cover plate 128 of the arc extinguishing chamber through a bellows 126 . Both the bellows 126 and the bottom of the fixed conductive rod 111 at the moving end are welded on the lower cover plate 128 of the arc extinguishing chamber. The upper end of the movable end fixed conductive rod 111 is welded with a movable end fixed large diameter magnetic field contact 109 , and the upper end of the movable end fixed large diameter magnetic field contact 109 is welded with a movable end fixed large diameter contact material 107 .

As shown in Figure 6, it is a schematic diagram of the axial section of the vacuum interrupter with a "swastika" magnetic field structure movable contact in the closed state of the present invention. The "swastika" small-diameter magnetic field contact on the static side 102 is in contact with the movable end movable magnetic field contact 108 of " swastika ". Then, the movable conductive rod 110 at the movable end forms a current path under the conduction condition of the arc extinguishing chamber. When the vacuum interrupter is in the closed state, the fixed fracture contact parts of the static end and the moving end do not participate in the conduction of the current.

Fig. 7 a is the structure diagram of the compound contact with the movable contact of the cup-shaped magnetic field structure of the present invention; the ring-shaped movable end small-diameter contact material 106 welded by the cup-shaped movable end movable magnetic field contact 108 is placed The moving end fixes the large-diameter cup-shaped magnetic field contact 109 and the welded moving end fixes the inside of the large-diameter annular contact material 107 . Fig. 7b is a structural schematic diagram of a compound contact with a movable contact of a "swastika" magnetic field structure according to the present invention. The "swastika" movable end movable magnetic field contact 108 is placed inside the movable end fixed large-diameter cup-shaped magnetic field contact 109 and the welded movable end fixed large-diameter annular contact material 107 .

The present invention is not limited to the above-mentioned preferred embodiments, and those skilled in the art can make modifications and changes to the vacuum interrupter with fixed breakouts and short-circuit current breaking capability of the present invention according to the teaching of the present invention. All these modifications and changes should fall within the protection scope of the present invention.

Claims (5)

1. A contact with a fixed fracture and short-circuit current breaking capability, including a static side structure part and a moving side structure part, characterized in that: The static-side structural part includes a static-side conductive rod (101), a static-side large-diameter magnetic field contact (104) welded to the lower end of the static-side conductive rod (101), and a static-side large-diameter magnetic field contact (104) welded to the lower end of the static-side large-diameter magnetic field contact (104). The static side large-diameter contact material (105), the static side small-diameter magnetic field contact (102) welded on the inner bottom surface of the static side large-diameter magnetic field contact (104), the lower end of the static side small-diameter magnetic field contact (102) The static side small-diameter contact material (103) is welded; the static-side small-diameter magnetic field contact (102) and the welded static-side small-diameter contact material (103) are placed on the static-side large-diameter magnetic field contact (104) Inside, the surface of the small-diameter contact material (103) on the static side is lower than the surface of the large-diameter contact material (105) on the static side by 2-7 mm; the inner diameter of the large-diameter contact material (105) on the static side bends toward the The large-diameter magnetic field contact (104) shrinks inside; The moving side structure part includes a movable end movable conductive rod (110), a movable end movable magnetic field contact (108) welded on the upper end of the movable end movable conductive rod (110), and a movable end movable magnetic field contact welded on the movable end. (108) The small-diameter contact material (106) at the upper end of the movable end; the movable conductive rod (110) at the movable end is connected to the lower cover plate (128) of the arc extinguishing chamber through a bellows (126); the bellows (126) is provided with a movable end fixed conductive rod (111), and the bellows (126) and the bottom of the movable end fixed conductive rod (111) are welded on the lower side cover plate (128) of the arc extinguishing chamber; the movable end The upper end of the fixed conductive rod (111) is welded with a movable end fixed large-diameter magnetic field contact (109), and the upper end of the movable end fixed large-diameter magnetic field contact (109) is welded with a movable end fixed large-diameter contact material (107); During the arcing process, the moving end movable magnetic field contact (108) moves down with the movable conductive rod (110), and the arc is between the static side small diameter contact material (103) and the moving end small diameter contact material ( 106) Arcing and burning, and the movement stop position of the small-diameter contact material (106) at the moving end is placed inside the fixed large-diameter contact material (107) at the moving end, and the surface of the small-diameter contact material (106) at the moving end is lower than The surface of the fixed large-diameter contact material (107) at the movable end is 2-7mm; The static-side small-diameter magnetic field contact (102) and the welded static-side small-diameter contact material (103) and the moving-end movable magnetic field contact (108) and the welded moving-end small-diameter contact material (106) are formed The movable fracture contact is in the static side large-diameter magnetic field contact (104) and welded static side large-diameter contact material (105) and the moving end fixed large-diameter magnetic field contact (109) and welded dynamic The inside of the fixed fracture contact formed by the fixed large-diameter contact material (107) realizes the electric field shielding and protection of the fixed fracture contact for the movable fracture contact, and avoids the surface of the movable fracture contact during the capacitive closing process. Effect of formed defects on breakdown. 2. The contact with fixed fracture and short-circuit current breaking capability according to claim 1, characterized in that: the static side small-diameter magnetic field contact (102) and the welded static-side small-diameter contact material (103) and the movable end movable magnetic field contact (108) and the welded small-diameter contact material (106) of the movable end are a "cup-shaped" magnetic field contact structure matching the dynamic and static sides, a "coil" magnetic field contact structure, and " Swastika-shaped magnetic field contact structure or "spiral groove" magnetic field contact structure; The interior of the static side large-diameter magnetic field contact (104) and the welded static side large-diameter contact material (105) and the moving end fixed large-diameter magnetic field contact (109) and the welded moving end fixed large-diameter contact material ( 107) is a "cup-shaped" magnetic field contact structure or a "coil" magnetic field contact structure that matches the dynamic and static sides. 3. The contact with fixed fracture and short-circuit current breaking capability according to claim 2, characterized in that: the "cup-shaped" magnetic field contact structure is a "cup-shaped" transverse magnetic contact structure or "cup shape” longitudinal magnetic contact structure; the “coil” magnetic field contact structure is a “coil” transverse magnetic contact structure or a “coil” longitudinal magnetic contact structure. 4. The contact with fixed fracture and short-circuit current breaking capability according to claim 2, characterized in that: the "swastika" magnetic field contact structure and the "spiral groove" magnetic field contact structure are transverse magnetic contacts header structure. 5. A vacuum interrupter with a fixed fracture, characterized in that it comprises the contact with a fixed fracture and capable of breaking short-circuit current, a housing and a shield according to any one of claims 1 to 4.