Abstract:
A vacuum interrupter, including: an insulating housing; a movable end cap; a stationary end cap; a pair of movable and stationary contacts; and a pair of shields. The pair of shields is fixed on the movable end cap and the stationary end cap, respectively. The insulating housing, the movable end cap, and the stationary end cap cooperate to form a closed space. The closed space includes a movable fracture and a stationary fracture. The movable fracture is formed by the pair of movable and stationary contacts for carrying rated current and disconnecting capacitive load whereby achieving breaking performance of the vacuum interrupter. The stationary fracture is formed by the pair of shields. When the pair of stationary and movable contacts reaches a full open position, the stationary contact and the movable contact enter the pair of shields, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of International Patent Application No. PCT/CN2012/071840 with an international filing date of Mar. 2, 2012, designating the United States, now pending, the contents of which, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 14781 Memorial Drive, Suite 1319, Houston, Tex. 77079. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a vacuum interrupter. 
         [0004]    2. Description of the Related Art 
         [0005]    Recent studies have found that the heavy breakdown has an affinity to the high-frequency inrush current. As the contact surface is locally ablated by the high-frequency current during the close of the switch, fusion welding occurs on the contact, and the surface structure of the contact is damaged, thereby increasing the field emission coefficient β of the contact surface. 
         [0006]    A typical vacuum interrupter generally includes a pair of movable contacts. For example, a power-off and disconnecting switch device equipped with a vacuum box includes different positions of movable contacts inside the vacuum interrupter for controlling the connection, breaking, and disconnection of the current. For another example, a high voltage vacuum switch achieves anti-high-voltage property of the vacuum interrupter by controlling a pair of the movable contacts to be disposed inside a pair of shield contacts at a full open position. Although multiple working positions of the vacuum interrupter are disposed, the current breaking function is not independent from the insulating function after the disconnection. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the above-described problems, it is one objective of the invention to provide a vacuum interrupter that has independent breaking function and insulating function and employs a movable contact to achieve the breaking function and a stationary contact to achieve the insulating function. Besides, the vacuum interrupter is applicable to in breaking the capacitive load, such as, a back-to-back capacitor bank and a single capacitor bank, and particularly applicable to the field of the reactive power compensation in the electric power system. 
         [0008]    To achieve the above objective, in accordance with one embodiment of the invention, there is provided a vacuum interrupter, comprising: an insulating housing; a movable end cap; a stationary end cap; a pair of movable and stationary contacts; and a pair of shields. The pair of shields is fixed on the movable end cap and the stationary end cap, respectively. The insulating housing, the movable end cap, and the stationary end cap cooperate to form a closed space having a vacuum state. The closed space comprises a movable fracture and a stationary fracture. The movable fracture is formed by the pair of movable and stationary contacts for carrying rated current and disconnecting capacitive load whereby achieving breaking performance of the vacuum interrupter. The stationary fracture is formed by the pair of shields which are fixed on the movable end cap and the stationary end cap, respectively. When the pair of stationary and movable contacts reach a full open position, the stationary contact and the movable contact enter the pair of shields, respectively, so that a DC recovery voltage resulting from the break of capacitive current is exerted on the stationary fracture whereby achieving insulating performance of the vacuum interrupter. 
         [0009]    In a class of this embodiment, one or several of the movable fracture(s) are provided. The vacuum interrupter comprising a plurality of the stationary fractures is advantageous in that the DC recovery voltage after breaking the capacitive current is exerted on the stationary fractures. When one stationary fracture is broken down, other stationary fractures will not be broken down simultaneously, thus, the line current will not be produced, that is, the heavy breakdown phenomenon will not occur in the vacuum interrupter. The delay heavy breakdown of the vacuum interrupter during the switching of the capacitive load is effectively decreased. 
         [0010]    In a class of this embodiment, the vacuum interrupter comprising the stationary fracture is applicable to an operating mechanism to form a vacuum load switch, a vacuum contactor, or a vacuum breaker. Meanwhile, the vacuum load switch and the vacuum contactor formed by the vacuum interrupter are able to match with a fuse to form a special combined electrical apparatus for switching capacitive load. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention is described hereinbelow with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1  is a cross-sectional view of a vacuum interrupter comprising one stationary fracture in accordance with one embodiment of the invention; 
           [0013]      FIG. 2  is a cross-sectional view of a vacuum interrupter comprising two stationary fractures in accordance with one embodiment of the invention; and 
           [0014]      FIG. 3  is a cross-sectional view of a vacuum interrupter comprising three stationary fractures in accordance with one embodiment of the invention. 
       
    
    
       [0015]    In the drawings, the following reference numbers are used:  1 . Insulating housing;  2 . Movable end cover;  3 . Stationary end cover;  4 . Bellows;  5 . Movable conductive rod;  6 . Stationary conductive rod;  7 . Movable end shield;  8 . Fixed end shield;  9 . Stationary fracture;  10 . Movable contact;  11 . Stationary contact;  12 . Movable fracture;  13 . Main shield;  14 . End shield;  201 . First insulating housing;  202 . Second insulating housing;  203 . First movable end cap;  204 . Second movable end cap;  205 . Stationary end plate;  206 . First bellows;  207 . Second bellows;  208 . First movable conductive rod;  209 . Second movable conductive rod;  210 . First movable end shield;  211 . Second movable end shield;  212 . Stationary end shield;  213 . First stationary fracture;  214 . Second stationary fracture;  215 . First movable contact;  216 . Second movable contact;  217 . Stationary contact;  218 . First movable fracture;  219 . Second movable fracture;  301 . Insulating housing;  302 . Movable end cap;  303 . Stationary end cap;  304 . Bellows;  305 . Movable conductive rod;  306 . Stationary conductive rod;  307 . Movable end shield;  308 . Stationary end shield;  309 . First shield;  310 . Second shield;  311 . Movable contact;  312 . Stationary contact;  313 . Movable fracture;  314 . First stationary fracture;  315 . Second stationary fracture; and  316 . Third stationary fracture. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0016]    For further illustrating the invention, experiments detailing a vacuum interrupter are described below. It should be noted that the following examples are intended to describe and not to limit the invention. 
         [0017]    As shown in  FIG. 1 , a vacuum interrupter comprising one stationary fracture comprises a closed space formed by an insulating housing  1 , a movable end cap  2 , and a stationary end cap  3 ; and an inner part of the closed space is in the vacuum state. A movable conductive rod  5  passes through the movable end cap  2  to allow one end of the movable conductive rod  5  to be disposed inside the closed space and the other end of the movable conductive rod  5  to be disposed outside the closed space, and the movable conductive rod  5  is capable of moving upward and downward. The end of the movable conductive rod  5  disposed inside the closed space is nested within a bellows  4  and comprises an end point being fixed together with a movable contact  10 . One end of the bellows  4  is fixed on the movable end cap  2 , and the other end of the bellows  4  is fixed on the movable conductive rod  5 . A stationary conductive rod  6  passes through the stationary end cap  3  to allow one end of the stationary conductive rod  6  to be disposed inside the closed space and the other end of the stationary conductive rod  6  to be disposed outside the closed space. A stationary contact  11  is fixed on an end point of the end of the stationary conductive rod  6  disposed inside the closed space. The movable fracture  12  is formed between the movable contact  10  and the stationary contact  11 . The stationary fracture  9  is formed by a movable end shield  7  and a stationary end shield  8  inside the closed space. The movable end shield  7  and the movable end cap  2  are fixed together, and the stationary end shield  8  and the stationary end cap  3  are fixed together. The movable contact  10  and the stationary contact  11  respectively enter the movable end shield  7  and the stationary end shield  8  after reaching the full open position. 
         [0018]    A main shield  13  is disposed inside the closed space and is fixed on a middle part of the insulating housing  1  of the vacuum interrupter outside the stationary fracture  9 . 
         [0019]    An inner part of the closed space is provided with end shields  14 , the end shields  14  are fixed on the movable end cap  2  and the stationary end cap  3  outside the movable end shield  7  and stationary end shield  8 , respectively. 
         [0020]    Working principle of the vacuum interrupter is as follows: in the process of closing the capacitive load, the movable contact  10  moves close to the stationary contact  11  under the force of an operating mechanism. When the movable fracture  12  is unable to bear the voltage exerted between the contacts, the pre-breakdown phenomenon occurs, the rated current rushes from the movable contact  10  to the stationary contact  11 , and finally the two contacts press against each other. When the capacitive load is disconnected, the movable contact  10  is separated from the stationary contact  11  and produces an electric arc under the force of the operating mechanism, and the arc disappears at the current zero, thus, the breaking of the capacitive current is finished by the movable fracture  12 . When the movable fracture  12  reaches a full open position, the movable contact  10  and the stationary contact  11  enter the movable end shield  7  and the stationary end shield  8 , respectively. From the perspective of the electric field distribution, the movable contact  10  and the stationary contact  11  are shielded by the movable end shield  7  and the stationary end shield  8 , respectively, and the DC recovery voltage is exerted on the stationary fracture  9 , that is, the insulating performance of the vacuum interrupter is determined by the stationary fracture  9 . In the whole switching process, only the surfaces of the movable contact  10  and the stationary contact  11  will be eroded or damaged by the current, but the insulating performance of the vacuum interrupter will not decrease. Thus, the heavy breakdown probability during the breaking of the capacitive current is effectively decreased. 
         [0021]    The number of the movable contact and the stationary contact can be one or several, respectively. As shown in  FIG. 2 , the number of the movable fractures and the fixed fractures are two. The vacuum interrupter comprises a closed space formed by a first insulating housing  201 , a second insulating housing  202 , a first movable end cap  203 , and a second movable end cap  204 . An inner part of the closed space is in the vacuum state. A middle part of the closed space is provided with a stationary end plate  205 . The closed space is divided into a first closed space and a second closed space by the stationary end plate  205 . The stationary contact  217  is fixed on the stationary end plate  205 . A first movable conductive rod  208  passes through the first movable end cap  203 , one end of the first movable conductive rod  208  is disposed inside the closed space, and the other end of the movable conductive rod  208  is disposed outside the closed space. The first movable conductive rod  208  is capable of moving upward and downward. The end of the first movable conductive rod  208  disposed inside the first closed space is nested within a first bellows  206  and comprises an end point being fixed together with a first movable contact  215 . One end of the first bellows  206  is fixed on the first movable end cap  203 , and the other end of the first bellows  206  is fixed on the first movable conductive rod  208 . The second movable conductive rod  209  passes through the second movable end cap  204 . One end of the second movable conductive rod  209  is disposed inside the second closed space, and the other end of the second movable conductive rod  209  is disposed outside the second closed space. The second movable conductive rod  209  is capable of moving upward and downward. The end of the second movable conductive rod  209  disposed inside the second closed space is nested within a second bellows  207  and comprises an end point being fixed together with a second movable contact  216 . One end of the second bellows  207  is fixed on the second movable end cap  204 , and the other end of the second bellows  207  is fixed on the second movable conductive rod  209 . A first movable fracture  218  is formed between the first movable contact  215  and the stationary contact  217 . A second movable fracture  219  is formed between the second movable contact  216  and the stationary contact  217 . A first movable end shield  210  is fixed on the first movable end cap  203 , a second movable end shield  211  is fixed on the second movable end cap  204 . A stationary end shield  212  is fixed on the stationary end plate  205 . A first stationary fracture  213  is formed between a first movable end shield  210  and the stationary end shield  212 , and a second stationary fracture  214  is formed between the second movable end shield  211  and the stationary shield  212 . The first movable contact  215  and the second movable contact  216  enter the first movable end shield  210  and the second movable end shield  211 , respectively, when the first movable fracture  218  and the second movable fracture  219  reach a full open position. The first movable contact  215 , the second movable contact  216 , and the stationary contact  217  are shielded by the first movable end shield  210 , the second movable end shield  211 , and the stationary end shield  212 , respectively, from the perspective of the electric field distribution. 
         [0022]    Working principle of the vacuum interrupter comprising the two stationary fractures is as follows: in the process of closing the capacitive load, the rated current is carried by the first movable contact  215 , the second movable contact  216 , and the stationary contact  217 , while the first movable fracture  218  and the second movable fracture  219  formed by the three contacts are used to finish the breaking function of the capacitive current during the disconnection of the capacitive load. When the first movable fracture  218  and the second movable fracture  219  reach the full open position, the first movable contact  215  and the second movable contact  216  move inside the first movable end shield  210  and the second movable end shield  211 , respectively. From the perspective of the electric field distribution, the first movable contact  215 , the second movable contact  216 , and the stationary contact  217  are shielded by the first movable end shield  210 , the second movable end shied  211 , and the stationary end shield  212 , respectively; and the DC recovery voltage is exerted on both the first stationary fracture  213  and the second stationary fracture  214 . As long as the two stationary fractures are not broken down simultaneously, the line current will not be produced, that is, the heavy breakdown phenomenon will not occur in the vacuum interrupter. Thus, the performance of the vacuum interrupter during the switching of the capacitive load is much reliable. 
         [0023]    When the number of the stationary fractures is three, as shown in  FIG. 3 , the vacuum interrupter comprises the closed space formed by the insulating housing  301 , the movable end cap  302 , and the stationary end cap  303 , and the inner part of the closed space is in the vacuum state. A movable conductive rod  305  passes through the movable end cap  302  to allow one end of the movable conductive rod  305  to be disposed inside the closed space and the other end of the movable conductive rod  305  to be disposed outside the closed space, and the movable conductive rod  305  is capable of moving upward and downward. The end of the movable conductive rod  305  disposed inside the closed space is nested within a bellows  304  and comprises an end point being fixed together with a movable contact  311 . One end of the bellows  304  is fixed on the movable end cap  302 , and the other end of the bellows  304  is fixed on the movable conductive rod  305 . A stationary conductive rod  306  passes through the stationary end cap  303  to allow one end of the stationary conductive rod  306  to be disposed inside the closed space and the other end of the stationary conductive rod  306  to be disposed outside the closed space. A stationary contact  312  is fixed on an end point of the end of the stationary conductive rod  306  disposed inside the closed space. The movable fracture  313  is formed between the movable contact  311  and the stationary contact  312 . The movable end shield  307  and the movable end cap  302  are fixed together, and the stationary end shield  308  and the stationary end cap  303  are fixed together. The movable contact  311  and the stationary contact  312  respectively enter the movable end shield  307  and the stationary end shield  308  when reaching the full open position. A first shield  309  and a second shield  310  are fixed inside the insulating housing  301 . A first stationary fracture  314  is formed between the movable end shield  307  and the first shield  309 . A second stationary fracture  315  is formed between the first shield  309  and the second shield  310 . A third stationary fracture  316  is formed between the second shield  310  and the stationary shield  308 . 
         [0024]    Working principal of the vacuum interrupter comprising the three stationary fractures is as follows: in the process of closing the capacitive load, the rated current is carried by the movable contact  311  and the stationary contact  312 , while the movable fracture formed by the two contacts are used to finish the breaking function of the capacitive current during the disconnection of the capacitive load. When the movable fracture  313  reaches the full open position, the movable contact  311  and the stationary contact  312  moves inside the movable end shield  307  and the stationary end shield  308 , respectively. From the perspective of the electric field distribution, the movable contact  311  and the stationary contact  312  are shielded by the movable end shield  307  and the stationary end shield  308 , respectively, and the DC recovery voltage is exerted on the first stationary fracture  314 , the second stationary fracture  315 , and the third stationary fracture  316 , so that the performance of the vacuum interrupter during switching of the capacitive load is much reliable. 
         [0025]    Furthermore, the vacuum interrupter comprising the stationary fracture is applicable to different operating mechanisms to form a vacuum load switch, a vacuum contactor, or a vacuum breaker. Meanwhile, the vacuum load switch and the vacuum contactor formed by the vacuum interrupter are able to match with a fuse to form a special combined electrical apparatus for switching the capacitive load. A protective property of the fuse is avoid from the inrush current in inputting capacitive load, that is, the fuse is not allowed to move during the inrush phase. Under a rated working condition, the protective property of the fuse matches with load characteristics. In failure cases, a firing pin device carried by the fuse make the vacuum load switch or the vacuum contactor finish the break-brake operation. 
         [0026]    While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.