CN112185772A - Circuit breaker - Google Patents

Abstract

The application relates to a circuit breaker, which comprises a main shell and a tripping mechanism arranged in the main shell; the tripping mechanism comprises a contact frame, an electromagnetic trip and a main shaft which is rotatably arranged in the main shell; the contact frame and the electromagnetic release are respectively arranged on two sides of the main shaft, the contact frame is linked with one side of the main shaft, and one end of the electromagnetic release is linked with the other side of the main shaft; the contact frame swings around the main shaft in a direction opposite to the action of the electromagnetic release under the driving of the electromagnetic release; an arc extinguishing mechanism is further arranged in the main shell, and the contact end of the contact head frame is opposite to the contact end of the arc extinguishing mechanism; this application has the space overall arrangement that can improve the circuit breaker inside, makes things convenient for the effect of tripping device's installation.

Description

Circuit breaker

Technical Field

The application relates to the field of circuit breakers, in particular to a circuit breaker.

Background

The current circuit breaker refers to a switching device capable of closing, carrying and opening/closing a current under a normal circuit condition and a current under an abnormal circuit condition within a prescribed time.

The circuit breaker in the related art is generally composed of a contact system, an arc extinguishing system, an operating mechanism, a trip mechanism, a housing, and the like. The tripping mechanism is an important component for promoting the automatic tripping of the switch in an operating system, the tripping mechanism acts as a force fulcrum during the closing process and at the closing position of the circuit breaker, and when the circuit breaker automatically trips, the tripping mechanism releases the fulcrum to enable the circuit breaker to enter a free opening state.

In view of the above-mentioned related art, the inventor believes that although there are various embodiments of the trip mechanism of the circuit breaker, the structure of the trip mechanism is relatively complicated; when the tripping mechanism is installed, the tripping mechanism has a severe spatial layout condition inside the circuit breaker, so that the defect of complicated installation process is caused.

Disclosure of Invention

In order to improve the inside spatial layout of circuit breaker, make things convenient for tripping device's installation, this application provides a circuit breaker.

The application provides a circuit breaker adopts following technical scheme:

a circuit breaker comprises a main shell, a tripping mechanism arranged in the main shell; the tripping mechanism comprises a contact frame, an electromagnetic trip and a main shaft which is rotatably arranged in the main shell; the contact frame and the electromagnetic release are respectively arranged on two sides of the main shaft, the contact frame is linked with one side of the main shaft, and one end of the electromagnetic release is linked with the other side of the main shaft; the contact frame swings around the main shaft in a direction opposite to the action of the electromagnetic release under the driving of the electromagnetic release; an arc extinguishing mechanism is further arranged in the main shell, and the contact end of the contact frame is opposite to the contact end of the arc extinguishing mechanism.

By adopting the technical scheme, when the tripping mechanism is installed, the oscillating ends of the contact frame and the electromagnetic tripping device can be installed on the front side and the rear side of the main shaft in advance, and then the left end and the right end of the main shaft are installed in the main shell; the contact frame and the electromagnetic release are pre-installed outside the main shell, so that the assembly difficulty can be reduced; when the main shaft is installed, only two ends of the main shaft are respectively inserted into the corresponding side walls of the main shell, and the main shaft is installed in place in one step; the installation condition of the internal space of the circuit breaker is reduced, the spatial layout of the internal space of the circuit breaker is improved, and the assembly efficiency is improved; and the structure is relatively simple, and the tripping is rapid and sensitive.

Preferably, the main shaft is provided with an installation seat facing the contact head frame, the contact head frame is provided with a through waist-shaped hole, and the installation seat is provided with an installation pin penetrating through the waist-shaped hole; and the mounting pins are provided with mounting sleeves which are respectively positioned on two sides of the contact frame, and the mounting sleeves are contacted with the side walls of the contact frame.

By adopting the technical scheme, when the contact frame is installed, the installation pin sequentially penetrates through the installation sleeve and the waist-shaped hole, and then two ends of the installation pin are fixed on the installation seat; the contact frame is clamped by the mounting sleeves arranged on the two sides of the contact frame, so that the stability of the contact frame during swinging can be improved; when the electromagnetic release is electrified and swings downwards, the electromagnetic release drives the main shaft to rotate around the central shaft of the electromagnetic release, and the contact frame is pushed upwards and completes the closing action along with the rotation of the main shaft; the contact holder is ensured to rotate smoothly under the action of the kidney-shaped hole.

Preferably, the contact head frame is coaxially provided with a contact spring, and the contact head frame is also provided with an insulating sleeve and a spring gland along the telescopic direction of the contact spring; the insulating sleeve and the spring gland are respectively positioned at two sides of the contact spring; annular convex edges are formed on the outer surface of the insulating sleeve at intervals, and the spring gland is pressed on the mounting sleeve downwards by the contact spring.

By adopting the technical scheme, when the contact frame is switched on, the mounting sleeve drives the spring gland to push upwards along with the swinging of the mounting sleeve, and the contact spring is pushed by the spring gland to keep a compressed state; when the brake is switched off, the contact spring in a compressed state can quickly complete the brake switching-off action, so that the contact end of the contact frame is ensured to be smoothly separated, and the brake switching-off speed is improved; meanwhile, the creepage distance is increased through the convex edge formed on the insulating sleeve, so that the stability and the safety of the electrical performance can be ensured.

Preferably, the electromagnetic release comprises a coil holder installed in the main housing, and a connecting rod rotatably arranged on the main shaft; and a pressing plate facing the coil holder is arranged on the connecting rod.

By adopting the technical scheme, the coil base generates magnetism after being electrified, then the pressing plate and the connecting rod are driven to rotate downwards and attract each other with the upper end of the coil base, and at the moment, the contact frame positioned on the other side of the main shaft is lifted upwards to complete the switching-on action; the automatic closing device has the effects of high closing action speed and quick response.

Preferably, an opening auxiliary mechanism is arranged in the main shell, and the opening auxiliary mechanism and the electromagnetic release are positioned on the same side of the main shaft along the length direction; the opening auxiliary mechanism comprises a support column, a return spring arranged on the support column and a spring pressure plate arranged on the support column in a sliding manner; the reset spring is located between the support column and the spring pressure plate, a brake separating pressing sheet located above the spring pressure plate is arranged on the main shaft, and the brake separating pressing sheet is abutted to the spring pressure plate.

By adopting the technical scheme, when the contact frame is in a closing state, the opening pressing sheet presses the spring pressing plate downwards under the action of the electromagnetic release; at the moment, the reset spring ensures the compression state, and the reset spring in the compression state at the moment of opening the brake generates reverse elasticity and pushes the main shaft to rotate reversely around the central shaft of the main shaft; the pressing plate and the coil base can be smoothly and quickly separated under the action of the reset spring, so that the contact frame can quickly complete the opening action, the response speed of the opening action is further improved, and the opening action is quicker and more sensitive.

Preferably, a manual brake separating mechanism is arranged on the main shell; the manual brake separating mechanism comprises a manual brake separating shaft, a manual brake separating plate and a support separating support seat; the branch frame supporting seat is arranged in the main shell and close to the electromagnetic release, the manual brake separating shaft is arranged in parallel with the main shaft, and the manual brake separating shaft is rotatably arranged on the branch frame supporting seat; a cutting groove is formed in one end, close to the electromagnetic release, of the manual brake separating shaft, and a connecting block is formed at the upper end of the connecting rod; the opening of the cutting groove faces to the bottom of the connecting block; the manual separating brake plate is positioned on the outer side wall of the main shell, one end of the manual separating brake shaft penetrates out of the outer side wall of the main shell, and the manual separating brake shaft is connected with the manual separating brake plate after penetrating out.

By adopting the technical scheme, when an emergency occurs, the manual brake separating plate arranged on the outer side of the main shell is rotated downwards, and the manual brake separating plate drives the manual brake separating shaft to rotate around the central shaft of the manual brake separating plate along with the rotation of the manual brake separating plate; the opening of the cutting groove on the manual brake separating shaft faces the bottom of the connecting block, and the manual brake separating shaft drives the connecting block to be lifted in the direction away from the coil base along with the rotation of the manual brake separating shaft, so that the operation of separating the brake of the contact frame by manual operation is realized; therefore, when an emergency occurs, the opening can be conveniently realized through external operation, and the safety in use is improved.

Preferably, manual separating brake mechanism is still including setting up the separating brake spring in manual separating brake board one side, separating brake spring one end is connected with main casing body lateral wall, the separating brake spring other end is connected with manual separating brake board.

By adopting the technical scheme, the manual brake separating plate can be kept in a stable state under the action of the brake separating spring; when the opening is realized by operating the manual opening plate, the opening spring is in a stretching state; when the pressure on the manual brake separating plate is removed, the manual brake separating plate can realize automatic reset under the action of the brake separating spring, so that the next manual brake separating can be carried out smoothly.

Preferably, the main housing is provided with an accommodating seat positioned above the main shaft, and an accommodating cavity is formed in the accommodating seat; the arc extinguishing mechanism comprises a vacuum arc extinguishing chamber arranged in the accommodating cavity and a copper bar connecting end arranged at the output end of the vacuum arc extinguishing chamber; the copper bar link extends to the main casing body outside, just be provided with insulating apron on the copper bar link, insulating apron compresses tightly the copper bar link downwards.

By adopting the technical scheme, the vacuum arc-extinguishing chamber can quickly extinguish the electric arc generated during opening, so that the electric arc can be effectively prevented from being re-ignited after the alternating current naturally crosses zero, and further accidents and accidents can be reduced; and can compress tightly the copper bar link downwards through insulating cover plate to can realize the spacing fixed to vacuum interrupter, make vacuum interrupter can be by stable and firm fixing hold the intracavity.

In summary, the present application includes at least one of the following beneficial technical effects:

1. the contact frame and the electromagnetic release are pre-installed outside the main shell, so that the assembly difficulty can be reduced; when the main shaft is installed, only two ends of the main shaft are respectively inserted into the corresponding side walls of the main shell, and the main shaft is installed in place in one step; the installation condition of the internal space of the circuit breaker is reduced, and the assembly effect is improved; the structure is relatively simple, and the tripping is rapid and sensitive;

2. the pressing plate and the coil base can be smoothly and quickly separated under the action of the reset spring, so that the contact frame can quickly complete the opening action, the response speed of the opening action is further improved, and the opening action is quicker and more sensitive.

Drawings

Fig. 1 is a schematic overall structure diagram of an embodiment of the present application.

Fig. 2 is a partial structural schematic diagram highlighting a trip mechanism in an embodiment of the present application.

Fig. 3 is a partial structure diagram of a contact frame according to an embodiment of the present application.

Fig. 4 is an exploded view of a portion of an embodiment of the present application highlighting an arc extinguishing mechanism.

Fig. 5 is a partial schematic structural view of the embodiment of the present application highlighting a manual opening mechanism.

Description of reference numerals: 1. a main housing; 11. an accommodating seat; 12. an accommodating chamber; 2. a tripping mechanism; 21. a contact head frame; 211. a kidney-shaped hole; 212. a contact spring; 213. an insulating sleeve; 214. a spring gland; 215. a convex edge; 23. an electromagnetic release; 231. a coil holder; 232. a connecting rod; 233. pressing a plate; 234. connecting blocks; 24. a main shaft; 241. a mounting seat; 242. mounting a pin; 243. installing a sleeve; 3. an arc extinguishing mechanism; 31. a vacuum arc-extinguishing chamber; 32. a copper bar connecting end; 33. an insulating cover plate; 4. a brake-separating auxiliary mechanism; 41. a support pillar; 42. a return spring; 43. a spring platen; 44. opening a brake and pressing a sheet; 5. a manual brake separating mechanism; 51. a manual brake separating shaft; 511. grooving; 52. a manual gate separating plate; 53. a support seat is divided; 54. a brake separating spring.

Detailed Description

The present application is described in further detail below with reference to figures 1-5.

The embodiment of the application discloses a circuit breaker. Referring to fig. 1 and 2, the circuit breaker includes a main housing 1, and a trip mechanism 2, an arc extinguishing mechanism 3, an auxiliary opening mechanism 4, and a manual opening mechanism 5 are disposed in the main housing 1. When the tripping mechanism 2 is installed, the tripping mechanism 2 is preassembled outside the main shell 1, and then the tripping mechanism 2 is installed inside the main shell 1, so that the installation condition of the internal space of the circuit breaker can be reduced, and the assembly efficiency is improved; the tripping mechanism 2 has a relatively simple structure, and is very quick and sensitive in opening and closing actions.

As shown in fig. 1 and 2, the trip mechanism 2 includes three sets of vertically arranged contact holders 21, a main shaft 24 disposed along the horizontal direction, and an electromagnetic trip 23. The left and right ends of the main shaft 24 are rotatably arranged on the inner side wall of the main housing 1, and the contact holder 21 and the electromagnetic release 23 are respectively positioned on the front and rear sides of the main shaft 24. Three groups of mounting seats 241 which are uniformly arranged at intervals are fixedly arranged on the main shaft 24, and the lower ends of the three groups of contact frames 21 are respectively arranged on the respective corresponding mounting seats 241.

As shown in fig. 2 and 3, a waist-shaped hole 211 is formed in the bottom of the contact holder 21 in the height direction thereof, and the waist-shaped hole 211 penetrates the bottom of the contact holder 21 from left to right. Each set of the mounting bases 241 has a mounting pin 242 disposed along the horizontal direction, and the mounting pin 242 passes through the kidney-shaped hole 211. Two mounting sleeves 243 are movably arranged on the mounting pin 242 and are respectively positioned on the left side and the right side of the contact holder 21, and the mounting sleeves 243 respectively press the lower end of the contact holder 21 on the mounting pin 242 from the two sides.

As shown in fig. 2 and 3, the contact holder 21 is coaxially sleeved with a contact spring 212 that extends and contracts along a length direction of the contact holder 21, the contact holder 21 is further fixedly sleeved with an insulating sleeve 213 that is located above the contact spring 212, and annular convex edges 215 are sequentially and uniformly formed on an outer surface of the insulating sleeve 213 from top to bottom at intervals. The lower end of the contact head frame 21 is further sleeved with a spring gland 214 positioned below the contact spring 212, and the spring gland 214 is movably arranged on the contact head frame 21 along the extension and contraction direction of the contact spring 212. The upper end of the contact spring 212 is abutted against the bottom of the insulating sleeve 213, and the lower end of the contact spring 212 presses the spring gland 214 downwards against the upper end face of the mounting sleeve 243.

As shown in fig. 3 and 4, the top of the main housing 1 is provided with three accommodating seats 11 corresponding to the positions of the lower contact frames 21 one by one, and an accommodating cavity 12 with an opening penetrating up and down is formed in the accommodating seat 11. The arc extinguishing mechanism 3 comprises three vacuum arc extinguishing chambers 31 which are respectively arranged in the corresponding accommodating cavities 12, and the top contact ends of the contact frames 21 are respectively inserted from the lower end openings of the corresponding accommodating cavities 12 and are opposite to the contact ends of the corresponding vacuum arc extinguishing chambers 31. The arc extinguishing mechanism 3 further comprises three groups of copper bar connecting ends 32, the number of each group of copper bar connecting ends 32 is two, and the two copper bar connecting ends 32 located in the same group are arranged at the contact ends of the corresponding vacuum arc extinguishing chambers 31 respectively. The one end that the contact frame 21 was kept away from to copper bar link 32 extends to the outside of main casing body 1, and the top that holds seat 11 has through the bolt screwing to compress tightly upside copper bar link 32 at the insulating cover plate 33 of vacuum interrupter 31 upper end, has still realized under the effect of insulating cover plate 33 that the upper end opening that will hold chamber 12 is covered and is closed.

As shown in fig. 1 and 2, the electromagnetic release 23 includes a cylindrical coil holder 231 mounted on the inner side wall of the bottom of the main housing 1, and a connecting rod 232 having an upper end disposed on the main shaft 24. The connecting rod 232 is vertically disposed, and a connecting block 234 having a rectangular shape is formed at the top of the connecting rod 232. The connecting block 234 is provided with a through hole opened along the length direction of the main shaft 24, the main shaft 24 passes through the through hole of the connecting block 234 through a plug pin, and the connecting block 234 is rotatably arranged on the plug pin along the vertical direction. The bottom of the connecting rod 232 is fixedly provided with a disk-shaped pressing plate 233, and the pressing plate 233 is opposite to the upper end face of the lower coil seat 231. When the coil holder 231 is powered on, it will generate magnetism and attract the connecting rod 232 downwards, at this time, the contact holder 21 at the other end of the main shaft 24 will be pushed upwards, and the closing action is completed.

As shown in fig. 1 and 2, an opening auxiliary mechanism 4 for assisting the circuit breaker to perform an opening operation is further disposed in the main housing 1, and the opening auxiliary mechanism 4 and the electromagnetic release 23 are both located on the same side of the main shaft 24 along the length direction. The opening auxiliary mechanism 4 comprises a support column 41 vertically arranged, a return spring 42 sleeved on the support column 41, and a spring pressure plate 43 arranged on the support column 41. The return spring 42 is located between the support column 41 and the spring pressure plate 43, and the spring pressure plate 43 is slidably disposed on top of the support column 41 along the extending and retracting direction of the return spring 42. An opening pressing sheet 44 extending above the spring pressing plate 43 is fixedly mounted on the main shaft 24, and when the contact holder 21 is in a closing state, the opening pressing sheet 44 presses the spring pressing plate 43 downwards, and at the same time, the return spring 42 is in a compressed state. When the electromagnetic release 23 is de-energized, the spring pressure plate 43 will push the opening pressure plate 44 to rotate upward, thereby helping the contact holder 21 to open the switch smoothly.

As shown in fig. 2 and 5, the main housing 1 is further provided with a manual opening mechanism 5, and the manual opening mechanism 5 includes a manual opening shaft 51, a manual opening plate 52, an opening support base 53, and an opening spring 54. The bottom of the sub-frame support base 53 is fixedly installed on the inner side wall of the main housing 1, and the sub-frame support base 53 is close to the side of the electromagnetic release 23. The manual opening/closing shaft 51 is inserted into the opening/closing support base 53 from the outer side wall of the main housing 1 in the longitudinal direction of the main shaft 24, and then passes through the opening/closing support base 53, and the manual opening/closing shaft 51 is rotatably disposed in the opening/closing support base 53. The manual opening brake separating shaft 51 which penetrates out of the support bracket 53 is provided with a cutting groove 511 with an opening opposite to the bottom of the connecting block 234, and the upper surface of the cutting groove 511 is parallel to the bottom of the connecting block 234. One end of the manual opening shaft 51 far away from the connecting block 234 penetrates out of the outer side wall of the main shell 1, and the manual opening plate 52 is fixedly arranged on the manual opening shaft 51 penetrating out of the outer side wall of the main shell 1.

As shown in fig. 2 and 5, an insertion column located on one side of the manual opening/closing plate 52 is fixedly mounted on the outer side wall of the main housing 1, one end of the opening spring 54 is fixed to the insertion column, and the other end of the opening spring 54 is fixed to the manual opening/closing plate 52. The upper surface of the manual opening/closing plate 52 is kept horizontal by the opening/closing spring 54, and when the manual opening/closing plate 52 is rotated downward, the manual opening/closing plate 52 drives the manual opening/closing shaft 51 to rotate around its central axis. Since the cutting slot 511 on the manual opening shaft 51 opens toward the bottom of the connecting block 234, the manual opening shaft 51 will drive the connecting block 234 to lift away from the coil holder 231 as the manual opening shaft 51 rotates, and at this time, the operation of opening the contact holder 21 by hand is realized.

The implementation principle of the circuit breaker in the embodiment of the application is as follows: when the trip mechanism 2 is to be mounted, the contact holder 21 and the connecting rod 232 of the electromagnetic trip 23 are mounted on the front and rear sides of the main shaft 24 in advance, and then the left and right ends of the main shaft 24 are mounted inside the main casing 1. The difficulty of assembly can be reduced by pre-mounting the contact frame 21 and the connecting rod 232 outside the main housing 1. When the main shaft 24 is installed, only two ends of the main shaft 24 are respectively inserted into the corresponding side walls of the main shell 1, and the main shaft 24 is installed in place in one step. The installation condition of the internal space of the circuit breaker is reduced, and the assembly efficiency is improved; and the structure is relatively simple, and the tripping is rapid and sensitive.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (8)

1. A circuit breaker comprises a main shell (1), a tripping mechanism (2) arranged in the main shell (1); the method is characterized in that: the tripping mechanism (2) comprises a contact frame (21), an electromagnetic trip (23) and a main shaft (24) which is rotatably arranged in the main shell (1); the contact frame (21) and the electromagnetic release (23) are respectively arranged on two sides of the main shaft (24), the contact frame (21) is linked with one side of the main shaft (24), and one end of the electromagnetic release (23) is linked with the other side of the main shaft (24); the contact frame (21) is driven by the electromagnetic release (23) to swing around the main shaft (24) along the direction opposite to the action of the electromagnetic release (23); an arc extinguishing mechanism (3) is further arranged in the main shell (1), and the contact end of the contact head frame (21) is opposite to the contact end of the arc extinguishing mechanism (3).

2. A circuit breaker according to claim 1, wherein: the main shaft (24) is provided with an installation seat (241) facing the contact frame (21), the contact frame (21) is provided with a through waist-shaped hole (211), and the installation seat (241) is provided with an installation pin (242) penetrating through the waist-shaped hole (211); the mounting pin (242) is provided with mounting sleeves (243) which are respectively positioned on two sides of the contact rack (21), and the mounting sleeves (243) are in contact with the side wall of the contact rack (21).

3. A circuit breaker according to claim 2, wherein: the contact head frame (21) is coaxially provided with a contact spring (212), and the contact head frame (21) is also provided with an insulating sleeve (213) and a spring gland (214) along the telescopic direction of the contact spring (212); the insulating sleeve (213) and the spring gland (214) are respectively positioned at two sides of the contact spring (212); annular convex edges (215) are formed on the outer surface of the insulating sleeve (213) at intervals, and the contact spring (212) presses the spring gland (214) downwards onto the mounting sleeve (243).

4. A circuit breaker according to claim 1, wherein: the electromagnetic release (23) comprises a coil holder (231) arranged in the main shell (1) and a connecting rod (232) rotatably arranged on the main shaft (24); the connecting rod (232) is provided with a pressing plate (233) facing the coil holder (231).

5. A circuit breaker according to claim 4, wherein: an opening auxiliary mechanism (4) is arranged in the main shell (1), and the opening auxiliary mechanism (4) and the electromagnetic release (23) are positioned on the same side of the main shaft (24) along the length direction; the opening auxiliary mechanism (4) comprises a supporting column (41), a return spring (42) arranged on the supporting column (41), and a spring pressure plate (43) arranged on the supporting column (41) in a sliding manner; the reset spring (42) is positioned between the support column (41) and the spring pressure plate (43), the main shaft (24) is provided with a brake separating pressing sheet (44) positioned above the spring pressure plate (43), and the brake separating pressing sheet (44) is abutted to the spring pressure plate (43).

6. A circuit breaker according to claim 4, wherein: a manual brake separating mechanism (5) is arranged on the main shell (1); the manual brake separating mechanism (5) comprises a manual brake separating shaft (51), a manual brake separating plate (52) and a support separating support seat (53); the sub-frame supporting seat (53) is arranged in the main shell (1) and close to the electromagnetic release (23), the manual brake separating shaft (51) and the main shaft (24) are arranged in parallel, and the manual brake separating shaft (51) is rotatably arranged on the sub-frame supporting seat (53); one end of the manual brake separating shaft (51) close to the electromagnetic release (23) is provided with a cutting groove (511), and the upper end of the connecting rod (232) is provided with a connecting block (234); the opening of the cutting groove (511) faces the bottom of the connecting block (234); the manual branch flashboard (52) is located the main casing body (1) lateral wall, the manual branch floodgate axle (51) one end is worn out from the main casing body (1) lateral wall, after wearing out the manual branch floodgate axle (51) are connected with the manual branch flashboard (52).

7. A circuit breaker according to claim 6, wherein: the manual opening mechanism (5) further comprises an opening spring (54) arranged on one side of the manual opening plate (52), one end of the opening spring (54) is connected with the outer side wall of the main shell (1), and the other end of the opening spring (54) is connected with the manual opening plate (52).

8. A circuit breaker according to claim 1, wherein: an accommodating seat (11) positioned above the main shaft (24) is arranged on the main shell (1), and an accommodating cavity (12) is formed in the accommodating seat (11); the arc extinguishing mechanism (3) comprises a vacuum arc extinguishing chamber (31) arranged in the accommodating cavity (12) and a copper bar connecting end (32) arranged at the output end of the vacuum arc extinguishing chamber (31); copper bar link (32) extend to main casing body (1) outside, just be provided with insulating apron (33) on copper bar link (32), insulating apron (33) compress tightly copper bar link (32) downwards.

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