RU2368975C1 - Contact system for fast-acting automatic circuit breaker - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is related to double-break contact systems of low-voltage automatic circuit breakers. Contact system is equipped with two "П"-shaped yokes with coaxial openings at their side walls, which divide each yoke into "П"-shaped and fork-shaped arms. The second ends of pressing springs are made in the form of extended hooks, lengths of which are not less than length of yokes. The yokes themselves are mounted inside drum between its internal and external disks at distances R from axis of rotation at formed coaxial cylindrical extensions, with height of not more than thickness of yoke side walls. Cylindrical thrusts are installed on both sides of rotary contact holder at distance r from axis of drum rotation, provided that r is less than R. In internal disks of drum radius slots are arranged opposite to thrusts. Yokes with their openings are installed on cylindrical protrusions of internal and external disks with the possibility of interaction of fork-shaped arms with thrusts of contact holder, passing through radius slots of internal disks, and extended hooks of pressing springs are placed between side walls of yokes and are fixed on "П"-shaped arms of these yokes.

EFFECT: higher efficiency and reliability of short-circuit current disconnection, improved current-limiting properties.

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Description

The present invention relates to electrical engineering, in particular to high-speed low-voltage circuit breakers, in particular to two-burst contact systems in the form of a rotary contact bridge, used for high-speed protection against short-circuit currents with current limitation.

Known double-contact contact systems of high-speed circuit breakers, breaking short-circuit currents with different current limiting factors, the principle of operation of which is based on accelerated electrodynamic dilution of contacts when large emergency currents occur and fast (in a time significantly less than 5 ms) introducing high resistance in the form of an electric circuit of an arc formed between breakable contacts (see the book by S. Dzierzbicki, E. Valchuk “Current-limiting circuit breakers alternating current ”. - L .: Energoizdat, 1982, pp. 63-67, Fig. 3.15; 3.16, TL-type switches of the Japanese company Terasaki, as well as descriptions of US patents: No. 7,005,594B2 dated February 28, 2006, H01H 3/00 ; No. 7.145.419B2 dated December 5, 2006, H01H 75/00). Two-contact systems can be implemented with translational movement of movable contacts both in Terasaki type TL circuit breakers and with rotary movement, the designs of which are shown in the descriptions of the listed US patents. Due to the structural and technological advantages of rotational motion over translational motion and balance with respect to the axis of rotation, the design of symmetrical rotary bridges has been used predominantly. The accelerated opening of the contacts is always counteracted by the efforts of the pressing springs and the ability to return the contacts to their original position after the forced opening by electrodynamic forces. To reduce the influence of pressing springs and to ensure the impossibility of contact return, devices are used to block the reverse movement of contacts after they are opened by electrodynamic forces. The design of these devices, as a rule, use kinematics with the transition of the contact holder through the so-called dead position. Such a device is shown in detail in Fig. 2-7, p. 34 in the book by S. Dzierzbicki, E. Valchuk, "Current-limiting AC circuit breakers." If the point A belonging to the movable contact 3 (see Fig. 2-7), in which the upper end of the pressing spring 5 is fixed, crosses the line passing through the points BC (where point C is the axis of rotation of contact 3, and point B is the place attaching the lower end of the spring 5 to the drive shaft 1 that is stationary during electrodynamic waste, then the spring 5 reaches its maximum force, and then, after going through this dead position, tilts contact 3 to the off state and holds it, preventing it from re-closing. In the contact two-bursting system in the form of a rotary bridge according to US patent No. 7005594B2, the dead position that the bridge overcomes with electrodynamic rejection is created by performing cam surface 113, 115 on the cylindrical surface of the drive drum 110 (see Figure Fig. 8 in the description of this patent) , 116, along which, with the help of a roller 155, rotating on an axis 151, the end of the pressing spring 142, mounted on this axis, is moved. The fixation of the bridge 120 after electrodynamic rejection and the guaranteed non-return of the contacts 121 to the closed position is ensured when the roller 155 gets its cylindrical surface 131 (see Fig. 4) into the groove 116. The disadvantage of this design is the large angle of rotation of the contact bridge 120 to fix it in the groove 116, which requires the development of sufficient electrodynamic forces to breed the switch contacts at this angle. This means that a circuit breaker with such a contact system will be operational only with a sufficiently high limiting short-circuit current, and when the values of the short-circuit current are slightly lower than the values of this limiting current, repeated short-circuiting and welding of the contacts are possible. This reduces the reliability of the contact system, narrows the range of short circuit currents in which the contact system can provide a tripping process with current limitation.

The two-burst contact system in the form of a rotary contact bridge according to US patent No. 7,145,419В2 dated December 5, 2006, H01H 75/00, which is the prototype of the claimed technical solution, also has a similar design.

In the prototype (see figures Fig. 5-11 in the description of US patent No. 7,145,419B2), the contact system of a high-speed circuit breaker consists of fixed contacts at the terminals of the switch and movable contacts on a rotary two-arm contact holder (bridge) located inside the drum, which is made in in the form of coaxially fixed two internal and two external disks. A rotary contact holder is installed between two internal disks of the drum with the possibility of contacting with fixed contacts and is spring-loaded with pressure springs. Pressing springs are installed at one end on the contact carrier, and others on the inner discs of the drum via an axis with rollers. The rollers 66a, 66b (see Fig. 7) are in contact with the outer cylindrical surface of the inner discs on which the cam surfaces 42a, 42b, 42c, 42d are made. The conjugation of surfaces 42b and 42c creates a dead position of kinematics, which is overcome with electrodynamic rejection. The fixation of the contact holder after electrodynamic rejection under the action of electrodynamic forces arising in the contact joints at short-circuit currents, and guaranteed non-return of the contacts to the closed position is ensured when the rollers 66a, 66b are moved to the radial recesses 42d on the internal disks. The disadvantage of the prototype, as previously discussed contact system, is also a large angle of rotation of the contact holder, at which it must be discarded by electrodynamic forces for reliable fixation. Due to the increased angular displacement (and the accompanying friction losses in this case), the speed decreases and, as a result, the current-limiting properties of the contact system deteriorate. The noted disadvantage of the prototype also leads to an increase in the threshold value of the short circuit current at which reliable fixation of the discarded bridge is possible. To eliminate these drawbacks, it is necessary to create such a kinematic connection between the discarded contact holder and the pressure springs, which would allow the springs to be moved through the dead position with a smaller angle of rejection of the contact holder and make the contact holder faster to fix.

The technical result achieved by the claimed invention is to increase the speed and reliability of disconnecting short circuit currents, improving the current-limiting properties of the contact system.

The specified technical result is achieved in that the contact system for a high-speed circuit breaker with a double gap, containing the lower and upper conclusions with fixed contacts, a rotating drum, consisting of coaxially fixed two internal and two external disks, a rotary two-arm contact holder with movable contacts mounted between the internal drum disks with the possibility of contacting with fixed contacts, pressure springs, one ends of which are fixed to the contact holder barely, and the second on the drum, the drive rod for communication with the switch mechanism, is equipped with two U-shaped rockers with coaxial holes on their side walls symmetrically located relative to the axis of rotation of the drum, dividing each beam into U-shaped and fork-shaped shoulders, and each outer disk mounted in the drum relative to the inner disk at a distance not less than the thickness of the rocker arm, while the second ends of the pressure springs are made in the form of elongated hooks, the length of which is not less than the length of the rocker arm, on each in the morning and outer disks, two coaxial cylindrical protrusions are formed symmetrically with respect to the axis of rotation of the drum and at distances R from the axis against each other, with a height not exceeding the thickness of the side walls of the rocker arms, on the rotary contact holder, at a distance r from the axis of rotation of the drum from condition r is less than R and symmetrically relative to the axis of rotation, cylindrical stops are installed on both sides, radius grooves are made in the inner disks of the drum against the stops, and the rocker arms are mounted on their cylindrical holes stupas of internal and external disks with the possibility of interaction with fork-shaped shoulders with contact carrier stops passing through the radial grooves of the internal disks, and elongated hooks of pressure springs are placed between the side walls of the rocker arms and fixed on the U-shaped shoulders of these rocker arms.

Supply of the contact system with two U-shaped rockers symmetrically positioned relative to the axis of rotation of the drum with coaxial holes on their side walls, dividing each rocker into U-shaped and fork-shaped shoulders, installing these rockers on cylindrical protrusions formed on each inner and outer disks with a distance R from the axis of rotation of the drum with the possibility of interaction with forked shoulders mounted on the contact carrier at distances r (and from the condition r is less than R) from the axis of rotation of the cylindrical with support legs, making radial grooves in the inner disks to move the stops in them, making one of the hooks of the pressing springs elongated, and with a length of at least the length of the rocker arm and securing the springs with extended hooks on the U-shaped arms of the rocker arm with the placement of the elongated hooks between the walls of the rocker arm to carry out the kinematic connection of the pressure springs between the contact holder and the drum in such a way that the angle of rotation of the contact holder until the transition of the pressure springs through the "dead" position is Twain reduced. Consequently, in case of electrodynamic rejection, reliable fixation of the contact holder occurs earlier, which ultimately increases the speed of the contact system and improves the current-limiting properties of the circuit breaker.

The proposed design of the contact system for a high-speed circuit breaker is shown in Fig.1-8.

Figure 1 shows a General view of the contact system of the pole of the switch in the on state. Figure 2 shows an axonometric image of the contact system in disassembled form, giving a general idea of the internal structure of the structure and the shape of its parts. Figure 3 is an axonometric image of the structure in assembled form when conventionally removed the right outer disk of the drum (right view in figure 1), and Figure 4 - when conventionally removed the left outer disk of the drum (left view in figure 1). Figure 5-8 sequentially depicts the position of the contact holder without the outer disk of the drum: with a closed contact system - Figure 5; after electrodynamic rejection at the moment of transition through the dead position - Fig.6; in a fixed state after going through a dead position - Fig.7; after operation of the circuit breaker under the action of the maximum release - Fig. 8.

The contact system (see Fig. 1) consists of the terminals 2 installed in the housing 1 of the lower 2 and upper 3 circuit breakers with fixed contacts 4, 5. The movable contacts 6, 7 are mounted on a rotary two-arm contact holder 8. The contact holder is mounted for rotation inside the drum 9 The drum consists of two internal 12, 13 and two external disks 14, 15 coaxially connected with rivets 10, 11. In the switch housing, the drum 9 is capable of rotation on two cylindrical bosses 16 projecting from the external disks 14, 15 under the air by the action of the free trip mechanism (the mechanism is not shown in the figures) on the drive rods 17, 18. The necessary pressing force between the movable and fixed contacts (see the disassembled drum structure 9 in figure 2) is created by pressing springs 19, 20, one ends of which are fixed to pins 21, 22 of the contact holder 8 (for the installed springs, see figure 3-8). The second ends of the springs are made in the form of elongated hooks 23, 24 and are mounted on the drum by means of new structural elements, namely, by means of two U-shaped rockers 25, 26 symmetrically located relative to the axis of rotation of the drum with coaxial holes 27, 28 on their side walls 29, 30 (see section BB of the extension element A in FIG. 2). Holes 27, 28 divide each beam into a U-shaped 31 and a fork-shaped 32 shoulders. The elongated hooks 23, 24 are fixed on the lintels of the U-shaped shoulders 31 of the rocker arms 25, 26 and placed between the walls 29, 30 of these rocker arms. The length of the hooks is slightly larger than the length of the rocker arm, so as not to interfere with the rotation of the rocker arm and make the design of the drum 9 more compact with a small axial size. Each rocker with its holes 27, 28 is mounted on two molded, on each pair of internal and external disks 13, 15 and 12, 14 at a distance R (see figure 5) from the axis of rotation of the drum, coaxial cylindrical protrusions 33, 34 and 35, 36. Moreover, the axial length of each of the protrusions 33-36 does not exceed the thickness t of the side walls 29, 30 of the rocker arm, and each outer disk is mounted relative to the internal one at a distance of not less than the thickness N of the rocker arm 25, 26. Such conditions are necessary for the rotation of the rocker arm between the inner and outer discs on the protrusions 33, 34; 35, 36 and free movement of the elongated hooks of the springs between the walls 29, 30 of the rocker arm. In addition, on the rotary contact holder 8 at a distance r from the axis of rotation of the drum from the condition r is less than R (see FIG. 5, FIG. 2) and cylindrical stops 37, 38 are installed symmetrically with respect to the axis of rotation on both sides (see also FIG. 3, Fig. 4), and in the inner disks of the drum against the stops there are radius grooves 39, 40 (see Fig. 2). The cylindrical stops 37, 38 pass through the radial grooves 39, 40 and protrude from the inner discs (see FIG. 5, section B-B) to a length of not more than the thickness t of the side walls 29, 30 with the possibility of interaction with the fork arms 32 without interfering free movement of the elongated hooks 23, 24 of the spring between the side walls of the rocker arm. The contact holder 8 can freely rotate inside the drum on the axes 41 belonging to the internal disks 12, 13. To compensate for the impact on the operation of the contact bridge uneven wear in two pairs of contacts 4, 6; 5, 7 and technological errors in the manufacture of parts in the contact holder, the central hole 42 is ellipsoidal, and to limit the angular displacement of the contact holder in the internal disks, sector-shaped samples 43, 44 are made. The maximum angle of rotation of the rocker arm is limited by curly surfaces 45 made in the external disks 14, 15 (see Fig. 2 and 7). The self-introduction of the contact system after the release mechanism is activated under the action of the releases is provided by the introduction of the latch 46 of the extreme position of the contact holder 8. The latch 46 is mounted on the housing 1 of the switch (Fig.6-8).

The contact system of a high-speed circuit breaker operates as follows.

With manual operation of the circuit breaker at rated currents, as well as when triggered by the action of an independent release, the contact system operates as in all circuit breakers and can occupy the "On" position shown in Fig. 5 and the "Disconnected" position shown in Fig. 8. The contact holder 8 rotates together with the drum 9. The drum is driven by a free trip mechanism for the drive rods 17, 18 (the free trip mechanism of the circuit breaker due to its wide popularity is not shown in the figures). The necessary pressing force in the contact pairs 4, 6 and 5, 7 is created by the combined action of the springs 19, 20. The force of the springs is transmitted to the contact holder 8 through pins 21, 22 on one side and through the rotating arms 25,26 and cylindrical stops 37, 38 on the other . The magnitude of the pressing force is determined both by the working force of the springs themselves, and by the place of installation of the pins 21, 22 and the stops 37, 38 on the contact holder. The necessary failure for the correct operation of the contact joint during wear of the contacts is ensured by the gap z between the contact holder 8 and the edges of the sector-shaped samples 43, 44 (see Fig. 5). During manual operation and operation of the circuit breaker under the action of an independent release, the rocker arms and springs move little, shifting by small distances to sample contact dips.

When large short-circuit currents occur, the proposed contact system works differently. As soon as the electrodynamic forces arising from the short-circuit currents in the contact joints 4, 6 and 5, 7, (see Fig. 6) exceed the forces of the pressing springs 19, 20, the contact holder starts to rotate clockwise, increasing the angle of the solution between the movable and fixed contacts. In this case, the pin 22 with the right end of the spring 20 and the stop 37 also rotate clockwise. However, the emphasis 37, acting on the fork-shaped arm 32 of the rocker arm 26, causes the beam to rotate counterclockwise. Since the elongated hook 24 of the spring 20 is fixed to the U-shaped arm 31 of the rocker arm, the elongated hook of the spring also moves counterclockwise, accelerating the spring to reach its maximum force, i.e. accelerating the arrival of the contact system to its dead position, determined by the angle of the solution Y. The angle Y depends on the ratio of the distance r from the center of the drum to the installation site of the stop 37 to the distance R from the center of the drum to the axis of rotation of the rocker arm 26. At a selected distance R, the angle Y decreases from increase r. However, the kinematics operability condition must be met: r is less than R. Thus, the proposed contact system ensures that the pressure springs are moved through the dead position at a smaller angle of contact carrier rejection, and thus increases the speed and reliability of disconnecting short circuit currents. The operation of the spring 19 and the rocker arm 25 from the back of the contact holder 8 (if the front side is taken in the form of Fig.6) occurs in a similar way. The placement on the two sides of the same type of device for creating the efforts of pressing and tipping the contact holder through the dead position was made to equalize the forces acting on the left 4, 6 and right 5, 7 contact pairs. With further movement of the contact holder under the action of contact electrodynamic forces (see Fig.7), i.e. when going through a dead position, the contact system capsize. Rocker 26, rotating counterclockwise, stops contacting with the stop 37 and comes into contact with a fixed inner surface 45 on the outer disk 15. The spring 20 is now rigidly connected at one end to the fixed drum (resting against the surface 45 through the beam), and the second through a pin 22 with a contact holder, transmitting to the contact holder a force already directed towards opening the contacts. Further, the contact holder 8 moves not only under the action of electrodynamic forces, but also under the action of pressing springs 19, 20, which make it impossible to return contacts and their repeated closure, and also fix the contact holder in the discarded state, pressing it against the walls of sector-shaped samples 43, 44 on internal disks 12, 13. This eliminates the welding of contacts and increases the reliability of the contact system. The contact system returns to its initial state (see Fig. 8) when the free trip mechanism is triggered by the action of the maximum current release (not shown), which responds to short circuit currents. Due to the inertia of the free trip mechanism, its operation occurs later than electrodynamic rejection, or at least only begins during the rejection. When triggered, the mechanism, acting on the drive rods 17, 18, starts to rotate the drum 9 clockwise with the contact holder and rests the shoulder of the contact holder in the latch 46. Further, the rotation of the drum occurs when the contact holder is stationary. Since one end of the spring 20 on the pin 22 is stationary, and the second moves together with the beam, which is affected by the figured surface 45, the spring, stretching, again occupies a dead position. Passing through the dead position, the spring will bring the rocker 26 out of contact with the surface 45 and will further bring this rocker into contact with the stop 37 by means of a fork-shaped arm 32. The contact system is ready to turn on again.

In view of the foregoing, the proposed contact system of a high-speed circuit breaker allows one to obtain a dead position at smaller contact solution angles and to achieve electrodynamic rejection of movable contacts with guaranteed their fixation in a discarded state, i.e. without repeated faults, earlier than in the prototype (with equal disconnected short circuit currents with the prototype). This increases the reliability of disconnecting short circuit currents. Reducing the time of contact separation guaranteed without repeated faults makes it possible earlier, without delays, to introduce an electric arc into the contact-arc system, which positively affects the speed of short-circuit current shutdown and improves the current-limiting properties of the circuit breaker.

Thus, the inventive contact system for high-speed circuit breaker in the described design ensures the achievement of the declared technical result.

Claims (1)

A contact system for a fast double breaker circuit breaker comprising lower and upper leads with fixed contacts, a rotating drum, consisting of two internal and two external disks fixed coaxially, a rotary two-arm contact holder with movable contacts, mounted between the internal disks of the drum with the possibility of contacting with fixed contacts, pressure springs, one ends of which are fixed on the contact holder, and the second on the drum, the drive rod for communication and with a switch mechanism, characterized in that it is equipped with two U-shaped rocker arms symmetrically arranged relative to the axis of rotation of the drum with coaxial holes on their side walls, dividing each rocker arm into U-shaped and fork-shaped shoulders, and each outer disk is mounted in the drum relative to the inner the disk at a distance not less than the thickness of the rocker arm, while the second ends of the pressure springs are made in the form of elongated hooks, the length of which is not less than the length of the rocker arm, on each inner and outer discs two coaxial cylindrical protrusions are formed symmetrically with respect to the axis of rotation of the drum and at distances R from the axis against each other, with a height not exceeding the thickness of the side walls of the rocker arms, on a rotary contact holder, at a distance r from the axis of rotation of the drum from condition r is less than R and symmetrical with respect to the axis of rotation with cylindrical stops are installed on both sides, radius grooves are made in the inner disks of the drum against the stops, and the rocker arms are mounted with their holes on the cylindrical protrusions of the inner and outer Disc fork-shaped to cooperate with the stops of the contact arms extending through the slots of the internal radius disks, and pressing the elongated hooks springs are placed between the side walls of the rocker arm and mounted on U-shaped arms of the rockers.

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