Operating device for circuit breakers

Abstract: Operating device for circuit breakers comprising a closing spring and an opening spring (2). After each completed closing operation, a motor (16) tensions the closing spring again which, while closing the circuit breaker, tensions the opening spring. The closing spring is kept tensioned by a closing latch (6). The circuit breaker (20) is kept closed and the opening spring (2) is kept tensioned by a trip latch (7). The operating device is composed around only one shaft (3), which provides a simple design with relatively few components. On the shaft (3) a driver lever (4) is fixed. Upon closing of the circuit breaker, the driver lever (4) is connected, by a latching engagement (43,53), to an operating lever (5), connected to the movable contact of the circuit breaker, and pulls said lever along. The operating lever (5) is eccentrically mounted in relation to the shaft (3) in such a way that the levers (4,5) after a certain rotating movement, for example 90°, are disengaged from each other.

Description: The invention relates to an operating device for circuit breakers according to the precharacterising part of claim 1. Such an operating device is previously known from EP-A-0 320 614. The operating device according to the invention is primarily intended for SF₆-breakers for open outdoor switchgear with a rated voltage of the order of magnitude of 40 kV and higher, but the operating device may advantageously be used also for other types of circuit breakers, for example metal-enclosed circuit breakers insulated with SF₆ gas. The EP-A-0 186 171 discloses in operating device which comprises a closing spring which exerts a torque on a driving shaft, as well as an opening spring which exerts a torque on an opening shaft aligned with the driving shaft, the operating shaft being connected to the movable contact of the circuit breaker. For connection of the shafts for closing of the circuit breaker and simultaneous tensioning of the opening spring, the operating device includes a connection device which comprises a star wheel, fixed to the driving shaft, with at least two arms which are adapted, upon closing of the circuit breaker, to cooperate with a carrier latch mounted on the operating shaft. This latch comprises a relatively large number of movable parts, which means a complication of the design. The EP-A-0 320 614 discloses in operating device of the above-mentioned kind, which also has two different shafts. A driving shaft, to which a closing spring and a spring tensioning equipment for the closing spring are connected, is provided for closing the circuit breaker and tensioning the opening spring. Further, there is an operating shaft to which the circuit breaker and the opening spring are connected. In order to close the circuit breaker and tension the opening spring the operating shaft is provided with the lever, at the free end of which is arranged a role. This role is adapted to engage with curved disk fixed on the driving shaft. The curved disk is provided with a peripheral cut-out which defines in angular rotational section of the driving shaft where the engagement between the operating lever and the driving shaft is abolished and the operating lever is free to rotate independently of the driving shaft. The invention aims at to provide an operating device of the above-mentioned kind which is simpler, more reliable, and less space-demanding than comparable prior art designs. To achieve this aim the invention suggests an operating device for circuit breakers according to the introductory part of claim 1, which is characterized by the features of the characterizing part of claim 1. Further developments of the invention are characterized by the features of the additional claims. According to the invention, the driver lever and operating lever of the operating device are provided with latching members, which during a closing operation are in engagement with each other, and the operating lever is eccentrically journalled in relation to the driving shaft, the latching members during the closing operation thus being displaced relative to each other in such a way that the latching engagement is successively reduced such that, after a certain angle of rotation, the operating lever is disengaged from the driver lever. By such an embodiment the advantage is obtained that the latching members for interconnecting the levers during the closing operation can be designed in a very simple manner without movable parts, for example in the form of projections or latching engagement surfaces on the levers. The operating device according to the invention can be constructed around only one shaft, which provides a simple design with relatively few components. This contributes to increase the reliability of the operating device. By way of example, the invention will now be described in greater detail with reference to the accompanying drawings showing in Figures 1 and 2 schematically an end view from the front and from the back, respectively, of an operating device according to the invention for a high-voltage circuit breaker designed, Figures 3-5 the central parts of the operating device in three different positions, namely, in the closed position of the circuit breaker (Figure 3), in the open position (Figure 4), and during a closing operation (Figure 5), Figure 6 a central section through the operating device along the line VI-VI in Figure 3, and Figure 7a-7d schematically the mode of operation of the operating device during opening and closing, respectively, of the circuit breaker. The operating device shown in the drawings is intended for high-voltage circuit breakers of, for example, the kind described in Asea Journal 1983, No. 3, pp. 16-21. The operating device comprises a closing spring 1 (Figure 2) and an opening spring 2 (Figure 1). The closing spring 1 is of the helically-wound flat bar type and exerts a torque on a driving shaft 3, on which a driver lever 4 is fixedly mounted. In the embodiment shown, the opening spring 2 is arranged in the bottom stand of the circuit breaker, whereas the closing spring 1 and the other parts of the operating device are arranged around the driving shaft 3 in a mechanism housing 10 (Figures 1 and 6). The driving shaft 3, which constitutes the only main shaft of the operating device, is journalled in an axial trunnion 11 arranged in the mechanism housing, as well as in a bearing 13 supported by a number of supporting arms 12 (Figure 6). On the axial trunnion 11, which surrounds the driving shaft 3, an operating lever 5 is eccentrically journalled in relation to the driving shaft 3. The operating lever 5 is connected to the movable contact 20 of the circuit breaker via an operating rod 21 (Figure 1) and a link mechanism symbolized by a dot-dashed line 22. The operating lever 5 is rotatable back and forth between two fixed positions, which correspond to the closed and open positions of the circuit breaker. The angle of rotation of the operating lever between the end positions is about 90°. A trip latch 7 is adapted, during normal operation, to keep the breaker contact 20 closed and the opening spring 2 tensioned. If the operating device is to be used for operation of a multi-pole high-voltage circuit breaker, a common operating rod 21 may be used for all the poles. The movable contact in each breaker pole is thereby connected to the operating rod via a link mechanism, and the opening spring 2 is suitably arranged close to the remote end of the operating rod 21, as shown in Figure 1. In This way the operating rod will only be subjected to tensile stresses. It may therefore be designed relatively slender and light since it need not be dimensioned for buckling strain. The closing spring 1 has its inner end fixed to the driving shaft 3 and its outer end to a cylindrical drum 15 surrounding the spring and being rotatably mounted on the driving shaft. The spring 1 is tensioned with the aid of a motor 16, which via a worm gear 17 rotates the drum 15. The shaft 3 is thereby maintained locked by a closing latch 6, which hooks up the driver lever 4. The driving motor 16 is supplied with voltage via two series-connected limit switches 18, one of which is controlled by the driving shaft 3 and the other by the drum 15. In case of power failure, the closing spring can be tensioned manually with the aid of a crank 19. The driver lever 4 is formed with two lever parts, one of the lever parts 41 (Figure 3) cooperating according to the invention with the closing latch 6, the other lever part 42 being provided with a latching projection 43. This latching projection 43 is adapted to cooperate with a corresponding latching projection 53 on the operating lever 5 in order to close the circuit breaker while simultaneously tensioning the opening spring 2. The end portion of the operating lever 5 is provided with a spring-loaded latching flap 52, which is adapted such that the lever 5 may pass freely past the trip latch 7 via the back way. The operating device is provided with a damping device 8 connected to the operating lever 5 (Figures. 1 and 3) for damping of the opening stroke. The path of action of the damping device may be changed by changing the extent of an oval connection slot 51 in the operating lever. The mode of operation of the operating device during an operating sequence will now be described with reference to Figures 7a-7d: Figure 7a shows the operating device in the normal operating position (corresponding to Figure 3), the breaker contact 20 being closed and both the closing spring 1 and the opening spring 2 being tensioned. The closing spring 1 is maintained tensioned by the closing latch 6, whereas the trip latch 7 maintains the breaker contact 20 closed and the opening spring 2 tensioned. In this position the breaker is ready, upon an opening impulse, to carry out a breaking operation with automatic reclosing after a certain period of time. Figure 7b shows the operating device and the breaker during an opening operation. The opening operation is initiated by energizing the magnet coil of the trip latch 7, whereupon the trip latch is released and the opening spring 2 carries out the contact opening. The movement of the movable contact system is slowed down by the damping device 8. During the opening operation, the operating lever 5 is turned clockwise, and its latching projection 53 engages with the latching projection 43 of the driver lever 4 (corresponds to the position according to Fig. 4). The closing spring 1 is still tensioned. Figure 7c shows the operating device and the breaker during a closing operation. Closing of the breaker is initiated by energizing the magnet coil of the closing latch 6, whereupon the closing latch is released, and the closing spring 1 turns the driving shaft 3 with the driver lever 4 counter-clockwise. The driver lever 4 thereby pulls along with it the eccentrically mounted operating lever 5 counter-clockwise, the breaker contact thus being brought to the closed contact position while at the same time the opening spring 2 is tensioned. At the end of the movement, the operating lever 5 is hooked up by the trip latch 7, and the breaker is ready for renewed opening operation. Because the operating lever 5 is eccentrically mounted on the driving shaft 3, the latching engagement between the latching projections 43, 53 of the driver lever and the operating lever will be successively reduced during the closing movement, and after a movement of about 90°, the operating lever is disengaged from the driver lever (corresponds to the position according to Figure 1 and Figure 5). Thereafter, the driver lever 4 will continue its rotating movement until the lever part 41 is hooked up by the closing latch 6. During this latter part of the movement of the driver lever, the closing spring 1 arrives at an almost completely non-tensioned state. The driver lever 4 moves 360° in the same direction for each closing of the breaker and each spring tensioning of the closing spring 1. Figure 7d shows the operating device during that part of the operating sequence when the closing spring 1 is tensioned. The breaker is then in the closed position and the opening spring 2 is tensioned. After completed closing operation (Fig. 7c), the supply circuit to the motor 16 is closed by the limit switch 18. This causes the motor 16 to start and since the driving shaft 3 with the driver lever 4 is hooked up by the closing latch 6, the closing spring 1 will be tensioned. When the closing spring is completely tensioned, the limit switch 18 will break the circuit to the motor. The invention in not limited to the embodiment shown but several variants are possible within the scope of the claims. For example, the closing spring need not necessarily be a helical spring but the following alternatives are possible: tension spring or compression springs which may be influenced by a crank arm with a one-turn movement, torsion springs in the form of a rod, helically-wound spring which is turned around its main axis. The same alternative possibilities are available for the opening spring, which may advantageously also consist of a helical spring wound from a flat rod in the same way as the closing spring shown in the embodiment. Furthermore, the opening spring need not always be separately mounted in spaced relationship to the other components of the operating device, as shown in the embodiment, but in certain cases it may be more suitable for all the parts of the operating device to be arranged close to one another and possibly enclosed within a common mechanism housing. Regarding the damping device 8, instead of being active upon opening only, this may be designed to be double acting, such that it provides damping both upon closing and upon opening. Damping upon closing may also be provided with a damping device which is influenced by a cam arranged on the driving shaft 3. The movements of the driver lever 4 and the operating lever 5 upon closing and opening, respectively, are not limited to the angles of rotation applicable to the exemplified embodiment, but the operating device may be formed with entirely different angles of rotation, for example 120°, 180° etc.

Claims: Operating device for circuit breakers comprising an operating lever (5) connected to the movable contact (20) of the circuit breaker, the operating lever being rotatable back and forth between two fixed positions which correspond to the closed and open position of the circuit breaker, an opening spring (2), a closing spring (1) which exerts a torque on a driving shaft (3) which has only one direction of rotation, a driver lever (4) fixed to the driving shaft, a tensioning device (16,17) for tensioning the closing spring, a closing latch (6) for maintaining the closing spring in tensioned state, and a trip latch (7) for maintaining the opening spring in tensioned state and the contacts of the circuit breaker closed, the driver lever (4) being adapted, upon a closing operation, to be connected to the operating lever (5) for closing the circuit breaker while simultaneously tensioning the opening spring (2), characterized in that the operating lever (5) is rotatably and eccentrically arranged around the driving shaft (3), that the driver lever (4) and the operating lever (5) are provided with latching members (43,53) which during a closing operation are engaged with each other, and that said latching members (43,53) during the closing operation are displaced relative to each other in such a way that the latching engagement is successively reduced and terminated at the end of the closing operation. Operating device according to claim 1, characterized in that the driver lever (4) is formed with two lever parts (41,42), one of which (42) supports the latching member (43) of the lever, whereas the other (41) is adapted to cooperate with the closing latch (6). Operating device according to claim 1 or 2, characterized in that said latching members (43,53) of the driver lever (4) and the operating lever (5) consist of a latching projection or a latching engagement surface on the respective lever. Operating device according to any of the preceding claims, characterized in that the closing spring (1) consists of a spiral spring, wound from flat rod and arranged around the driving shaft (3). Operating device according to any of claims 1 to 3, characterized in that the closing spring (1) consists of a helically wound spring twistable about its main axis. Operating device according to any of the preceding claims, characterized in that it comprises a damping device (8) connected to the operating lever (5) for damping of the closing operation of the circuit breaker. Operating device according to any of the preceding claims intended for a multi-pole high-voltage circuit breaker in which the movable contact (20) in each breaker pole is connected via a link mechanism to an operating rod (21) common to all poles, characterized in that one end of the operating rod is connected to the operating lever (5) and the other end to the opening spring (2). Operating device according to any of the preceding claims, characterized in that the operating rod (5) is adapted to be rotated about 90° between the closed and open positions of the circuit breaker. Operating device according to any of the preceding claims, characterized in that the driver lever (4) is adapted to be rotated 360° upon each closing operation.

Inventors: AKESSON ULF, HOEGLUND LEIF, PAULSSON ANDERS, AKESSON, ULF, HOEGLUND, LEIF, PAULSSON, ANDERS, Höglund, Leif
Applicants: ASEA BROWN BOVERI, ASEA BROWN BOVERI AB
Application year: 1991
Main classification: H01H3
IPC codes: H01H3