OPERATING DEVICE FOR ELECTRIC SWITCHING DEVICE

Abstract: An operating device for operation of an electric switching device comprising a motor (12) and a carrier means, which includes a driving part (5, 9) and a driven part (7), whereby the motor via the driving part transmits a movement to the driven part which is in mechanical connection with the electric switching device. The driving part has, from an initial position, a closing direction and an opening direction and returns to the initial position after a completed operation. Between the driving part and the driven part, there is a play which allows a manual operation.

Description: Operating device for Plpc.tric switching device TECHNICAL FIELD The present invention relates to a motor-operated operating device of the kind described in the preamble to claims 1 and 8 and a method for operation of en electric switching device which is described in the preamble to claim 11. The operating device is intended for connection to an electric switching device and, in particular, to an electric switching device with a rotating operating shaft with different directions for closing and opening operations. BACKGROUND ART Certain switch disconnectors, for example ABB Kraft AB's switch disconnector of type NAL/NALF designed for medium voltage, has an operating spring in the form of a torsion spring, which gives the contacts of the disconnector a rapid movement upon opening and closing of the disconnector. The operating spring is mechanically connected to an operating shaft for tensioning the spring and to the contacts of the disconnector. In one embodiment of this disconnector, the spring is tensioned with the aid of an operating device connected to the operating shaft until a dead centre is passed, whereby opening and closing, respectively, take place. In another embodiment, the operating spring is tensioned but the movement is stopped after passage of the dead centre. The relevant operation can then be released with the aid of, for example, a release magnet. Prior art motor-operated devices have a screw driven by an electric drive motor by means of a gear comprising a worm gear. A nut is moved axially along the screw upon rotation thereof, and the nut is connected to the operating spring of the disconnector via a lever mechanism. It has proved that the screw is subjected to large axial forces and that large fric¬ tional forces arise in the mechanism. This makes possible a strong construction of the operating device and a drive motor with such a high power that, for economical reasons, an ac motor is required. The mechanism is also relatively compli¬ cated. These factors result in a high manufacturing cost. The high motor power also increases the costs of control and switching means for the drive motor of the operating device and makes it difficult or impossible to arrange battery stand¬ by operation of the operating device in an economically reasonable way. From DE 311 47 27, a spring-operated operating device iε previously known, the duty of which is to constitute a simple and space-saving device where a drive spring common to both directions is to carry out the operating movement rapidly. The operating device comprises a motor-driven drive pulley which, via a pin, drives a first cam disk in which the operating spring is arranged. The first cam disk drives, via a pin, a second cam disk which is connected to an electric switching device. The drive pulley engages with the first cam disk after a rotation of about 90°, whereupon the drive pulley rotates the first cam disk with the drive spring applied thereon to an upper dead-centre position at about 180°, in which the first cam disk engages with the second cam disk. When the dead- centre position has been passed, the cam disks continue the movement of the force from the drive spring, whereby switching takes place. During each operation, the drive pulley and the first cam disk move one full turn, which means that a manual operation of an electric switching device with one closing and one opening direction cannot be carried out. A disadvantage of the known device is that three discs are needed to make possible one operation. A further drawback with the device is that an operating spring is used and that this must be pre- stressed by a motor. The spring must then be oversized by about 20 % to give sufficient safety and to overcome friction losses. The motor, in turn, must be oversized by about 20 % to be able to prestress the operating spring in a reliable manner. One further disadvantage of these prior art operating devices is that they have insufficient flexilibity during mounting, that is, that they cannot be mounted in an arbitrary manner in relation to the disconnector, for example on an optional side of the disconnector. SUMMARY OF THE INVENTION The invention aims to provide a motor-operated device of the kind described in the introductory part of the description, which - has fewer components and may be given a simpler and more compact design, may be manufactured at a lower cost, requires lower drive motor power, has a high flexibility as regards mounting, and which allows manual operation of the electric switching device by means of an operating handle or the like without being obstructed by the operating device. What characterizes an operating device according to the inven- tion will become clear from the characterizing part of claims 1 and 8. The method for operating an electric switching device according to the invention exhibits the characteristic features described in the characterizing part of claim 11. Additional advantages will be clear from the characterizing parts of the claims which depend on the independent claims. By arranging the operating device with one driving part and one driven part, between which a play is arranged which corre¬ sponds to the movement of a complete operation, the need of an additional component to complete the operation is eliminated. In the device according to the invention, the screw mechanism is completely eliminated and replaced by rotating components in the form of a rotating carrier means. In this way, the large axial forces of the prior art devices are completely eliminated. The large friction losses from which the known devices suffer are also considerably reduced. This, in turn, permits the mechanism to be made simpler and more compact and with fewer components, permits the drive motor to be designed for considerably lower power, and thus permits the necessary components for switching and control of the drive motor to be made simpler and less expensive. Altogether, this means that an operating device according to the invention can be manufac¬ tured at a cost which is greatly reduced compared with what has previously been possible. Further, an operating device according to the invention is given maximum flexibility during the mounting, where necessary after a simple switching of the direction of rotation of the drive motor. It may be mounted on an optional side of a dis¬ connector or another electric switching device, it may be mounted upside down, etc. The low necessary driving power makes it possible to allow the drive motor to constitute a dc motor for low power. It has proved that in a typical operating device according to the invention, the required drive motor power is reduced to only 10-15 % of the power of corresponding prior art operating devices. In addition to the positive effect this has on the cost, weight and space requirement of the device, it has the positive effect that the motor, upon voltage drop out during operational disturbances, can be simply driven by a stand-by battery. In a preferred embodiment of the invention, one of the two parts of the carrier means is made as an operating wheel with a carrier and the other part as a cam disk coaxially rotating with the operating wheel. The operating wheel then suitably constitutes the driving part of the carrier means and is designed as a gear wheel, driven by the drive motor via the gear, with a carrier applied to the gear wheel, which provides a simple design of the operating device. In a preferred embodiment of the invention, a spur gear (a straight-toothed spur gear with parallel input and output shafts) is arranged between the drive motor and the carrier means, which results in a low manufacturing cost and low fric¬ tion losses. Preferably, the operating device is designed such that the driving part of the carrier means after an operation is always returned to an original position by the drive motor. In this way, the advantage is achieved that the electric switching device, in a simple manner, can always be operated manually without being obstructed by the operating device. The advantageous properties of an operating device according to the invention have proved to make possible the use of remote operation of disconnectors to a considerably greater extent than what has been previously practically and economi¬ cally possible, which entails considerable advantages for the operation of a switchgear installation BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in greater detail in the following with reference to the accompanying Figures la, lb and 2, wherein Figure la shows the operating device viewed in a direction which is perpendicular to the axes of the device. Figure lb shows the device viewed in the direction of the axes from that side which is intended for mounting to an electric switching device, and Figure 2 shows an electric circuit diagram for the operating device. DESCRIPTION OF THE PREFERRED EMBODIMENTS As is clear from Figure 1, the operating device has a chassis with parallel end members 1 and 2 and is made of zinc-plated steel sheet. In the end member 1 a first sliding bearing 3 of a suitable plastic material is arranged. The operating device is intended to be mounted on an electric switching device (not shown) in such a way that the free end of the operating shaft 4 of the electric switching device is able to rotate in the bearing. An operating wheel in the form of a gear wheel 5 is journalled in the lower part of the bearing 3 in Figure la and can rotate around an axis coinciding with the axis of rotation of the shaft 4. In the end member 2 a second sliding bearing 6 is arranged, in which a cam disk 7 is journalled. Also this bearing is preferably made of a suitable plastic material. The axis of rotation of the cam disk coincides with the axes of rotation of the shaft 4 and the operating wheel 5. The profile of the cam disk has the appearance shown in Figure lb with a first circular section 71 with a smaller radius and a second circular section 72 with a larger radius. The first section occupies a centre angle of about 150° and the second section the remainder of the circumference of the cam disk. The boundaries between the two sections consist of the shoulders 73 and 74. The cam disk has a central hole for the shaft 4, and the cam disk and the shaft are provided with splines which connect the cam disk to the shaft in the direction of rotation. Between the operating wheel 5 and the cam disk 7, a liner 8 is arranged, for example in the form of a coating on or an insert in the operating wheel of a plastic material with low fric¬ tion. The liner is intended to ensure that the cam disk and the operating wheel under all circumstances, even after a lengthy downtime outdoors, are able to move relative to each other with low friction. On the operating wheel 5, a carrier 9 in the form of a steel pin is arranged. The carrier is arranged such that, during a clockwise movement of the operating wheel in Figure lb, it may be brought into contact with the shoulder 73 of the cam disk and thereafter bring the cam disk with it during continued clockwise movement. The cam disk is shown in the figure in a position displaced in the clockwise direction to be able to show the shape of the shoulder 73. Normally, the pin 9 is in contact with the shoulder 73. In the same way, during a counterclockwise movement of the operating wheel in Figure lb, the carrier may be brought into contact with the shoulder 74 of the cam disk and thereafter bring the cam disk with it during continued counterclockwise movement. The operating wheel 5 is in engagement with and is driven by a cylindrical intermediate gear wheel 10 which is journalled in the end members 1 and 2. The intermediate gear wheel 10 is driven via a gearbox 11 from a dc motor 12. The gearbox is adapted to provide a great reduction, for example from a motor speed of about 3000 rpm to a rotational speed of the operating gear wheel of 10 seconds per revolution. Because all the axes of rotation in the operating device are parallel, all the gear wheels of the device, including the gear wheels in the gear¬ box, may be designed as straight-toothed spur wheels, which provides low friction and low manufacturing costs. A printed circuit board 13 is mounted inside the end member 1 and supports a terminal block 14, three microswitches Si, S2 and S3 as well as the required electrical connections between these units. The microswitches are placed such that they are influenced by the carrier 9, and a microswitch is activated when the carrier is located in front of the switch. As will be shown below, the switch SI defines an initial position of the operating wheel 5, and the switches S2 and S3 define end positions for clockwise and counterclockwise movement, respec- tively, of the operating wheel. The end members have four mounting holes 18, 19, 20, 21, which are each placed symmetrically in a respective corner. In this way, four different, inverted mounting positions of the opera- ting device are made possible, rotated 180° relative to each other. The operating device is provided with a housing or enclosure (not shown for the sake of clarity) , in which also further components, for example the relays Rl and R2 shown in Figure 2, may be mounted. Figure 2 shows an electric circuit diagram for the operating device. The device is supplied with +24 V direct voltage, which makes possible operation from a stand-by battery during interruptions in the ordinary voltage supply. The motor is controlled by means of two dc relays Rl and R2. The relay Rl activates the motor for rotation in one direction for closing of the electric switching device, and the relay R2 activates the motor for rotation in the opposite direction for opening of the electric switching device. With the aid of the pushbutton T, a closing operation of the switching device is initiated, and with the aid of a push¬ button F, an opening operation of the switching device is initiated. All the switching devices are shown in Figure 2 in non-acti¬ vated positions. Since the two relays Rl and R2 are non-acti¬ vated, the armature of the motor is short-circuited by two relay contacts as is clear from the figure, whereby the motor, as soon as none of the relays picks up, immediately brakes and stops. In the initial position, the operating wheel 5 assumes the position shown in Figure lb where the carrier 9 lies straight in front of and activates the microswitch Si. The contact thereof is then open. The other contacts assume the positions shown in Figure 2. The cam disk 7 is shown in the figure in the position it assumes when the electric switching device is opened. For closing operation, the pushbutton T is activated, whereby the relay Rl picks up and the motor starts rotating, and the operating wheel 5 rotates in the clockwise direction in Figure lb. As soon as the carrier 9 has left the switch SI, the relay Rl becomes self-activated via the contacts S1-S2-R1, and the pushbutton can be released. The carrier is brought to make contact with the shoulder 73 of the cam disk and, under con¬ tinued rotation, brings the cam disk along with it and hence also the shaft 4 of the electric switching device. During this movement, the operating spring of the electric switching device is tensioned successively. When during this movement a dead-centre position of the electric switching device is passed, the closing operation is released, and the shaft 4 and the cam disk move in the clockwise direction. At completed closing movement, the cam disk has moved so far that the shoulder 73 has moved to or past the position which is defined by the switch S2. The motor and the operating wheel continue to rotate until the carrier reaches the switch S2. This is activated, and its contact assumes the lower position in Figure 2. The relay Rl then loses its self-activation and falls, whereby the relay R2 receives voltage via the contacts S1-S2-R1 and picks up. The relay immediately becomes self- activated via the contacts S1-S3-R2. The motor now rotates in the opposite direction, that is, the operating wheel 5 rotates in the counterclockwise direction in Figure lb. The rotation continues until the carrier reaches the switch Si, whereby the relay R2 loses its self-activation, the relay falls and the motor is braked and stops. The operating wheel and the carrier now again assume the initial position shown in Figure lb. The cam disk 7 is in such a position that the shoulder 74 is at or somewhat to the left of the carrier in the figure, and the operating device and the electric switching device are ready for an opening operation. In a corresponding way an opening operation is initiated by activation of the pushbutton F, and the function corresponds to the function during closing. The relay R2 picks up and becomes self-activated, the operating wheel 5 rotates in the counterclockwise direction in Figure lb, and the carrier 9 comes into contact with the shoulder 74 and brings the cam disk along with it while tensioning the operating spring of the electric switching device. When the dead-centre position of the electric switching device has been passed, the opening operation is released, and the cam disk then moves in the counterclockwise direction to the position shown in the figure. The operating wheel continues its rotation until the carrier in its end position activates the switch S3, whereupon the operating wheel and the carrier return to the initial position in the manner described above. The operating device thus permits the electric switching device while the operating movement is in progress to complete the operating movement without being obstructed by the operating device. By the embodiment of the cam disk described above, and since the carrier is adapted to return to the initial position after each operation, the electric switching device can be operated manually with the aid of an operating handle or the like, both in open position for closing of the electric switching device and in closed position for opening the electric switching device, without the operating device obstructing the movement. Because the direction of rotation of the drive motor of the operating device can be changed in a simple manner, for example by shifting closing and opening signalling, an operating device according to the invention can be used for mounting on an optional side of an electric switching device. The low required drive motor power in an operating device according to the invention makes possible the use of simple and inexpensive relays for controlling the motor instead of the considerably more expensive contacts which are necessary at higher motor powers. The simplicity, low cost and mounting flexibility of the operating device make possible the arrangement of remote operation of, for example, switch disconnectors to a conside¬ rably greater extent than what has previously been possible in practice. During remote operation, the relays of the operating device are supplied with closing and opening signals, respec¬ tively, via a signalling line instead of (or in parallel with) the pushbuttons T and F in Figure 2. The operating device according to the invention has been described above with reference to a switch disconnector, but it may alternatively be used for other types of electric switching devices, for example circuit breakers and dis¬ connecting switches. The operating device and its function have been described with reference to such an electric switching device where, while tensioning the operating spring of the electric switching device, the operation is automatically released when a dead- centre position of the mechanism of the switching device has been passed. However, the operating device can be used for tensioning of an operating spring also in other types of electric switching devices, for example such where an operation is released by a release magnet or the like releasing a tensioned operating spring. An operating device according to the invention can also, as an alternative, be used for operation of an electric switching device which has no operating spring and where no requirements for fast operation are made, for example ordinary disconnecting switches. In this connection, it provides the same advantages as those mentioned above. In the advantageous embodiment described above, the driving part of the carrier means is in the form of a gear wheel with a carrier, and the driven part is in the form of a cam disk. Alternatively, of course, the cam disk may be connected to the drive motor and hence constitute the driving part, m which case the carrier is arranged on the driven part. In the embodiment shown, the edge of the cam disk 7 is shaped as two circular arcs with different radii. Since it is only the shoulders 73 and 74 of the disk that are brought into contact with the carrier and that have any real function, it is, in principle, irrelevant how the other parts of the disk are shaped. The portion 71 of the disk between the shoulders, however, should be shaped such that the carrier of the opera¬ ting wheel is able to move freely between the shoulders without coming into contact with the disk. For the same reason, one part of the carrier means need not be m the form of a cam disk, or the other part thereof be m the form of a wheel with a carrier arranged thereon, but both parts of the carrier means may be formed in an arbitrary manner which allows a defined clearance of a suitable size between the two parts. Although advantageous, the operating device according to the invention is not limited to comprising only a rotating move¬ ment. The device can arbitrarily comprise a linear movement or a combination of a linear movement and a rotating movement. The decisive factor is that between the driving part and the driven part there is a play which corresponds to an operating movement .

Claims: CLAIMS 1. An operating device for operation of an electric switching device, comprising a motor (12) and a carrier means, which includes a driving part (5, 9) and a driven part (7) , whereby the motor via the driving part transmits a movement to the driven part which is in mechanical connection with the elec¬ tric switching device, characterized in that the driving part from an initial position has a closing direction and an opening direction, whereby the driving part returns to the initial position after a completed operation and that, between the driving part and the driven part, there is a play which allows a manual operation. 2. An operating device according to claim 1, characterized in that the driving part comprises a carrier pin (9) which transmits the movement to the driven part in a first direction via a first shoulder (73) arranged in the driven part, and in a second direction via a second shoulder (74) arranged in the driven part, between which shoulders there is arranged a portion (71) in which the carrier pin is freely displaceable corresponding to a operating movement. 3. An operating device according to claim 1 or 2, characterized in that a corrosion-inhibiting liner (8) is arranged between the driving part and the driven part. 4. An operating device according to claims 1-3, characterized in that the driving part comprises an opera- ting wheel (5) and the driven part comprises a cam disk (7) connected to a rotating operating shaft (4) of an electric switching device. 5. An operating device according to claim 4, characterized in that the operating wheel (5) comprises a gear wheel (5) driven by the drive motor via a gear (11) . 6. An operating device according to claims 2-5, characterized in that the clearance portion (71) between the first shoulder (73) and the second shoulder (74) of the driven part (7) is arranged along a circular sector with a tangential extent smaller than half a revolution. 7. An operating device according to claims 4-6, characterized in that the axis of rotation of the drive motor (12) and the axis of rotation of the operating wheel (5) and the cam disk (7) are parallel and that the motor drives the operating wheel via a cylindrical gear (11). 8. An operating device for operation of an electric switching device, comprising a drive means (12, 13), a driving part (5, 9) and a driven part (7), whereby the motor imparts to the driving part a movement which the driving part transmits to the driven part, which is in mechanical connection with the electric switching device, characterized in that the drive means comprises a dc motor (12) which, for achieving brake action during a non-activated state, is short-circuited, and an electric drive circuit (13) which includes relays (Rl, R2) for connection of the motor and for switching of its direction of rotation. 9. An operating device according to claim 8, characterized in that the drive circuit (13) comprises a first position sensor (Si) adapted to define an initial position of the driving part (5, 9) as well as control means (Rl, R2 ) connec¬ ted to the position sensor and to the motor (12) and adapted, after a completed operating movement, to return said driving part to the initial position. 10. An operating device according to claim 9, characterized in that the drive circuit (13) comprises second position sensors (S2, S3) which are connected to the control means and adapted to define end positions for an operating movement of the driving part (5), and that the control means are adapted, after initiation of an operating movement, to bring the driving part to rotate to an end position and, thereafter, to bring the driving part to rotate in the opposite direction until the initial position has been achieved. 11. A method for operation of an electric switching device, comprising a drive means (12, 13) and a carrier means inclu¬ ding a driving part (5, 9) and a driven part (7), whereby the force caused by the drive means is transmitted to the driving part, the movement of which is transmitted to the driven part which is in mechanical connection with the electric switching device, characterized in that the driving part from an initial position is adapted to move in a closing direction and in an opening direction directed opposite to said closing direction, the driving part being brought to return to the initial position after a completed operation, and that a play is arranged between the driving part and the driven part which permits a manual operation.

Inventors: ANDERSSON ANDERS, ANDERSSON, ANDERS
Applicants: ABB NORDKOMPONENT AB, ANDERSSON ANDERS, ANDERSSON, ANDERS
Application year: 1996
Main classification: H01H3
IPC codes: H01H3