Abstract:
A circuit breaker includes at least two stationary contact devices, at least two movable contact devices and at least one drive device. The at least one drive device is operatively connected to the at least two moving contact devices. The contact-making between at least one stationary contact device and at least one moving contact device and the contact-making between at least one further stationary contact device and at least one further moving contact device each take place at different times during the connection process.

Description:
[0001]    The present application hereby claims priority under 35 U.S.C. § 119 on German patent application number DE 102 61 855.0 filed Dec. 20, 2002, the entire contents of which are hereby incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    The invention generally relates to a circuit breaker.  
         BACKGROUND OF THE INVENTION  
         [0003]    Specifically designed switching apparatuses are required for switching high voltages and currents, and these can generally be combined under the term circuit breaker. The configuration of all such circuit breakers essentially includes one or more stationary contact devices and one or more moving contact devices, and at least one drive unit, which is operatively connected to the moving contact devices. The drive unit allows the moving contact devices to be connected to and disconnected from stationary contact devices, which results in closing or opening of the circuits which are connected to the contact devices.  
           [0004]    A defined switching characteristic must be achieved in order to provide a highly selective circuit breaker, and this is dependent on exact dimensioning of the circuit breaker. The drive forces in highly selective circuit breakers are dimensioned for a connection process in the event of a short circuit. The drive energy which is required for connection of the circuit breaker is used partially to overcome mechanical forces, with the remainder being used to overcome electrodynamic current loop forces. It is desirable to reduce the drive energy that is required, since this allows smaller dimensioning of the drive, transmission, latching and contact devices.  
           [0005]    One known measure for reducing the electrodynamic component is to optimize the current loop. This has the disadvantage that this compensates for the fact that the current loop has a compensating effect on the desired current.  
           [0006]    Optimization of the mechanical component is also known from DE 100 48 659 A1. In this case, it is proposed that two contact force springs, which act at different switching positions, be provided in order to ensure an advantageous switching path dependency for the force that is required for connection. This has the disadvantage that the addition of the switching forces that are required for the moving switching contacts to make at the same time results in a high total force, which represents a major barrier for the drive mechanism.  
           [0007]    According to DE 101 37 422 C1, it is known, in the case of a drive (which is in the form of a toggle lever system) for the contact mount, for the point at which the coupling rod acts on the contact mount to be designed to be adjustable with respect to the rotation point of the contact mount. The aim of this is to keep the torque on the drive shaft constant, although the contact force of the individual contact mounts can be adjusted.  
           [0008]    According to DE 299 17 860 U1, on the one hand, the contact force can be adjusted just by the variability of the length of the coupling rod, that is to say via the contact travel.  
           [0009]    Furthermore, according to DE 40 06 452 C2, the contact travel is variable, to be precise simply by reinsertion of a hinge point on a coupling lever. As such, the required contact separation can be chosen for two rated voltages.  
           [0010]    DE 198 56 773 C2 discloses a drive for a high-voltage circuit breaker with a transmission, whose drive lever arm is connected to the coupling rod via a further lever, which has a guide in which the drive lever arm can be moved. If the drive lever arms of the switch poles are rotated through a few degrees with respect to one another, then different speed profiles can be achieved for the switch poles during the switching movement. However, the switching movement starts and ends at the same time.  
           [0011]    With respect to the switching forces at the end of the switching movement, the problem of a correspondingly high total force still remains, with all of these solutions.  
           [0012]    DE 195 25 286 C2 discloses a multipole vacuum interrupter, in which the electromagnetic influence (which occurs in particular in this case) between adjacent vacuum tubes which reduces the switching capacity, is reduced in that the central interrupter is opened before the outer interrupters during opening of the switch. The outer interrupters, which are further away from one another, can then be opened at the same time, since they have less influence on one another. In the case of mechanical circuit breakers without vacuum interrupters, it is, in fact, the current loop forces within the phases themselves which, on the other hand, have to be coped with.  
         SUMMARY OF THE INVENTION  
         [0013]    An embodiment of the invention includes an object of providing a circuit breaker, which includes an improved connection capacity and/or which needs less energy for connection.  
           [0014]    According to an embodiment of the invention, an object may be achieved by a circuit breaker. The circuit breaker includes at least two stationary contact devices, at least two contact devices which can move relative to them and at least one drive device. Further, the contact-making between at least one stationary contact device and at least one moving contact device and the contact-making between at least one further stationary contact device and at least one further moving contact device take place at different times during the connection process.  
           [0015]    By having contact making occur at different times, this reduces the maximum force in the force profile resulting from the addition of all the individual contact switching forces. This advantageously results in a reduction in the maximum drive force that is required, which makes it possible to reduce the energy that is required by the circuit breaker during the connection process. This allows the drive, transmission, latching and contact devices to be dimensioned to be smaller. Furthermore, the reduced and broadened force maximum results in the circuit breaker having an improved connection capacity.  
           [0016]    One embodiment of the invention provides for the drive device to include a switching shaft, by which a torque can be transmitted in a manner which is particularly simple to handle to two or more contact devices. Provision is furthermore preferably made for the switching shaft to include at least one switching shaft lever which is preferably connected to the switching shaft. The use of at least one switching shaft lever allows positioning along a greater positioning travel for the same switching shaft positioning angle.  
           [0017]    Furthermore, one embodiment of the invention provides for the drive device to include at least two coupling devices, each of which is operatively connected to one of the switching shaft levers and to one of the moving contact devices. This provides the capability for transmission of the drive torque over a greater distance than would be feasible by way of shaft cantilever arms on their own. In particular, provision is preferably made for at least one coupling device to include a coupling rod, which offers the capability to transmit force in a manner which can be handled particularly easily.  
           [0018]    Provision is also made in a particularly preferred manner for the coupling points of the at least one switching shaft lever for coupling of the coupling devices to be in mutually different positions with respect to the switching shaft axis. This can be achieved, for example, by different angular positions of the corresponding switching shaft levers. This results in one moving contact device lagging behind another, which leads to the contact devices making at different times. In consequence, the individual drive forces for the contact devices are also added with a time offset, which, in the end, considerably reduces the maximum total force and allows the drive, transmission, latching and contact devices to be dimensioned to be smaller.  
           [0019]    This can also be achieved by at least two coupling rods preferably having different lengths to one another. As such, different positioning movements of the contact devices are achieved for the same positioning angle of the switching shaft. This once again results in the contacts of the corresponding contact devices making at different times.  
           [0020]    In particular, provision can preferably be made for all of the coupling points to the coupling device of the switching shaft levers to be in the same position with respect to the switching shaft axis, in a preferred manner with a different coupling rod length. This allows the range of components for the switching shaft, for example when using the same switching shaft configuration for different embodiments of circuit breakers, to be reduced. Provision can likewise advantageously be made for all of the coupling rods to have the same length, with the making of the moving contact devices at different times being achievable, for example, by different positioning of the coupling points to the coupling device of the switching shaft lever with respect to the switching shaft axis. Thus, the range of components for the coupling rod can be minimized and manufacturing errors resulting from incorrect coupling rods being fitted can be avoided.  
           [0021]    In one embodiment of the invention, for example for the switching of three-phase devices, the circuit breaker includes a three-pole configuration. Furthermore, for example for the switching of three-phase devices with a neutral conductor, the circuit breaker includes a four-pole configuration.  
           [0022]    Finally, one embodiment of the invention provides for the time at which the contacts of one pole make and the time at which the contacts of the other poles make during the connection process to differ from one another, in a particularly preferably manner such that the times at which the contacts of the three poles touch during the connection process differ from one another and, particular preferably such that the times at which the contacts of all the poles make during the connection process differ from one another. Since the drive forces which are required to switch the individual poles are additive, it is advantageous for at least two, but best of all all, of the contact devices to make at different times, since this makes it possible to minimize the total maximum force. This thus allows the drive, transmission and contact devices to be dimensioned to be smaller.  
           [0023]    Further preferred refinements and embodiments of the invention result from the other features. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    The present invention will become more fully understood from the detailed description of preferred embodiments given hereinbelow and the accompanying drawings, which are given by way of illustration only and thus are not limitative of the present invention, and wherein:  
         [0025]    [0025]FIG. 1 a  shows switching poles of a conventional multipole circuit breaker;  
         [0026]    [0026]FIG. 1 b  shows switching poles of a multipole circuit breaker with contact devices which make contact at different times;  
         [0027]    [0027]FIG. 2 a  shows switching force diagrams for conventional two-pole circuit breakers;  
         [0028]    [0028]FIG. 2 b  shows switching force diagrams for multipole circuit breakers with contact devices which make at different times;  
         [0029]    [0029]FIG. 3 shows a structogram of the mechanism of a three-pole circuit breaker with contact devices which make at different times, and  
         [0030]    [0030]FIGS. 4 a  and  4   b  show angular positions of the joints at the coupling points. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    [0031]FIG. 1 a  shows, schematically, the switching principle of a conventional multipole circuit breaker  1  with moving contact devices  4  which make contact at the same time. FIG. 1 b  shows an embodiment of the present invention including a multipole circuit breaker  10  with moving contact devices  14  which make contact at different times, for comparison. The illustrations in each case show the stationary contact devices  2  and  12  and the respective moving contact devices  4  and  14  for two poles. The respective drive devices  6  and  16  for the respective contact devices  4  and  14  are indicated in FIGS. 1 a  and  1   b , respectively.  
         [0032]    In a circuit breaker  1  of the conventional type, as is shown in FIG. 1 a , the moving contact devices  4  of the individual switching poles move virtually synchronously and are each in the same relative positions with respect to the stationary contact devices  2 , for example at the time t 1 . The contacts of the two poles thus make contact at the same time t 2  during the connection process.  
         [0033]    The behavior of the exemplary embodiment according to the invention as illustrated in FIG. 1 b  is different. In this case, the contacts of the second pole make contact at a time t 1 , while the contact device  14  for the first pole is still moving. The contacts of the first pole also make contact at a time t 2 , so that both current paths are now connected.  
         [0034]    [0034]FIGS. 2 a  and  2   b  show the principle of the addition of the switching forces F 1  and F 2  on two individual poles of a multipole circuit breaker  1  or  10  to produce a total force F tot , which has to be applied by the respective drive device  6  or  16 , illustrated schematically on the basis of force/time graphs. A distinction is in this case drawn between a circuit breaker  1  of the conventional type with synchronous switching processes (FIG. 2 a ) and a circuit breaker  10  of an embodiment of the present invention, with moving contact devices  14  which make contact at different times (FIG. 2 b ).  
         [0035]    As can be seen from FIG. 2 a , the two graphs have virtually the same time profile for the individual pole switching forces. The addition of the switch force profiles F 1  and F 2  thus results approximately in twice the individual forces, with a maximum at F max .  
         [0036]    In contrast, in the exemplary embodiment of the invention shown in FIG. 2 b , the time switching force profile F tot  for the first pole is delayed in time with respect to that of the second pole F 2 . The overall profile F tot  of the two individual pole switching forces in consequence has a shape which differs from the profile of the individual pole switching forces.  
         [0037]    In this specific example, there is a flattened area whose maximum F max  is considerably lower than that in FIG. 2 a . Thus, with the circuit breaker  10  whose moving contact devices  14  make contact at different times, the maximum total force F max  which needs to be applied for connection purposes counter to the mechanical and electrodynamic forces is less. This, in the end, allows the drive, transmission, latching and contact devices to be dimensioned to be smaller.  
         [0038]    [0038]FIG. 3 shows, schematically, the structogram of the mechanism of a three-pole circuit breaker  10  of an embodiment of the present invention, with the current paths R, Y and B. The circuit breaker  10  includes a switching shaft  18  with three switching shaft levers  20 ,  20  and  22 , three moving contact devices  14 , three coupling devices  24  in the form of coupling rods of the same length, two outer coupling rods of which are respectively connected to one of the outer switching shaft levers  20  and to one of the moving contact devices  14 , and the central, third of which is operatively connected to the central, third switching shaft lever  22  and to the central, third contact device  14 , as well as a stationary contact device  12  in each case, for each current path.  
         [0039]    The switching shaft levers  20  and  22  have coupling point  26  for coupling of the associated coupling device. The coupling points  26  on the switching shaft levers  20  for the phases R and B are arranged offset with respect to that for the phase Y, in that angular positions which are not the same as those for the switching shaft lever  22  for the phase Y are chosen for the switching shaft levers  20  for the outer phases. A drive torque which acts on the switching shaft  18  is transmitted via the kinematic chain to the moving contact devices  14 .  
         [0040]    During the connection process, the moving contact devices  14  move towards the stationary contact devices  12 . During this process, the contact device  14  for the phases R and B leads that for the phase Y owing to the different position of the coupling point  26  on the switching shaft levers  22 . The contacts on the phase Y thus also make with a time delay. The different angular positions of the joints at the coupling points  26  also results in the drive being released more easily at the time of connection. This advantageously results in a higher switching shaft speed at the time at which the contacts make, and thus in an improved switching capacity.  
         [0041]    [0041]FIGS. 4 a  and  4   b  show, schematically, the angular positions φ 1  and φ 2  of the joint at the coupling point  26  of the switching shaft lever  22  (FIG. 4 a ) and at the coupling point  26  (FIG. 4 b ) of the switching shaft lever  20  at the time at which the circuit breaker  10  is connected. The change in position of the coupling point  26  on the switching shaft lever  22  with respect to the coupling points  26  of the switching shaft levers  20  has been achieved by changing the angular position φ 2  of the switching shaft lever  20  in FIG. 4 b  in comparison to that of the switching shaft lever  22  on the switching shaft  18 , with the switching shaft lever  20  on the coupling rods  24  having the same length. This therefore results in a more obtuse angle φ 2  in FIG. 4 b  between the switching shaft lever  20  and the coupling device  24  in comparison to the angle φ 1  in FIG. 4 a  between the switching shaft lever  22  and the coupling device  24 .  
         [0042]    For the same forward movement of the coupling device  24  in FIG. 4 b , the torque which has to be overcome by the drive of the switching shaft and which results from the total force of the switching pole is less than in FIG. 4 a . This results in the drive being released more easily at the time of connection, resulting in a reduction in the required drive energy. This allows the drive, transmission, latching and contact devices to be dimensioned to be smaller. The simplified release also leads to a higher switching shaft speed at the time at which the contacts make contact. This results in an improved connection capacity with regard to electrodynamic current loop forces.  
         [0043]    Exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.