Patent Application
20230290593
The present invention relates to an electric current switch.
Electric switches for medium- and high voltage switchgear are subject to electric arcing during current interruption and contact making events. Suppressing the arcs is important to protect the electric switch itself and electric devices connected to the electric switch.
Effects of arcs may be suppressed by appropriate material selection of arcing contact areas of the connecting parts of the electric switch that can withstand and reduce the arcing. Further, arc-extinction can be provided by application of an appropriate gas onto the arc, such as the often-used gas SF6.
However, there is still room for improvements with regards to arc-extinction as is set out in more detail below.
In view of the above-mentioned and other drawbacks of the prior art, it is an object of the present invention to provide an electric current switch that at least partly alleviates the deficiencies with prior art.
According to a first aspect of the invention, there is provided an electric current switch comprising: a housing; a contact lever comprising a proximal end and a distal end, the contact lever being rotatable at a pivot point at the distal end, the contact lever comprising a lever main contact area and a lever arcing contact at the proximal end; a fixed contact assembly configured to receive the contact lever in a closed position of the contact lever, the fixed contact assembly comprising a fixed main contact and a fixed arcing contact, the fixed contact assembly being fixed relative the housing accommodating the fixed contact; the contact lever is configured to rotate about the pivot point between the closed position and an open position, the electric current switch further comprising a nozzle fixedly arranged to surround the position of the fixed arcing contact, the nozzle comprising at least one outlet to provide a flow of cooling gas towards the fixed arcing contact, the flow of cooling gas being in the proximal direction of the contact lever as when the contact lever in the closed position.
The present invention is at least partly based on the realization that a less complex electric current switch with improved cooling of the arcing contacts and the regions in their vicinity can be provided by fixing the nozzle at the fixed contact assembly. Thus, with the proposed electric switch, the contact lever moves for switching between the closed and the open positions, whereas the nozzle and the fixed contact assembly are static with respect to the housing, thereby requiring only a small number of moving parts. Further, the invention is also based on the realization to provide the cooling gas in a proximal direction of the contact lever, towards an arc root, which advantageously provides for reduced amounts of hot gas flowing towards the fixed main contacts. Instead, the hot gas flows proximally, preferably away from the fixed main contacts.
The housing provides an assembly base for the electric switch. The pivot point is preferably fixed in relation to the housing.
In the closed position of the contact lever, an electric current may pass between the lever main contact area and the fixed main contact. In the open position, the contact lever and the fixed contact are not in contact whereby an electric current may not pass between them.
In the closed position, the lever main contact area mate with the fixed main contact.
In embodiments, the nozzle may comprise at least one inlet for compressed gas, the electric current switch comprising a puffer connected via hoses or pipes to the inlets, the puffer is configured to provide the compressed cooling gas to the nozzle. Puffers are known per se and here provides an advantageous way to timely provide cooling gas to the nozzle via the hoses or pipes. Further, the puffer advantageously provides the possibility to use various cooling gases such as air or other gas mixtures.
The cooling gas may for example comprise at least one background gas component selected from the group consisting of CO2, O, N2, H2, air, N2O, in a mixture with a hydrocarbon or an organo fluorine compound. For example, the cooling gas may comprise dry air or technical air. The cooling gas may in particular comprise an organofluorine compound selected from the group comprising of: a fluoroether, an oxirane, a fluoramine, a fluoroketone, a fluoroolefin, a fluoronitrile, and mixtures and/or decomposition products thereof. In particular, the cooling gas may comprise as a hydrocarbon at least CH4, a perfluorinated and/or partially hydrogenated organofluorine compound, and mixtures thereof. The organofluorine compound is preferably selected from the group comprising of: a fluorocarbon, a fluoroether, a fluoroamine, a fluoronitrile, and a fluoroketone; and preferably is a fluoroketone and/or a fluoroether, more preferably a perfluoroketone and/or a hydro fluoroether, more preferably a perfluoroketone having from 4 to 12 carbon atoms and even more preferably a perfluoroketone having 4, 5 or 6 carbon atoms. In particular, the perfluoroketone is or comprises at least one of: C2F5C(O)CF(CF3)2 or dodecafiuoro-2-methylpentan-3-one, and CF3C(O)CF(CF3)2 or decafluoro-3-methylbutan-2-one. The cooling gas preferably comprises the fluoroketone mixed with air or an air component such as N2, O2, and/or CO2. Another possible cooling gas is SF6.
In embodiments, a drive mechanism of the puffer is configured to push on the contact lever when it moves from the closed position towards the open position, and while pushing on the contact lever it causes a flow of the compressed gas through the hoses or pipes to the nozzle. Advantageously, the drive mechanism ensures that the cooling gas is timely ejected to suppress the arc.
In embodiments, the nozzle may be fixedly attached to the fixed contact assembly to ensure that the cooling gas is provided towards an arc root. Further, with the nozzle attached to the fixed contact assembly, a more compact electric switch is provided compared to having the nozzle be arranged separately from the fixed contact assembly.
In embodiments, the nozzle may comprise an inclined surface angled with respect to an axis along which the contact lever is configured to move in the nozzle, the inclined surface reaches away from the fixed main contact so that at least a portion of the outlet gas is directed away from the lever arcing contact and the fixed arcing contact. Advantageously, the inclined surface provides for improved guiding of hot cooling gas away from the fixed contact.
In embodiments, the fixed arcing contact of the fixed contact assembly may comprise an inclined portion angled with respect to a contact section configured to make contact with the lever arcing contact of the contact lever, the inclined portion being adapted for guiding cooling gas in the proximal direction. Advantageously, the inclined surface provides for improved guiding of hot cooling gas away from the fixed main contact where the contact lever main contact area makes contact with the fixed contact.
In embodiments, the electric current switch may further comprise an earth contact configured to receive the contact lever in an earthed position of the contact lever, the contact lever is configured to rotate about the pivot point between the earthed position, the closed position, and the open position. The earth contact may be fixed in relation to the housing. Thus, the contact lever may be moved to three positions, while the earth contact, the fixed contact, and the nozzle are fixed in relation to the housing.
In embodiments, the fixed contact and the earth contact may be stationary with respect to the pivot point when the contact lever moves between the earthed position, the closed position, and the open position.
In embodiments, the nozzle may comprise a receiving portion for the contact lever, the receiving portion is adjacent to the fixed arcing contact of the fixed contact and is offset in the proximal direction of the contact lever as defined when the contact lever in the closed position, so that the receiving portion is spaced apart from the contact lever in the proximal direction. This provides for further improved guiding of the hot cooling gas away from the fixed main contact.
In embodiments, the nozzle may comprise a through-hole in the proximal direction for guiding cooling gas away from the fixed arcing contact.
In embodiments, the lever contact may comprise a cut-out adjacent to the lever arcing contact of the contact lever. The cut-out advantageously reduces the amount of hot cooling gas that reaches in the distal direction of the contact lever. The cut-out is distally located in relation to the lever arcing contact.
In embodiments, the nozzle may comprise two outlets arranged on opposite sides of an opening of the nozzle adapted to receive the contact lever so that the outlets are arranged on opposite sides of the contact lever in the closed position, the outlets are configured to cooperatively create a flow of cooling gas in the proximal direction towards the fixed arcing contact. The combination of the two outlets creates an improved proximal-directed flow towards the arc root. The proximal directed flow may be split in two directions: along the arc towards the contact lever, and along the fixed arcing contact of the fixed contact assembly.
In embodiments, the nozzle may comprise an outlet arrangement adapted so that the outlet is located in the cut-out when the contact lever is in the closed position.
In embodiments, the outlets may be configured to direct the compressed gas at an angle in the range of 0-90 degrees with respect to the contact lever when it is in the closed position. In possible implementations, the angle is in the range of 10-75 degrees, or preferably in the range of 15-60 degrees with respect to the contact lever when it is in the closed position
In embodiments, the contact lever may be a knife contact, and the electric current switch may be a knife switch.
Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.
These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein:
In the present detailed description, various embodiments of the present invention are herein described with reference to specific implementations. In describing embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the scope of the invention.
The electric current switch 100 comprises a contact lever 104 comprising a proximal end 106 and a distal end 108. The contact lever 104 is rotatable at a pivot point 110 at the distal end 108. The pivot point 110 provides for the contact lever 104 to be rotatable about a rotation axis 112. The contact lever 104 comprising a lever arcing contact 114 at the proximal end 106 and a lever main contact area 141 adapted to make contact with a fixed main contact 152 of a fixed contact assembly 116.
The electric current switch 100 further comprises the fixed contact assembly 116 configured to receive the contact lever 114 in a closed position. The fixed contact comprising a fixed arcing contact 115, better seen in
The contact lever 104 is configured to rotate about the pivot point 110 between the closed position and an open position. In other words, the contact lever can rotate about the axis 112 so that the proximal end 106 is received in the fixed contact assembly 116 so that an electric current may flow between the lever main contact area (141) of the contact lever 104 and the fixed main contact 152 of the fixed contact assembly 116. In the perspective of
During a current interruption, when the contact lever 104 moves from the closed position to the open position, or during a current making event when the contact lever 104 moves from the open position to the closed position, an arc may be produced between the contact lever 104 and the fixed contact assembly 116. The arcs are produced at the lever arcing contact 114 of the contact lever 104 and the fixed arcing contact 115 of the fixed contact assembly 116. The arcing contacts are adapted to be durable and able to withstand the arc by appropriate material selection. Arcing contact materials may be various electrical conducting and heat resistant alloys, typical containing Tungsten.
To further suppress the arcs, the electric current switch 100 further comprises a nozzle 118 fixedly arranged to surround the position of the fixed arcing contact 115 of the fixed contact assembly 116, as illustrated in
In the example embodiment shown in
The nozzle 118 comprises at least one inlet 126 for receiving compressed gas and a puffer 128 connected via hoses 130 or pipes 130 to the inlets 126. The puffer is configured to provide the compressed cooling gas to the nozzle 118.
The puffer 128 is configured to provide the compressed gas when the contact lever 104 is moved for current interruption process to timely provide the cooling gas for suppressing an arc. For this, an actuator or rod 132 of the puffer 128 is pulled by a drive mechanism 133 and moves together with the contact lever 104 when the contact lever 104 moves from the closed position towards the open position. In this way, the compressed cooling gas is caused to flow through the hoses 130 or pipes 130 to the nozzle 118. A puffer generally operates by the compression of an enclosed volume of gas, whereby the gas is ejected out from the puffer via the hoses 130 or pipes 130 from the enclosed volume. In other words, the gas is forced out from the enclosed volume by the compression of the enclosed volume.
If the contact lever is further moved to the earthed position at earth contact 124, the drive mechanism 133 will stay in a middle position and thus not follow the contact lever 104 all the way to the earthed portion.
During a current making event, when the contact lever 104 moves into the nozzle from the open position, the drive mechanism 133 moves to push back the piston inside the puffer 128 via the rod 132.
The puffer can be filled during a current making events in various ways. For example, by implementing one-way gas vent for the puffer gas can freely fill the puffer without creating a counter force on the contact lever 104. Alternatively, by letting the puffer actuator 132 move in slowly by the drive mechanism 133 before the contact lever 104 starts the current making operation. As a further alternative, the puffer can be filled by sucking in gas through the nozzle 118.
Preferably, and as is better illustrated in
With further reference to
The outlets 120a-b are configured to direct the compressed gas at an angle α in the range of 0-90 degrees, or 10-75 degrees, or most preferably 15-60 degrees with respect to the contact lever 104 when it is in the closed position. The angle is with respect to the surface of the lever main contact area 141 on the proximal end 106 of the contact lever 104, shown in
In a similar configuration, the fixed arcing contact 115 of the fixed contact assembly 116 comprises an inclined portion 144 angled with respect to a contact section 148 configured to contact the lever arcing contact 114 of the contact lever 104. The inclined portion 144 is adapted for guiding cooling gas in the proximal direction away from the fixed contact assembly 116. Thus, the upward directed flow 150 of compressed cooling gas is split in two directions at the arc root: along the arc towards the contact lever 104 and guided by the inclined surface 140, and in the opposite direction along the fixed arcing contact 115 of the fixed contact assembly 116 guided by the inclined portion 144. The angles and dimensions of the outlets holes and nozzle may be selected such that very little hot gas flows downwards to the fixed main contact 152 of the fixed contact assembly 116, better seen in
With further reference to
The cut-out 205 advantageously reduces the amount of hot cooling gas that can flow downwards into the fixed main contact 152 of the fixed contact assembly 116 shown in
Turning to
Optionally, and as illustrated in
The electric current switch 100 of the herein disclosed embodiments is preferably a knife switch in which the contact lever 104, 204 is a knife contact. In this case, the proximal end 106 of the contact lever may be blade-shaped with two opposite parallel surfaces, where one of the surfaces is the surface of the lever main contact area 141.
The nozzle and arcing contacts of the fixed contact assembly and the contact lever described herein may be dimensioned and shaped in various ways and are not limited to the specific configuration shown in the drawings.
For example, the shape of the outlets 120a,b may be rectangular, elliptical, circular or generally polygonal. The size of the outlets, either the sides of a rectangular or square outlet, or the diameter of a circular or elliptical outlet may be in the range of 4 mm to 10 mm, for example about 6 mm.
Further, the nozzle 118 may be made from a suitable material appropriate for medium voltage applications. Example materials include Polytetrafluoroethylene (PTFE), Perfluoroalkoxy alkane (PFA), and Fluorinated ethylene propylene (FEP).
Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art.
Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22161353.2 | Mar 2022 | EU | regional |
