EP4664504A1

EP4664504A1 - A compressed gas device for a multiphase rotary break switch

Info

Publication number: EP4664504A1
Application number: EP24181850.9A
Authority: EP
Inventors: Maciej Mruczek; Björn Lindqvist; Mussie WELDEAB
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2024-06-13
Filing date: 2024-06-13
Publication date: 2025-12-17
Also published as: WO2025256915A1

Abstract

The present invention relates to a compressed gas device (102) for an electrical multiphase rotary electric current switch (100) comprising a common switch operating shaft (112) for more than one of the phases, the device comprises: a housing (130), a piston (140), a rotatable shaft (132) connectable to and rotatable by the switch operating shaft, the rotatable shaft comprises a guiding structure (142a-b) on a radially outwards facing surface (144) of the shaft, the guiding structure being configured to engage with a guiding element (148) in the opening of the piston, wherein the guiding structure comprises a first portion (142a) and a second portion (142b).

Description

Field of the Invention

The present invention relates to a compressed gas device for a multiphase rotary break switch.

Background

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 using a so-called puffer.
A puffer often includes a piston that moves in a puffer volume for building up a gas pressure for subsequent ejection onto the arc region. The movement of the piston is coupled to the movement of one of the connecting parts of the switch so that the arc-extinction can be synchronized with the interruption of the electric current, i.e., when the switch is in an open position.
It is further desirable to, for each pole of the switch, include decoupling / de-latching mechanisms to disconnect knife and piston when switch is being operated from an open position to an earth position.
For switches with multiple poles the puffers suffer from increased cost due to multiple parts being used and may create risk of low durability/ robustness of de-latching mechanism.

Summary

In view of the above-mentioned and other drawbacks of the prior art, it is an object of the present invention to provide a compressed gas device for a multiphase rotary break switch that at least partly alleviates the deficiencies with prior art.
According to a first aspect of the invention, there is provided a compressed gas device for a multiphase rotary electric current switch comprising a common switch operating shaft for more than one of the phases, the device comprises: a housing forming a compressed gas volume, the housing comprising at least one gas outlet; a piston movable linearly in the gas volume to compress the gas inside the volume, a rotatable shaft connectable to and rotatable by the switch operating shaft, the rotatable shaft is arranged with its rotation axis through an opening of the piston, the rotatable shaft comprises a guiding structure on a radially outwards facing surface of the shaft, the guiding structure being configured to engage with a guiding element in the opening of the piston, wherein the guiding structure comprises a first portion and a second portion, the first portion and the guiding element are configured such that when the first portion and the guiding element are engaged, a rotation of the shaft about its rotation axis cause a linear motion of the piston along the rotation axis of the shaft, and the second portion and the guiding element are configured such that when the second portion and the guiding element are engaged, a rotation of the shaft about its rotation axis is de-coupled from the linear motion of the piston.
The present invention is at least partly based on the realization of a compressed gas device that is common to all phases of the multiphase rotary break switch. In other words, all phases share the same common puffer chamber.
The compressed gas device utilizes the rotary motion of the switch to compress the gas a eject it to all phases for arc-extinction at the respective pole piece. The switch operating shaft drives the piston via the guiding structure, or equally termed scroll mechanism, which translates the rotary motion of the switch operating shaft to a linear motion of the piston. Since the de-coupling between the switch operating shaft and the piston is integrated with the guiding structure, separate de-latching mechanisms for each phase are advantageously not needed. Thus, engagement of the first portion with the guiding element during rotation of the shaft causes a linear motion of the piston along the rotation axis of the shaft, and engagement of the second portion with the guiding element results in decoupling the shaft's rotation from the piston's linear motion.
Advantageously, the shape of the guiding structure and guiding elements, such as grooves or trenches thereof, can be adapted to tune the compression characteristic of the gas to get certain pressure build-up and volume blow depending on the angular position of the switch operating shaft.
A multiphase rotary break switch comprises, for each phase, a contact lever that is rotatable between a closed position, an open position, and an earth position. In the closed position of the contact lever, an electric current may pass between the contact lever and a 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 contact lever may mate with the fixed main contact. In the earth position, the contact lever is in contact with a fixed earth contact. In the earth position, the contact lever may mate with the fixed earth contact.
The gas may for example comprise at least one background gas component selected from the group consisting of CO₂, O₂, 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 may comprise the fluoroketone mixed with air or an air component such as N₂, O₂, and/or CO₂. Another possible cooling gas is SF₆. The cooling gas may comprise air or an air component such as N₂, O₂, and/or CO₂ without the fluoroketone.
In embodiments, the contact lever may be a knife contact, and the rotary electric current switch may be a knife switch.
In an embodiment, the guiding structure may be a groove or trench in the outwards facing surface of the shaft, and the guiding element is a pin or ball-bearing that fits in the groove or trench. In case of a ball-bearing, a set of metal or high strength synthetic material balls may couple the scroll mechanism and the piston. This decreases the friction between the scroll mechanism and the piston during the movement of the piston. The use of a groove or trench in combination with a pin or ball-bearing ensures precise and controlled movement of the piston within the housing. This configuration allows for more accurate control over the linear movement of the piston, leading to more efficient compression and decompression cycles within the compressed gas device. Further, the guiding structure being integrated on the shaft directly interacts with the piston, allowing for a more compact and integrated compressed gas device with reduced need for additional components that might otherwise be necessary to achieve the same function, thereby simplifying the overall compressed gas device.
In an embodiment, the first portion of the groove or trench may guide the guiding element along the rotation axis of the shaft, and the second portion of the groove or trench may maintain the position of the guiding element along the rotation axis of the shaft. Each portion of the groove is thus tailored for its specific function reducing the risk of mechanical failure due to mismatch or inappropriate use. Once the guiding element reaches the second portion, the piston maintains its position along the axis of the shaft, thereby decoupling the motion of the switch operating shaft with the piston motion. Advantageously, this de-coupling mechanism is integrated in the compressed gas device, even inside the housing thereof.
In an embodiment, a bent groove or trench portion may connect the first and the second portions. This provides an advantageously transition between linear motion of the piston to maintained position, that is robust and reliable, and that may guide a guiding pin or guide ball-bearing. The bent groove portion can advantageously be designed to prevent the guiding element (e.g., a pin or ball-bearing) from becoming jammed at the transition point between the groove portion portions.
In an embodiment, the first portion may comprise a first end and a second end which are displaced along the rotation axis of the shaft. Thereby, a linear motion of the piston along the shaft may be provided. In addition, the controlled movement limits set by the displaced ends of the groove ensure that the piston compresses the gas within the chamber to the optimal volume and pressure. Furthermore, in an embodiment, the second portion may comprise a first end and a second end which are not displaced along the rotation axis of the shaft. Thereby providing a decoupling effect where the piston no longer moves linearly despite the switch operating shaft is rotated.
In an embodiment, the compressed gas device may comprise multiple guiding elements and multiple guiding structures. This provides a more robust and reliable guiding of the piston in the housing. The multiple guiding elements may be equally distributed about a circumference of the opening where the shaft of the compressed gas device is arranged. The guiding elements protrudes radially inwards in the opening towards the rotation axis of the rotatable shaft.
In an embodiment, the compressed gas device may comprise an anti-rotation mechanism between the housing and the piston. In other words, the housing and the piston are prevented from rotating with respect to each one another about the rotation axis of the rotatable shaft. Advantageously, this facilitates for a reliable and repeatable linear motion of the piston in the housing.
In an embodiment, the anti-rotation mechanism may include an inwards extending protrusion in the housing and an opening or hole in the piston, or an outwards extending protrusion in the piston and an opening or hole in the housing.
In an embodiment, the protrusions may be made from a low-friction material. For example, the low-friction material may be a self-lubricating thermoplastic material.
In an embodiment, the compressed gas device may comprise multiple gas outlets. Thereby facilitating providing compressed gas to the pole pieces of multiple phases.
In an embodiment, the de-coupling may occur when the switch operating shaft operates the electric current switch from an open state to an earth state. It is also envisaged that de-coupling point or timing can be set to a different position of the switch, before open position, to control compression level and speed.
In an embodiment, the compressed gas device may comprise a one-way valve for gas intake in the housing. The one-way valve may be located in the wall of the housing. The one-way valve allows for gas-intake in one stroke of the switch operating shaft during rotation thereof in one rotational direction and for maintaining a closed housing during another stroke of the switch operating shaft during rotation thereof in the opposite rotational direction.
According to a second aspect, there is provided a multiphase electric current switch comprising the compressed gas device according to the first aspect.
In an embodiment, the multiphase electric current switch may comprise hoses that guide gas from the outlet of the compressed gas device to each pole of the multiphase electric current 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.

Brief Description of the Drawings

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:

Fig. 1 illustrates an example multiphase electric current switch according to embodiments of the invention;
Fig. 2 illustrates a compressed gas device according to embodiments of the invention;
Fig. 3 illustrates a piston and a rotatable shaft according to embodiments of the invention; and
Fig. 4 is a cross-section of a compressed gas device according to embodiments of the invention.

Detailed Description of Example Embodiments

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.
Fig. 1 illustrates a multiphase electric current switch 100 comprising a compressed gas device 102.
The multiphase electric current switch 100 comprises a set of rotatable contact levers 104a, 104b, and 104c, one for each of three phases, and fixed main contacts 106a, 106b, 106c, one for each of the three phases. The fixed main contacts 106a-c are electrically connected to a voltage bus bar.
The contact levers 104a-c are rotatable about a rotation axis 110 by a common switch operating shaft 112. The contact levers 104a-c are mechanically fixed to the common switch operating shaft 112.
In an open position as shown in fig. 1, the contact levers 104a-c are not in contact with the fixed main contacts 106a, 106b, 106c. Rotating the common switch operating shaft 112 counter-clockwise as indicated by arrow 114 causes the contact levers 104a-c to mate with the fixed main contacts 106a, 106b, 106c. The switch 100 is then in the closed position where electric current can flow between the contact levers 104a-c, the fixed main contacts 106a, 106b, 106c, and the voltage bus bar 108.
Rotating the common switch operating shaft 112 clockwise, e.g., opposite arrow 114 from the position shown in fig. 1 causes the contact levers 104a-c to mate with earthed main contacts 116c (only one is shown schematically) connected to Earth potential.
The compressed gas device 102 is configured to eject gas from its outlets 120a-c to extinguish arcs between the contact levers 104a-c and the fixed main contacts 106a, 106b, 106c when the common switch operating shaft 112 rotates to transition the switch 100 from the closed position to the open position. The gas is guided by hoses 122a,b,c from the multiple outlets 120a-c of the compressed gas device 102 to each pole piece 106a-c of the multiphase electric current switch 100. Each pole comprises a nozzle connected to the respective hose 122a-c to eject the compressed gas from the compressed gas device 102.
Fig. 2 illustrates a compressed gas device 102 according to embodiments of the invention. The compressed gas device 102 comprises a housing 130 forming a compressed gas volume. In the housing, at least one gas outlet 120 is formed that connects to the compressed gas volume inside the housing 130. The gas outlet 120 is connectable to a hose for guiding compressed gas from the compressed gas volume to the pole piece or main contact of a phase of the switch 100.
In a center hole of the housing is a rotatable shaft 132 arranged. The rotatable shaft has a center longitudinal hole 134 or cavity that is configured to receive the common switch operating shaft 112. The geometry of the hole 134 and the geometry of the common switch operating shaft 112 is such that they are not rotatable with respect to each other once engaged, that is, it is an anti-rotation geometry. In this example, the circumference of the common shaft switch operating shaft 112 and the shape of the hole 134 are polygonal. However, other anti-rotational geometries are also envisaged such as oval. The rotatable shaft 132 is thus connectable to and rotatable by the switch operating shaft 112.The rotatable shaft 132 is rotatable about the axis 110 with respect to the housing 130.
The compressed gas device 102 comprises a one-way valve 136 for gas intake in the housing 130. The one-way valve 136 may comprise a set of through holes 138 (only one is numbered) in the housing 130 and a springloaded sealing plate inside the housing that seals the holes, and allows for opening the holes 138 when the pressure inside the housing 130 is below that of the surrounding atmosphere, more precisely, the one-way valve 136 allows for suction of new gas into the volume after a gas ejection event. In other words, the one-way valve 136 is configured to close the gas volume when pressure is built inside the volume during a gas ejection action and allow depressurize the gas volume when the piston returns to its initial position without the need to suck gas through hose and nozzle system connected to the outlet 120.
The housing 130 comprises an inwards extending protrusion 154 as part of an anti-rotation mechanism between the housing 130 and the piston.
The housing is substantially cylindrical along the rotation axis 110.
Fig. 3 illustrates a piston 140 and the shaft 132 and fig. 4 is a cross-section of the compressed gas device 102.
The rotatable shaft 132 comprises a guiding structure 142a, 142b, on a radially outwards facing surface 144 of the shaft 132. The shaft 132 is arranged in an opening 146 of the piston 140, the opening 146 being better seen in fig. 4.
The guiding structure comprises a first portion 142a and a second portion 142 that are configured to engage with a guiding element 148 in the opening of the piston 140. In this embodiment, the guiding structure is a groove 142a, 142b or trench in the outwards facing surface 144 of the shaft 132, and the guiding element is a pin or ball-bearing 148 that fits in the groove 142a, 142b or trench. The ball-bearings 148 are preferably made from a metal or high strength synthetic material to decrease the friction during piston movement.
The piston 140 is here realized as a disc-shaped piston although other shapes are also envisaged. The piston 140 is movable linearly in the gas volume to compress the gas inside the volume. The outer circumference 139 of the piston 140 is sealed against the inner wall surface 131 of the housing 130 to allow for compressing the gas in the volume 150. Furthermore, the piston 140 is sealed against the rotatable shaft 132 and the rotatable shaft 132 is sealed against the housing 130 to allow for compression of the gas volume 150.
The guiding structure 142a-b and the guiding element 148 are configured such that a rotary motion of the shaft 132, caused by the rotation of the common switch shaft 112, translates to a linear motion of the piston 140 along the axis 110. More specifically, the first portion 142a and the guiding element 148 are configured such that when the first portion 142a and the guiding element 148 are engaged, a rotation of the shaft 132 about its rotation axis 110 cause a linear motion of the piston 140 along the rotation axis 110 of the shaft 132. The piston moves linearly along the axis 110 to compress the volume 150 inside the housing 130 such that gas is ejected out from the outlet 120. In other words, the first portion 142a of the groove or trench guides the guiding element 148 along the rotation axis 110 of the shaft 132.
When the rotatable shaft 132 rotates clockwise, opposite arrow 114 with respect to the housing 130, and with the piston being rotatably locked with respect to the housing 130, the force applied by the inclined first portion groove 142a on the pin or ball-bearing 148 acts with at least one component to push the piston 140 along the rotation axis 110 in the direction 111 which cause compression of the gas volume 150. More specifically, the side wall of the groove 142a applies a force on the pin or ball-bearing 148 of the piston 140 when the rotatable shaft 132 rotates opposite the direction 114.
The first portion 142a may be tuned to achieve a predetermined compression characteristic to get certain pressure build-up and volume blow depending on the angular position of the shaft 132.
The second portion 142b and the guiding element 148 are configured such that when the second portion 142a and the guiding element 148 are engaged, a rotation of the shaft 132 about its rotation axis 110 is de-coupled from the linear motion of the piston 140. Thus, the second portion 142b of the groove or trench maintains the position of the guiding element 148 along the rotation axis 110 of the shaft 132. That is, the guiding element 148 does not move linearly along the axis 110 once it enters the second portion 142b.
The first groove portion 142a comprises a first end 142aa and a second end 142ab. The first end 142aa and the second end 142ab are displaced along the rotation axis 110. In other words, as the guiding element 148 travels along the first groove 142a, the piston 140, being connected or fixed to the guiding element 148 moves along the axis 110, as indicated by arrow 111.
The second groove portion 142b comprises a first end 142ba and a second end 142bb which are not displaced along the rotation axis 110 of the shaft 132. That is, as the guiding element 148 travels along the second groove 142b, the piston 140, being connected or fixed to the guiding element 148 does not move along the axis 110, and thus maintains its axial position. This means that the shaft 132 can rotate without the piston 140 moving linearly along the axis, thereby the rotation of the shaft 132 is decoupled from the piston 140.
A bent groove portion 152 connects the first portion 142a and the second portion 142b. More precisely, the bent portion 152 connects the second end portion 142ab of the first groove 142a with the first end portion 142ba of the second groove 142b.
Preferably, the compressed gas device 102 comprises multiple guiding elements 148 and multiple guiding structures 142a,b.
To prevent rotation of the piston along the axis 110, there is an anti-rotation mechanism between the housing 130 and the piston 140. The anti-rotation mechanism includes an inwards extending protrusion 154 in the housing 130 and an opening 156 or hole in the piston 140. The inwards extending protrusion 154 is elongated and guides the linear motion of the piston 140. That is, the opening 156 of the piston 140 slides along the elongated inwards extending protrusion 154. The opening 156 and/or the inwards extending protrusion 154 may be made from a low-friction material such as self-lubricating thermoplastic material.
The de-coupling between the rotation of the shaft 132 and the motion of the piston preferably occurs when the switch operating shaft 112 operates the electric current switch 100 from an open state to an earth state. However, de-coupling timing can be set to a different position of the switch 100, before open position, to control compression level and speed of the compressed gas device 102.
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.

Claims

A compressed gas device (102) for an electrical multiphase rotary electric current switch (100) comprising a common switch operating shaft (112) for more than one of the phases, the device comprises:
a housing (130) forming a compressed gas volume, the housing comprising at least one gas outlet (120);

a piston (140) movable linearly in the gas volume (150) to compress the gas inside the volume,

a rotatable shaft (132) connectable to and rotatable by the switch operating shaft, the rotatable shaft is arranged with its rotation axis (110) through an opening (146) of the piston, the rotatable shaft comprises a guiding structure (142a-b) on a radially outwards facing surface (144) of the shaft, the guiding structure being configured to engage with a guiding element (148) in the opening of the piston, wherein the guiding structure comprises a first portion (142a) and a second portion (142b),

the first portion and the guiding element are configured such that when the first portion and the guiding element are engaged, a rotation of the shaft about its rotation axis cause a linear motion (111) of the piston along the rotation axis of the shaft, and

the second portion and the guiding element are configured such that when the second portion and the guiding element are engaged, a rotation of the shaft about its rotation axis is de-coupled from the linear motion of the piston.
The compressed gas device according to claim 1, wherein the guiding structure is a groove or trench in the outwards facing surface of the shaft, and the guiding element is a pin or ball-bearing that fits in the groove or trench.
The compressed gas device according to claim 2, wherein the first portion of the groove or trench guides the guiding element along the rotation axis of the shaft, and the second portion of the groove or trench maintains the position of the guiding element along the rotation axis of the shaft.
The compressed gas device according to any one of claims 2-3, wherein a bent groove or trench portion (152) connects the first and the second portions.
The compressed gas device according to any one of claims 2-4, wherein the first portion comprises a first end (142aa) and a second end (142ab) which are displaced along the rotation axis of the shaft.
The compressed gas device according to any one of claims 2-5, wherein the second portion comprises a first end (142ba) and a second end (142bb) which are not displaced along the rotation axis of the shaft.
The compressed gas device according to any one of claims 2-6, comprising multiple guiding elements and multiple guiding structures.
The compressed gas device according to any one of the preceding claims, comprising an anti-rotation mechanism between the housing and the piston.
The compressed gas device according to claim 8, the anti-rotation mechanism includes an inwards extending protrusion (154) in the housing and an opening (156) or hole in the piston, or an outwards extending protrusion in the piston and an opening or hole in the housing.
The compressed gas device according to any one of claims 8 and 9, wherein the protrusions are made from a low-friction material.
The compressed gas device according to any one of the preceding claims, comprising multiple gas outlets (120a-b).
The compressed gas device according to any one of the preceding claims, wherein the de-coupling occurs when the switch operating shaft operates the electric current switch from an open state to an earth state.
The compressed gas device according to any one of the preceding claims, comprising a one-way valve (134) for gas intake in the housing.
A multiphase electric current switch (100) comprising the compressed gas device according to any one of the preceding claims.
The multiphase electric current switch according to claim 14, comprising hoses (122a-c) that guide gas from the outlet of the compressed gas device to each pole of the multiphase electric current switch.