This invention relates generally to switches used to connect and disconnect electric circuits. In an example, this invention relates to a progressively contacting switch that uses a combination of sacrificial and conducting contacts to improve reliability and performance.
Switches can connect and disconnect electric circuits by causing contacts to close or open. But when large amounts of current flow through switches, arcs of electric current can form during opening and closing, causing the contacts to heat up (ohmic heating) and plasma to be deposited on the contact. Over time, through repeated opening and closing, the contacts can wear down and form a thin bridge, causing an increase in impedance. This increase in impedance causes unnecessary heat, damages components, and interferes with power transmission.
Hence, new solutions are needed that improve the reliability and conductivity of switches.
Certain aspects and features include an electrical switch. The switch includes a movable set of contacts connected to an input. The movable set of contacts include a first sacrificial contact formed of a first metal and a first conducting contact formed of a second metal. The switch includes a set of contacts connected to an output. The set of contacts includes a second sacrificial contact formed of the first metal and a second conducting contact formed of the second metal. The switch further includes an element configurable to connect the movable set of contacts such that the first sacrificial contact connects with the second sacrificial contact at a first time, thereby causing a current to flow from the input to the output, and while the first sacrificial contact remains connected to the second sacrificial contact, the first conducting contact connects with the second conducting contact at a second time that is after the first time.
These illustrative examples are mentioned not to limit or define the disclosure, but to provide examples to aid understanding thereof. Additional examples and further description are provided in the Detailed Description.
These and other features, aspects, and advantages of the present disclosure are better understood when the following Detailed Description is read with reference to the accompanying drawings, where:
Aspects of the present disclosure include a progressively contacting switch. Non-limiting examples of a switch include a contactor and a relay. The progressively contacting switch prevents early erosion of switch contacts by providing a sacrificial set of contacts that closes before a normal set of contacts closes. The sacrificial contacts, which are more durable in nature than the normal set of contacts, make initial contact when the switch closes and are more resilient to current arcing and resulting high temperatures. As a result, the progressively contacting switch can last longer than existing switches. Further, by reducing generated heat, a smaller relay or contactor with less copper, silver, or other rare metals may possible, thereby reducing cost.
Applications of the progressively contacting switch include, but are not limited to power delivery systems, high current relays, contactors, switches, and electric meters. For example, electric meters using the progressive switch benefit from a lower amount of generated heat, improved performance, and longer equipment lifespan. The progressively contacting switch allows improvement in a maximum number of switch closures before failure. In contrast, each closing of a switch in the current solutions results in a degradation of the contact that ultimately leads to premature failure.
The progressively contacting switch includes two sets of contacts. Each set of contacts includes a sacrificial contact connected to a conducting contact. The sacrificial contacts can be constructed of an electrically conductive material that is durable and resistant to heat caused by arc erosion. The conducting contacts can be constructed of a material that has a high electrical conductivity. When the switch is closed, the two sets of contacts connect to each other such that the sacrificial contacts make contact with each other first, thereby bearing the bulk of any electrical arcing and heat. Once the two sacrificial contacts have made contact, the two conducting contacts connect with each other, conducting the bulk of the current with lower impedance due to the higher conductivity of the conducting contacts relative to the sacrificial contacts.
Turning now to the Figures,
Switch 101 includes connections 110, 111, 112, and 113, sacrificial contacts 102 and 104, and conducting contacts 103 and 105. When switch 101 is closed, connections 110 and 112 are connected. As shown, connection 111 and 113 are always connected. But switch 101 can be configured in a double pole, double throw configuration such that connections 111 and 113 can also be connected or disconnected. Examples of other configurations are single pole, double throw and double pole, double throw.
Sacrificial contacts 102 and 104 and conducting contacts 103 and 105 can be made of different types of metal. For example, while still electrically conductive, sacrificial contacts 102 and 104 can be fabricated from more durable material. By having a higher melting point, sacrificial contacts 102 and 104 can better withstand arcing and heat caused by electricity. Hence, sacrificial contacts 102 and 104 may in some cases be made of a material that has a lower electrical conductivity and/or a higher melting point than the materials which are used to form conducting contacts 103 and 105.
Conducting contacts 103 and 105 can be made of a material that has a high electrical conductivity. In some cases, the material used can have a higher electrical conductivity than the material used for the sacrificial contacts 102 and 104. Examples of suitable materials for conducting contacts 103 and 105 include silver, copper, gold, aluminum, zinc, nickel, brass, bronze, or alloys thereof. Examples of suitable materials for sacrificial contacts 102 and 104 include tungsten, Multilam, aluminum, zinc, nickel, brass, bronze, platinum, steel, lead, and alloys thereof.
The sacrificial contacts and the conducting contacts can be organized into sets. For example, a first set of contacts could include sacrificial contact 102 and conducting contact 103 and a second set could include sacrificial contact 104 and conducting contact 105. For example purposes, two sets are shown, but any number of sets are possible. Further, any number of sacrificial and conducting contacts are possible. For example, in high current applications, each set might have multiple sacrificial and/or conducting contacts.
In an aspect, switch 101 is manually operated. In this case, a user can move an element, actuator, or rocker mechanism to open or close the switch. In turn, the mechanism opens or closes the sacrificial contacts and the conducting contacts as described herein. One or more sets of contacts can be movable. For example, a first pair of contacts that includes sacrificial contact 102 and conducting contact 103 can be moveable whereas a second pair of contacts that includes sacrificial contact 104 and conducting contact 105 that are fixed, or vice versa. In some cases, both more than one set of contacts.
Switch 101 can be in an open position, a closed position, or in transition between open and closed positions. For example, in an open position, no contacts are connected, and no current flows between connection 110 and 112. As the switch 101 is closed, the switch 101 enters a transition in which sacrificial contact 102 connects with sacrificial contact 104, causing current to flow between connections 110 and 112 via sacrificial contacts 102 and 104. When in transition, conducting contacts 102 and 104 are not connected.
In the closed position, sacrificial contacts 102 and 104 are connected and conducting contacts 103 and 105 are also connected. In the closed position, the current flows between connection 110 and connection 112 in one or more paths. For example, current can flow via sacrificial contacts 102 and 104 and also between conducting contacts 103 and 105. In some cases, a majority of a total current flows between the conductive contacts 103 and 105. The closing and opening of switch 101 is discussed further with respect to
When switch 101 is in transition or closed position, current can flow from connection 110 to connection 112 or vice versa. Thus, switch 101 can be used for alternating or direct current applications. Further, when switch 101 is in closed position, any current flow can divide across the sacrificial contacts and the conducting contacts.
In an aspect, the switch 101 includes an intermediate set of contacts that make contact after the sacrificial contacts but before the conducting contacts. In this case, the sacrificial contacts are the least conductive but are the most robust, the conducting contacts are the most conductive but the least robust, and the intermediate contacts are balanced between being robust and conductive. For example, the intermediate contacts can be less robust but more conductive than the sacrificial contacts and more robust and less conductive than the conducting contacts.
Open position 301a represents an open state in which no contacts are connected and no current flows through switch 101. Transition position 301b represents a transition state in which current flows through the sacrificial contacts 302b and 304b. Closed position 301c represents a closed state in which current flows through both conducting contacts 303c and 305c and sacrificial contacts 302c and 304c.
Process 200 assumes that the switch is in open position 301a. Sacrificial contacts 302a and 304a are not connected. Conducting contacts 303a and 305a are not connected. No current can flow through the switch.
At block 201, process 200 involves connecting the first sacrificial contact to the second sacrificial contact, thereby causing a current to flow from the input to the output. The switch moves from open position 301a to transition position 301b. In transition position 301b, sacrificial contact 302b is connected to sacrificial contact 304b, which allows current to flow through the switch. But conducting contact 303b and conducting contact 305b are not connected.
At block 202, process 200 involves connecting the first conducting contact with the second conducting contact at a second time that is after the first time while the first sacrificial contact remains connected to the second sacrificial contact. Accordingly, the switch moves from transition position 301b to closed position 301c.
In closed position 301c, conducting contact 303b is connected to conducting contact 305b and sacrificial contact 302b is connected to sacrificial contact 304b. Current flows through the switch via both conducting contacts 303b-305b and sacrificial contacts 302b-304b. Because sacrificial contacts 302a and 304a make contact before conducting contacts 303b and 305b, sacrificial contacts 302a and 302b, absorb more of any arcing and minimize the electrical arcing and erosion of conductive contacts 303b and 305b. The switch may be in closed position 301 for a substantial amount of time before the switch is disconnected.
At block 203, process 200 involves disconnecting the first conducting contact from the second conducting contact at a third time that is after the second time while the first sacrificial contact remains connected to the second sacrificial contact. Blocks 203 and 204 are discussed with respect to
At block 204, process 200 involves disconnecting the first sacrificial contact from the second sacrificial contact at a fourth time that is after the third time, thereby causing the current to cease flowing from the input to the output. At block 204, the switch returns to open position 301a.
In another aspect, as depicted in
In an example, when a voltage signal is applied between contacts 520 and 521, relay coil is activated and causes a magnetic field, which in turn moves the switch such that the sacrificial contacts and conducting contacts operate consistently as described with respect to
Switch 501 can be in a default-open or default-closed position. Switch 501 is configured such that an electromagnetic field generated in relay coil 530 causes switch 501 to move from an open to a closed position or from a closed to an open position. In other aspects, switch 501 can receive one or more control signals. For example, a first control signal can cause switch 501 to close and a second control signal can cause switch 501 to open. Alternatively, switch 501 can default in either closed or open state, and a presence of a control signal can change the state from open to closed or closed to open.
While the present subject matter has been described in detail with respect to specific aspects thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily produce alterations to, variations of, and equivalents to such aspects. Accordingly, it should be understood that the present disclosure has been presented for purposes of example rather than limitation and does not preclude inclusion of such modifications, variations, and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.
Number | Name | Date | Kind |
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3158721 | Delaney | Nov 1964 | A |
3218428 | Gauthier | Nov 1965 | A |
3238339 | Fehling | Mar 1966 | A |
4680562 | Bratkowski | Jul 1987 | A |
4713504 | Maier | Dec 1987 | A |
4926018 | Buxton | May 1990 | A |
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8941269 | Flegel | Jan 2015 | B1 |
20080073327 | Annis | Mar 2008 | A1 |
Number | Date | Country |
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9404775 | Jun 1994 | DE |
1962316 | Aug 2008 | EP |
2474989 | Jun 2012 | EP |
2686448 | Jul 1993 | FR |
2691574 | Nov 1993 | FR |
S58-034329 | May 1983 | JP |
Entry |
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Translation og FR2686448 (original doc. published Jul. 23, 1993) (Year: 1993). |
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