SWITCH WITH PROGRESSIVE CONTACTING AND METHOD FOR ITS OPERATION

Description

TECHNICAL FIELD

[0001] This invention relates to a progressively contacting switch and a corresponding method for operating it, that uses a combination of sacrificial and conducting contacts to improve reliability and performance.BACKGROUND

[0002] 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.

[0003] Hence, new solutions are needed that improve the reliability and conductivity of switches.SUMMARY

[0004] In accordance with the invention, an electrical switch as set forth in claim 1 and a corresponding method of operating the electrical switch as set forth in claim 10 are provided.

[0005] Further embodiments of the invention are inter alia disclosed in the dependent claims.

[0006] EP 2 474 989 A relates to a sequential switching device with surrounding heterogeneous joint points structure, in which the exterior of a middle conductive joint point is surrounded by a heterogeneous external joint point structure, so that a time delay is generated between the two joint points during the sequential ON / OFF operations, so the service life of joint points of a mechanical joint point switch can be prolonged, and the voltage drop and thermal loss of joint point are reduced, especially characterized in that the engagement and stability of joint points are enhanced.

[0007] FR 2 691 574 Al describes an electrical contact device for high intensity direct current circuit that has two sacrificial contacts on elastic strips which maintain button contacts until after principal double contacts separate. The device includes principal contacts which have a contact zone of lowest possible resistance, and are held together by the movement of an insulating block acting through guide rods and compression springs. The block moves to separate the principal contacts while each sacrificial contact is closed by a single leaf spring acting on the connecting strip. The sacrificial contact is broken when there is no risk of breakdown except at the sacrificial contacts which are damage resistant and replaceable. The sacrificial contacts are self-clearing by relative displacement. The fixed contacts may be welded in bimetallic material to allow different materials to connect the contacts.

[0008] DE 94 04 775 Ul relates to a contact system with tungsten pre-contact for switching relays for high inrush current peaks. The contact system is for relays in horizontal or vertical design with one tungsten leading contact, which takes over the high switch-on peaks, and one main contact made of silver or silver with oxide components, which closes with a delay and carries the continuous load. This contact arrangement can be used in existing sizes without changing the connection grid.

[0009] JP 558 34329 U relates to a contact made of a noble metal having a small melting point and a low electric resistance value, a metal contact having a larger electric resistance value than that of the noble metal contact and having a high melting point, and a pair of these contacts being provided as a pair with the fixed contact plate and the movable contact plate A contact opening and closing device which is so arranged as to confront one having the same performance so as to be separated from each other and which has a higher melting point than the contacts made of precious metal having a lower melting point than the contacts made of precious metal having a low melting point.BRIEF DESCRIPTION OF THE FIGURES

[0010] 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: Figure 1 illustrates an example of a progressively contacting switch, according to an aspect of the present disclosure. Figure 2 illustrates an example of a process for closing and opening a progressively contacting switch, according to an aspect of the present disclosure. Figure 3 illustrates an example of a progressively contacting switch moving from the closed to the open position, according to an aspect of the present disclosure. Figure 4 illustrates an example of a progressively contacting switch moving from the open to the closed position, according to an aspect of the present disclosure. Figure 5 illustrates an example of an electrically-controlled progressively contacting switch, according to an aspect of the present disclosure. DETAILED DESCRIPTION

[0011] The present invention is defined in the independent claims. Further embodiments are the subject-matter of the dependent claims.

[0012] Aspects of the present disclosure include a progressively contacting switch. Nonlimiting 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.

[0013] Applications of the progressively contacting switch according to the invention include electric meters. The 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.

[0014] 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.

[0015] Turning now to the Figures, Figure 1 illustrates an example of a progressively contacting switch, according to the invention. Figure 1 depicts switch environment 100, which includes switch 101, power source 120, and load 130. Switch 101 can connect or disconnect power source 120 from load 130. Examples of power sources include distribution transformers, generators, and batteries. Examples of loads include customer premises, lights, and mechanical devices.

[0016] 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.

[0017] Sacrificial contacts 102 and 104 and conducting contacts 103 and 105 are 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 are 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.

[0018] Conducting contacts 103 and 105 are made of a material that has a high electrical conductivity. The material used has 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.

[0019] The sacrificial contacts and the conducting contacts are organized into sets. A first set of contacts includes sacrificial contact 102 and conducting contact 103 and a second set includes 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.

[0020] 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.

[0021] 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.

[0022] 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 Figures 2-4.

[0023] 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.

[0024] 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.

[0025] Figure 2 illustrates an example of a process 200 for closing and opening a progressively contacting switch, according to the invention. Process 200 can be implemented by an electronic control mechanism that causes a mechanical device to open or close the contacts of switch 101. For discussion purposes, process 200 is discussed with respect to Figures 3 and 4.

[0026] Figure 3 illustrates an example of a progressively contacting switch moving from the open to the closed position. Figure 3 depicts switch positions 301a-c. Open position 301a includes sacrificial contacts 302a and 304a and conducting contacts 303a and 305a. Transition position 301b includes sacrificial contacts 302b and 304b and conducting contacts 303b and 305b. Closed position 301c includes sacrificial contacts 302c and 304c and conducting contacts 303c and 305c.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 Figure 4.

[0033] Figure 4 illustrates an example of a progressively contacting switch moving from the closed to the open position. Figure 4 depicts switch positions 301a-c as depicted in Figure 3. Returning to Figure 2, at block 203, the switch is at transition position 301b. In transition position 301b, sacrificial contact 302b is connected to sacrificial contact 304b, which allows current to flow through the switch.

[0034] 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.

[0035] In another aspect, as depicted in Figure 5, the switch is controlled by an externallygenerated electrical signal.

[0036] Figure 5 illustrates an example of an electrically-controlled progressively contacting switch, according to an aspect of the present disclosure. Figure 5 depicts switch environment 500, which includes progressively contacting switch 501, which includes sacrificial contacts 102 and 104, conducting contacts 103 and 105, connections 110 and 112, relay coil 530, and control contacts 520-521.

[0037] 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 Figures 1-4.

[0038] 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.

Claims

1. An electrical switch (101, 501) for an electric meter comprising: a movable first member comprising a first set of contacts (102, 103; 302, 303) arranged serially along the first member, the first member connected to an input (110) and comprising: a first sacrificial contact (102, 302) arranged at a distal portion of the first member relative to the input and formed of a first metal having a first electrical conductivity and a first melting point; a first conducting contact (103, 303) arranged at a proximal portion of the first member relative to the input and formed of a second metal having a second electrical conductivity that is greater than the first electrical conductivity and a second melting point that is lower than the first melting point; and a second member comprising a second set of contacts (104, 105; 304, 305) arranged serially along the second member, the second member connected to an output (112) and comprising: a second sacrificial contact (104, 304) arranged at a distal portion of the second member relative to the output and formed of the first metal; and a second conducting contact (105, 305) arranged at a proximal portion of the second member relative to the output and formed of the second metal; an element (530) configured to connect the movable set of contacts (102, 103; 302, 303) with the set of contacts (104, 105; 304, 305) such that: the first sacrificial contact (102, 302) connects with the second sacrificial contact (104, 304) at a first time, thereby causing a current to flow, via the first sacrificial (102, 302) contact and the second sacrificial contact (104, 304), from a power source (120) to an electrical load (130), while the first sacrificial contact (102, 302) remains connected to the second sacrificial contact (104, 304), the first conducting contact (103, 303) connects with the second conducting contact (105, 305) at a second time that is after the first time causing an additional current to flow, via the first conducing contact (103, 303) and the second conducting contact (105, 305), from the power source (120) to the electrical load (130).

2. The electrical switch (101, 501) of claim 1, further comprising an additional input configured to receive an additional signal, wherein receiving the additional signal causes a disconnection of the first set of contacts (102, 103; 302, 303).

3. The electrical switch (101, 501) of any one of claims 1 or 2, wherein the element (530) is further configured to disconnect the first set of contacts (102, 103; 302, 303) such that: while the first sacrificial contact (102, 302) remains connected to the second sacrificial contact (104, 304), the first conducting contact (103, 303) disconnects from the second conducting contact (105, 305) at a third time that is after the second time, and the first sacrificial contact (102, 302) disconnects from the second sacrificial contact (104, 304) at a fourth time that is after the third time, thereby causing the current to cease flowing from the input (110) to the output (112).

4. The electrical switch (101, 501) of any one of claims 1-3, wherein when the first conducting contact (103, 303) connects with the second conducting contact (105, 305), an additional current flows between the first conducting contact (103, 303) and the second conducting contact (105, 305), wherein the additional current is greater than the current.

5. The electrical switch (101, 501) of claim 1, wherein the first metal is an alloy comprising tungsten and the second metal is an alloy that comprises one or more of tungsten and the second metal comprises one or more of silver or copper.

6. The electrical switch (101, 501) of any one of claims 1 to 5, wherein the electrical switch (501) is electrically controllable by a relay coil (530).

7. The electrical switch (101, 501) of any one of claims 1 to 6, further comprising a second input (111) and a second output (113) connecting the power source (120) to the electrical load (130).

8. The electrical switch (101, 501) of claim 7, wherein the second input (111) connects to the second output (113) via a connector independent of a state of the movable set of contacts (102, 203; 302, 303).

9. The electrical switch (101, 501) of any one of claims 1 to 8, wherein the electrical switch (101, 501) is a single-pole double-throw switch.

10. A method for operating the electrical switch (101, 501) of any one of claims 1 to 9 comprising the steps of: connecting the first sacrificial contact (102, 302) to the second sacrificial contact (104, 304), thereby causing a current to flow from the input (110) to the output (112); while the first sacrificial contact (102, 302) remains connected to the second sacrificial contact (104, 304), connecting the first conducting contact (103, 303) with the second conducting contact (105, 305) at the second time that is after the first time; while the first sacrificial contact (102, 302) remains connected to the second sacrificial contact (104, 304), disconnecting the first conducting contact (103, 303) from the second conducting contact (105, 305) at a third time that is after the second time; and disconnecting the first sacrificial contact (102, 302) from the second sacrificial contact (104, 304) at a fourth time that is after the third time, thereby causing the current to cease flowing from the input (110) to the output (112).