CN118176557A

CN118176557A - Electrical switching apparatus for reducing arc energy and corrosion in contact systems

Info

Publication number: CN118176557A
Application number: CN202280073299.6A
Authority: CN
Inventors: T·奥特; M·卡纳贝; L·威斯奇戈尔
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2021-09-30
Filing date: 2022-09-30
Publication date: 2024-06-11

Abstract

The present disclosure relates to an electrical switching apparatus for electrically connecting a first electrical conductor (28, 28 a) to a second electrical conductor (30, 30 a). The electrical switching apparatus includes: a first circuit path having a first resistance or impedance; and a second circuit path having a second resistance or impedance lower than the first resistance or impedance. The electrical switching apparatus is configured to provide a connection sequence for electrically connecting the first and second electrical conductors. The connection sequence comprises: a) A first electrical connection state in which the first and second electrical conductors are not electrically connected; b) A second electrical connection state in which the first and second electrical conductors are electrically connected through the first circuit path and not through the second circuit path; c) A third electrical connection state in which the first and second electrical conductors are electrically connected through the first circuit path and the second circuit path; and d) a fourth electrical connection state in which the first and second electrical conductors are electrically connected through the second circuit path and not through the first circuit path. During the connection sequence, the electrical switching apparatus moves from the first electrical connection state to the fourth electrical connection state sequentially through the second electrical connection state and the third electrical connection state.

Description

Electrical switching apparatus for reducing arc energy and corrosion in contact systems

Technical Field

The present disclosure relates generally to electrical devices, such as switching systems, for providing circuit interruption.

Background

Electrical systems, such as switching systems, are used to provide circuit interruption. When such a system is electrically connected or disconnected under an electrical load, an arc may be generated. Arcing can cause corrosion of components, negatively impacting system performance. In some cases where the arc energy is high enough, a short circuit associated with ionization may occur. Improvements in this regard are desirable.

Disclosure of Invention

The present disclosure relates generally to an electrical connection device including a multi-stage contact system that is sequenced to reduce arc energy generated by electrical connection and disconnection of the system under an electrical load. The electrical connection device may also reduce corrosion of the contact system caused by the arc. The electrical connection means comprises first and second circuit paths having different resistances or impedances. When electrically connected under load, the circuit path with the higher resistance is connected before the circuit path with the lower resistance to reduce arc energy. Similarly, when electrically disconnected under load, the circuit path with the lower resistance is disconnected before the circuit path with the higher resistance to reduce arc energy. The term "resistance" as used herein is generally defined to mean the comprehensive expression of any and all forms of impediments to electron flow in an electrical system. For example, in a direct current system, the resistance may be quantified using a real value (e.g., ohmic resistance); in an ac system, the resistance may represent a component of the impedance, where the impedance is quantified by a combination of real (e.g., ohmic) and imaginary values.

In one example, the electrical connection means is integrated in a rotary switch, wherein the electrical resistance of the circuit paths is made different by providing the first and second contacts of different materials having different electrical resistivities. In another example, the electrical connection means may be integrated in a linear switch, wherein the resistances of the circuit paths are made different by providing pad contacts made of different materials having different resistivities. In some examples, materials with higher resistivity (i.e., lower conductivity) are also more corrosion resistant than materials with lower resistivity (i.e., higher conductivity). In one example, the material with higher resistivity comprises stainless steel, while the material with lower resistivity comprises copper or silver, or aluminum, or a combination thereof.

The electrical connection device according to the present disclosure facilitates reducing arc energy during electrical connection and disconnection and facilitates reducing arc-related corrosion of the connection device. The electrical connection means may be comprised in a rotary switch and a linear switch.

The present disclosure solves the above-mentioned arcing problem with a new and cost-effective solution. The electrical connection means of the rotary switch of the present disclosure comprises two contact elements which may be made of two different materials. For example, the first contact element may be made of a higher resistivity material (e.g., stainless steel) and the second contact element may be made of a lower resistivity material (e.g., copper, silver, or aluminum). The different materials are electrically connected in sequence during the switching phases of connection and disconnection to help reduce arcing. The linear switch may comprise four contact elements, wherein the first and second contacts are made of a first material and the third and fourth contacts are made of a second material different from the first material.

One aspect of the present disclosure relates to an electrical switching apparatus for electrically connecting a first electrical conductor to a second electrical conductor. The electrical connection device includes: a first circuit path having a first resistance; and a second circuit path having a second resistance lower than the first resistance. The electrical switching apparatus is configured to provide a connection sequence for electrically connecting the first and second electrical conductors. The connection sequence comprises: a) A first electrical connection state in which the first and second electrical conductors are not electrically connected; b) A second electrical connection state in which the first and second electrical conductors are electrically connected through the first circuit path and not through the second circuit path; c) A third electrical connection state in which the first and second electrical conductors are electrically connected through the first circuit path and the second circuit path; and d) a fourth electrical connection state in which the first and second electrical conductors are electrically connected through the second circuit path and not through the first circuit path. During the connection sequence, the electrical switching apparatus moves from the first electrical connection state to the fourth electrical connection state sequentially through the second and third electrical connection states.

Another aspect of the present disclosure relates to an electrical switching apparatus for electrically connecting a first electrical conductor to a second electrical conductor. The electrical switching apparatus includes: a first circuit path having a first electrical impedance; and a second circuit path having a second electrical impedance lower than the first electrical impedance. The electrical switching apparatus is configured to provide a connection sequence for electrically connecting the first and second electrical conductors. The connection sequence comprises: a) A first electrical connection state in which the first and second electrical conductors are not electrically connected; b) A second electrical connection state in which the first and second electrical conductors are electrically connected through the first circuit path and not through the second circuit path; c) A third electrical connection state in which the first and second electrical conductors are electrically connected through the first circuit path and the second circuit path; and d) a fourth electrical connection state in which the first and second electrical conductors are electrically connected through the second circuit path and not through the first circuit path. During the connection sequence, the electrical switching apparatus moves from the first electrical connection state to the fourth electrical connection state sequentially through the second and third electrical connection states.

These and other features and advantages will become apparent upon reading the following detailed description and upon reference to the accompanying drawings. Various additional aspects will be set forth in the description that follows. These aspects may relate to individual features and combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad concepts upon which the embodiments disclosed herein are based.

Drawings

The following drawings illustrate specific embodiments of the disclosure and therefore do not limit the scope of the disclosure. Embodiments of the present disclosure will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.

Fig. 1, labeled "prior art," shows a top view of an example rotary switch in an open position.

Fig. 2 shows a top view of the rotary switch of fig. 1 in a closed position.

Fig. 3-7 illustrate a connection sequence for a rotary switch having an electrical switching apparatus in accordance with the principles of the present disclosure.

Fig. 8 to 11 show the turn-off sequence of the rotary switch of fig. 3 to 7.

Fig. 12 shows an exploded view of a conventional linear switch in an open position.

Fig. 13 shows a side cross-sectional view of the linear switch of fig. 12 in a closed position.

Fig. 14-17 illustrate a connection sequence for a linear switch with an electrical switching apparatus in accordance with the principles of the present disclosure.

Fig. 18 to 20 show the turn-off sequence of the linear switch of fig. 14 to 17.

Fig. 21 illustrates a perspective view of an example two-stage switchgear for use with the electrical switching apparatus of the present disclosure, the two-stage switchgear shown in an open position and including first and second plungers, first and second sleeves, and a bi-directional ramp according to the principles of the present disclosure.

Fig. 22 shows a perspective view of the two-stage switching device of fig. 21 without the first and second sleeves.

Fig. 23 shows an exploded view of the two-stage switching device of fig. 21.

Fig. 24 shows a perspective view of the bi-directional ramp of fig. 21.

Fig. 25 shows the two-stage switching device in an intermediate rotational position after rotating the bi-directional ramp counter-clockwise to move the first and second plungers in opposite directions.

Fig. 26 shows the two-stage switching device in the on position.

Fig. 27 shows the two-stage switching device of fig. 26 without the first and second sleeves.

Detailed Description

Various embodiments of the present invention will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. References to various embodiments do not limit the scope of the invention. Furthermore, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments.

As shown in fig. 1, a conventional rotary switch 10 is depicted in an open position. The rotary switch 10 may include a first stationary contact 12 and a second stationary contact 14. The rotary switch 10 further comprises a rotary contact arm 16 comprising a first movable contact 18 and a second movable contact 20. Fig. 2 shows the rotary switch in a closed position, wherein the rotary contact arm 16 interconnects the first and second stationary contacts 12, 14 with the respective first and second movable contacts 18, 20.

The rotary switch 10 further includes an arc chute 22 disposed adjacent the contacts to extinguish an arc generated when the contacts are operated to open or close. Such arc chambers typically include a plurality of conductive plates onto which the arc is transferred, stretching and cooling the arc over the plates until it is extinguished. One challenge in current interruption/switching is driving an arc into the arc interruption chamber.

The present disclosure also relates to improving an electrical switching apparatus to reduce arc energy during electrical connection and disconnection under an electrical load. In order to protect electrical equipment from the damaging effects of an arc, switches are provided with multiple circuit paths having different resistances that can be used in sequence to reduce arc energy and reduce arc related contact and enclosure corrosion. In some examples, one circuit path may include contacts made of a corrosion resistant material having a first resistivity, while another circuit path may include contacts made of a material having a second resistivity that is lower than the first resistivity.

Referring to fig. 3, an example rotary switch 24 is depicted in accordance with the principles of the present disclosure. Rotary switch 24 may be used in electrical switches (e.g., disconnectors) for industrial and hazardous applications. Fig. 3 to 7 show the rotary switch 24 during connection, and fig. 8 to 11 show the rotary switch 24 during disconnection.

The rotary switch 24 includes an electrical connection device 26 (e.g., an electrical switching device) for electrically connecting a first electrical conductor 28 to a second electrical conductor 30 in accordance with the principles of the present disclosure.

The rotary switch 24 includes a first contact 32 and a second contact 34. The first and second contacts 32, 34 may be fixed contacts. The first and second contacts 32, 34 may each comprise two coupling materials separated by an insulator. In some examples, the two materials may be different materials. In some examples, one material M ₁ has a higher resistivity than the second material M ₂ to reduce arc energy during electrical disconnection or connection. In some examples, the first material M ₁ may be a more arc-corrosion resistant material than the second material M ₂. In one example, the first material comprises stainless steel and the second material may comprise copper, silver, nickel, or a combination of copper, silver, and nickel.

In other examples, the first and second contacts 32, 34 may be made of the same material. In such a configuration, the first or second electrical conductors 28, 30 may be made of a higher resistance material, or alternatively, resistors may be added to the system.

Still referring to fig. 3, the rotary switch 24 includes a rotary contact arm 36 (e.g., switch member, rotary switch member) having a first rotary contact 38 at a first end 40 and a second rotary contact 42 at a second end 44. The rotary contact arm 36 rotates in a clockwise direction as indicated by arrow 46 to move the first and second rotary contacts 38, 42 of the rotary contact arm 36 relative to the first and second contacts 32, 34 between the open and closed positions. A shaft (not shown) enables the rotating contact arm 36 to rotate in the direction of arrow 46.

The electrical connection means 26 of the rotary switch 24 comprises a first circuit path 48 (see fig. 5) having a first resistance and a second circuit path 50 (see fig. 7) having a second resistance lower than the first resistance. In some examples, separate resistors may be added for each of the first and second circuit paths 48, 50. In other examples, more than one resistor may be provided, one resistor for each of the first and second circuit paths 48, 50.

During operation, the rotary switch 24 may be actuated to initiate rotational movement of the rotary contact arm 36. For example, the operating handle may interact with a circuit breaker operating mechanism to control the on and off positions of the rotary switch 24.

Fig. 3 shows the rotary contact arm 36 in a first electrically connected state, wherein the first and second electrical conductors 28, 30 are not electrically connected. That is, the rotary switch 24 is shown in an open or off position. The electrical connection means 26 of the rotary switch 24 may be configured to provide a connection sequence to turn the switch to an on position for electrically connecting the first and second electrical conductors 28, 30.

The connection sequence may include the following states: a) A first electrical connection state (see fig. 3) in which the first and second electrical conductors 28, 30 are not electrically connected; b) A second electrically connected state (see fig. 5) in which the first and second electrical conductors 28, 30 are electrically connected by the first circuit path 48 and not by the second circuit path 50; c) A third electrical connection state (see fig. 6) in which the first and second electrical conductors 28, 30 are electrically connected by the first circuit path 48 and the second circuit path 50; d) A fourth electrical connection state (see fig. 7) in which the first and second electrical conductors 28, 30 are electrically connected through the second circuit path 50 and not through the first circuit path 48.

During the connection sequence, the electrical connection means 26 of the rotary switch 24 are moved from the first electrical connection state to the fourth electrical connection state sequentially through the second and third electrical connection states. The rotary contact arm 36 rotates to switch the electrical switching apparatus 26 between the first, second, third, and fourth electrical connection states.

The rotating contact arm 36 is depicted in fig. 4 to show the positional arrangement between the first electrical connection state and the second electrical connection state. As the rotary contact arm 36 pivots, the first and second rotary contacts 38, 42 may move into contact with the first and second contacts 32, 34 (see fig. 5) to provide a second electrical connection state. That is, the first and second rotary contacts 38, 42 are rotated to the first material M ₁ of the first and second contacts 32, 34 to create the high-resistance first circuit path 48. In the second electrically connected state, due to the high resistance and short contact time, current can flow and cause a small amount of heating of the system.

Turning to fig. 6, the continuous movement of the rotary contact arm 36 allows the first and second rotary contacts 38, 42 to move into contact with the low resistance first and second contacts 32, 34 (i.e., the second material M ₂) while also maintaining contact with the high resistance first and second contacts 32, 34 (i.e., the first material M ₁) to provide a third electrically connected state. That is, in the third electrically connected state, the first and second circuit paths 48, 50 are connected in parallel. The current may flow primarily through the low resistance material M ₂ of the first and second contacts 32, 34.

Fig. 7 shows the rotating contact arm 36 rotated such that the first and second rotating contacts 38, 42 are in contact with only the low resistance first and second contacts 32, 34 (i.e., the second material M ₂) to provide a fourth electrical connection state. That is, in the fourth electrically connected state, only the second circuit path 50 is connected, and the first and second contacts 32, 34 of high resistance (i.e., the first material M ₁) are separated.

Fig. 8-11 illustrate an off sequence of the rotary switch 24, wherein the rotary contact arm 36 rotates in a counterclockwise direction as indicated by arrow 52. Fig. 8 shows the low and high resistance first and second contacts 32, 34 being reconnected together such that the first and second electrical conductors 28, 30 are electrically connected by the first and second circuit paths 48, 50.

In fig. 9-10, the low resistance first and second contacts 32, 34 are separated. In this way, the first and second electrical conductors 28, 30 are electrically connected only by the high resistance first circuit path 48. Fig. 11 shows the first and second electrical conductors 28, 30 electrically disconnected such that no current flows through either of the first and second circuit paths 48, 50 and the rotary switch 24 is in an open or off position.

Turning now to fig. 12 to 13, a prior art switching device is described. The switching device comprises a plurality of linear switches 56, each corresponding to a separate interrupter chamber. Further details of such a switch are disclosed in PCT patent application No. wo 2020/098970, which is incorporated herein by reference in its entirety.

Each linear switch 56 includes a fixed contact 58 supported by a base 60. Each fixed contact 58 includes a contact pad 51. The contact pads 51 are separated by a gap which may be closed by a linearly movable bridge 53 having contact pads 55 aligned with the contact pads 51 of the fixed contacts 58. The fixed contact 58 includes a clamp 57 having a clamping screw 59 for electrically connecting an electrical conductor (e.g., wire/cable) to the fixed contact 58. The movable bridge 53 is spring biased by a spring 61 (see fig. 13) to a closed position in which the contact pads 55 of the bridge 53 are in contact with the contact pads 51 of the fixed contacts 58 such that the fixed contacts 58 are electrically connected to each other by the bridge 53. The cam actuated plunger 63 is adapted to move the bridge 53 linearly away from the fixed contact 58 against the bias of the spring 61 to an open position (see fig. 12) in which the fixed contacts 58 are not electrically connected together by the bridge 53. Actuation of cam actuated plunger 63 allows bridge 53 to move between an open and a closed position. When the bridge 53 is in the closed position, an electrical connection is provided between the fixed contact 58 and the corresponding wire/cable to which it is electrically connected. When the bridge is in the open position, the electrical connection between the fixed contacts 58 is broken.

Turning to fig. 14, another electrical connection device 26a is shown as being included in the second embodiment as part of a linear double contact switch 62, which is an electrical switch designed to separate loads. The linear dual contact switch 62 may include a movable contact unit 64 including a contact bridge 66 (e.g., a switch member) that moves linearly along the Y-axis. In the open state, the linear dual contact switch 62 is in the open position with the contact bridge 66 open to depict a first electrical connection state in which the first and second electrical conductors 28a, 30a are not electrically connected. The contact bridge 66 may remain in the open position due to the axial force indicated by arrow 68. The force indicated by arrow 68 may be applied by an actuator, such as a rotary cam actuator, and may oppose the spring force generated by compression spring 70.

The contact bridge 66 includes a first contact 72, a second contact 74, a third contact 76, and a fourth contact 78. In some examples, the first and second contacts 72, 74 are made of a first material and the third and fourth contacts 76, 78 are made of a second material. Similar to the first and second materials of the first and second contacts 32, 34 described above, the first material of the first and second contacts 72, 74 may have a higher resistivity than the second material of the third and fourth contacts 76, 78. In other examples, in examples where the first, second, third, and fourth contacts 72, 74, 76, 78 are made of the same material, resistors may be added to the linear dual contact switch 62 to provide different resistances to different circuit paths. The first and second electrical conductors 28a, 30a and the contact bridge 66 may be made of a second material having a lower resistivity.

Referring to fig. 15-17, the electrical connection device 26a may be configured to provide a connection sequence for electrically connecting the first and second electrical conductors 28a, 30 a. The electrical connection means 26a comprises a first circuit path 80 (see fig. 15) having a higher resistance (i.e. a first resistance) and a second circuit path 82 (see fig. 17) having a lower resistance than the first circuit path 80 (i.e. a second resistance).

In the semi-closed state, electrical connection may be made through the first circuit path 80 to provide a second electrical connection state, as shown in fig. 15, in which the first and second electrical conductors 28a, 30a are electrically connected. The first and second electrical conductors 28a, 30a are not electrically connected by the second circuit path 82. For example, by rotating the switch handle of the device, the rotational motion will cause the actuator to move the contact bridge 66 linearly in the same direction as the force of the spring 70 (i.e., downward as shown). Thus, as the contact bridge 66 moves downward, the spring 70 extends (i.e., decompresses). The contact bridge 66 moves downwardly to a position where the first and second contacts 72, 74 make physical contact with the fixed contacts 84, 86, which are also made of a high resistance material. When the electrical switching apparatus 26a is in the second electrically connected state, the contact bridge 66 electrically connects the first and second contacts 72, 74, but does not connect the third and fourth contacts 76, 78. As contact bridge 66 moves downward, the actuator simultaneously pushes contacts 92, 94 upward and causes spring 90 to compress. Contacts 92, 94 are electrically connected to electrical conductors 28a, 30a, respectively, and are positioned in alignment with contacts 76, 78, respectively. Spring 90 provides a downward spring load on contacts 92, 94 against which the actuator resists.

First circuit path 80 includes a first contact 72 electrically connected to first electrical conductor 28a via a fixed contact 84 and a second contact 74 electrically connected to second electrical conductor 30a via a fixed contact 86 (see fig. 15). Second circuit path 82 includes third contact 76 electrically connected to first electrical conductor 28a via contacts 92, 94 and fourth contact 78 electrically connected to second electrical conductor 30a (see fig. 17).

In the closed circuit state, electrical connection may be made through the second circuit path to form a third electrically connected state shown in fig. 16, wherein the first and second electrical conductors 28a, 30a are electrically connected through the first and second circuit paths 80, 82. When the electrical switching apparatus is in the third electrically-connected state, the contact bridge 66 is electrically connected to the contacts 84, 86 through the first and second contacts 72, 74 and is also electrically connected to the contacts 92, 94 through the third and fourth contacts 76, 78. That is, when contacts 72, 74 are positioned on contacts 84, 86, the actuator continues to move low resistance contacts 92, 94 upward until contacts 92, 94 engage contacts 76, 78 and contact bridge 66 simultaneously provides a closed circuit across first and second circuit paths 80, 82. However, since the resistance of the second circuit path 82 is low, a main current flows through the second circuit path 82.

A fourth electrical connection state is shown in fig. 17, wherein the first and second electrical conductors 28a, 30a are electrically connected through the second circuit path 82 and not through the first circuit path 80. When the electrical connection device 26a is in the fourth electrical connection state, the contact bridge 66 electrically connects the third and fourth contacts 76, 78 to the contacts 92, 94 and does not connect the first and second contacts 72, 74 to the contacts 84, 86. That is, the actuator continues to move contacts 92, 94 upward such that bridge 66 and contacts 72, 74 are lifted from contacts 84, 86. When the bridge 66 and contacts 92, 94 move together simultaneously upward, the spring 70 is compressed, further compressing the spring 90 of the contact element 88. In this way, the first and second contacts 72, 74 are separated from the fixed contacts 84, 86, and current flows only through the third and fourth contacts 76, 78 and the low resistance contacts 92, 94 of the low resistance material.

During the connection sequence, the electrical switching apparatus 26a moves from the first electrical connection state to the fourth electrical connection state sequentially through the second electrical connection state and the third electrical connection state. The contact bridge 66 is linearly movable in a first direction D ₁ (see fig. 15) to transition the electrical switching apparatus from the first electrical connection state to the second electrical connection state. The contact bridge 66 is linearly movable in a second direction D ₂ (see fig. 17) opposite to the first direction to switch the electrical switching apparatus from the third electrical connection state to the fourth electrical connection state.

Turning to fig. 17-20, the electrical connection device 26a is configured to provide a disconnect sequence for electrically disconnecting the first and second electrical conductors 28a, 30 a. During the disconnection sequence, the electrical connection device 26a may be moved sequentially from a fourth electrical connection state (see fig. 17) to a first electrical connection state (see fig. 20) through third and second electrical connection states (see fig. 18 and 19). That is, from the state of fig. 17, the contact bridge 66 and contacts 92, 94 are moved in the first direction D ₁ so that the first and second contacts make contact with the contact pins 24 located on the fixed contacts 84, 86, as shown in fig. 18. Continuing to move contacts 92, 94 downward, contact set 26a is shifted to a half-open position in which third and fourth contacts 76, 78 are separated from low resistance contacts 92, 94 such that only low resistance contacts 72, 74, 84, 86 are connected. That is, the first and second electrical conductors 28a, 30a are electrically connected by the first circuit path 80 and not by the second circuit path 82. Finally, the bridge 66 is lifted from the contacts 84, 96 to switch the contact arrangement 26a to the open or circuit breaking position. Fig. 20 shows the electrical connection device 26a in an open or circuit-breaking position in which the first and second electrical conductors 28a, 30a are not electrically connected. It should be appreciated that the disconnection sequence may be caused by operation (e.g., rotation) of the cam actuator in a direction opposite to the direction in which the cam actuator moves to drive the electrical connection sequence.

Fig. 21-27 illustrate a spring-biased plunger assembly 96 (e.g., a two-stage switching device, a spring-biased element) that is used with the electrical connection device 26a to make the described sequence connection. The spring biased plunger assembly 96 is movable between an on and off position for electrically connecting or disconnecting the first and second electrical conductors 28a, 30a.

The spring biased plunger assembly may include a plurality of plungers axially movable in opposite directions along a plurality of ramps. The ramps may be executed at different pitches to achieve different speeds during movement. For example, one plunger may move slower than another plunger.

In the illustrated example, the spring-biased plunger assembly 96 may include a first plunger 98, a second plunger 100, a first sleeve 102 (e.g., an inner sleeve), a second sleeve 104 (e.g., an outer sleeve), and a bi-directional ramp 106 having inner and outer ramps 108, 110 (see fig. 24) over which the first and second plungers 98, 100 move. The inner and outer ramps 108, 110 curve in opposite helical directions such that when the bi-directional ramp 106 rotates counterclockwise 120, the first plunger 98 moves downward on the inner ramp 108, the second plunger 100 moves upward on the outer ramp 110, and when the bi-directional ramp 106 rotates clockwise 122, the first plunger 98 moves upward on the inner ramp 108, and the second plunger 100 moves downward on the outer ramp 110. The first plunger 98 may provide the above-described axial movement indicated by arrow 68 (see fig. 14) and the second plunger 100 may provide the opposite axial movement indicated by arrow 49 (see fig. 15).

The first plunger 98 is slidably carried within a first sleeve 102. The first plunger 98 includes a first rail 112 configured to be received in a first guide slot 114 defined in the first sleeve 102 to allow the first plunger 98 to move axially therein. The second plunger 100 may also include a second guide rail 116 configured to be received in a second guide slot 118 defined in the second sleeve 104 to allow the second plunger 100 to move axially therein.

When the electrical switching apparatus 26a is switched between an on (see fig. 26) and an off (see fig. 21) position for electrically connecting or disconnecting the first and second electrical conductors 28a, 30a, the inner and outer ramps 108, 110 spiral in opposite directions for driving the respective first and second plungers 98, 100 in opposite directions.

Fig. 21 shows the first plunger 98 in its extreme position on the inner ramp 108 and the second plunger 100 in its zero position on the outer ramp 110. Fig. 22 shows the spring biased plunger assembly 96 in an open position, with the first and second sleeves 102, 104 not shown. When the bi-directional ramp 106 is rotated counterclockwise as indicated by arrow 120, the first and second plungers 98, 100 may move axially in opposite directions. That is, the first plunger 98 may move axially in the first direction D ₁, while the second plunger moves axially in the second direction D ₂. The first plunger 98 may have a leg 130 that travels along the inner ramp 108 of the bi-directional ramp 106. The second plunger 100 may also have legs 128 that travel along the outer ramp 110 of the bi-directional ramp 106.

When the linear dual contact switch 62 is in the open position as shown in fig. 14, the first plunger 98 may support the contact bridge 66 while the second plunger 100 supports the contacts 92, 94. When the bi-directional ramp 106 rotates counterclockwise, the first plunger 98 will travel downward on the internal ramp 108 due to the downward load from the spring 70, causing the contact bridge 66 to descend until the contacts 72, 74 are located on the contacts 84, 86, while the second plunger 100 begins to move in the opposite upward direction to lift the contacts 92, 94 toward the contacts 76, 78 and compress the spring 90.

As the bi-directional ramp 106 continues to rotate counterclockwise, the first and second plungers 98, 100 will continue to move in opposite directions to an intermediate point, as shown in fig. 25. At an intermediate point, the contact bridge 66 may close, as shown in fig. 16. The first plunger 98 may continue to move in the first direction D ₁ and the second plunger 100 may continue to move in the second direction D ₂, which allows the contacts 92, 94 to move upward to make contact with the third and fourth contacts 76, 78.

Turning to fig. 26-27, the bi-directional ramp 106 continues to rotate counterclockwise, moving the first plunger 98 to its zero position and the second plunger 100 to its end position. In this position, the contact bridge 66 may be lifted by the second plunger 100, as shown in fig. 17, to break contact between the first and second contacts 72, 74 and the fixed contacts 84, 86, while maintaining the connection between the contact bridge 66 and the contacts 92, 94.

The bi-directional ramp 106 defines an opening 124 for receiving an extension member 126 of the first plunger 98 as the first plunger 98 moves relative to the second plunger 100. In some examples, a stop (not shown) may be provided within the spring biased plunger assembly 96 to limit axial movement of the first and second plungers 98, 100 by preventing the bi-directional ramp 106 from tipping over.

When electrical connection device 26a is moved from the on position to the off position for electrically disconnecting first and second electrical conductors 28a, 30a, bi-directional ramp 106 may rotate clockwise as indicated by arrow 122. When the bi-directional ramp 106 is rotated clockwise to open the linear dual contact switch 62, the first plunger 98 may be moved axially along the inner ramp 108 in the second direction D ₂ and the second plunger 100 may be moved axially along the outer ramp 110 in the first direction D ₁ to open the first and second electrical conductors 28a, 30a. That is, as the second plunger 100 moves in the first direction D ₁, the contacts 92, 94 may move downward to separate the connection between the third and fourth contacts 76, 78 and the low-resistance contacts 92, 94. The bi-directional ramp 106 continues to rotate clockwise, continuing to move the first plunger 98 in the second direction D ₂ and the second plunger 100 moving in the first direction D ₂ to lift the contact bridge 66 and disconnect the first and second contacts 72, 74 from the fixed contacts 84, 86.

From the foregoing detailed description, it will be evident that modifications and variations can be made without departing from the scope of the claims.

Claims

1. An electrical switching apparatus for electrically connecting a first electrical conductor to a second electrical conductor, the electrical switching apparatus comprising:

A first circuit path having a first resistance;

A second circuit path having a second resistance lower than the first resistance; and

The electrical switching apparatus is configured to provide a connection sequence for electrically connecting the first electrical conductor and the second electrical conductor, the connection sequence comprising: a) A first electrical connection state in which the first electrical conductor and the second electrical conductor are not electrically connected; b) A second electrical connection state in which the first electrical conductor and the second electrical conductor are electrically connected through a first circuit path and not through the second circuit path; c) A third electrical connection state in which the first electrical conductor and the second electrical conductor are electrically connected through the first circuit path and the second circuit path; and d) a fourth electrical connection state, wherein the first electrical conductor and the second electrical conductor are electrically connected through the second circuit path but not through the first circuit path, wherein during the connection sequence the electrical switching apparatus moves from the first electrical connection state to the fourth electrical connection state sequentially through the second electrical connection state and the third electrical connection state.

2. An electrical switching apparatus for electrically connecting a first electrical conductor to a second electrical conductor, the electrical switching apparatus comprising:

a first circuit path having a first electrical impedance;

A second circuit path having a second electrical impedance lower than the first electrical impedance; and

3. An electrical switching apparatus according to claim 1 or 2 wherein said electrical switching apparatus comprises a rotary switching apparatus.

4. An electrical switching apparatus according to claim 1 or 2 wherein the electrical switching apparatus comprises a linear switching apparatus.

5. The electrical switching apparatus of claim 1 or 2 wherein the first circuit path includes a first contact electrically connected to the first electrical conductor and a second contact electrically connected to the second electrical conductor, wherein the second circuit path includes a third contact electrically connected to the first electrical conductor and a fourth contact electrically connected to the second electrical conductor, and wherein the electrical switching apparatus includes a switching member that: a) Electrically connecting the first contact and the second contact and not connecting the third contact and the fourth contact when the electrical switching apparatus is in the second electrically connected state; b) Electrically connecting the first contact and the second contact and also electrically connecting the third contact and the fourth contact when the electrical switching apparatus is in the third electrically connected state; and c) electrically connecting the third contact and the fourth contact and not connecting the first contact and the second contact when the electrical switching apparatus is in the fourth electrical connection state.

6. The electrical switching apparatus of claim 5 wherein the switching member is a rotary switching member that rotates to transition the switching apparatus between the first, second, third, and fourth electrical connection states.

7. The electrical switching apparatus of claim 5 wherein the first and second contacts are made of a first material and the third and fourth contacts are made of a second material, wherein the first material has a higher resistivity and is more corrosion resistant than the second material.

8. The electrical switching apparatus of claim 7 wherein the first material comprises stainless steel and the second material comprises copper, silver, or nickel, or a combination thereof.

9. The electrical switching apparatus of claim 5 wherein said switching member moves linearly.

10. The electrical switching apparatus of claim 9 wherein the switching member moves linearly in a first direction to transition the electrical switching apparatus from the first electrical connection state to the second electrical connection state, and wherein the switching member moves linearly in a second direction opposite the first direction to transition the electrical switching apparatus from the third electrical connection state to the fourth electrical connection state.

11. The electrical switching apparatus of claim 5 wherein said first, second, third and fourth contacts are made of the same material composition having a lower resistivity.

12. The electrical switching apparatus of claim 11 further comprising a resistor made of a higher resistance material.

13. An electrical switching apparatus as claimed in claim 1 or 2, further comprising a spring biasing element configured to provide a mechanical force in the electrical switching apparatus for connecting or disconnecting the first and second electrical conductors.

14. The electrical switching apparatus of claim 13 wherein the spring-biased element comprises a first plunger and a second plunger axially movable in opposite directions along a bi-directional ramp.

15. The electrical switching apparatus of claim 14 wherein the first and second plungers are axially movable within the respective first and second sleeves when the bi-directional ramp rotates in a clockwise or counter-clockwise direction.

16. The electrical switching apparatus of claim 15 wherein the first plunger is axially movable along an inner ramp of the bi-directional ramp and the second plunger is axially movable along an outer ramp of the bi-directional ramp.

17. The electrical switching apparatus of claim 13 wherein the spring-biased element comprises a plurality of elements configured to convert rotational motion to linear motion.

18. The electrical switching apparatus of claim 17 wherein the plurality of elements includes plungers axially movable in opposite directions along a plurality of ramps.