Current switch

Abstract

A current switch (100) comprising: a first fixed electrical contact (102); a second fixed electrical contact (104) electrically connected to the first fixed electrical contact; a movable single-sided electrical contact (106) configured to make a single-sided connection and disconnection with the first fixed electrical contact to create and disconnect an electrical current in the current switch (100); the movable second electrical contact (112; 302; 402, 402; 502) configured to move in contact with the second fixed electrical contact after the formation of the current and to be disconnected from the second fixed electrical contact prior to the disconnection of the current; wherein the electrical connection between the movable second electrical contact and the second fixed electrical contact is realized by means of a first contact in the slot (114; 306; 406), where one of the movable second electrical contact and the second fixed electrical contact includes one of the double-sided contact and the slot, and the other of the movable second electrical contact and the second fixed electrical contact includes the other of the double-sided contact and the slot.

Description

Technical Field

[0001] This invention relates to a current switch. Background Technology

[0002] Electrical switches used in medium and high voltage switchgear are subjected to large currents. In the event of a short circuit and before the short-circuit protection device clears the fault, the extremely high current in the contacts of the electrical switch can cause the contacts to separate, which can severely damage the switch and surrounding equipment.

[0003] Short-circuit coordination between contacts and short-circuit protection devices is challenging, especially for large switches that also require very large circuit breakers. Furthermore, because large switches often operate slowly, the time when contacts are exposed to short-circuit current can become too long, leading to excessive energy release that could damage the switch. Summary of the Invention

[0004] In view of the above and other disadvantages of the prior art, the object of the present invention is to provide a current switch that at least partially mitigates the shortcomings of the prior art.

[0005] According to a first aspect of the invention, a current switch is provided, comprising: a first fixed electrical contact; a second fixed electrical contact electrically connected to the first fixed electrical contact; a movable one-sided electrical contact configured to connect and disconnect from the first fixed electrical contact on one side to form and disconnect a current in the current switch; and a movable second electrical contact configured to move in contact with the second fixed electrical contact after forming a current and to disconnect from the second fixed electrical contact before disconnecting the current; wherein the electrical connection between the movable second electrical contact and the second fixed electrical contact is achieved by a double-sided contact connected in a slot, wherein one of the movable second electrical contact and the second fixed electrical contact includes the double-sided contact and one of the slots, and the other of the movable second electrical contact and the second fixed electrical contact includes the double-sided contact and the other of the slots.

[0006] The present invention is at least in part based on an implementation with parallel contacts, wherein normal operation is handled by a first system having single-sided contacts, which is separate from a second system having double-sided contacts, which keeps the circuit closed in the event of a short circuit. The first system performs normal operation, while the second system handles the short-circuit condition and is particularly suitable for conducting high currents.

[0007] The groove also forms a double-sided contact. Therefore, in the second system, the matching of two double-sided contact elements can be considered.

[0008] Since the bilateral contacts do not need to conduct current during normal operation, the contact force in the second system (i.e., the contact force between the bilateral contacts) can be relatively low, or at least lower than the contact force between the first fixed electrical contact and the movable single-sided electrical contact during normal operation. This reduces wear on the bilateral contacts and simplifies their actuator mechanism.

[0009] A one-sided contact is a contact that contacts a fixed electrical contact only on one side. That is, only one surface of the contact forms and disconnects electrical contact with the first fixed electrical contact. Therefore, "one-sided" refers to the side where the electrical connection is made.

[0010] A single-sided contact includes a single surface adapted to contact a corresponding surface of a fixed electrical contact for conducting current between the single-sided contact and the fixed electrical contact.

[0011] A double-sided contact includes two separate surfaces that contact the corresponding surfaces of a mating contact. A double-sided contact may include two parallel surfaces, either facing each other or facing opposite directions.

[0012] In other words, one of the double-sided contact and the corresponding mating contact has an outward-facing contact point and the other has an inward-facing contact point, wherein the contact with the inward-facing contact point includes two parallel paths or branches for current.

[0013] In the event of a short circuit, the contacts on both sides are confined within the slot due to the rigid fit of the contact components, or due to the force generated when a large current passes through the parallel branches of the slot.

[0014] In the closed position of an electrical switch, current can flow between the stationary contacts and their respective mating contacts. In the open position, the stationary contacts and their respective mating contacts are not in contact, and therefore current does not flow between them.

[0015] In this embodiment, the electrical connection between the dual-sided contacts and the slot can be formed on the opposing sides inside the slot. The dual-sided contacts engaging with the two opposite sides inside the slot ensure a more stable and reliable electrical connection. This configuration reduces the likelihood of contact separation during a short circuit.

[0016] In an embodiment, the movable second electrical contact and the second fixed electrical contact can be configured such that the electrical connection between them is configured to be maintained in the event of a short-circuit fault that would cause the movable single-sided electrical contact to separate from the first fixed electrical contact. In other words, the movable second electrical contact is configured to be confined within the second fixed electrical contact in the event of a short circuit, thereby protecting the electrical switch and surrounding equipment. That is, sudden separation of the movable second electrical contact and the second fixed electrical contact is prevented in the event of a short circuit, allowing the short-circuit protection device to clear the fault.

[0017] In an embodiment, a single-sided movable electrical contact can be configured for switching and turning on, while a second movable electrical contact can be configured for turning on. Preferably, the single-sided movable electrical contact handles normal operation, and the second movable electrical contact handles turning on in the event of a short circuit.

[0018] In one embodiment, the current switch may further include an actuator mechanism configured to synchronize the movement of a movable single-sided electrical contact and a movable second electrical contact. The actuator mechanism improves the timing between the movable single-sided electrical contact and the movable second electrical contact during switching operations, thereby improving the reliability of the electrical switch.

[0019] In an embodiment, the current switch may include a separate arcing contact configured to close the electrical connection before a movable single-sided electrical contact. Preferably, the dual-sided contacts should close simultaneously with or slightly after the movable single-sided electrical contact, and should slightly open or simultaneously open before the movable single-sided electrical contact. The single-sided electrical contact is hereby considered the main contact, which is configured to handle the formation and disconnection of current and the conduction of current during normal operation. The dual-sided contacts are configured to handle high currents during short circuits.

[0020] In one embodiment, the movable second electrical contact may include a slot, and the second fixed electrical contact includes a double-sided contact. That is, the slot is located on the movable second electrical contact, which moves to connect with the fixed double-sided contact. The slot may be formed as a result of movement of the movable second electrical contact.

[0021] In one embodiment, the movable second electrical contact may include a single slot, and the movable second electrical contact is movable by angular movement.

[0022] In an embodiment, the movable second electrical contact may include two slots, one at each end of the movable second electrical contact, and each of the two slots is configured to connect to the receiving fixed double-sided contact of the second fixed electrical contact.

[0023] The movable second electrical contact may include two parallel conductors that are attracted to each other by a force generated by the current flowing through them. This force is known as the Lorentz force generated by the current conduction. Since the currents through the two parallel conductors are parallel and in the same direction, an attractive force will be generated between the two halves of the movable second electrical contact. These attractive forces will further increase the contact force at the electrical contact point, where the attractive force can be greater than the separation force generated at the contact point.

[0024] In this embodiment, the movement of the movable second electrical contact is linear. In the case of two parallel conductors, the parallel conductors can move linearly toward each other to form a groove and make contact with the double-sided contacts.

[0025] In one embodiment, the movable second electrical contact may include double-sided contacts, and the second fixed electrical contact includes a groove.

[0026] In this embodiment, the electrical connection between the first fixed electrical contact and the one-sided movable electrical contact can be in parallel with the electrical connection between the second fixed electrical contact and the second movable electrical contact. That is, when the first fixed electrical contact and the one-sided movable electrical contact are separated, current can still flow between the second fixed electrical contact and the second movable electrical contact.

[0027] In an embodiment, the movable first electrical contact and the movable second electrical contact can be operated by an actuator system that allows for independent operation.

[0028] In this embodiment, the movable single-sided electrical contact and the first fixed contact have a single rest position, which operates differently from manual operation, enabling the generation, carrying, and disconnection of current under normal circuit conditions, including operational overload conditions. That is, the movable single-sided electrical contact and the first fixed contact are contactors according to the IEC product standard IEC60947-4-1.

[0029] Other features and advantages of the invention will become apparent when examined in light of the appended claims and the following description. Those skilled in the art will recognize that different features of the invention can be combined to create embodiments other than those described below, without departing from the scope of the invention. Attached Figure Description

[0030] These and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, which illustrate exemplary embodiments of the invention, wherein:

[0031] Figure 1 An example current switch according to an embodiment of the present invention is shown;

[0032] Figure 2 The sequential movement of a movable single-sided contact and a movable second electrical contact according to an embodiment of the present invention is shown;

[0033] Figure 3A An exemplary movable second electrical contact and a second fixed contact in the disconnected position are shown according to an embodiment of the present invention;

[0034] Figure 3B An exemplary movable second electrical contact and a second fixed contact in a closed position are shown according to an embodiment of the present invention;

[0035] Figure 4A An exemplary movable second electrical contact and a second fixed contact in the disconnected position are shown according to an embodiment of the present invention;

[0036] Figure 4B An exemplary movable second electrical contact and a second fixed contact in a closed position are shown according to an embodiment of the present invention; and

[0037] Figure 5 An exemplary movable second electrical contact and a second fixed contact in a closed position are shown according to an embodiment of the present invention. Detailed Implementation

[0038] In this detailed description, various embodiments of the invention are described with reference to specific implementations. Specific terminology is used in the described embodiments for clarity. However, the invention is not limited to the chosen specific terminology. While specific exemplary embodiments are discussed, it should be understood that this is merely for illustrative purposes. Those skilled in the art will recognize that other components and configurations can be used without departing from the scope of the invention.

[0039] Electrical contact in a contactor is achieved by bringing two or more contact elements together, often referred to as "forming current." When the contacts are held together and current flows, it conducts current. When the contacts are separated, it disconnects current. These are the three basic functions of a contactor: forming, conducting, and disconnecting. During forming and disconnecting, electric arcs are often generated, and these arcs must be handled by the contacts and the rest of the system. When conducting, the contacts should have good conductivity to minimize power loss. Therefore, the contacts in a contactor need to be both arc-resistant and have good conductivity, but these two requirements are often conflicting. As a result, the chosen contact material is a compromise between different requirements, but not optimal for either one, and a large amount of contact material is required as it corrodes during forming and disconnecting operations. Contact materials are typically silver-based alloys or composites; therefore, they represent high cost.

[0040] One way to avoid material trade-offs is to divide the contacts into two or more parallel branches, with separate branches for switching (forming and disconnecting) and other separate branches for conduction. This allows for different contact materials for switching and conduction, such as using a highly arc-resistant material in the switching branch and a well-conducting material in the conducting branch.

[0041] The resistance in an electrical contact depends on the contact force between the contact components. For a component with a contact force "F", the resistance is related to the contact force "F". c "Resistivity ρ and hardness H held together"v For two equal contact components, the so-called contraction resistance R is defined by the following relationship:

[0042]

[0043] Therefore, ensuring high contact force F c It is beneficial.

[0044] Antiparallel currents generate Lorentz forces "F" that attempt to separate the two contact components. l The force is proportional to the square of the current i:

[0045] F I ~i 2

[0046] The Lorentz force must be generated by the contact force F. c Compensation. This is acceptable for normal current levels. However, when contacts are exposed to extremely high currents, such as during a short circuit, holding the contact components together becomes very difficult. If the contacts separate with a high current, a high power will be released, which can damage the contactor and other nearby equipment. This problem is addressed by the embodiments described herein.

[0047] Figure 1 A current switch 100 according to an embodiment of the present invention is shown conceptually.

[0048] The current switch 100 includes a first fixed electrical contact 102 and a second fixed electrical contact 104 electrically connected to the first fixed electrical contact 102.

[0049] A movable one-sided electrical contact 106 is configured to connect to and disconnect from a first fixed electrical contact 102 on one side, in order to form and disconnect current in the current switch 100. In other words, the movable one-sided electrical contact 106 can move along axis 108 toward the first fixed electrical contact 102 until contact is formed between the movable one-sided electrical contact 106 and the first fixed electrical contact 102. Figure 1 In the current switch 100, the current cannot flow from one side 110a to the other side 110b, or in other words, it cannot flow between the poles of the current switch 100. Once a connection is formed between the movable single-sided electrical contact 106 and the first fixed electrical contact 102, current can flow between sides 110a-b, or similarly, between the poles of the current switch 100.

[0050] Furthermore, the movable second electrical contact 112 is configured to move in contact with the second fixed electrical contact 104 after current is generated, and to disconnect from the second fixed electrical contact 104 before the current is disconnected. The movement of the movable single-sided electrical contact 106 and the second electrical contact 112 is sequential, such that the movable single-sided electrical contact 106 makes contact before the movable second electrical contact 112 moves to contact the second fixed electrical contact 104. Furthermore, to disconnect the current, the sequential movement causes the movable second electrical contact 112 to disconnect its contact with the second fixed electrical contact 104 before the movable single-sided electrical contact 106 disconnects the current.

[0051] The electrical connection between the movable second electrical contact 112 and the second fixed electrical contact 104 is formed by a double-sided contact connected in a slot 114, creating another double-sided contact. One of the movable second electrical contact and the second fixed electrical contact includes a double-sided contact and one of the slots, while the other includes a double-sided contact and the other of the slots. In this exemplary embodiment, the movable second electrical contact 112 is a double-sided electrical contact 112, and the slot 114 is included in the second fixed electrical contact 104.

[0052] The double-sided contact 112 moves linearly 116 to form or disconnect its connection in the groove 114 of the second fixed electrical contact 104. Each of the second fixed electrical contacts 104 has a groove 114.

[0053] The single-sided contact 106 has a single side 118 at which it makes contact with the first fixed electrical contact 102. When the single-sided contact 106 moves linearly to the first fixed electrical contact 102, the single side 118 contacts the first fixed electrical contact 102, allowing current to flow between poles 110a and 110b.

[0054] The double-sided contact 112 has two sides 120a and 120b, which face opposite directions but are parallel. The sides 120a and 120b contact corresponding sides 122a and 122b in the groove 114 to form a connection between the double-sided contact 112 and the groove 114. The sides 122a-b of the groove face each other.

[0055] The movable double-sided contact 112 makes contact with the inner walls 122a-b of the groove 114 at its sides 120a-b. In the event of a short circuit, the movable double-sided contact 112 is confined within the groove 114, and the separation force (Lorentz force) will only push the double-sided contact 112 from one side 122a to the other side 122b. In this way, the movable second electrical contact 112 and the second fixed electrical contact 104 are configured such that the electrical connection between them is configured to be maintained in the event of a short circuit fault that causes the movable single-sided electrical contact 106 to separate from the first fixed electrical contact 102.

[0056] The electrical connection between the first fixed electrical contact 102 and the single-sided movable electrical contact 106 is in parallel with the electrical connection between the second fixed electrical contact 104 and the second movable electrical contact 112.

[0057] The electrical connection between the first fixed electrical contact 102 and the single-sided movable electrical contact 106 facilitates the normal operation of the current switch 100. That is, during normal operation, current conduction primarily occurs through the first fixed electrical contact 102 and the single-sided movable electrical contact 106. In the event of a short circuit, high current is conducted through the electrical connection between the second fixed electrical contact 104 and the second movable electrical contact 112. This means that during normal operation, the contact force between the electrical connection of the second fixed electrical contact 104 and the second movable electrical contact 112 can be lower than the contact force between the first fixed electrical contact 102 and the single-sided movable electrical contact 106. During normal operation, most of the current is conducted through the first fixed electrical contact 102 and the single-sided movable electrical contact 106, while during a short circuit, the current is conducted through both contacts 104 and 112.

[0058] Figure 2 The sequential movement of the movable single-sided contact 106 and the movable second electrical contact 112 is shown.

[0059] At point "A", the circuit is open. When "B" is formed, the single-sided contact 106 closes, current begins to flow, some arcing may occur, and good conductivity is established. When "C" is continuously connected, the movable second electrical contact 112 also closes, and conductivity is relatively high. Because the single-sided contact 106 and the first fixed contact 102 have already established good conductivity, no arcing will occur. When disconnected, the movable second electrical contact 112 will move out of the slot 114, and no arcing will occur because the single-sided contact 106 and the first fixed contact 102 maintain good conductivity. Afterward, the movable single-sided contact 106 will open and disconnect the current. The closing sequence is ABC, and the disconnecting sequence is the reverse, CBA.

[0060] Figure 3AAn exemplary movable second electrical contact 302 and a second fixed electrical contact 304 in the disconnected position according to an embodiment are shown. Here, the movable second electrical contact 302 includes a groove 306, and the second fixed electrical contact is a double-sided contact 304.

[0061] In this embodiment, the movable second electrical contact 302 includes two slots 306, with one slot on each end 310a-b of the movable second electrical contact 302. Each of the two slots 306 is configured to connect with the receiving fixed dual-sided contacts 304a-b of the second fixed electrical contact 304.

[0062] The movable second electrical contact 302 includes two parallel conductors 312a and 312b. The end portions 314a-b of the parallel conductors 312a and 312b include a bent portion 316, which forms a groove 306 between the end portions 314a and 314b.

[0063] Disconnecting the movable second electrical contact 302 and the fixed electrical contact 304 causes the two parallel conductors 312a-b to move linearly away from each other in opposite directions, as indicated by arrow 320. This movement can be achieved in many different ways, such as using a spring or other actuators capable of moving the two parallel conductors 312a-b.

[0064] Figure 3B An exemplary movable second electrical contact 302 and a second fixed electrical contact 304 in the closed position are shown. To close the movable second electrical contact 302 and the second fixed electrical contact 304, two parallel conductors 312a-b move linearly toward each other as indicated by arrow 322. During normal operation, no current needs to be conducted between the movable second electrical contact 302 and the second fixed electrical contact 304, as conduction is handled by the first fixed electrical contact and the single-sided electrical contact. Therefore, during normal operation, the contact force between the movable second electrical contact 302 and the second fixed electrical contact 304 is less than the contact force between the movable single-sided electrical contact and the first fixed electrical contact. During a short circuit, separation typically occurs between the movable single-sided electrical contact and the first fixed electrical contact, a high current flows in the two parallel conductors 312a-b, and the two parallel conductors 312a-b attract each other by the force generated by the current in the two parallel conductors 312a and 312b. This force is the Lorentz force generated during current conduction. The attractive force will further increase the contact force at the contact point between the two parallel conductors 312a-b. The attractive force can be greater than the separation force generated at the contact point under short-circuit conditions.

[0065] The fixed double-sided contact 304a-b can be provided in the form of a knife contact or a blade contact.

[0066] Figure 4A An exemplary movable second electrical contact 402 and a second fixed electrical contact 404 in the disconnected position according to an embodiment are shown. Here, the movable second electrical contact 402 includes a groove 406, and the second fixed electrical contact is a two-sided contact 404, such as a knife contact or blade contact.

[0067] In this embodiment, the movable second electrical contact 402 includes a single groove 406 on one end 408a of the second electrical contact 402. The other end 408b is rotatably connected to the fixed second fixed electrical contact 404.

[0068] The connection between the movable second electrical contact 402 and the second fixed electrical contact 404 is disconnected, and the movable second electrical contact 402 is rotated to cause an angular movement indicated by arrow 420.

[0069] Figure 4B An exemplary movable second electrical contact 402 and a second fixed electrical contact 404 in a closed position according to an embodiment are shown. Here, the movable second electrical contact 402 rotates about its pivot point 422 such that a slot 406 surrounds and contacts the second fixed electrical contact 404. In this closed position, current can flow between the movable second electrical contact 402 and the second fixed electrical contact 404. The movable second electrical contact 402 is connected to a conductor 405 at its end 408b.

[0070] Figure 5 An exemplary movable second electrical contact 502 and a second fixed electrical contact 504 in a closed position according to an embodiment are shown. The movable second electrical contact 502 rotates at its end 408b about its pivot point 422 such that a groove 506 at its end 408a surrounds and contacts the second fixed electrical contact 504. In this closed position, current can flow between the movable second electrical contact 502 and the second fixed electrical contact 504. The length L of the two parallel conductors 512a,b is greater than half of the total length X of the movable second electrical contact 502, such as approximately or greater than 60%, approximately or greater than 75%, or approximately or greater than 90% of the total length X. For longer parallel conductors 512a,b, their ability to bend (as indicated by arrow 520) is improved, especially their ability to bend inward due to the attractive force caused by the parallel current, which increases the contact force during a short circuit.

[0071] In some embodiments, the current switch may include a separate arc contact configured to close the electrical connection prior to a first movable electrical contact. In this case, a third connection step is included before current is generated using the movable single-sided electrical contact.

[0072] The movable single-sided electrical contact and the first fixed contact have a single rest position, which is operated in a manner different from manual operation, enabling the formation, carrying, and disconnection of current under normal circuit conditions (including operating overload conditions). The movable single-sided electrical contact and the first fixed contact can be devices defined as contactors in IEC product standard IEC60947-4-1.

[0073] The movement of the movable single-sided electrical contact and the movable second electrical contact can be controlled in different ways to allow for synchronized movement. In one possible implementation, they are operated by separate actuator systems that allow for independent operation. In other possible implementations, the current switch may include an actuator mechanism configured to synchronize the movement of the movable single-sided electrical contact and the movable second electrical contact.

[0074] Although the invention has been described with reference to specific exemplary embodiments thereof, many different substitutions, modifications, etc., will become apparent to those skilled in the art.

[0075] Furthermore, by studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The fact that certain measures are recited in mutually different dependent claims does not imply that combinations of these measures cannot be advantageously used.

Claims

1. A current switch (100), comprising: First fixed electrical contact (102); The second fixed electrical contact (104) is electrically connected to the first fixed electrical contact; A movable one-sided electrical contact (106) is configured to connect to and disconnect from the first fixed electrical contact on one side to generate and disconnect current in the current switch (100). A movable second electrical contact (112; 302; 402; 502) is configured to move in contact with the second fixed electrical contact after the current is formed and to disconnect from the second fixed electrical contact before the current is disconnected. The electrical connection between the movable second electrical contact and the second fixed electrical contact is via a double-sided contact connected in a slot (114; 306; 406), wherein one of the movable second electrical contact and the second fixed electrical contact includes the double-sided contact and the slot, and the other of the movable second electrical contact and the second fixed electrical contact includes the double-sided contact and the slot.

2. The current switch according to claim 1, wherein the electrical connection between the dual-sided contact and the slot is formed on the facing sides inside the slot.

3. The current switch according to any one of claims 1 to 2, wherein the movable second electrical contact and the second fixed electrical contact are configured such that the electrical connection between the movable second electrical contact and the second fixed electrical contact is configured to be maintained in the event of a short-circuit fault causing the movable single-sided electrical contact to separate from the first fixed electrical contact.

4. The current switch according to any one of the preceding claims, wherein the single-sided movable electrical contact is configured for switching and turning, and the second movable electrical contact is configured for turning.

5. The current switch according to any one of the preceding claims further includes an actuator mechanism configured to synchronize the movement of the movable single-sided electrical contact and the movable second electrical contact.

6. The current switch according to any one of the preceding claims, comprising a separate arc contact configured to close the electrical connection prior to the first movable electrical contact.

7. The current switch according to any one of the preceding claims, wherein the movable second electrical contact includes the groove, and the second fixed electrical contact includes double-sided contacts.

8. The current switch of claim 7, wherein the movable second electrical contact comprises a single slot, and the second electrical contact is movable by angular movement.

9. The current switch according to any one of claims 7 or 8, wherein the movable second electrical contact comprises two slots, one slot at each end of the movable second electrical contact, each of the two slots being configured to connect with a receiving fixed double-sided contact of the second fixed electrical contact.

10. The current switch of claim 9, wherein the movable second electrical contact comprises two parallel conductors that are attracted to each other by a force generated by the current in the two parallel conductors.

11. The current switch according to any one of claims 7 to 10, wherein the movement of the movable second electrical contact is a linear movement.

12. The current switch according to any one of claims 1 to 6, wherein the movable second electrical contact comprises a double-sided contact, and the second fixed electrical contact comprises the groove.

13. The current switch according to any one of the preceding claims, wherein the electrical connection between the first fixed electrical contact and the single-sided movable electrical contact and the electrical connection between the second fixed electrical contact and the second movable electrical contact are in parallel.

14. The current switch according to any one of the preceding claims, wherein the movable first electrical contact and the movable second electrical contact are operated by separate actuator systems to allow independent operation.

15. The current switch according to any one of the preceding claims, wherein the movable single-sided electrical contact and the first fixed contact have a single rest position, and the movable single-sided electrical contact and the first fixed contact are operated in a manner other than manual operation, capable of forming, carrying and disconnecting current under normal circuit conditions including operating overload conditions.

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