MXPA97007781A

MXPA97007781A - Electrical current switch apparatus with arc tornad extinguishing mechanism

Info

Publication number: MXPA97007781A
Application number: MXPA/A/1997/007781A
Authority: MX
Inventors: Klaus Moldovan Peter; Allan Juds Mark
Original assignee: Eaton Corporation
Priority date: 1996-10-09
Filing date: 1997-10-09
Publication date: 1998-04-01

Abstract

The present invention relates to an electrical current switching apparatus, comprising: first and second power terminals, a stationary contact electrically connected to the first power terminal, a movable contact that selectively links the stationary contact to complete an electrical connection between the first and second power terminals, an actuator for moving the movable contact towards and away from engagement with the stationary contact, and an arc extinguishing chamber having a plurality of spacer plates adjacent to the movable and stationary contacts, each plate the plurality of first separating plates having an element having a surface of an electrically conductive, non-ferrous material, and having a magnet that produces a magnetic field around the element, which causes an arc to move around the surface of the element.

Description

ELECTRICAL CURRENT SWITCH APPARATUS WITH TORNÁCO ARC EXTINGUISHING MECHANISM BACKGROUND OF THE INVENTION This invention relates to apparatus for interrupting electrical current, such as direct current electricity (DC); and more particularly to such apparatuses having a mechanism for extinguishing arcs formed between switch contacts during separation. DC electricity is used in a variety of applications such as battery-powered systems, motor gears and DC accessory circuits. Contact devices are typically provided between the DC source and the load to apply and remove electrical energy to the load. The weight, reliability and ability to interrupt and switch high voltage DC are important considerations for developing the contact device. Furthermore, in many applications, relatively large continuous arcing currents must be interrupted when contacts are separated from the contact device, thereby requiring a mechanism to extinguish the arcs. The contact devices and the previous DC switches incorporated one or more arc extinguishing chambers, often referred to as arc slides, as described in U.S. Patent No. 5,416,455, for extinguishing arcs that formed between the contacts of the switch. The arc extinguishing chambers may comprise a series of spaced apart spacing plates of electrically conductive, non-ferrous material, such as copper. In DC switch devices, the permanent magnets on the sides of the series of separator plates establish a magnetic field through the arc extinguishing chamber that directs the arc towards the array of separator plates. The arc then propagates from one divider plate to another in the series and eventually the arc covers a number of free spaces between the separator plates, thereby accumulating sufficient arc voltage such that the arc is extinguished. By design, the arc in the DC switching devices is stabilized at a point on a given divider plate to uniformly accumulate the arc voltage in the series of separator plates. This concentration of energy at one point erodes the metal plate, particularly when the duration of the arc is relatively long, as occurs with inductive loads. SUMMARY OF THE INVENTION A general objective of the present invention is to provide an improved switching device for electric current. Another object is to provide a current-interrupting apparatus with a mechanism that extinguishes arcs that are formed while separating the contacts from the switch. A further objective of the present invention is to reduce arc-induced erosion of the components of the extinguishing mechanism. Still another objective is to provide internal magnetic fields that cause the arc to continuously move around the surfaces of the arc extinguishing mechanism. These and other objects are achieved by an electric current-breaking apparatus that includes a pair of terminals with a stationary contact electrically connected to an energy terminal. A movable contact selectively links the stationary contact to establish an electrical connection between the two terminals. An arc extinguishing chamber is adjacent to the movable and stationary contacts and has a plurality of a first type of spacer plates. Each of these separator plates has an element of an electrically conductive, non-ferrous material, with an opening that maintains a permanent magnet that produces a magnetic field around the element. The interaction of an arc within the chamber with this magnetic field causes the arc to move around the surface of the element. In this way, the arc does not collide in the element in one place for a long time and the element is subjected to reduced erosive forces.

In the preferred embodiment, each of the first type of separator plates has a first member of non-magnetic material with an opening inside which the permanent magnet is received and a second member of a magnetic material that abuts the first member and having a notch within which a portion of the first member is located. A housing of an electrically conductive, non-ferrous material extends at least partially around the first and second members and provides a surface for striking the arch. Another magnet assembly may be provided adjacent to the movable and stationary contacts to establish a magnetic field that causes the DC electric arc to move toward the arc extinguishing chamber.

Figure 1 is a cutaway view of a DC contact device incorporating an arc extinguishing chamber according to the present invention; Figure 2 is an isometric view of a type of spacer plate used in the arc extinguishing chamber; Figure 3 is a cross-sectional view of the extinguishing chamber along line 3-3 of Figure 1; Y Figure 4 is an isometric view of two adjacent separator plates in the extinguishing chamber and outlines the interaction of the magnetic field and the electric current. Detailed Description of the Invention With reference to Figure 1, a sealed, electromagnetic single pole contact device 10 has a plastic housing 12 with first and second energy terminals 14 and 16. The first energy terminal 14 is connected to a first stationary contact 15 attached to the housing and the second power terminal 16 is connected to a second stationary contact 17. Within the contact device 10 is an electromagnetic solenoid 18 which nests in recesses in the interior surfaces of the housing 12. The solenoid 18 it has an annular coil 20, a core 21 and an armature 22 located within the central opening 24. The armature 22 includes an arrow 26 which passes through the core 21 and is connected to a movable contact arm 28, which in the state The closed contact device 10 bridges the two stationary contacts 15 and 17, completing an electrical path between terminals 14 and 16. Ca The end of the movable contact arm 28 has a contact pad 30, which in the closed state abuts on a mating contact pad 32 in the stationary contact 15 or 17 associated with that end of the movable contact arm. A spring assembly 33 biases the movable contact arm 28 and the armature 22, so that the contact device 10 is in a normally open position when the solenoid coil 20 is de-energized, as illustrated in Figure 1.

Each end of the movable contact arm 28 extends towards a separate arc extinguishing chamber. The two arc extinguishing chambers are mirror images of one another, the chamber 34 being visible in figure 1. The arc extinguishing chamber 34 is formed by two stacks 36 and 38 of spaced apart plates, with a clearance 39 between the stacks. Each stack 36 and 38 comprises a row formed by two types of separator plates 40 and 42 that are interlocked in an alternating fashion along the stack. Note that the upper separating plate in the inner end stack 36 is connected by a braided wire to the other energy terminal with respect to the one below which the stack is. Specifically, the upper spacer plate 40a in the end internal stack 36 below the second energy terminal 16 is connected by a braided wire 41 to the first energy terminal 14. Another braided wire 43 connects a separator plate of the fire extinguishing chamber. arc below the first power terminal 14 to the second power terminal 16. The first type of spacer plate 40 is shown in detail in Figure 2 and has an external U-shaped housing 44 with a curved end closed facing the space free central 39 of the arc extinguishing chamber 34, as illustrated in Figure 1. The housing 44 is formed of an electrically conductive, non-ferrous material, such as copper, and extends around a body 46. This body 46 has a non-magnetic inner member 48, of aluminum or plastic for example, which nests in the lower part of the opening of the U-shaped housing 44. This inner member 48 has an opening 50 therethrough, with half the diameter of the opening located within a convex protuberance 52 of the member internal. A permanent magnet 54 is positioned within the opening 50 of the inner member 48 of the body 46 with the poles of the magnet 54 located on the outer surfaces of the inner member which abut in the housing 44. The body 46 also has an outer member 56, of a magnetic material such as iron, which fits against the inner member 48 within the U-shaped housing 44. The outer member 56 has a curved concave notch 58 that mates with the convex protuberance 52 of the inner member 48 so that the outer member extends about half of the permanent magnet 54 and acts as a magnetic flux guide. The orientation of the permanent magnet 54 establishes a separate magnetic field around each of the first type of separator plates. Referring again to Figure 1, the second type of separator plate 42 is a U-shaped part of electrically conductive, non-ferrous material, such as copper. The closed curved end of each second spacer plate 42 faces the central clearance 39 of the arc extinguishing chamber when it is stacked alternatingly with the first spacer plates 40. In both stacks 36 and 38, the first spacer plates 40 are oriented with similar poles of their magnets looking at each other. In a stack, for example, the north pole of the first separator plate 40 faces upwards in FIG. 1. The south pole of the next one of the first separator plates 40 is directed upwards, with a second separator plate 42 placed between them. . The third of the first spacer plates 40 in the stack has a north pole oriented upwards. First subsequent separator plates in the stack continue to be oriented with this alternating magnetic polarization. Because the contact device 10 interrupts direct current, another magnetic field is used to move arcs towards the arc extinguishing chamber 34. Referring to FIG. 3, that magnetic field is produced through the free space 39 of the arc extinguishing chamber 34 by a permanent magnet assembly 60. This assembly comprises a permanent magnet 62 located outside the plastic housing 64 of the arc extinguishing chamber 34 along the height of that chamber. The permanent magnet 62 is magnetically coupled to a pair of U-shaped members, of iron 66 and 68 which abut on the outer surface of this magnet and extend around opposite sides of the arc extinguishing chamber 34. A pair of plastic clamps 70 and 72 hold the spacer plates 40 and 42 in notches of the plastic housing 64 and close that housing. The coupling of the permanent magnet 62 with U-shaped members 66 and 68 establishes a magnetic field through the arc extinguishing chamber 34 (vertically in FIG. 3), which directs electrical arcs formed between the contact pads 30 and 32. towards the separator plates 40 and 42, as will be described. With reference to Figure 1, when the contact device 10 opens, the armature 22 and the attached contact arm 28 move away from the stationary contacts 15 and 17, which causes the contact pads 30 and 32 to separate and move apart. move to the position shown. As the contact pads 30 and 32 separate, an arc 77 can be formed therebetween. The force produced by the interaction of the arc current with the magnetic field of the external permanent magnet 62 (FIG. 3) causes the arc 77 to move from the contact pad 32 outwardly along the stationary contact 17., towards the outer stacking 38 of the arc extinguishing chamber 34. At the same time, the arc 77 moves from the other contact pad 30 at the tip of the movable contact arm 28. By continuing to separate contact pads and 32, the arc propagates along the stationary contact 17 and the upper spacer plate in the external stack 38. The arc then bridges the free spaces between the adjacent spacer plates 40 and 42 in the external stack 38. Eventually, the The arc travels down the outer stack to the point where the other end of the arc travels to the upper separator plate 40a in the internal stack 36. When the arc 77 is joined to the upper plate 40a in the internal stack 36, the arc in the another arc-extinguishing chamber for the stationary contact 15 is shorted and completely extinguished due to the connection of that upper plate 40a to the energy terminal 14 opposed by the braided wire 41. However, the arc 77 is not extinguished in that moment and continues to propagate further down to each subsequent separator plate 40 and 42 in each stack. This action forms a separate sub-arc in the clearance between adjacent spacer plates 40 and 42. Eventually, the arc 77 encompasses a sufficient number of clearances between the spacer plates, accumulating a considerable arc voltage and extinguishing the arc. As the arc moves toward the arc extinguishing chamber 34, it also interacts with the individual magnetic fields produced by the permanent magnet 54 in each of the first type of separator plates 40. Specifically, each of these inner magnets 54 produces a field that it extends around its respective first spacer plate 40, as sketched by lines 78 in FIG. 4. The interaction of the arc current with this magnetic field around each plate causes the arc 77 to move in circles on the surface of the arc. Separator plate housing 44. In this way, the arc energy is not limited to a point on the housing surface, as was the case in the previous arc chambers, and in this way the erosive effects of the arches striking the plates Separators are reduced in the design of the present. The outer member 56 of each first spacer plate 40 acts as a flow guide. If this member were made of non-magnetic material, such as the inner member 48, the magnetic flux line would travel around the outer edge 79 of the separator plate and strike the adjacent U-shaped member 66 or 68 of the fire extinguishing chamber. arc, as is evident from Figure 3. Because the U-shaped members 66 or 68 are magnetically polarized by the permanent magnet 62 outside the arc-extinguishing chamber housing, they are short with the magnetic flux lines 78 on the outer portion of the first separator plate 40. Thus, the flow lines do not travel around the outer edge of the first separator plate and do not travel to the lower part of the separator plate housing 44 in Figure 4. From this Thus, an arc in that outer portion of the lower surface will not find a magnetic field and will not move around the lower surface of the housing 44. However, making the outer member 56 of magnetic material, such as iron, the outer member guides the magnetic flux through the portion of the first separator plate adjacent the outer edge 79. After passing through the outer member 56, these flow lines emerge from the bottom of housing 44 and are bent through the air to the middle section of the lower surface of the housing. In this way, a magnetic field is established through the upper and lower complete surfaces of each first separator plate, so that it does not matter where an arc strikes those surfaces, as the arc will interact with the magnetic field, causing arc movement around of the accommodation surface.

Claims

1. An electrical current switching apparatus, comprising: first and second power terminals; a stationary contact electrically connected to the first power terminal; a movable contact that selectively links the stationary contact to complete an electrical connection between the first and second power terminals; an actuator for moving the movable contact towards and out of engagement with the stationary contact; and an arc extinguishing chamber having a plurality of spacer plates adjacent to the movable and stationary contacts, each plate of the plurality of first spacer plates having an element having a surface of an electrically conductive, non-ferrous material, and having an magnet that produces a magnetic field around the element, which causes an arc to move around the surface of the element. The electric current-breaking apparatus, as defined in claim 1, wherein each plate of the plurality of first separator plates comprises: a member of non-magnetic material with an aperture within which the magnet is received; and wherein the element is a housing formed of an electrically conductive, non-ferrous material, which extends at least partially around the member. 3. The electric current switching apparatus, as defined in claim 1, wherein a plate of the plurality of first separator plates is electrically connected to the second terminal. The electric current-breaking apparatus, as defined in claim 1, wherein each plate of the plurality of first separator plates comprises: a first member of non-magnetic material with an aperture within which the magnet is received; a second member of a magnetic material that meets the first member; and wherein the element is a housing formed of an electrically conductive, non-ferrous material, at least partially extending around the first and second members. 5. The electric power switching apparatus, as defined in claim 4, wherein the first member has a curved edge; and the housing is U-shaped, with a curved inner surface against which the curved edge meets. 6. The electric current switching apparatus, as defined in claim 4, wherein the second member has a notch within which a portion of the magnet is located. 7. The electric current switching apparatus, as defined in claim 1, further comprising a plurality of second interlacing spacer plates with the plurality of first spacer plates. The electric current-breaking apparatus, as defined in claim 7, wherein each plate of the plurality of second separator plates has a U-shape. 9. The electric current-breaking apparatus, as defined in claim 1, further comprising a magnet assembly adjacent to both the stationary contact and the movable contact and establishing a magnetic field that causes an electric arc to move toward the arc extinguishing chamber. 10. The electric current switching apparatus, as defined in claim 1, wherein the magnet of each separator plate is a permanent magnet. 11. An electrical current switching apparatus, comprising: a stationary contact; a movable contact that selectively links the stationary contact to complete an electrical circuit; an actuator for moving the movable contact towards and out of engagement with the stationary contact; an arc extinguishing chamber adjacent to the movable and stationary contacts and including two rows of spacer plates with a gap between them, the spacer plates in each row being spaced from each other, each spacer plate having a first member of non-magnetic material with an opening within which a permanent magnet is received and having a housing formed of an electrically conductive, non-ferrous material that extends at least partially around the first member, the permanent magnet producing a magnetic field around the separator plate which causes an electric arc moves through a surface of the housing; and a magnet assembly adjacent to the stationary contact and movable contact to establish a magnetic field that causes an electric arc to move toward the arc extinguishing chamber. The electric current-breaking apparatus, as defined in claim 11, wherein each separator plate further comprises a second member of a magnetic material that abuts the first member, and having a notch within which a portion of the member is located. permanent magnet, and where the accommodation extends over part of the second member. 13. The electric current switching apparatus, as defined in claim 11, wherein the first member has a curved edge facing the free space; and the housing is U-shaped with a curved inner surface against which the curved edge meets. 14. An electrical current switching apparatus, comprising: a stationary contact; a movable contact that selectively links the stationary contact to complete an electrical circuit; an actuator for moving the movable contact towards and out of engagement with the stationary contact; an arc extinguishing chamber adjacent to the movable and stationary contacts and including two rows of separator plates with a gap between them, the separator plates in each row being separated from each other, each row formed by a group of a first type of plates interleaved separators with a group of a second type of separator plates, wherein the first type of separator plates has a first member of non-magnetic material with an opening inside which a permanent magnet is received and has a housing formed of an electrically conductive material , non-ferrous, extending at least partially around the first member, the permanent magnet producing a magnetic field around the first member that causes an electric arc to move around the housing; and a magnet assembly adjacent to the stationary contact and movable contact to establish a magnetic field that causes an electric arc to move toward the arc extinguishing chamber. 15. The electrical power switching apparatus, as defined in claim 14, wherein each first type of separator plate further comprises a second member of magnetic material that abuts the first member and having a notch within which a portion is located. of the permanent magnet, and where the housing extends over part of the second member. 16. The electric power switching apparatus, as defined in claim 14, wherein the first member has a curved edge facing the free space; and the housing is U-shaped, with a curved inner surface against which the curved edge meets. 17. The electric power switching apparatus, as defined in claim 14, wherein each second type of separator plate has a U-shape with a curved end facing the free space.