EP3742464A1

EP3742464A1 - High-current contact system

Info

Publication number: EP3742464A1
Application number: EP19175912.5A
Authority: EP
Inventors: Sebastian Breisch; Arda Tueysuez; Ondrej FRANTISEK
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2019-05-22
Filing date: 2019-05-22
Publication date: 2020-11-25

Abstract

High-current switch 100, 200 comprising: a first contact member 110, 210 having N first contact elements 113, 213; a second contact member 120, 220 having N second contact elements 113, 213, wherein in a closed state of the switch 100, 200, the N first contact elements 113, 213 and the N second contact elements 113, 213 are configured to form N contact points 115, 215; the first contact member 110, 210 having M first conductor sections 114, 214 and the second contact member 120, 220 having M second conductor sections 114, 214, wherein in a closed state of the switch 100, 200, the M first conductor sections 114, 214 and the M second conductor sections 114, 214 are configured to form M pairs of adjacent conductor sections 116, 216 in which the current is conducted in the same direction.

Description

FIELD OF INVENTION

The present invention relates to a high-current contact system and to the use of such a high-current contact system in a switch in a switchgear system.

BACKGROUND OF THE INVENTION

Contact systems for switches for high-currents are well known in the prior art. Such high-current switches are typically used to close and open electric circuits in which several 100 A are conducted and are used in particular for switchgear systems of industrial plants. For example, document EP 0 788 126 A1 discloses a switch for high-currents comprising a fixed contact member and a moving contact member. When switching electric circuits with high current intensity, it is important to take into account that repulsion forces occur between the contact points, which increase by the square of the current intensity. These electromagnetic repulsion forces occur due to the current concentration in the contact points and are also known as so called separation forces or blow-off forces. For quantification several theories have been developed, experimentally been validated and further improved by various persons. One of the first researchers was Ragnar Holm after whom one formula description of the separation force, the Holm force, was named.
The Holm force may lead to a contact separation and arc formation between the contact points, which in turn may weld the contact points together or may lead to a removal of the material at the area of the contact points. At lower current intensities, these forces are typically compensated by spring arrangements or the like, which press the contact points against each other. With medium or higher currents, these forces can no longer be compensated by spring arrangements alone and further measures are necessary to avoid such a contact separation. In this respect, mechanical blocking means are typically used to prevent such a contact separation of the contact points. However, this leads to bulky and/or complicated designs. Moreover, a mechanical blocking may not be possible in monostable devices that are required to have one position at rest. Therefore, it is found that a further need exists to provide a switch for high-currents comprising an alternative solution for avoiding contact separation.

SUMMARY OF THE INVENTION

In the view of the above, it is an object of the present invention to provide a high-current contact system for a switch with which contact separation can be avoided. In addition, it is an object of the present invention to provide a high-current contact system for a switch having a structure avoiding contact separation, but without the mandatory need to use mechanical blocking means.
These and other objects, which become apparent upon reading the following description, are solved by the subject-matter of the independent claims. The dependent claims refer to preferred embodiments of the invention.
According to the invention, a high-current contact system is provided comprising: a first contact member having N first contact elements; a second contact member having N second contact elements, wherein in a closed state of the contact system, the N first contact elements and the N second contact elements are configured to form N contact points; the first contact member having M first conductor sections and the second contact member having M second conductor sections, wherein in a closed state of the contact system, the M first conductor sections and the M second conductor sections are configured to form M pairs of adjacent (overlapping) conductor sections in which the current is conducted in the same direction.
In other words, it is proposed that in a closed state of the contact system, M pairs of adjacent (overlapping) conductor sections are provided in which the current is conducted in the same direction. By means of such an arrangement, due to the magnetic flux, a force occurs which presses the M conductor sections together. This force is also known as so called Lorentz force, which can be used in the present case to compensate the Holm force. The occurring Lorentz force is dependent from the currents conducted in the M conductor sections, the angle between the respective M conductor sections, the distance between the M conductor sections and the length of the M pairs of adjacent overlapping conductor sections.

HIGH-CURRENT CONTACT SYSTEM

FIELD OF INVENTION

BACKGROUND OF THE INVENTION

SUMMARY OF THE INVENTION

In the view of the above, it is an object of the present invention to provide a high-current contact system for a switch with which contact separation can be avoided. In addition, it is an object of the present invention to provide a high-current contact system for a switch having a structure avoiding contact separation, but without the mandatory need to use mechanical blocking means.
These and other objects, which become apparent upon reading the following description, are solved by the subject-matter of the independent claims. The dependent claims refer to preferred embodiments of the invention.
According to the invention, a high-current contact system is provided comprising: a first contact member having N first contact elements; a second contact member having N second contact elements, wherein in a closed state of the contact system, the N first contact elements and the N second contact elements are configured to form N contact points; the first contact member having M first conductor sections and the second contact member having M second conductor sections, wherein in a closed state of the contact system, the M first conductor sections and the M second conductor sections are configured to form M pairs of adjacent (overlapping) conductor sections in which the current is conducted in the same direction.
In other words, it is proposed that in a closed state of the contact system, M pairs of adjacent (overlapping) conductor sections are provided in which the current is conducted in the same direction. By means of such an arrangement, due to the magnetic flux, a force occurs which presses the M conductor sections together. This force is also known as so called Lorentz force, which can be used in the present case to compensate the Holm force. The occurring Lorentz force is dependent from the currents conducted in the M conductor sections, the angle between the respective M conductor sections, the distance between the M conductor sections and the length of the M pairs of adjacent overlapping conductor sections.
The term contact member is to be understood broadly and includes any member that is suitable for opening or closing a circuit with a corresponding contact element. The term contact element is also broadly understood and includes any element arranged to provide a contact point, i.e. a current path between the first contact member and the second contact member, with a corresponding contact element in a closed state of the switch. The contact elements can be provided by a corresponding geometry of the contact member, for example a protrusion, or by a structure arranged onto the contact member, such as a contact pad or the like. Notably, in this respect it is also possible that two or more contact points are provided at one corresponding geometry of a contact member. Adjacent conductor sections are conductor sections that are designed to provide a Lorentz force due to the currents flowing in the same direction. Notably, the Lorentz force is also dependent on the angle between the M conductor sections forming the M pairs of adjacent conductor sections, wherein the Lorentz force is maximum, if the conductor sections are parallel. Thus, in order to maximize the Lorentz force, it is preferred that in a closed state of the switch, the M pairs of adjacent conductor sections are arranged in parallel forming M pairs of adjacent and parallel conductor sections. However, the present invention is not limited to a strict parallel arrangement of the M pairs of adjacent conductor sections, but includes also non-parallel arrangements of the M pairs of adjacent conductor sections. It is only important that a Lorentz force can be provided which can either be used to fully compensate the Holm force or at least to partially compensate the Holm force in such a way that complex mechanical blocking means are at least no longer absolutely necessary.
It is preferred that N is greater than or equal to 2, wherein N is preferably 3. This makes it possible to divide the (total) current between several contact points and thus to reduce the Holm force at one contact point accordingly. In this context, it should be noted that the Holm force increases or decreases with the square of the current, i.e. by dividing the (total) current, the maximum Holm force occurring at one contact point could be significantly reduced. In the particularly preferred embodiment, one contact member comprises three contact elements, so that three contact points are provided, through which about one third of the (total) current is conducted.
It is further preferred that M is greater than or equal to 2, wherein M is preferably 3, and wherein M is preferably equal to N. This arrangement makes it possible to divide the (total) Lorentz force so that the corresponding conductor sections do not have to be designed for the maximum (total) Lorentz force. It is in particular preferred that each of the M pairs of adjacent conductor sections is assigned to a corresponding N contact point. In this preferred design, the "reduced" Holm forces can thus be compensated or reduced by respectively assigned and also "reduced" Lorentz forces.
Preferably, in a closed state, the N contact points and the M pairs of adjacent conductor sections are evenly distributed around a longitudinal axis of the contact members. By evenly distributing the N contact points and the M pairs of adjacent conductor sections around a longitudinal axis of the contact member, the occurring forces can also be evenly distributed on the contact member. It is further preferred that the N contact points and the M pairs of adjacent conductor sections are evenly distributed in a plane around the longitudinal axis of the contact member.
It is preferred that the N contact elements and the M conductor sections are provided on arm elements, which are evenly distributed around a longitudinal axis of the contact members. An arm element is an area that has a certain amount of elasticity, for example provided by a "free cut", so that it can be bent elastically relative to the longitudinal axis of the contact member. The elasticity is preferably provided in such a way that the arm element can absorb the bending moments caused by the forces acting on it.
Preferably, the length of the M pairs of adjacent conductor sections is selected such that the attraction force due to the Lorentz force is greater or equal to the repulsion force of the N contact points due to the Holm force. In this preferred embodiment, the length of the M pairs of adjacent conductor sections is selected in such a way that the Lorentz forces completely compensate for the occurring Holm forces and, if needed, to provide an additional contact force to press the N contact elements together. In the latter particularly preferred embodiment, additional spring means and/or mechanical blocking means can therefore in principle be completely omitted. However, in practice, the use of such spring means is preferred for providing an initial contact force for the contact members to ensure a low contact resistance, particularly also in case low currents are flowing. In practice, the use of such spring means can be minimized, and mechanical blocking can be completely omitted.
It is further preferred that the first and second contact member are identical. The advantage of identical contact member designs is that both contact members can be produced using a single production process. In addition, if both contact members have the same design, the assembly of a switch according to the invention is simplified to such an extent that no distinction between the contact members has to be made here either.
Preferably, the contact system is configured to conduct nominal currents greater than 100 A, preferably about 4000 A. In this respect, it is further preferred that the total contact area of the N contact points being between 200 mm² and 600 mm², preferably between 300 mm² and 500 mm² and particularly preferably 400 mm².
In a first preferred embodiment of the invention, in a direction along a longitudinal axis of the contact member, the contact member has a circular shape, wherein the N contact elements and the M conductor sections being evenly distributed on the circumference of the circle. In this respect, it is further preferred that the diameter of the circle being between 40 mm and 150 mm, preferably between 60 mm and 130 mm and particularly preferably between 70 mm and 110 mm. The circular design of the contact member and the even arrangement of the N contact elements and M conductor sections on the circumference of the circle provide a comparatively compact and particularly preferred design of such a contact member. In particular, the N contact elements and the M conductor sections can be arranged on elastic arm elements in a particularly advantageous way, as such a design allows corresponding undercuts to be made in a straightforward manner.
In a second preferred embodiment of the invention, in a direction along a longitudinal axis of the contact member, the contact member has a uniform triangular shape, wherein the N contact elements and the M conductor sections being evenly distributed with respect to the circumcircle of the triangle. In this respect, it is further preferred that the circumcircle of the uniform triangle being between 50 mm and 160 mm, preferably between 70 mm and 140 mm and particularly preferably between 80 mm and 120 mm. The triangular shape of the contact member can also provide a comparatively compact structure with the preferred elastic arm elements.
The present invention also relates to the use of a high-current contact system in a switch as explained above in a switchgear system of an industrial plant or a power generation plant, such as a renewable power generation plant.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is described exemplarily with reference to the enclosed figures, in which

Figure 1: is a schematic view of a first preferred embodiment of a contact member according to the present invention;
Figure 2: is a schematic view of a first preferred embodiment of a contact system according to the present invention;
Figure 3: is a schematic top-view of the contact system shown in figure 2;
Figure 4: are schematic views of the contact system shown in figures 2 and 3;
Figure 5: is a schematic view of the first preferred contact member, wherein the occurring Holm and Lorentz forces are indicated by arrows;
Figure 6: is a schematic view of a second preferred embodiment of a switch according to the present invention;
Figure 7: is a schematic top-view of the contact system shown in figure 6; and
Figure 8: is a schematic view of the second preferred contact member, wherein the occurring Holm and Lorentz forces are indicated by arrows.

DETAILED DESCRIPTION OF EMBODIMENTS

Figures 1 to 5 show a first preferred embodiment of a contact system 100 according to the invention comprising two identical contact members 110, 120. A contact member 110, 120 comprises a support section 111, with which the contact member 110, 120 can be connected to a circuit, e.g. in a switchgear system of an industrial plant. The support section 111 is in the preferred embodiment rod-shaped, whereby the longitudinal axis of the contact member 110, 120 and of the contact system 100 also extends along support section 111 (cf. figure 4). As can be seen in figures 1 to 5, the contact member 110, 120, viewed in one direction along the longitudinal axis, has a substantially circular circumference.
As can be seen particularly in figure 1, a contact member 110, 120 comprises three arm elements 112, each of which is perpendicular to the support section 111. On each of the arm elements 112, a contact element 113 is provided at the end of a conductor section 114, i.e. in this preferred embodiment, N and M are equal to 3. In the shown preferred embodiment, the contact elements 113 are provided as contact pads. The contact elements 113 and the conductor sections 114 are arranged at the circumference of the circular circumference seen in a direction of the longitudinal axis.
As shown in figures 2 and 3, the contact members 110, 120 can be brought into contact with each other in such a way that corresponding contact elements 113 form contact points 115, so that a current can be conducted from one contact member 110 to the other contact member 120. To connect the two contact members 110, 120. As can be seen in particular in figure 3, in such an arrangement of the two contact members 110, 120, the conductor sections 114 are arranged adjacent to and parallel to one another at least in partial overlapping areas 116, so that in these overlapping areas 116 the currents are conducted parallel in the same direction when a current is conducted from one contact member 110 to the other contact member 120. The current flow through the contact members 110, 120 is illustrated in figure 3 by the arrows. In this example, the current enters the lower arranged contact member 110, indicated by means of the black arrows, and enters via the contact points 115, the upper arranged contact member 120, wherein in the overlapping areas 116, where the current is conducted in parallel and in the same direction, indicated by means of the shaded arrows, a Lorentz force component can be produced which presses the contact elements 113 against each other and which compensates for the Holm force occurring at the respective contact points 115 or provides a contact force exceeding this. Finally, the current exits the upper arranged contact member 112, indicated by means of the white arrows.
In the left illustration shown in figure 4, the elastic design of the arm elements 112 is shown, in which it is shown that the arm elements 112 can be bent upwards or downwards in order to mechanically absorb the corresponding Lorenz or Holm forces. Moreover, by means of the elastic design of the arm elements 112, also a self-aligning effect is provided, in case of an initial misalignment of the contact members 110, 120, e.g. in case only one current path through one pair of contact elements 113 is provided. This is because in case only one pair of contact elements 113 is contacted (as shown in figure 4), the separation force at this contact point is such high that the contact members 110, 120 will be separated, but by means of the elastic design of the arm elements 112, during the separation, they will align to an aligned arrangement, i.e. to an arrangement where all of the contact elements 113 are contacted. In the illustration on the right shown in figure 4, the current enters the upper arranged contact member 120, passes its arm elements 112 and enters the lower arranged contact member 110, also passing its arm elements 112, wherein the shaded arrows indicate how the current is at least partially led parallel and in the same direction.
Figure 5 shows examples of the Lorenz and Holm forces that might occur, wherein in figure 5 only one of the two contact members 110, 120 is shown for reasons of clarity. In this example, a nominal current of 4000 A and a short-circuit current of 100 kA were passed through contact system 100. In this example, the arm elements 112 have a cross-section of 15 × 10 mm and the contact areas 115 each have 150 mm². In this example, a Holm force of 1333 N and an opposing Lorentz force of 4363 N occur at each of the arm elements 112.
Figures 6 to 8 show a second preferred embodiment of a switch 200 according to the invention, which also comprises two identical contact members 210, 220. The second preferred embodiment of the switch 200 differs from the first preferred embodiment of the switch 100 particularly in that the contact elements 210, 220 are triangularly shaped in one direction along a longitudinal axis of the contact members 210, 220, which in turn corresponds to the extent of a support section 211.
The contact members 210, 220 each have three contact elements 213, which form contact points 215 in a connected state of the two contact members 210, 220, and conductor sections 214, which can form overlapping areas 216, in which the current is conducted in parallel and in the same direction, so that a corresponding Lorenz force can be generated in each of these overlapping areas 216. The contact elements 213 and the conductor sections 214 are in turn provided on arm elements 212. However, in this embodiment not on a circumference, but on the sides of a regular triangle. In this example, the current enters the lower arranged contact member 210, indicated by means of the black arrows, passes its arm elements 214 and enters via the contact points 215, the upper arranged contact member 220, also passing its arm elements 213, wherein in the overlapping areas 216, where the current is conducted in parallel and in the same direction, indicated by means of the shaded arrows, a Lorentz force component can be produced which presses the contact elements 213 against each other and which compensates for the Holm force occurring at the respective contact points 215 or provides a contact force exceeding this. Finally, the current exits the upper arranged contact member 212, indicated by means of the white arrows.
Figure 8 shows examples of the Lorenz and Holm forces that might occur in this second preferred embodiment, wherein in figure 8 only one of the two contact members 210, 220 is shown for reasons of clarity. In this example, a nominal current of 4000 A and a short-circuit current of 100 kA were passed through switch 200. The arm elements 212 have a cross-section of 15 × 10 mm and the contact areas 215 each have 150 mm². Based on this example, a Holm force of 1304 N and an opposing Lorentz force of 1957 N occur at each of the arm elements 212.
The present invention has been described in conjunction with the preferred embodiments as examples as well. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed invention, from the studies of the drawings, this disclosure and the claims. In the claims as well as in the description the word "comprising" does not exclude other elements or steps and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

REFERENCE SIGNS

100: contact system (first preferred embodiment)
110: first contact member
111: support section
112: arm element
113: contact element (N contact elements)
114: conductor section (M conductor sections)
115: contact point
116: overlapping area (M adjacent conductor sections)
120: second contact member
200: contact system (second preferred embodiment)
210: first contact member
211: support section
212: arm element
213: contact element (N contact elements)
214: conductor section (M conductor sections)
215: contact point
216: overlapping area (M adjacent conductor sections)
220: second contact member

Claims

High-current contact system (100, 200) comprising:
a first contact member (110, 210) having N first contact elements (113, 213);

a second contact member (120, 220) having N second contact elements (113, 213), wherein in a closed state of the switch (100, 200), the N first contact elements (113, 213) and the N second contact elements (113, 213) are configured to form N contact points (115, 215);

the first contact member (110, 210) having M first conductor sections (114, 214) and the second contact member (120, 220) having M second conductor sections (114, 214), wherein in a closed state of the switch (100, 200), the M first conductor sections (114, 214) and the M second conductor sections (114, 214) are configured to form M pairs of adjacent conductor sections (116, 216) in which the current is conducted in the same direction.
High-current contact system (100, 200) according to claim 1, wherein N is greater than or equal to 2, wherein N is preferably 3.
High-current contact system (100, 200) according to claim 1 or claim 2, wherein M is greater than or equal to 2, wherein M is preferably 3, and wherein M is preferably equal to N.
High-current contact system (100, 200) according to any one of the preceding claims, wherein in a closed state of the switch (100, 200), the M first conductor sections (114, 214) and the M second conductor sections (114, 214) are arranged in parallel forming the M pairs of adjacent conductor sections (116, 216).
High-current contact system (100, 200) according to any one of the preceding claims, wherein in a closed state of the switch (100, 200), the N contact points (115, 215) and the M pairs of adjacent conductor sections (116, 216), are evenly distributed around a longitudinal axis of the contact members (110, 120, 210, 220).
High-current contact system (100, 200) according to any one of the preceding claims, wherein the N contact elements (113, 213) and the M conductor sections (114, 214) are provided on arm elements (112, 212) which are evenly distributed around a longitudinal axis of the contact members (110, 120, 210, 220).
High-current contact system (100, 200) according to any one of the preceding claims, wherein the length of the M pairs of adjacent conductor sections (116, 216) is selected such that the attraction force due to the Lorentz force is greater or equal to the repulsion force of the N contact points (115, 215) due to the Holm force.
High-current contact system (100, 200) according to any one of the preceding claims, wherein the first contact member (110, 210) and second contact member (120, 220) are identical.
High-current contact system (100, 200) according to any one of the preceding claims, wherein the switch (100, 200) is configured to switch nominal currents greater than 100 A, preferably about 4000 A.
High-current contact system (100, 200) according to any one of the preceding claims, wherein the total contact area of the N contact points (115, 215) being between 200 mm² and 600 mm², preferably between 300 mm² and 500 mm² and particularly preferably 400 mm².
High-current contact system (100) according to any one of the preceding claims, wherein in a direction along a longitudinal axis of the contact member (110, 120), the contact member (110, 120) has a circular shape, wherein the N contact elements (113) and the M conductor sections (114) being evenly distributed on the circumference of the circle.
High-current contact system (100) according to claim 11, wherein the diameter of the circle being between 40 mm and 150 mm, preferably between 60 mm and 130 mm and particularly preferably between 70 mm and 110 mm.
High-current contact system (200) according to any one of the claims 1 to 10, wherein in a direction along a longitudinal axis of the contact member (210, 220), the contact member (210, 220) has a uniform triangular shape, wherein the N contact elements (213) and the M conductor sections (214) being evenly distributed on the circumcircle of the triangle.
High-current s contact system (200) according to claim 13, wherein the diameter of the circumcircle of the uniform triangle being between 50 mm and 160 mm, preferably between 70 mm and 140 mm and particularly preferably between 80 mm and 120 mm.
Use of a high-current contact system (100, 200) according to any one of the preceding claims in a switchgear system.