WO2003077372A1

WO2003077372A1 - Electrical sliding contact arrangement

Info

Publication number: WO2003077372A1
Application number: PCT/IB2002/005814
Authority: WO
Original assignee: Muller, Ottmar
Priority date: 2001-12-21
Filing date: 2002-12-23
Publication date: 2003-09-18
Also published as: AU2002361464A1; BE1014553A3

Abstract

In a contact arrangement for sliding and plug contacts in electrical devices and systems, in particular in electrical power engineering, and in open-loop and closed-loop control negineering, the contact element (4) of the contact arrangement being designed in the form of a screw-shaped helical spring (5) made from highlyy electrically conductive and springy material, which is fitted in a contact slot (3) arranged in one of two sections of current path (1,2) which can move relative to one another and which form the sliding or plug contacts, the contact slot has (3) has a form, by means of which, in the course of the two sections of current path (1,2) making contact, the turns (6) of the spring (5) can be brought into a position in which it is further deformed elliptically due to the compression resulting from the action of making contact and has a larger and a smaller spring constant, of which the larger spring constant is associated with the larger axis (14), which takes up a canted position with respect to its winding axis (15) during the compression of the spring (5), and the smaller spring constant is associated with the smaller axis (16) of each coil (6) of the spring (5).

Description

ELECTRICAL SLIDING CONTACT ARRANGEMENT

The invention relates to a contact arrangement for sliding and plug contacts in electrical devices and systems, in particular in electrical power engineering, and in open-loop and closed-loop control engineering, the contact element of the contact arrangement being designed in the form of a screw-shaped helical spring made from highly electrically conductive and springy material, which is fitted in a contact slot arranged in one of two sections of current path which can move relative to one another and which form the sliding or plug contacts.

With regard to the arrangement of a contact between two sections of current path which can move relative to one another and which form the sliding or plug contacts, a contact arrangement of this kind is essentially described, for example, in DD 237 558 Al. Here, the contact is in the form of a screw-shaped helical spring made from highly electrically conductive and springy material, which, in the fitted position, is deformed perpendicular to its winding axis in such a way that the sections of each coil of the spring that lie between the contact points are canted differently with respect to the winding axis.

Screw-shaped helical springs, the turns of which are canted with respect to the winding axis of the spring, and by means of which essentially a releasable connection of components arranged concentrically to one another can be achieved while simultaneously guaranteeing electromagnetic shielding and electrical conductivity, are also known according to the spring mechanism of US-PS 5,411,348. Here, the spring is arranged in a slot in one of the components arranged concentrically to one another, and, after engaging in a further slot in the second of the components arranged concentrically to one another, in combination prevents unintentional separation of these components - see also the sealing arrangement according to US-PS 5,474,309. With this spring mechanism and the sealing arrangement, it is disadvantageous that, although they take into account the electromagnetic shielding and the electrical conductivity, they are not, however, suitable for transmitting the continuous currents of up to 4000 A and short circuit currents of up to 100 kA to be controlled by devices and systems in electrical power engineering. Particularly inherent with these solutions, and also with that according to DD 237558 Al, is the disadvantage that the manufacture of the screw-shaped helical springs, the turns of which are canted with respect to the winding axis, is very expensive, as the required spring characteristics can only be achieved with the material used - Cu alloys - by additional heat treatments so that universal use of these springs is limited.

The invention is based on the object of creating a contact arrangement in accordance with the pre-characterising clause of claim 1, by means of which not only a greater range of contact forces is taken into account while significantly reducing the manufacturing costs but also the transmission of continuous currents at least of up to 4000 A and short circuit currents at least of up to 100 kA is controlled.

According to the invention, this is achieved by the contact slot having a form, by means of which, in the course of the two sections of current path, which can move relative to one another, making contact, the turns of the spring can be brought into a position in which it is further deformed elliptically due to the compression resulting from the action of making contact and has a larger and a smaller spring constant, of which the larger spring constant is associated with the larger axis of each turn of the spring, which takes up a canted position with respect to its winding axis during the compression of the spring. These two spring constants, which are achieved by the highly elliptical deformation of the turns of the spring, make a significant contribution to it being possible to considerably increase the range of the contact forces compared with the spring constants, which a conventional, slant-wound, screw-shaped helical spring has in a symmetrical arrangement.

At the same time, however, along with the increase in the range of the contact forces as a result of the invention, there is also a significant influence with regard to the costs by the deformation of the turns of the screw-shaped helical spring, which is made from highly electrically conductive and springy material, being transferred from the industrial manufacturing area, and thus out of the manufacturing costs, to the particular application, i.e. to the electrical device or power engineering system.

This is achieved by a special shaping of the contact slot in the contact arrangement, which forces the turns of the spring to take up the necessary position due to the action of making contact. This means that identically shaped, screw-shaped helical springs can be pressed into the contact slot, regardless of whether the turns have a basically circular or elliptical shape.

According to a preferred design of the contact slot, this has a constriction in its insertion area, which extends in a conical fashion inside the contact slot and in which two side walls, which run parallel to one another and border the contact slot, adjoin this constriction in the form of the conically shaped extension, the second side wall of these two side walls, which lies in the direction of movement of the moving or sliding section of current path when the sections of current path make contact, being shorter than the first side wall, which is opposite and is joined at its lower end to a base, which runs horizontally and which is joined to the lower end of the shorter of the two side walls that run parallel to one another by means of a base running upwards at an angle.

According to a further characteristic of the invention, due to their deformation within the contact slot, the turns of the spring are conductively connected to the section of current path in whose contact slot the spring is arranged via three roughly opposite contact points, it being possible, due to the compression of the turns of the spring, for a different contact force, which can be adapted to suit the different currents, to be exerted by the spring, which force is less at the three roughly opposite contact points than the contact force, which acts via the contact point between the turns of the spring and the section of current path, by means of which the compression of the turns of the spring takes place. At the same time, when simultaneously taking into account the current distribution, whereby the same current flows via the one contact point as via the three roughly opposite contact points together, the contact force acting in the one contact point is essentially equal to the sum of the contact forces acting at the three roughly opposite contact points. By the contact slot preferably being arranged in the fixed section of current path of the two sections of current path which can move relative to one another, which does not rule out the possibility of also making an arrangement in the moving section of current path, if the fixed section of current path is, for example, the fixed switch contact of a vacuum switch, this simultaneously results in a significant portion of the heat from the moving switch contact of the vacuum switch being conducted away via the three roughly opposite contact points of the turns of the spring to the fixed switch contact of the vacuum switch, which leads to the load on the moving switch contact being reduced so that the preferably silver-plated contact points of the surface of the turns of the spring, the contact slot and the moving switch contact do not suffer any damage due to the high temperatures.

According to a further feature of the invention, the deformation of the turns of the spring in the contact slot takes place in such a way that the roughly opposite contact points of the turns of the spring are arranged offset with respect to one another as a result of their axis, which, due to compression, takes up a canted position with respect to the winding axis of the spring, the offset corresponding to the size of the cant. As this results in a relatively large distance between the contact points, this has an advantageous effect on the dissipation of heat, for example. With this arrangement of the contact points, the lower area of the turns of the spring between the two lower contact points carries almost no current.

Based on the fact that the turns of the spring take up a canted position within the contact slot when they are compressed due to the force acting upon them, and using the contact arrangement according to the invention, in a further embodiment, any necessary contact force, which is required for the respective current transmission, can be realised by the magnitude of the force of the compression of the turns of the spring being determined by the diameter of the turns and/or by the thickness of the wire of the turns of the spring as well as by the material characteristics and by the pitch of the turns.

The effects intended by the invention can be achieved in a wide variety of electrical devices and systems in electrical power engineering. Thus, for example, not only in high-voltage electrical switching devices but also in busbar connections and in the connections of switchgear system components. Also, depending on the magnitude of the operating or short circuit currents to be transmitted, with these, at least two screw- shaped helical springs can be arranged in parallel with the contact slot designed according to the invention associated with each spring.

Based on the fact that the turns of the spring repel one another at large currents, resulting in movement of the feet of the turns of the spring, a further advantage of the contact arrangement according to the invention also consists, however, in the contact points being automatically cleaned so that the contact arrangement does not require any maintenance effort.

The effects intended by the invention are furthermore achieved by the following advantages:

The elliptical shaping of the turns and of the circular wire forming the turns consists in the contact point being formed fixed on the contact part opposite the slot, while, in the slot, the contact points are increased in size due to the larger radii, which is particularly advantageous both for current transmission and particularly for heat transmission.

The enforced deformation of the springs allows a reduction in the pitch of the turns and thus an increase in the number of turns per length of coil, which results simultaneously in a change in the radial and axial contact forces, which leads to a reduction in the contact resistance.

Furthermore, a wider tolerance range can be allowed due to the size of the turns, the turn pitch and the capability to rotate the turns in the slot.

The invention is described in more detail with reference to an exemplary embodiment.

In the associated drawings:

Figure 1 shows the section of a partial view of a contact arrangement of a high- voltage circuit breaker before contact is made, and Figure 2 shows the section of the contact arrangement according to Figure 1 after contact has been made.

The contact arrangement of a high-voltage circuit breaker shown in Figures 1 and 2 is based on two sections of current path 1 , 2 which can move relative to one another, of which the section of current path 1 is the moving switch contact and the section of current path 2 is the fixed switch contact of a high- voltage circuit breaker. In order to transmit high operating and short circuit currents, a contact arrangement is provided between the sections of current path 1, 2, i.e. the switch contacts, which consists essentially of a contact slot 3 arranged in the fixed section of current path 1, in which is arranged a screw-shaped helical spring 5 made from highly electrically conductive and springy material, which serves as a contact element 4. Due to the design of the contact slot 3, the turns 6 of the spring 5, the basic shape of which corresponds to that of a circle, have an elliptical shape once they have been fitted in the contact slot 3 and essentially fill the contact slot 3. At the same time, the contact slot 3 has a constriction 8 in its insertion area 7, which extends in a conical fashion inside the contact slot 3 so that the spring 5 is prevented from jumping out of the contact slot 3 during a disconnection process. Now, in order, in the course of making contact between the two sections of current path 1, 2 which can move relative to one another, to bring the turns 6 of the spring 5 to a position in which they are further elliptically deformed due to the compression resulting from the action of making contact, adjoining the conically shaped extension 9 of the contact slot 3 are two side walls 10, 11, which run parallel to one another and of which the side wall 10 is shorter than the side wall 11. Adjoining the side wall 11 is a base 12, which runs horizontally and which is joined to the side wall 10 by means of a base 13 running upwards at an angle.

While the position of the turns 6 of the spring 5 within the contact slot 3 before the sections of current path 1, 2 make contact, i.e. before the closing process, can be seen from Figure 1, the further deformation and position of the turns 6 of the spring 5 within the contact slot 3 after the compression resulting from the action of making contact is shown in Figure 2. At the same time, it can be seen from Figure 2 that the larger axis 14 of the turns 6 is canted with respect to its winding axis 15. A larger spring constant is associated with this axis 14 compared with the smaller axis 16 of the turns 6. However, Figure 2 also shows that the turns 6 of the spring 5 are conductively connected to the fixed section of current path 2 via three roughly opposite contact points 17, 18, 19, which are arranged offset from one another, and are conductively connected to the moving section of current path 1 via the contact point 20, so that the same current flows via the contact point 20 as via the contact points 17, 18, 19 together. In order to ensure this distribution of current, according to the basic rules of contact resistance, the contact force in the contact point 20 is greater than that in the contact points 17, 18, 19, the magnitude of the contact forces also being affected by the turns 6 of the spring 5 turning over due to the compression resulting from the action of making contact, the magnitude of the compression force being determined by the diameter of the turns and their wire thickness.

It is noted that the present invention is not limited to electrical power engineering applications of high current and/or high voltage, but also relates to open-loop and closed-loop control engineering applications which may apply low current and/or low voltage.

Claims

1. A contact arrangement for sliding and plug contacts in electrical devices and systems, in particular in electrical power engineering, and in open-loop and closed-loop control engineering, the contact element (4) of the contact arrangement being designed in the form of a screw-shaped helical spring (5) made from highly electrically conductive and springy material, which is fitted in a contact slot (3) arranged in one of two sections of current path (1, 2) which can move relative to one another and which form the sliding or plug contacts, characterized in that the contact slot (3) has a form, by means of which, in the course of the two sections of current path (1, 2), which can move relative to one another, making contact, the turns (6) of the spring (5) can be brought into a position in which it is further deformed elliptically due to the compression resulting from the action of making contact and has a larger and a smaller spring constant, of which the larger spring constant is associated with the larger axis

(14), which takes up a canted position with respect to its winding axis (15) during the compression of the spring (5), and the smaller spring constant is associated with the smaller axis (16) of each coil (6) of the spring (5).

2. The contact arrangement as claimed in claim 1, characterized in that the turns (6) of the spring (5) have the basic shape of a circle before they are pressed into the contact slot (3) and take an elliptical shape once they have been pressed into the contact slot (3).

3. The contact arrangement as claimed in claim 1, characterized in that the turns (6) of the spring (5) have an elliptical shape before they are pressed into the contact slot (3).

4. The contact arrangement as claimed in claim 1 and 2, characterized in that the contact slot (3) has a constriction (8) in its insertion area (7), which extends in a conical fashion inside the contact slot (3), and in that two side walls (10, 11), which run parallel to one another and border the contact slot (3), adjoin this conically shaped extension (9), the second side wall (10) of these two side walls, which lies in the direction of movement of the moving or sliding section of current path (1) when the sections of current path (1, 2) make contact, being shorter than the first side wall (11), which lies opposite and which is joined at its lower end to a base (12), which runs horizontally and which is joined to the lower end of the shorter of the two side walls (10, 11) that run parallel to one another by a base (13) running upwards at an angle and also borders the contact slot (3).

5. The contact arrangement as claimed in claim 4, characterized in that, due to the deformation of the turns (6) of the spring (5) within the contact slot (3), the turns (6) are galvanically connected to the section of current path (1, 2) in whose contact slot (3) the spring (5) is arranged via three roughly opposite contact points (17, 18, 19), it being possible, due to the compression of the turns (6) of the spring (5), for a different contact force, which can be adapted to suit the different currents, to be exerted by the spring (5), which is less at the three roughly opposite contact points (17, 18, 19) than the contact force, which acts via the contact point (20) between the turns (6) of the spring (5) and the section of c rent path (1, 2), by means of which the compression of the turns (6) of the spring (5) takes place.

6. The contact arrangement as claimed in claim 5, characterized in that, when simultaneously taking into account the current distribution, whereby the same current flows via the contact point (20) as via the contact points (17, 18, 19) together, the contact force acting in the contact point (20) is essentially equal to the sum of the contact forces acting in the contact points (17, 18, 19).

7. The contact arrangement as claimed in claim 6, characterized in that the roughly opposite contact points (17, 18, 19) of the turns (6) of the spring (5) are arranged offset with respect to one another as a result of their axis (14), which, due to compression, takes up a canted position with respect to the winding axis (15) of the spring (5), in such a way that the offset corresponds to the size of the cant.

8. The contact arrangement as claimed in claim 7, characterized in that the magnitude of the force of the compression of the turns (6) of the spring (5) can be determined by the diameter of the turns (6) and/or by the thickness of the wire of the turns (6) of the spring (5) as well as by the material characteristics and by the pitch of the turns (6).

9. The contact arrangement as claimed in claim 8, characterized in that the screw- shaped helical springs (5) are designed as closed turns of any shape and are mechanically connected at their ends, preferably by means of welding.

10. The contact arrangement as claimed in claim 9, characterized in that at least two screw-shaped helical springs (5) are arranged in parallel with the contact slot (3) associated with each spring (5).