DE1236053B - Electrical switch, in particular vacuum switch - Google Patents

Description

GERMAN WTW ^ PATENT OFFICE

EDITORIAL

German class: 21 c - 35/09

Number: 1236 053

File number: G 43045 VIII d / 21 c

J 236 053 filing date: March 11, 1965

Opened on: March 9, 1967

The invention relates to an electrical switch, in particular a vacuum switch, with two Contact pieces, at least one of which includes a tubular part with two end faces, of where the end face facing the other contact piece serves as the arc starting point running surface, and with an arrangement for forcing the stream flowing through the tubular member into a path, which has a component extending in the circumferential direction of the tubular part.

To make the arc travel along the electrodes of the switch without the length of the same To enlarge by blowing away, it is known from German Patent 312 134, annular Use contact pieces with leads that are coaxial with the contact pieces and are traversed by the current to be interrupted. On a similar one The principle is based on the mode of operation of a switch that is described in German patent 553 639 is. This switch contains two pairs of pin-shaped contact pieces, each of which is one contact piece each pair arranged within a spirally wound, current-carrying, conical spring and is attached to this in such a way that the electrodynamic Forces act on the contact piece in question in the direction in which the switch-off movement of the contact piece takes place. The innermost turn of the spring is with the contact piece and with its outermost turn on the inside of the open end of a cup-shaped, the spring enclosing Arranged component, which also serves as a power supply. The one flowing through the spring Electricity creates an electromagnetic field that creates an arc when it is switched off can rotate around the rod-shaped contact pieces.

Finally, from the German patent specification 695 475, an electrical switch of the type mentioned at the beginning Kind of known, one of which is a contact piece in the shape of an annular disk and the other contact piece is cup-shaped. The cup-shaped contact piece, the front side of which acts as a contact surface at the open end is formed, is a pot magnet coaxially opposite, the one rod-shaped, from a magnet coil surrounding central pole and a hollow cylindrical outer pole, between which iahe their free ends, the annular disc-shaped contact piece is arranged. The pot magnet delivers ; in a magnetic field, the one between the cup-shaped contact piece and the washer-shaped

Electrical switch, in particular
Vacuum switch

Applicant:

General Electric Company,
Schenectady, NY (V. St. A.)

Representative:

Dr.-Ing. E. Sommerfeld and Dr. D. v. Bezold,
Patent Attorneys, Munich 23, Dunantstr. 6th

Named as inventor:

Allan Nunns Greenwood, Media, Pa. (V. St A.)
Claimed priority:

V. St. v. America March 16, 1964 (351937)

Contact piece can rotate burning arc around the common axis of the contact pieces.

The invention is based on an electrical switch with two contact pieces, of which at least one as in the last mentioned known switch has a tubular part with two end faces contains, of which the end face facing the other contact piece is used as an arc starting point running surface serves, and which further comprises an arrangement that controls the stream flowing through the tubular member Forces on a path that has a component extending in the circumferential direction of the tubular part.

In the switch according to the invention, a slotted contact piece is also used, as shown at is known from the German Auslegeschrift 1 088 132.

The object of the invention is to provide a switch of the type mentioned, which is characterized by a simple, robust structure and can be easily manufactured. In particular should a circular movement of the arc starting points without complicated shaped slots in the contact pieces and without additional magnetic coils or the like.

The objects of the invention are in an electrical switch, in particular vacuum switch, the achieved in that the tubular part has a slot between runs in the circumferential direction of the tubular part mutually offset points of the end faces,

709 518/367

and that the rear end face facing away from the sheet running surface is provided with a power supply which allows the major part of the flow to enter at a region of the rear end face which can be next to the intersection of the slot with the rear end face and on the other side of the Like all points of the sheet running surface, the slot is located in the axial direction with the entry area cursing.

Preferably, the tubular part is opposite to the contact-making surface on its surface Area due to a number of circumferentially spaced supports made of a material lower Conductivity supported. In the vicinity of the slot in the tubular part there is preferably a support element made of a metal of relatively high conductivity.

According to a further embodiment of the invention, an arrangement is provided which causes all arcs to arise between the contact pieces at locations which are at least 90 ° along the circumference of the tubular part from the current entry area. In particular, an arrangement for producing a contact between the contact pieces is arranged on the side of the slot opposite the entry region and close to it.

According to a further embodiment of the invention, a support element is lower in the tubular part Conductivity provided a slot aligned with this.

The invention is described below on the basis of exemplary embodiments in conjunction with the drawing explained in more detail. It shows

F i g. 1 is a cross-sectional view of a vacuum switch according to a first embodiment of FIG Invention, the contact pieces of the switch are shown in the closed state,

FIG. 2 is an enlarged perspective view of the contact piece arrangement of the FIG. 1 shown Switch; the contacts are shown separated, but their spacing is exaggerated drawn large to make their construction clearly visible;

F i g. 3 shows a sectional view of part of the FIG. 2 contact piece arrangement shown,

F i g. FIG. 4 is a sectional view of another part of the FIG. 2 contact piece arrangement shown,

F i g. Figure 5 is a partially sectioned side view of a somewhat modified contact piece construction and

F i g. 6 shows a further modified contact piece construction.

The switch shown in FIG. 1 contains a largely evacuated piston 10 with a middle part 11 made of insulating material and two metal caps 12, 13 closing its ends. The middle part and the end caps are connected to one another in a vacuum-tight manner at 14.

Two separable contact pieces 17, 18 , which are shown in the closed position, are arranged within the piston 10. The upper, fixed contact piece 17 is attached to a conductive rod 17 a, the upper end of which is integrally connected to the upper end cap 12 . The lower contact piece 18 is movable and attached to a conductive actuating rod 18 a, which is displaceable in the vertical direction. The operating rod 18 a extends through a

Opening in the lower end cap 13, and a flexible metal bellows 20 seals the rod 18 a with respect to the end cap 13 and allows a vertical displacement of the rod without the vacuum in the piston 10 being impaired. As FIG. 1 shows, the bellows 20 is connected at its ends to the actuating rod 18 a or the end cap 13 in a vacuum-tight manner.

With the lower end of the actuating rod 18 a, a suitable actuating arrangement, not shown, is coupled which allows the contact piece 18 to be moved downwards to open the circuit and to lift off from the electrode 17 or to move upwards to close the circuit. The processes involved in opening the switch are discussed in greater detail below.

The contact pieces 17, 18 each contain a short tubular part 25 made of a highly conductive metal, e.g. B. Copper. The tubular parts 25 each have two end faces 26, 27 which run transversely to the longitudinal axis of the tubular parts and are spaced apart along this. The end surfaces 26 lie opposite one another and form arc running surfaces, as will be explained in more detail below. The other end faces 27 represent the rear sides of the tubular parts 25 .

Two contact projections 30, 31 spaced apart in the circumferential direction are hard soldered to the arc running surfaces 26 of the contact pieces. When the contact pieces are closed, the contact projections 30, 31 of the two electrodes touch one another. This forms two parallel current paths through which the current can flow between the contact pieces 17, 18 when the switch is closed. The contact projections 30, 31 should consist of a suitable, weld-resistant metal that ensures easy separation of the contact pieces when the switch is opened.

If the electrode 18 is moved downwards when the switch is opened, an arc is created between the parts 30 or 31 of the electrodes. As will be explained in more detail, this arc immediately runs at high speed over the surface 26, whereby the interruption in one of the next current zero crossings is facilitated. In FIG. 2, such an arch 32 is shown in a position which it currently assumes during its movement over the running surface 26. Since the arc begins to burn at the contact parts 30 or 31 , the parts are sometimes referred to below as arc ignition parts of the electrodes.

As the F i g. 1 and 2 show, the rohrför-shaped parts 25 each have a slot 28 which extends between the end surfaces 26, 27 . This: slot 28 intersects the sheet running surface 26 at a point which is a considerable distance d in the circumferential direction from the intersection of the slot with the rear side 27 . The slot 28 is so deep that it extends completely through the tubular part 25 in the radial direction. The two opposing pieces of the rohrför shaped part 25 with respect to the slot 28 are thus completely separated from one another by the slot. To hold the ge slotted tubular parts 25 is in close Ab was next to the backs 27 of these parts, a back plate 34 is provided, which also prevents the tubular parts from being deformed by the forces occurring in the operation of the switch. this

Backplate 34 is preferably made of a highly conductive material, e.g. B. Copper. The two back plates 34 are mechanically firmly connected to the conductive rods 17 a and 18 a, for example by brazing, and have a low electrical resistance. The tubular parts 25 are attached to the associated back plate 34 by a number of circumferentially spaced pins 42 which are brazed to the tubular part 25 at one end and to the back plate 34 at the other end.

In each contact piece, only one of these pins is made of a material of high electrical conductivity, such as copper, while the others are made of a material that is poorly electrically conductive, such as stainless steel. In Fig. 2, the copper pin is designated by 40 and the other pins by 42. For reasons still to be explained, the copper pin 40 has a significantly larger cross section, for example ten times the cross section of the other pins 42.

F i g. 3 shows a larger-scale cross-sectional view of a preferred construction of the connection between the copper pin 40 on the one hand and the tubular part 25 and the back plate 34 on the other hand. As shown, the pin 40 has a tapered piece at one end which fits into an opening 43 of the back plate 34. At the other end, the pin 40 is provided with a slot which receives one end of the tubular part 35. All of the adjacent surfaces of the pin 40 and the components 25 and 34 , respectively, are connected by brazing.

F i g. 4 shows a preferred construction for the connection between the stainless steel pins 42 and the tubular part 25 or the back plate 34. For this purpose, the tubular part 25 and the back plate 34 have aligned openings 45 into which the tapered ends of the steel pin 42 fit. Here, too, the adjacent surfaces are connected by brazing.

In each of the two contact pieces, the copper pin 40 carries the predominant part of the total current flowing between the back plate 34 and the tubular part 25. This is because the conductivity of copper is about fifty times that of the stainless steel of which the other pins 42 are made, and the cross-section of the copper pin is many times that of the individual steel pins 42. Since most of the flow from the back plate 34 enters the tubular part 25 through the pin 40 , the connection between the pin 40 and the tubular part 25 is also to be referred to here as the entry area.

The copper pin 40 is arranged at each contact piece with respect to the slot 28 so that each point of the circumference of the arc running surface 26, which is aligned in the axial direction with the connection area between the pin 40 and the tubular part 25 , is on the side of the slot 28 opposite this connection lies. The slot 28 therefore forces the current which flows between the pin 40 and a circumferentially corresponding (axially aligned) point of the sheet running surface 26 on a path which has a component directed along the circumference. The resulting current between the pin 40 and an arc starting at any point on the arc running surface 26 therefore always has, calculated as a whole, a component running in the circumferential direction.

Since the resulting current between the pin 40 and any arcuate starting point on the surface 26 always has a component running in the circumferential direction, a current loop is created in any position of the arc on the running surface 26 , the arms of which are connected by the arc and effectively in the circumferential direction with respect to the arch. From Fig. 2 it can be seen, for example, that the current flowing through the arch 32 flows along a loop L, the arms of which, shown in broken lines, extend in the circumferential direction of the tubular parts 25 to the arch. Such a current loop is always present, irrespective of where the running surface 26 is attached to the arc. A current flowing in a looped path is known to be accompanied by a magnetic field which tends to elongate the loop, and since the arms of the loop L extend circumferentially, the magnetic field results in a circumferential force which pulls the arc 32 from the in F i g. 2 drives in the circumferential direction to the right over the running surface 26. If you look at the contact pieces in FIG. 2 would be viewed from above, this circumferential movement would be counterclockwise. In any position of the sheet on the sheet running surface 26 there is therefore a magnetic force which acts in the circumferential direction and which drives the sheet in a counterclockwise direction. The movement of the bow results from Ampere's rule.

The slot 28, pin 40 and the arrangement which causes the majority of the current to flow through pin 40 will hereinafter, because of the role they play in causing the current to circulate in the arc as described above to force, sometimes referred to as the current direction determining arrangement.

If only the lower contact piece 18 is considered for the moment, it can be seen that the arc continues to move further away from the copper pin 40 when it moves away from the position shown in FIG. 2 further rotates in the counterclockwise direction, and the lower arch base gets an increasingly larger component extending in the circumferential direction. The consequence of this is that an increasingly greater force, directed in the circumferential direction, acts on the arch when it moves from the direction shown in FIG. 2 moves on in the counterclockwise direction. The magnetic force acting on the sheet is greatest when the sheet has migrated counterclockwise on the sheet running surface 26 to the point on the left edge of the slot 28 , since the current path between the pin 40 and the lower arc attachment point is then around the entire tubular Part 25 extends around. The slot 28 is so narrow that it can be overrun by the sheet. The counterclockwise magnetic force along the circumference, which prevails when the sheet has reached the left edge of the slot 28 , will then drive the sheet over the slot so that the orbital movement of the sheet over the sheet running surface 26 can last so long, until the arc finally goes out. An advantage of the present arrangement is that the magnetic force causing the arc to circulate has the greatest value when

Claims (1)

the arc reaches the slot 28 so that the arc can easily skip the slot. From the above explanation it can be seen that the magnetic force resulting from the course of the current through the lower contact piece 18, which sets the arc into circulation, is weakest when the arc starts immediately to the right of the slot 28, as shown in FIG. 2 shows. In a preferred embodiment of the invention, this is compensated for in that the slot in the upper contact piece is arranged at least approximately opposite the slot in the lower contact piece. So if the current flowing through the lower contact piece has a relatively small circumferential component, as shown in FIG. 2, on the other hand, the current flowing through the upper contact piece has a relatively large circumferential component. Correspondingly, the current flowing through the lower contact piece has a relatively large circumferential component when the current flowing through the upper contact piece has a relatively small circumferential component. The above-described movement of the sheet over the sheet running surfaces 26 has the advantage that the evaporation of the electrode material is suppressed and the distribution of the vapors produced is promoted. This increases the speed with which the vacuum regains its insulation strength, the risk of reignition after a current zero crossing is reduced, and the interruptibility of the switch is increased accordingly. It should be noted that the areas 30, 31 of the electrodes at which the arc is initially formed lie in areas in which the magnetic force acting in the circumferential direction on the arc is relatively large. For example, if you look at the current paths between the pin 40 and the two ignition areas of the lower contact piece, you can see that the ignition area 30 is practically offset by an angular range of 360 ° with respect to the pin 40, while the area 31 is an angular distance of about 180 ° from Has pin 40. A sheet drawn in one of these areas is therefore subject to a high magnetic force acting in the circumferential direction from the start, which quickly drives it away from the ignition area over the running surface 26. With the present arrangement, no delay is required to move the sheet into a position in which the circumferential movement can begin. The immediate commencement of the orbital movement of the sheet is very desirable, since the erosion of the contact areas 30, 31 and the amount of the total vapors produced are substantially reduced. There is hardly any need to point out that the contact pieces are in principle simply constructed and can be easily manufactured, since essentially only a short tubular component 25 with a single slot 28 is required. This slot 28 can also run in a straight line and can therefore be easily produced by sawing. Another advantage of the illustrated contact piece construction is that it can withstand high mechanical forces without damage. Since the tubular part 25 contains only a single slot 28, there are no mechanically weak finger-shaped or lobe-shaped parts that could be damaged by the high forces occurring during operation of the switch. The pins 40, 42 provide a mechanically strong connection between the back plate 34 and the tubular member 25 at a series of spaced points along the entire circumference of the tubular member so that it is firmly supported and secured against deformation. Both contact pieces are preferably designed in the manner shown, but the invention also includes arrangements in which only one of the contact pieces of a switch is shaped in the manner described. Such an arrangement is shown, for example, in FIG. 5 shown, in which the upper contact piece like the contact piece 17 of FIG. 1 and 2 is formed, while the lower contact piece has the shape of a flat disk 18, the parts located in the vicinity of the circumference of which then bear against the contact areas 30, 31 of the upper contact piece. The magnetic forces that set the arc in circulation are in the case of the one shown in FIG. 5 arrangement shown smaller than in the preferred embodiment; however, this is easily permissible for switches with certain core values. The magnetic forces that set the arc in circulation can be increased in the case of the contact pieces shown by forcing an even larger percentage of the total current to flow through the pin 40. This can be achieved, for example, by providing the tubular part 25 of the steel pins 42 with slots which are aligned with these steel pins. Such a slot 50 is shown in FIG. 6 shown. The slots 50 obstruct the flow of flow through a steel pin 42 into the tubular portion 25 and lengthen and narrow its path. The resistance of the current path in question is accordingly greater and more current flows through the copper pin 40, as desired such metal vapor intercepting shield 52 is provided. Such arrangements are known (see e.g. U.S. Patent 2,892,911). During the manufacture of the vacuum switch described, the parts contained in the flask are largely freed from sorbed gases and other impurities in order to prevent the vacuum from being impaired when the switch is in operation. For this purpose, the usual methods in vacuum technology can be used. The exemplary embodiments described can be modified in the most varied of ways without going beyond the scope of the invention. Patent claims: 1. Electrical switch, especially vacuum switch, with two contact pieces, one of which at least one includes a tubular portion with two end faces, the other of which is Contact piece facing end surface serves as an arc starting point running surface, and with a Arrangement that forces the flow flowing through the tubular part on a path that is one has components running in the circumferential direction of the tubular part, characterized in that that the tubular part,