US2962570A - Electric switch - Google Patents

Description

Nov. 29,` 1960 H. THOMMEN ELEcTRc SWITCH i 3 Sheets-Sheet 1 Filed June 25, 1959 INVENTOR Hans 77mm m en 372W, JW a mw' TTORNEYS Nov. 29, 1960 H. THOMMEN 2,962,570

ELECTRIC SWITCH Filed June 25, 1959 5 Sheets-Sheet 2 INVENTOR HCL/7.5 Thom 1778/7 BY @JMX/OWL ATTORNEYS Nov. 29, 1960 H. THOMMEN ELECTRIC SWITCH 3 Sheets-Sheet 5 Filed June 25, 1959 INV ENTOR x, PJM

TTORNEYS www1 United States Patent ELECTRIC SWITCH Hans Thommen, Baden, Switzerland, assigner to Aktiengesellschaft Brown, Boveri 8: Cie, Baden, Switzerland Filed June 25, 1959, Ser. No. 822,897

Claims priority, application Switzerland .lune 28, 1958 4 Claims. (Cl. 200-148) The present invention relates to electrical switches of the type actuated by compressed air for interrupting heavy electrical loads. These heavy duty switches are commonly known as gas blast switches and the present invention is concerned with a switch of this type wherein at least two switching points, i.e. two sets of contacts, are arranged in series between an input terminal and an output terminal, one of these contact sets being electrically paralleled by a resistance having a low ohmic value and the two sets of contacts being actuated practically simultaneously but with a slight interval in 'time therebetween such that the set of contacts paralleled by the resistance open iirst thus to shunt the current ilow through the resistance and decrease the current, this action being followed immediately by opening of the -other set of contacts thereby interrupting the residual current which had been ilowing through the resistance.

The object of the present invention is to provide an improved structural arrangement for an electrical switch of the type as described above which requires less space than those previously developed and which also has other advantages.

For power switches of previous design having two circuit breaking points connected in series and with a low ohmic resistance paralleling one such breaking point, it has been necessary to connect in high resistances, for better potential distribution over all the switching points, which resistances are temporarily connected in parallel to their respective switching points at the time current flow through the switching points is interrupted. In addition, still other switching points have been provided in order to effectively isolate the switch from the high voltage supply after the main power breaking switching points on the switch have been actuated to open position. Such an arrangement requires a large number of switching elements which necessitates a greater overall structural height for the switch assembly, the height increasing as the operating voltage for the switch increases. An obvious advantage in space factor is obtained when the construction is such as to keep the height of the switch as low as possible, and a principal purpose of the present invention is to make it possible to construct a satisfactorily operative switch of .the type described having a relatively low overall height.

Efforts have been made in the past to reduce the overall height and space requirement of the switch. For example, it has been known to supply the pressure gas, -i.e. the compressed air in common to all switching points. Also, valves have been arranged in common for serving a plurality of switching points. Also, the paralleling resistances have been placed outside of the switching place, and the electrical connections between the switching points and these resistances have heretofore been effected through electrically conductive metallic anges or through intermediate rings on the tubular insulators through which compressed airis carried to the switching points.

In accordance with the present invention, a favorable space factor for the switch is achieved in that the two sets of contacts which establish the two series connected switching points are arranged preferably horizontally in spaced relation by means of axially aligned tubular in sulators which serve to convey compressed air to the sets of contacts at the outer ends thereof. A casing forms a support for the inner end portions of these tubular in sulators which protrude into the casing and the casing also encloses a valve structure which when actuated serves to place the interior of the casing, Vwhich is always lled with air under pressure, in communication with the inner ends of the tubular insulators, thus admitting compressed air from the casing into the insulators for flow therethrough to the sets of contacts and effecting their separation. Also enclosed within the casing is the low ohmic resistance element above referred to and which is connected in parallel with one set of the contacts. By placing this resistance element within the casing which contains compressed air, the resistance element will be cooled by the air. Preferably the casing wall is made of electrically conductive material and is electrically connected to the input terminal side of one set of contacts, one end of the resistance being connected to the casing wall and the other end of the resistance being connected to a point of potential intermediate the two sets of series connected contacts through the valve structure which is also electrically conductive and which surrounds and is in electrical contact with a conductor extending between the two sets of contacts through the tubular insulators which serve to carry the compressed air from the casing to the sets of contacts. Preferably the conductor extending through the insulators is in the form of a rod and the opposite ends thereof terminate in xed contact members for the two sets of contacts, the other contact member of each set being movable away from the end of its associated fixed contact member by the compressed air. Such construction thus places the resistance element in parallel with one set of the contacts closest to the input terminal.

The foregoing objects and advantages as well as others will become more apparent from the following detailed description of several embodiments and which are illustrated in the accompanying drawings wherein:

Fig. l is a view in side elevation with certain parts shown in section of one embodiment of the invention employing only two sets of load breaking contacts connected in series and with a resistance element connected in parallel with one set of these contacts closest to the input terminal of the switch;

Fig. 2 is a condensed electrical circuit diagram of the switch components shown in Fig. 1;

Fig. 3 is a view similar to Fig. 1 but showing a modiiication wherein the switch comprises four sets of load breaking contacts connected in series and using one resistance element connected in parallel across two of the lfour sets of series arranged contacts;

Fig. 4 is a condensed circuit diagram of the switch components shown in Fig. 3; and

Fig. 5 is a view in elevation of still another embodiment employing a multiple arrangement of switches each having a construction according to the embodiment shown in Fig. 3.

With reference now to Fig. l, the improved switch construction in accordance with the present invention comprises an upstanding tubular insulator column 1, the lower end of this column being placed in communication with a source of compressed air such as a supply 1 so that casing 2 will be filled with compressed air. Extending laterally outward through Opposite walls of casing 2 are two tubular insulators 4, 5 which are axially aligned. Interposed between the inner ends of insulators 4, 5 is a v-alve structure 6 comprising a pair of opposed piston elements 7, 8 slidable in a stationary sleeve 9 in engagement with the interior wall of lthe sleeve and which are urged away `from each other by means of a helical spring `10 disposed between the pistons. When in the position shown in Fig. l, piston 7 bears against and closes ofi the entrance 4a to the interior of insulator 4 and piston S similarly bears against and closes off the entrance 5a to the interior of insulator 5. Pistons 7 and 8 are provided with central apertures in axial alignment with insulators 4, 5 and through which a stationary conductive rod 11 is passed, the rod 11 extending also through insulators 4 and 5. Sleeve 9 is made of electrically conductive material as are also pistons 7 and 3, and the latter are in contact with the surface of rod 11.

Located vertically within casing 2 is a resistance element 12 having a relatively low ohmic value. The upper end of resistance element 12 is connected to the top wall of casing 2 and its lower end is connected to the valve sleeve 9. Consequently, this effects an electrical connection between the lower end o-f resistance element 12 and the conductor rod 11 through the pistons 7, 8.

Attached to the outer end of insulator 4 is a housing 13 containing a nozzle contact member 14 which is placed in axial alignment with rod 11. Nozzle contact member 14 is arranged for longitudinal sliding movement within its housing in a direction away from engagement with the left end 15 of rod 11, when compressed air is permitted to flow through the insulator 4, against the counter action exerted by a helical spring 16. The left end 15 of rod 11 and nozzle contact 14 thus constitute one set of load breaking contacts of the switch. The input terminal 17 to the switch is electrically connected to nozzle contact mem-ber 14 and also to casing 2. When compressed air forces the nozzle contact member 14 away from the stationary contact member 15 thus breaking the circuit between the two, air ows through the interior of the nozzle contact member and is permitted to escape to atmosphere through an outlet 18. A piston element 19 on the nozzle contact member 14 then serves to reclose the outlet 18, thus retaining the air pressure within the arc extinguishing chamber formed in part by the tubular insulator 4. As the contacts 14, 15 separate, current is thus forced to flow through the resistance element 12 since the latter is connected to input terminal 17 and stationary contact member 15 through casing 2 and valve 6.

Attached to the outer end of insulator 5 is a housing 20 containing a nozzle contact member 21 which is also in axial alignment with the conductive rod 11. Nozzle contact member 21 is also arranged for longitudinal sliding movement within its housing in a direction away from engagement with the right end 22 of rod 11, when compressed air is permitted to ow through insulator 5, against the counter action exerted by a helical spring 23. The right end 22 of rod 11 and nozzle contact member 21 thus constitue the other set of load breaking contacts of the switch. The output terminal 24 for the switch is electrically connected to nozzle contact member 21. When compressed air forces nozzle contact member 21 away from the stationary contact member 22 thus breaking the circuit between the two, air ilows through contact member 21 and is permitted to escape through an outlet 25. A piston element 26 on the nozzle contact member 21 then serves to reclose outlet 25 thus retaining air pressure within the arc extinguishing chamber formed in part by insulator 5.

It will be seen from Fig. l that tubular insulator 5 is somewhat longer than insulator 4 and for such reason will require slightly more time for the compressed air to reach the set of contacts 21, 22 than is required for the air to reach set of contacts 14, 15. Thus contacts 14, 15 will be interrupted first thus to require the current to ow through resistance 12, and then contacts 21, 22 will be interrupted thus breaking the flow of the residual current passing through resistance 12.

Returning to the control valve construction, the interior of valve sleeve 9 is in communication with a conduit 27 which passes downwardly and then laterally outward from casing 2. Associated with the conduit 27 is a two-way control valve 28 by which conduit 27 can be placed either in communication with the atmosphere or in communication with a source of compressed air at the same 'pressure as the air which is supplied tothe interior of casing 2.

in order to actuate the switch from the closed to open position, valve 28 is moved to the position wherein conduit 27 is vented Yto atmosphere. This also serves to place the interior of valve sleeve 9 in communication with the atmosphere and hence establish a pressure differential between the inner faces of pistons 7, 8 which lie within the valve sleeve and the outer faces of these pistons which are exposed to the pressure of the air within the casing which is higher than atmosphere. This pressure dierential is then sufficient to overcome the counter biasing action of spring 10 whereupon pistons 7, 8 move inwardly and become unseated from the entranceways 4a, 5a to insulators 4 and 5 and compressed air flows through these insulators and thence to the contact memrbers of the switch, separating them in the manner previously explained.

To reclose the switch, control valve 28 is shifted to the position admitting compressed air from the supply source for flow through conduit 27 into valve sleeve 9 thus to bring the pressure of ythe air within Valve sleeve 9 to the same pressure as that existing within casing 2 and hence equalizing the pressure on both sides of pistons 7, 8. These pistons then move outwardly by the counter action of spring 10 and reseat themselves upon the entranceways to insulators 4, 5 thus to remove the air pressure from the nozzle contacts 14, 21 whereupon their respective loading springs 16 and 23 will move the nozzle contacts 15 and 22.

In the modified embodiment according to Fig. 3, four sets of contacts are connected in series and the paralleling resistance element is connected in parallel with two of these sets of contacts in series.

In Fig. 3, a casing 2 of electrically conductive material is supported upon an insulator column 1 and casing 2 in turn supports the laterally extending insulator structures which are associated respectively with the four sets of contacts. It will be evident from a comparison `between Figs. l and 3 that the latter constitutes a modied assembly of two of the dual contact set units as shown in Fig. 1 and disposed parallel to each other in superposed relation. -In the interest of simplifying the Fig. 3 embodiment and eliminating an unnecessary duplicative description, the details of the contact structures have not been shown. Thus in the upper unit, numeral 31 designates the location. of one set of contacts and input terminal 32 is connected to the nozzle contact member thereof. Numeral 33 designates the location of the other set of contacts of the upper unit. The conductor rod connecting the stationary contact members of the upper dual switching point unit is designated by numeral 11' and corresponds to conductor rod 1'1 in Fig. l. Similarly, in the lower unit, numeral 34 designates the location of one set of contacts and numeral 35 designates the location of the other set of contacts, the nozzle contact member of contact set 35 being connected to the output terminal 36. The conductor rod connecting the stationary contact members of the lower dual switching point unit is designated by numeral 11 and corresponds to conductor rod 11 in Fig. l.

Casing 2 corresponds in function to 'casing 2Y of Fig. 1 in that it houses the two valve structures 6 each of which corresponds in function to valve 6 of Fig. 1 as well as the low ohmic resistance 12 which corresponds to resistance 1,2 of Fig. 1, and contains air under compression for introduction into the various insulators to actuate the switch contacts whenever the valves 6' are opened. However, casing 2 is electrically connected to the nozzle contact member of contact set 33 and also to the nozzle contact member of contact set 34. Resistance 1,2' isv connected between the two valve structures 6 and the latter are electrically connected to the upper and lower conductor rods 11' and 11". Consequently, as will be evident by reference to the electrical schematic diagram of Fig. 4, resistance 12 is thus connected in parallel across the series connection of the two inner contact sets 33 and 34. Also, as is evident from Fig. 4, casing 2 serves as part of the main conductive path for the load current through the switch.

Comparison between Figs. 3 vand 1 will also show that the two contact sets 33, 34 are each structurally similar to the set of contacts 14, 15 of Fig. l. It will be remembered from the previous description that contacts 14, 15 of Fig. 1 open rst because of the slightly shorter air path thereto from the valve Structure 6. For the same reason, in the Fig. 3 embodiment, when the valves 6 are opened, the contact sets 33, 34 will open rst and simultaneously thus forcing the current which had been flowing through these contacts into the parallel path for flow through resistance element 12. Shortly afterwards the two other sets of contacts 31 and 35 will open simultaneously so as to break the residual current owing through resistance 12'.

In order to make the potential distribution over the various switching points as uniform as possible, it is necessary to utilize additional resistances of high ohmic value. One of these, resistance unit 37, is electrically connected between the input terminal 32 and casing 2', and another resistance unit 38 is connected between casing 2 and output terminal 36. Operation of the Fig. 3 embodiment is generally the same as in Fig. l there being a control valve 28 for the two valve structures 6 through which air is exhausted and admitted for controlling operation of the four sets of contacts.

The embodiment illustrated in Fig. is for use on higher volta-ges than that for which the Fig. 3 embodiment is capable and comprises a plurality e.g. two of the four contact set units shown in Fig. 3 connected in series.

A detailed description of the construction of each four contact set units is therefore not believed to be necessary. However, it will be noted that the switch units are mounted in an upstanding manner upon a supply tank 40 for compressed air and that control valves 28' are adapted to be actuated by rods 41 which receive their movement from a drive or motor mechanism 42. Compressed air is supplied from tank 40 upwardly through insulator columns 1 into casings 2 and taps from the upper portions of the insulator columns 1 are provided to supply compressed air to valves 28 for flow into the valve structures 6 inside casings 2 when it is desired to close the four sets of contacts on each unit.

The embodiment of Fig. 5 also includes two upstanding tubular insulator columns 43, 44 at the top of each of which are located a pair of compressed air operated voltage disconnecting switching points 45 which are connected in series with the two series connected power switching units of four contact sets each. Operation of the voltage disconnecting switching points 45 is controlled by a valve 46. These switching points 45 bring about the desired voltage isolating gap when the power switch units are in a disconnected state and simultaneously disconnect the current owing through the high resistance. They are switched i.e. their contacts are opened shor-tly after the power switch units have been switched out to 6. s the disconnected state. Utilizing the principle shown in Fig. 5, multiples of the power switchunit may be connected in series so as to adapt the switching structure to any desired high voltage level.

In conclusion, the embodiments which have been described have the advantage that a considerable saving can be made in the overall height required. Also, housing of the resistance units within the casings which always contain compressed air serve to keep them cooler and hence increase correspondingly the load breaking capacity of the switch.

The embodiments which have been described can be used for all possible types of operation of compressed air switches. The power switching points can be permitted to reclose again immediately following their opening and satisfactory voltage isolation of the switch from the high voltage supply can be obtained through the use of voltage isolating switch structure connected in series with the power interrupting switch. The compressed air in the switch may,remain after the contacts are disengaged or ittmay be permitted to disappear again. The main valves can be housed at the bottom end of the supporting insulator column, or they can lie at the same potential as the power switching points and` be housed at the up per end of the insulator column. If the power switching points remain under pressure from the compressed air both in the engaged and disengaged state, then the valves for actuating the switching points are housed at their ends.

Moreover, the assembling of several switch units each embodying the principles of the invention can be made without significantly increasing the structural length of the switch as compared to the constructions which have been previously developed.

I claim:

1. In an electrical switch, the combination comprising two series connected groups of contacts, each said contact group including two series connected sets of contacts, an electrically conductive casing common to said groups of contacts, a resistance element disposed within said casing, means connecting said resistance element in parallel with a series arrangement of one set of contacts of each group, said two sets of contacts which are paralleled by said resistance element being arranged to open slightly in advance of the other two sets of contacts thus forcing current ow through said resistance element, and one contact of each set paralleled by said resistance element being electrically connected to said casing.

2. In an electrical switch, the combination comprising two sets of compressed air actuated contacts, each set of contacts including a stationary contact member and a movable nozzle contact member, said sets of contacts being supported in part by tubular insulators through which compressed air is delivered to said sets of contacts, said insulators being axially aligned and extending laterally outward from a casing, means providing the interior of said casing with compressed air, valve means disposed between the inner ends of said insulator means for controlling admission of compressed air thereto from said casing, said valve means including a pair of pistons slidable in a valve sleeve and subject to the pressure of the air in said casing, a spring between said pistons for urging said pistons in opposite directions against the entranceways to said insulator means and means for venting the interior of said valve sleeve to a lower pressure than that in said casing thereby to effect movement of said pistons in a direction away from said entranceways to said insulator means, `a conductor rod extending through said insulator means and said valve means and which serves to interconnect the stationary contact members of said contact sets, a resistance element located within said casing, land .means including a connection to said conductor rod for electrically connecting said resistance element in parallel with one of said sets of contacts and which is arranged to open slightly in advance of the other set of contacts.

3. An electrical switch as defined in claim 2 wherein lsaid resistance element connecting means includes said casing and valve means both of which are made of conductive material, said casing being connected to the input side of the contact set paralleled by said resistance element, said valve means being connected to said conductor rod, one end of said resistance element being connected to said valve means and the other end of said resistance element being connected to said casing.

4. In an electrical switch, the combination comprising a iirst group of two sets of compressed air actuated contacts arranged in series, a second group of two sets of compressed air actuated contacts arranged in series, said sets of contacts being supported respectively in part by tubular insulator means extending laterally outward from a casing made of electrically conductive material, means electrically connecting said casing to one contact of said first group of contact sets and `to one contact of said second group of contact sets such that all four sets of contacts are arranged in series between an input terminal and an output terminal, means providing the interior of said casing with compressed air, valve means for controlling admission of compressed air into said insulator means for flow therethrough to said sets of contacts, a resistance element located within said casing, and means connecting said resistance element in parallel with a series arrangement of the two sets of contacts of said first and second groups to which said casing is connected and which two sets of contacts open slightly in advance of the other two sets of contacts.

References Cited in the le of this patent UNTTED STATES PATENTS 2,627,005 Baker et al. Jan. 27, 1953 2,665,351 Forwald Jan. 5, 1954 2,747,055 Forwald May 22, 1956 FOREIGN PATENTS 535,799 Great Britain Apr. 22, 1941 582,599 Great Britain Nov. 2l, 1946 593,230 Great Britain Oct. 10, 1957

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