DD298462A7 - METHOD FOR FORMING VACUUM CHAMBERS - Google Patents

Abstract

The erfindungsgemäaesze method is applicable for the formation of vacuum switch chambers, z. B. for low voltage vacuum protection. Overall, it is intended to decisively reduce the technological outlay and make it possible to produce tiles. This object is achieved by the fact that the vacuum interrupters to be formed are heated from the inside by a large number of DC light arcs of low current intensity determined by the size of the vacuum interrupter and with a burning time of only a few seconds and a polarity alternating from circuit to circuit. wherein both the heat input and the cathode and anode processes and Metalldampfkondensationsvorgaenge be used for the desired Saeuberung the Innenflaechen the vacuum chambers. Fig. 1 {method; Formation; Vacuum interrupter; DC arc discharge; Polarization change; conclude; To open; Switching cycle; Arcing time; Break time; final temperature}

Description

For this 3 pages drawings

Field of application of the invention

The inventive concept relates to a method for forming vacuum interrupters, z. B. for low voltage contactors. These vacuum interrupters according to the known and conventional structure, consisting of a housing, an insulating section, a fixed and a metal bellows vacuum-tight and movably arranged switching piece and a fixed and movable supply must be cleaned and pumped in their interior so far that the chamber internal pressure does not exceed a value of 1 Pa during the entire storage and service life of eg over 10 ⁷ switching cycles. For this Formierungspiczeß, classified in a flow production, this process should serve.

Characteristic of the known technical solutions

In the previously known forming methods, the vacuum interrupters are heated in an oven by heat input from the outside in a time and equipment-intensive process, usually to a temperature of 35 (MOO ⁰ C, with a simultaneous pumping.) To clean the SchaltstOckoberfläche this with about A disadvantage of these known methods is the very high level of technical complexity, the long heating and heating time, the thermal load on the chamber outer parts and connecting elements located in the baking oven, and the high power consumption for the forming circuits with some kA and the overall several hours total forming process.

To improve this classical method, arrangements or methods have already become known in which a glow discharge is ignited inside the vacuum interrupter chamber and the necessary shaping effect is to be achieved both by the electrode processes and by the power conversion (DD-PS 13395; DD-PS 139047) ). Disadvantage of these arrangements is that the glow discharge can be maintained only at relatively high pressures, which are above the maximum allowable operating pressure in the vacuum interrupter chamber. To improve this, the additional use of magnetic fields has been proposed. Likewise, an arrangement was known from the combination of a formation by a glow discharge and a cleaning of the Elektrodonoberfläche by means of a DC vacuum arc in alternation with the glow discharge DD-PS 132 221).

Another disadvantage of this method is the relatively low power conversion in the glow discharge, which for reasons of occupational safety probsic higher voltage requirement of the glow discharge and the relatively high effort to maintain this.

There are other methods have become known in which a DC arc between the switching piece 6n pulled and maintained for a long time, until the thermal expansion of the movable feed and coupled thereto linkage the switching pieces are closed again and thus the arc goes out (DD-PS 246191). In

Extension of this method is still proposed a control arrangement in which u.a. Also, a polarity change of the DC nlichtbogens either tearing or interrupting the arc discharge when closing the switching pieces, caused by the thermal expansion of the movable feeder and the coupled linkage to be achieved (DD-PS 246192).

Disadvantage of this method or the required arrangement s! .Id the equipment expense for self-shorting of the DC arc by thermal expansion of parts and the high cost of their adjustment and in particular over a long time (up to 30 minutes) with the same polarity and at very small contact patch distances burning DC arc, which can lead to a very large load on the contactor surface, a high material erosion (which can account for 10-20% of the entering during the electrical life of the vacuum interrupter chamber and thus the life of the contact pieces too low) and to a flake on the contact piece surface leads, which in turn would reduce the dielectric strength inadmissible. Another major disadvantage of the necessary arrangements for the process is that u.a. not insignificant heat is removed from the vacuum interrupter chamber. In turn, a greater energy input is necessary with its adverse consequences on the switching pieces to achieve the required forming temperature.

Object of the invention

The aim of the invention is the decisive reduction of the plant technical effort, Minimiurung the effort and the required amount of energy for the forming process itself, a minimum stress of the switching pieces and a suitable for a flow production forming method sche'fen with a simultaneous improvement of the degree of formation.

Explanation of the essence of the invention

The idea underlying the invention is to propose a method of forming vacuum interrupters, with which optimum formation with a technology suitable for flow production is made possible with minimal technological, plant-technical and time expenditure.

According to the concept of the invention, this object is achieved in that the switching pieces to a constant opening, which is greater than the operational switching, preferably 2-3 mm, brought and that the closing and opening of the switching pieces takes place according to a time program in which a burning time the Gleichstromlichtbügen of 2-3 see is provided in a Formicrungsschaltung and that a switching pause is provided by the duration of the multiple of the time of a forming circuit, wherein the duration is such that the temperature reached by the forming circuits in each case at the parts to be heated from : inkt that after 60-70% of the total number of forming circuits, preferably 50-75, the final temperature of 200-250 ⁰ C, based on the chamber wall, achieved and kept constant until the end of Formierungsschajtungen.

By the constant opening of the contact pieces to a distance which is greater than the operational switching and the opening and closing of the switching pieces according to a time program, the vacuum interrupter chamber by a cycle of direct current arcs of certain, but larger number, but much shorter duration, low amperage, the safely prevents tearing of the arc discharge, but does not cause undue stress on the contactor surfaces, heated internally while simultaneously subjecting both the contactor surfaces and the wall surfaces or wall surfaces adjacent the contactor assembly to metal vapor during normal use of the vacuum interrupter chamber the condensation processes of contact material-metal damage are cleaned by drumming off the absorbed gas deposits.

Crucial is further that, in addition to a short Bogenbrenndaue: of only a few seconds, the polarity in a defined rhythm and at short intervals, z. After each shaping circuit, d. H. Also, from circuit to circuit of the individual or each vacuum switching chamber or even after a very limited number of forming circuits, the polarity of the forming arc is changed, whereby a one-sided ablation of the cathode and a one-sided precipitation at the anode, which in turn leads to dandruff and thus reduction of electrical strength or welding of the switching pieces would lead at higher current loads in an individual case, is avoided.

For the method according to the invention, in addition to the usual vacuum-technical part of a vacuum-tight coupling of the switching chamber to be formed with the Vakuumpumpstand only a simple actuator (magnetic drive, pneumatic drive u. Ä.) For closing and opening the switching pieces to a constant and greater distance than the operational switching DC power source required for currents of a few 100A and a clock. The vacuum switching chamber to be formed is connected via a load resistor for adjusting the Formierungsstromes and an arrangement for Polaritäuwechsel with the DC power source

 According to the concept of the invention, the entire formation process consists of the following steps:

- Construction, generation of the starting pressure, pumping down

- Forming circuits with a arc current of about 100-15OA at smaller, about 100-250 A for larger vacuum interrupters (eg for 630A rated current), igniting the DC arc discharge by briefly closing and opening the contact pieces to a distance of preferably 2-3 mm, burning time each DC arc 2-3sec, erase the arc discharge (eg by turning off the DC power supply), before the next forming circuit in the respective vacuum interchangeable chamber, either immediately after or after a short pause, in the following shaping circuit, ignition of the reverse polarity arc discharge, further process as previously described, once the arc discharge has been erased, the polarity is changed again;

- Pause for temperature compensation within the vacuum interrupter chamber and heat flow in the surfaces to be formed or chamber parts;

- Continuation of the program, preferably with one or two circuits and polarity changes and pauses until reaching the necessary temperature at the chamber parts to be formed and temperature stability (after about 60-70% of these load circuits);

- Continue these load circuits with DC arcs of alternating polarity with constant heating with about 40-30% of the total load circuits;

- Cooling of the vacuum interrupter chamber with simultaneous further pumping;

- Vacuum-tight closing (squeezing of the pumping nozzle) of the vacuum switching chamber.

Significant advantages of the method according to the invention are that the amount of energy converted in the load circuits in the DC vacuum arcs is biw. released heat is introduced into the switching pieces and discharged from there into the chamber walls, but that part of the heat generated is delivered directly to the chamber wall by the larger (a few mm) and constant distance of both switching pieces that the DC forming arcing at constant SchaltstUckabstand burn and thus cause only minimal stress on the contactor surfaces, that the DC arcs at the selected currents do not tear off, but their burning time are specified externally by the controller exactly and adhered to, that is transported by the polarity change piece material between the two switching pieces back and forth, so that thereby and by the predetermined constant SchaltstUckabstand exits only a minimal but sufficient proportion of metal vapor from the contact piece gap, condenses on the chamber inner walls and thereby adhering gas deposits drums off and this with a significantly higher efficiency than pure heating of these deposits by heat input from the outside. It is also essential that the disadvantages of the known solutions, in particular the formation with DC arcs very long burning time, tearing off the forming sheet and thus a greatly fluctuating arc burning time and shorting of the forming sheet by the slow thermal expansion of the feeders and the coupled linkage with all the adverse consequences of Vacuum arc extremely short length can be avoided. With a suitable and adapted to the respective vacuum chamber size selection of the switching sequences and pause times can be formed simultaneously and automatable with a system multiple vacuum interrupters.

Another and important advantage of this method is that the usual and prescribed forming temperature of 350 ⁰ C to about 450 ⁰ C to values of 200 ° C-250 ° C, based on the outer wall of the chamber portion of metal or the surfaces on which is encountered during operational switching in practical use in the vacuum protection contact material steam, can be lowered. This is a significantly lower stress on all sensitive components, such. B. the metal bellows and Isolierst! reached the corner. Additional side effects include time and energy savings.

embodiment The method according to the invention will be explained with reference to two embodiments. In the accompanying drawings show Fig. 1: the block diagram Fig. 2: the timing diagram of the switching cycle Figure 3: the Temperaturvar ^s aufvvi the formation!-End. 4: section through the Vakuumsrhaltkammer Fig. 5: another variant of the switching cycle

In Fig. 1 the basic structure of the required forming arrangement is shown. The DC power source 1 (eg, transformer and rectifier unit) is via power switch 2, a control device for polarity change 3 and the load resistor 4 for adjusting the Formierungsstromes with the forming vacuum switching chambers 5; 5.1; 5.2 connected. Furthermore, the respective associated drives 6; 6.1; 6.2 (eg magnets) and control magnets 7; 8 is connected to the control unit 9 (eg a shift drum).

FIGS. 2 and 5 show the flow of the forming process according to the invention on the basis of two variants. It is characterized with tj the closing time of the power switch 2, with t ₃ and t ₃ , the closing time of the control device for polarity change in the two positions, with U the short closing time of the switching pieces in the vacuum interrupter chamber 5, with tj and tj 'the burning time of this DC arc with the burning voltage Ue, with t _p the pause time to repetition of a switching cycle, consisting of again two forming circuits with a arc burning time of t ₈ and t _B '. The inventive method is particularly suitable for forming a plurality of vacuum interrupters simultaneously in one process, as an example shown in Figure 1, the vacuum interrupter chamber 5. 5.1; 5.2. At the beginning of the forming process, as shown in Figure 2, first the Polwendeschalter 3 is turned on, then power switch 2, immediately thereafter, the switching pieces are closed in the vacuum interrupter chamber 5 and immediately opened again. During this closing time t ₅ flows a current J, which is adjustable and determined by the resistor 4. After re-opening of the contact piece in the vacuum interrupter chamber 5 a Gieichstromvakuumbogen the size I ₈ burns. According to a part of the Erfimiungsgedankens while the current J ₈ should be sized depending on the switching piece material so that at least 2.-3 parallel Katodenfußpunkte arise, preferably thereafter at least 100-15OA. After a sheet burning time t _{a of} the forming DC arc is interrupted by turning off the power switch 2. Thereafter, the polarity is changed with switch 3 and another shaping circuit with J ', Jb' and T _B 'executed. This is followed by a pause t _p in which the amount of heat introduced in the interior of the vacuum switch chamber is diverted from the contact pieces to the other chamber parts. As a result, a uniform temperature distribution is achieved via a temperature compensation. In this pause time t _p for the first vacuum interrupter chamber, according to Fig. 1 switching chamber 5, according to the concept of the invention, the other vacuum interrupters 5.1; 5.2 and so on one after the other with the same rhythm.

After the switching cycle of the last vacuum switching chamber of the chamber lot to be formed or after the pause time tp, chamber 5, and then chamber 5.1, etc., are again switched with the same switching cycle according to FIG.

FIG. 5 shows a further variant of this forming process. This variant differs in particular in

that the pause time t _p becomes smaller and does not immediately follow two shaping positions with different polarity, but passes between a formation circuit with one polarity the time t _p until the next one

Forming circuit with the same switching chamber, but with reverse polarity. In Fig. 6, in addition to tj, the closing time of the power switch for the first shaping circuit for the Vacuum switching chamber 5 and t _2n the closing time for the n-th switching chamber in the lot to be formed

characterized.

Advantage of this variant is that the Polumschalteinrichtung 3 much less must be switched, thereby at

the same process time, the time t ₂ and the arc duration t _B can be extended and thus the fluctuations in the

Temperature can be reduced by heat and heat. Further variants of the forming process from a combination of these processes shown in FIG. 2 and FIG. 5 are possible. It is crucial, inter alia, that the change of polarity from circuit to circuit u.U. even after a few, but maximum

after 3-5 circuits of the same polarity, and the short arc burn time of 2-3 seconds and the described and desired effects of the formation current arc of low current are maintained.

According to the inventive idea is a vote of the arc burning time te with the arc current Jb and the Pause time t _p so that the product of Jb · te · Ue (where Ub is to be assumed as a constant) corresponding Amount of heat causes a steady increase in temperature and that during the pause time t _p no cooling, in particular the Chamber outer wall takes place until the heat supply and discharge are in balance on average, so after We ^! from about 60-70% of the total number of cycles, the temperature of the part of the to be formed Vacuum switch chambers remains the same. The individual values Ever. t _p and total number η of the forming circuits are included

depending on the size of the vacuum chamber size and type to be determined or optimized. As reference values can apply:

- for smaller vacuum interrupters (rated current up to approx. 25OA) for low-voltage contactors, t _B δ 2.5s; J ₈ S 150A; η = 120 forming circuits or (60 switching cycles)

- for larger vacuum interrupters (nominal currents up to approx. 630A) to S 2,5s; Jb S 200A; η = 120

For an automated process and system designed for this purpose, advantageously both t _B and η can be selected the same for different types of switching chambers and be varied. For the nesting of the individual switching chambers to be formed, an automated forming process can be realized for in each case an equal number of vacuum switching chambers or a continuous process consisting of coupling, pumping, pumping down time, shaping circuits, cooling time, squeezing and uncoupling. In the latter case, however, it is also important to adhere to a necessary heating time (determined by the pause time t _p ). Overall, the formation process can thus be reduced to a few hours (about 2-3 hours).

As a further and essential advantage of the method according to the invention, a significant reduction of the total effort is achieved in addition that after about 60-70% of the forming circuits to be reached and then kept constant temperature at the switching chamber walls only about 200 to 250 ° C, im This is in contrast to the previously indicated temperatures of 350-450 ° C. This is due to the condensation processes of the metal vapor 12 (FIG. 4) produced by the partial arcs 11 in the contact piece gap 10 at the metallic and advantageously potential switching components, eg chamber wall 13 and screen 14 to return. the achievable by the inventive process and principle temperature profile TK is shown in figure 3, where η, the number of forming circuits and t _F represents the time required to do so. Important, but is also advantageous that the connection lines or terminals by the low shape ierungsstrom can be kept very small and are interpreted with a very small cross-section. This is further necessary in the sense of the inventive idea that only a minimum amount of heat is derived from the switching chamber. Advantageously, according to the example in FIG. 4, the power supply to the fixed contact piece could take place via the exhaust pipe 16 located in the fixed electrode 15, wherein the coupling element with the pumping station and power supply could be implemented as a component.

The method according to the invention is particularly suitable for vacuum interrupters for low-voltage contactors. But it is also with appropriate adaptation of the parameters t _B , t _p , Jb, η for other vacuum interrupters, z. B. applicable for higher voltages.

Claims (3)

1. A method for forming vacuum interrupters consisting of movable and fixed contact piece with respective supply electrode, insulating section and a metal shell part, using a heating of the vacuum interrupter chamber by the power conversion in a DC arc discharge, wherein a control means a multiple closing and opening of the contact pieces , associated with a polarization change, characterized in that the switching pieces are brought to a constant opening which is greater than the operational switching, preferably 2-3 mm, and that the closing and opening takes place according to a time program in which a burning time of the DC arc of 2-3 seconds is provided in a forming circuit and that a switching pause is provided by the duration of the multiple of the time of a forming circuit, wherein the duration is such that the by the forming circuits respectively reached temperature on the parts to be heated does not decrease that after 60-70% of the total number of forming circuits in the amount of preferably 50-75 reaches the final temperature in the amount of 200-250 ⁰ C, based on the chamber wall, and to the end of the forming circuits is kept constant. 2. The method according to claim 1, characterized in that for each to be formed * vacuum switching chamber, a switching cycle is provided, consisting of two forming circuits with different polarity and that in each case after this switching cycle a switching pause is arranged. 3. The method according to claim 1, characterized in that each vacuum Scholtkammer to be formed performs a forming circuit and that thereafter the switching pause is provided and that at the end of this switching pause, the next shaping circuit but takes place with the reverse polarity.