DE2162991A1 - Current limiter with self-recovery capability - Google Patents

Description

1 · Σ2 - 35 December 15, 1971

1 a - 316

MITSUBISHI DENKI KABUSHIKI IUISl Tokyo, Japan

Stromegreiizer rait 'self-sufficiency

The invention relates to a current limiter with self-recovery capability with a first and a second electrode, with an insulating piece of pipe between the electrodes, the cavity of which contains a self-recovering current limiting material, with a surrounding the insulating earpiece Outer tube and with an insulating material packing between the outer tube and the insulating tube piece,

Such a self-recovering current limiter can contain a metal as a current limiting material, such as. B. Na, K, NaK, which in liquid at room temperature State has a high electrical conductivity. This current limiting material becomes when a strong Electricity evaporates due to Joule heat and becomes a Plasma with a high vapor pressure and a high electrical Resistance converted.

Thus the electric current is limited to one word, which is below a certain threshold. The vaporized metal cools down and is liquefied and regains its original electrical conductivity again. The conventional flow limiter grows

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Pressure in the closed cavity containing the current limiting material contains, considerably. Accordingly, it is required that the construction of the cavity be a has great mechanical strength.

Typical examples of conventional self-recovering current limiters, which is a flow restriction material in a closed Containing cavity are described in U.S. Patents 3,501,730 and 3,117,203.

fc Thus, it is the object of the present invention to provide a To create current limiter with self-recovery capability, which has great mechanical strength.

This object is achieved according to the invention in that the packing of insulating material has a coefficient of linear expansion has, which is below the B ^ iÄchungspunktes is greater than the linear expansion coefficient of the insulating Pipe section and which is equal to the linear expansion coefficient of the outer pipe is or less than the linear expansion coefficient of the outer pipe.

In the following the iSrfindung is explained in more detail with reference to drawings w,

Bs show:

1 shows a cross section of a current limiter according to the invention with self-recovery ability;

Fig. 2 shows a cross section of a further embodiment of the

current limiters according to the invention with self-recovery f ähiglce it;

3a shows a plan view of the outer tube;

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Fig. 3b is a plan view of the flange of the first electrode and

FIG. H shows a section through a current limiter according to FIG.

In the figures, the same reference numerals denote the same or corresponding components.

Structure 1:

In the first embodiment of the current limiter according to the invention with self-recovery capability shown in FIG. 1, the reference character 1 designates a second electrode with a flange 1a on the outer surface of the same and with an elongated hole 1b. An insulating pipe section 2 is located between this “electrode and a container-like metallic outer tube 3” in the bottom of which a first electrode k- is inserted.

The reference s se χ before η 5 denotes an Isolierniaterialpackung between the outer tube 3 and the second electrode 1 and the insulating tube section 2. A continuous cavity is in the first electrode k and in the second electrode 1, so that the electrical conductivity through the current limiting material can be maintained. The flange 1 a of the second electrode 1 is pressed down via an insulating washer 7 by means of a union nut 8 which is screwed onto the outer tube 3.

If the current is limited, the current limiting material, which is in the fine. Cavity 2a of the insulating pipe piece and located in the fine cavity 1a of the second electrode 1, evaporates and generates a high pressure. This pressure tends to push the second electrode 1 upwards. To prevent a

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the flange is used for such a process. 1a of the second electrode 1, which with the union nut 8 over the insulating washer 7 is pressed down.

Structure 2:

In this structure according to FIG. 2, the reference number 1 denotes a second electrode 1 with a flange 1a on the outer surface and with a long hole 1b as shown in FIG. 3b denotes an outer tube with a flange 3a and an opening 3h according to FIG. 3a. A first electrode h is screwed into the bottom of the outer tube 2. An insulating material pack 5 is located between the second electrode 1 and the insulating pipe section 2 on the one hand and the outer pipe 3 on the other hand.

The current limiter is produced by inserting the insulating pipe section 2 into the outer pipe 3 and then inserting the second electrode into the outer pipe 3, so that the flange 1a through the opening 3t ^ ^es flange 3a of the

Outer tube 3 slides. The second electrode 1 is then rotated by 90 so that the flange 1 a of the second electrode W overlaps with the flange 3 a of the outer tube 3. The insulating material is now packed and the current limiting material is filled into the hole 1b of the second electrode 1 and into the hole 2a of the insulating pipe section 2 via the needle valve 6.

The materials for the current limiter according to the invention are to be explained below. The insulating pipe section 2 preferably consists of a heat-resistant and alkali metal-resistant insulator made of beryllium oxide porcelain, aluminum oxide porcelain or the like. The first electrode and the second electrode k _f 1 should be low

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have electrical resistance and a linear Have expansion coefficients, whichever gMch is or lower than that of the metal of the outer tube 3 The electrodes are preferably made of copper or copper alloys, such as. B. Chromium-Copper.

The outer tube 3 should have the following properties:

(a) Non-magnetic metal

(b) no decrease in strength upon heat treatment at 500 ° C to 600 ° C

(c) high strength at room temperature after ilite treatment at 500 ° C to 600 ° C

(d) large coefficient of linear expansion, which is equal to or higher than that of copper or copper alloys, such as B. of chrome-copper.

In accordance with these requirements, stainless steel is particularly suitable or brass. It is particularly preferable to use stainless steel because of its strength. Hereinafter the insulating material pack 5 is to be explained in more detail. First of all, the requirements for mechanical strength should be explained. For the current limiters according to Fig. 1 and according to Fig. 2 the current limiting metal is into the long cavity 1b of the second electrode 1, and into the cavity 2a of the insulating pipe section 2. When evaporating, it creates a high pressure such as 3500-4000 kg / cm when the flow is limited. Accordingly this pressure results as the internal pressure in the cavity 2a of the insulating pipe section 2, so this is üohrstück 2 in the peripheral direction and in the axial direction under a large tensile stress. The beryllium oxide porcelain or that Has insulating pipe piece 2 alumina porcelain a high compressive strength, such as B. 100 lcg / ram, however

low tensile strength, such as B. about 10 kg / mm " .,

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If now a tensile stress is built up by the internal pressure is, the insulating pipe section 2 breaks, so that the filled flow limiting material penetrates to the outside and escapes. The current limiter is thrown out. With regard to these problems are encountered in the raw material for insulating material packaging 5 is of great importance. The manufacture of this insulating material pack is explained below will.

The current limiter according to FIG. 2 will first be considered P. If the second electrode 1, the insulating pipe section 2 and the outer roller 3 are assembled according to the figure and an organic insulating material is packed into the space, the insulating pipe section 2 is not under any external pressure. Thus, the insulating earpiece 2 remains below its inherent strength. IDs thus shows a low tensile strength. It is therefore impossible for the insulating pipe section to withstand an internal pressure of 3500 - KOOO kg / cm _r which is caused when the current is limited. The insulating pipe section 2 breaks immediately and the current limiter fails.

Il other hand, when a second electrode 1 Chroni-otahl, an insulating pipe section 2 of beryllia porcelain, and an outer tube 3 ^a US stainless steel SUS 27 are zusammengssetzt and maintained at 600 C, when the insulating material χ having a linear expansion coefficient of 18 10 is filled in, and when the whole thing is then cooled down, the following effects appear.

The linear expansion coefficient of the Be ry Hi umo :; id porcelain is 5 x io "" ⁱ . The beryllium oxide porcelain will thus strengthen the insulating pipe section 2 through the contraction of the outer pipe 3 with a linear expansion of 18 × 10 ^- and through the insulating material 5 in the peripheral direction and in the axial direction

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Subjected to compressive forces, i) _a init the insulating Rolirstiick against tensile stresses resistance, which delimits by the internal pressure of the evaporating material current i generates / ground. However, it is impossible to find such an insulation material. 3s there is only the option of shrinking.

The structure, function and manufacture of the invention The insulating material used is described in the following: A mixture of a powdery glass-like Material and a synthetic mica, in particular a synthetic fluorophlogopite mica, is called Rolling stock is used for the insulating material 5. The vitreous material preferably has the following properties:

(a) High coefficient of linear expansion

(b) remarkable drop in viscosity with increasing temperature on the transition temperature, which is in the range from 450 ° C - 500 ° C

(c) Transparency box less than 600C - 650C

(d) high insulation strength

(e) no corrosion of the synthetic fluorophlogpit mica at 600 ° C - 650 ° C.

It is preferred to use a compound which contains KqO, Na ₂ O, Li ₂ O, BaO or B ₂ ^ i as main components, and small amounts of PbO and SiOp as secondary components.

The synthetic gold fluoride mica preferably has one flat shape with a large particle size, around a To avoid reaction with the vitreous material and to ensure good flowability during compression molding, It is particularly preferred to use a mica with a particle size of 60-100 mesh / 2.5 cm. The amount of vitreous material out of the total of

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vitreous material and mica is preferably 70-30 percent by volume, If the vitreous material in Excessive amounts are present, the viscosity of the powdery mixture is lowered and it results good flowability when pressure forming in the heat. Thus, the insulating material in this pail can easily be used be packed. On the other hand, however, as described below, the consolidation point is lowered and the permanent contraction forces are reduced. Further the modulus of elasticity is also reduced and the strength decreases .. "If, on the other hand, too little vitreous "If material is available, packing the insulating material is made difficult and the result is an inferior packing. On the other hand, when full packing is achieved, high contraction forces persist and so do the result is a product with great strength.

The coefficient of linear expansion of the compression molded The molded product obtained in the heat depends on the raw materials. The molded product usually depends on the properties of the vitreous material. Ss expands considerably at around the softening point of the vitreous material the end. The coefficient of linear expansion of the molded Profc ducts at lower temperatures is for the present Invention very important. This expansion coefficient has the same or a lower value than the metal of the outer tube 3 », however, has a higher value than the porcelain of the insulating tube piece 2.

The following is a method for packing the insulating material explained.

example

50 percent by volume vitreous material made of K ₀ O, Li ₀ O, Na ₀ O, BaO, PbO, B ₀ O ₀ and SiO ₀ with an oiiior transition temperature of

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420 C and a particle size of less than 250 Masclien / 2.5 cm and 50 volume percent of a synthetic fluorophlogopite mica with a particle size of OO - 100 hashes / 2.5 cm are mixed and then at about 7 percent by volume Wetter added and mixed.

The molded product 9 shown in Fig. H is produced by molding this mixture under a pressure of 500 kg / cm using a metal mold at room temperature. The outer tube 3 consists of stainless steel SUS 27, the insulating Itohrstück 2 consists of beryllium oxide porcelain and the second slectrode 1 consists of chromium-copper alloy. The molded product 9 »consists of the mixture of the vitreous material and the mica. These parts are assembled according to FIG. K and kept in an electric furnace at 600 ° C. for 30 minutes. The whole is then placed in a mold and pressed with a pressure of 2 t / cm, the insulating material, which consists of the vitreous material and the mica, in the space between the insulating tube 2 and the electrode 1 on the one hand and the outer tube 3 On the other hand, when the molded product is cooled to 350 ° C, the compression is stopped and the molded product is cooled to room temperature.

■ The product obtained in this way with the packed insulating material is excellent as a current limiter as it protects against tensile stresses due to the internal pressure of the evaporated Current limiting material is resistant. The mass of glass like material and mica, which serves as the insulating material 5 of this example, has a linear expansion coefficient in the range of 11.5 x 10 ~ in the range of room temperature up to the softening point and a solidification point of ^ 50 ° C.

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The linear expansion or Kontraktionskoeffiaient the insulating material 5 is very large, when the insulating material is compressed at 600 ° C and cooled to ⁰ C k50. On the other hand, the insulating material has good flowability and it is compressed. Accordingly, the contraction does not create a gap or void in the packed insulating material. If the insulating material in the 100% packed state is cooled to the solidification point, ie to 450 C, the linear expansion coefficient is reduced to 11.5 x 10 "and the flowability disappears completely. Thus, the insulating material 5 is not caused by the contraction of the outer tube 3 is compressed while the insulating pipe section 2 is under the compressive pressure, but the insulating pipe section does not receive any compressive stress due to the contraction of the insulating material at temperatures which are above k50 ° C.

However, if this material is at a temperature below

e is cooled, the insulating material is compressed by the large contraction of the outer tube 3, wherein both the coraprassion tension caused by the contraction of the outer tube 5 as well as the compressive stress of the mass of vitreous due to the contraction Material and mica on the insulating pipe section 2 Beryllium oxide Poraellan with the smallest linear expansion coefficient, d »h. of 5 x 10 ~ can be transferred.

This leaves the insulating pipe section 2 made of beryllium oxide porcelain under high compressive stress. The compressive stress runs both in the periphery and in the axial direction. The strength increases considerably compared to free beryllium oxide porcelain.

With regard to these bodicingen, the procedure is similar to do ti Printing forme conditions in a rubber press after approval of pressure.

209829/0861 _B AD

The current limiter manufactured according to the invention with
Self recovery has a permanent compressive stress in your insulating pipe section 2, so that the
insulating llohrstück 2 has a great mechanical strength and against a high internal pressure during the
Stroni cut-off period is constant. Furthermore
the insulating material 5 is subject to distortion or softening at temperatures below 450 ° C. and it has a high heat resistance.

The mica powder has the shape of flat plates and is laminated in. Condition kept. Accordingly, the A mass of vitreous material and mica has a greater elastic strength than the vitreous material alone and it advantageously does not break down when changing of rapid heating and rapid cooling.

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Claims (2)

- 1 P - T E IJ T A W S Γ R Ü C II 3 . JS tr OmIIe ₁ J re user with self-recovery ability with a ^ "'' first and a uveiteu electrode, with an insulating j.iolirstüolr between the electrodes, the insulation of which contains an otron-limiting material with selasterliolunjs - ability, with an outer surface, the insulating .ilolirstüclc ungiut and with an insulating ■ ■ pack swiüiieii de;: i Aui3etirolir and doai insulating Itolir- P piece, dadurcix (jekeunzeiclmet that the insulating material (5) has a linear expansion coefficient, which is below the softening point greater than the "linear" usdelinuiaGslroerfizietit of the insulating JRoI piece (2) and which equals the linear output coefficient des -iußetirohrs (3) or smaller than the is the linear expansion coefficient of the outer tube (3). 2. Strombegrcnaer according to claim I _1, characterized in that the insulating material (5) is a mica powder and a vitreous Ilaterial with potassium oxide, sodium oxide, lithium oxide, barium oxide or boric anhydride as ^ Main components and with small amounts of lead oxide and Contains ilium oxide. 3 · Stroinbegrenzsr according to claim 2, characterized in, that the hengo of the vitreous material to the total of vitreous material and mica powder in the IJoreich, from 70 to 30 percent by volume. H. Current limiter according to one of claims 2 or 3 _f, characterized in that the mica powder has a particle size of 60-100 meshes / 2.5 cm and that the glassy powder has a particle size of less than P.'jO Ma ο cho n / 2.5 cm. 2 Π U l · i)! , b < _BAD ORlGfNAU - Ί j - 5. Current limiter according to one of claims 1 to h, characterized in that the insulating ilohr piece (2) is made of gelee raelian or ^ luaiiniunji-Porsellan. * J 6. Current limiter according to one of the claims 1 to 5 »dadurcli characterized in that the first electrode (k) is screwed to one end of the outer tube (3) and that a union nut (S) is screwed onto the other end of the outer tube (3) which engages a flange (1a) of the second electrode (i) via an insulating washer (7). 7. Current limiter according to one of claims 1 to 6, characterized characterized in that the outer tube (3) made of stainless steel or Brass is made. 8. Current limiter according to one of claims 1 to 5 or 7 » dadurcli characterized in that the outer tube (3) extends over the splash (1a) of the second electrode (1) extends out and has an inner flange (3a). 2.3.72- 2 (JJ ν ζ 0 / US b 1 ⁸ ^ ORIGINAL, Blank page