JPH0132673Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to suppressing the pressure inside the container of the switch. In addition, the switch referred to in this invention is
In particular, it refers to containers such as circuit breakers, current limiters, and electromagnetic switches, which usually cause arcs within small containers.

In the following, a circuit and a circuit breaker will be explained as an example.

FIGS. 1 to 3 are cross-sectional views of conventional circuits and disconnectors, each showing different operating states.

1 is a cover, 2 is a base, and the cover 1 and the base 2 constitute a container 3. A fixed contact 4 has a fixed contact 6 at one end of a fixed conductor 5, and the other end serves as a terminal portion to be connected to an external conductor (not shown). 7 is a movable contactor, and a movable conductor 8
It has a movable contact 9 facing the fixed contact 6 at one end. 10 is a movable contact device, and 11 is a movable arm, which is fixed to a crossbar 12 and configured to open and close each pole at the same time. 13 is the arc extinguishing room,
It is formed by a plurality of arc extinguishing plates 14 and side plates 15 supporting both sides thereof. Reference numeral 16 denotes a toggle link mechanism, which is composed of an upper link 17 and a lower link 18. One end of the upper link 17 is the cradle 19
The other end is connected to one end of the lower link 18 by shafts 20 and 21, respectively. The other end of the lower link 18 is connected to the movable arm 11 of the movable contact device 10. Reference numeral 22 denotes a tiltable operating handle, and 23 an operating spring, which is suspended between the shaft 21 of the toggle link mechanism 16 and the operating handle 22. Reference numerals 24 and 25 indicate thermal and electromagnetic tripping mechanisms, respectively, which when activated, trip bar 2 by bimetal 26 and movable iron core 27.
8 in a counterclockwise direction.
Reference numeral 29 is a latch whose one end is locked to the trip bar 28 and the other end is locked to the cradle 19.

When the operating handle 22 is tilted to the closed position with the cradle 19 locked to the latch 29, the toggle link mechanism 16 is extended, the shaft 21 is locked to the cradle 19, and the movable contact 9 is joined to the fixed contact 6.
This state is shown in FIG. Next, operation handle 2
2 to the open position, the toggle link mechanism 16 bends to separate the movable contact 9 from the fixed contact 6,
The movable arm 11 is locked to the cradle shaft 30. This state is shown in FIG. Furthermore, when an overcurrent flows through the circuit in the closed circuit state shown in FIG. The cradle 19 rotates clockwise around the center and is locked to the stopper shaft 31.
At this time, since the connection point between the cradle 19 and the upper link 17 exceeds the line of action of the operating spring 23, the spring force of the operating spring 23 causes the toggle link mechanism 16 to
is bent and the crossbar 12 interlocks each pole to automatically cut the sheath. This state is shown in FIG.

Next, the behavior of the arc that occurs when the circuit or breaker interrupts the current flow will be explained.

Now, when the movable contact 9 and the fixed contact 6 are in contact, the power is transferred from the power supply side to the fixed conductor 5, the fixed contact 6, the movable contact 9, and the movable conductor 8.
It is supplied to the load side via sequentially. In this state, if a large current such as a short circuit current flows through this circuit, the movable contact 9 will move to the fixed contact 6 as described above.
separated from At this time, an arc (FIG. 3) A is generated between the fixed and movable contacts 6 and 9, and an arc voltage is generated between the fixed and movable contacts 6 and 9. This arc voltage increases as the separation distance of the movable contact 9 from the fixed contact 6 increases, and at the same time, the arc A is attracted and expanded in the direction of the arc extinguishing plate 14 by magnetic force. and further rises. In this way, the arc current reaches a current zero point, the arc is extinguished, and the shearing is completed. However, this huge amount of arc energy injected eventually becomes thermal energy and completely escapes from the container, but it temporarily increases the temperature of the gas inside the container, which eventually leads to This will cause the gas pressure to rise rapidly. This could lead to deterioration of the insulation inside the circuit or disconnector, an increase in the amount of sparks emitted to the outside of the circuit or disconnector, which could lead to power supply short-circuit accidents or damage to the circuit or disconnector itself.

Next, we will discuss the energy consumption mechanism of the arc, which was the basis for creating this idea.

FIG. 4 shows an arc A generated between the contacts 4 and 7. In the figure, T indicates the flow of thermal energy conducted from the arc A to the contact and escapes, m indicates the flow of energy of metal particles escaping from the arc space, and R indicates the flow of energy due to light escaping from the arc space. In FIG. 4, the energy injected into the arc A is almost consumed by the three energy flows T, m, and R mentioned above. Of this, the heat escape T to the contact is minute, and most of the energy is carried away by m and R. Conventionally, in the energy consumption mechanism of arc A, m in the figure was overwhelming, and the energy of R was almost ignored, but recent research by the inventor and others has revealed that the energy of R, that is, It has now become clear that the energy consumption by light is enormous, reaching about 70% of the energy injected into Arc A.

That is, the consumption of energy injected into the arc can be analyzed as follows.

P _W = V・I=P _K +Pth+P _R P _K =1/2mV ² +m・Cp・T However, P _W : Instantaneous injection energy V: Arc voltage I: Current V・I: Instantaneous electrical energy injected into the arc P _K : Instantaneous energy consumption carried away by metal particles 1/2mV ² : Instantaneous energy consumption carried away when mg of metal particles fly away at velocity V m・Cp・T: Gas with constant pressure specific heat Cp (metal particle gas) Instantaneous energy consumption taken away when escaping at temperature T Pth: Instantaneous energy consumption escaping from the arc space to the electrode by heat conduction P _R : Instantaneous energy consumption radiated directly from the arc by light Consumption above The amounts vary depending on the contact shape and arc length, but for an arc of 10 to 20 mm, P _K = 10 to 20%, Pth = 5%, and P _R = 75 to 85%, respectively.

Next, FIG. 5 shows the situation when the arc A is confined in the container 3. When the arc A is confined in the container 3, the space inside the container 3 is filled with metal particles and becomes hot. In particular, the above-mentioned state is strong in the gas space Q around the arc positive column A (the space Q indicated by diagonal lines in the figure). Now, the light emitted by the arc A is emitted from the arc positive column A, and is irradiated onto the wall of the container 3 and reflected. The reflected light is scattered, passes through the high-temperature space filled with metal particles, and is irradiated onto the wall again. This process is repeated until the amount of light reaches zero. The path of light during this time is shown as Ra→Rb→Rc→Rd in the figure.

In the above process, the light emitted from arc A is consumed at the following two points.

(1) Absorption at the wall surface (2) Absorption by the arc space and surrounding (high temperature) gas space, that is, absorption by the gas space Additionally, the light emitted from arc A ranges from the far ultraviolet below 2000 Å to the far infrared above 1 μm. consists of a continuous spectrum and a line spectrum over all wavelength ranges. Even if the surface of a typical container wall is black, it only has the ability to absorb light within a range of about 4000 Å to 5500 Å.
In other ranges, only a portion is absorbed and most of it is reflected. However, absorption in the arc space and surrounding high temperature gas space is as follows.

When a gas space of length L having a uniform composition and temperature is irradiated with light of wavelength λ, the amount of light absorbed by the gas space can be calculated as follows.

Ia＝Ae・n・LIin……(1) Ia: Absorption energy by gas Ae: Absorption probability Iin: Irradiating light energy n: Particle density L: Optical path length through which light passes It shows the amount of absorbed energy with respect to wavelength λ. A is the absorption probability for a specific wavelength λ and is a function of wavelength λ, gas temperature, and particle type.

Regarding equation (1), according to the teachings of quantum mechanics,
The absorption coefficient A has the largest value for a gas in the same state as the light source gas that emits light (that is, the type of particles and temperature are the same) in both continuous and line spectra. That is, the light emitted from the arc space is absorbed most in the arc space and the surrounding gas space.

In equation (1), the amount of absorbed energy Ia of light is proportional to the optical path length L. As shown in Fig. 5, when the light from the arc space is reflected by the wall surface, L in equation (1) increases by the number of reflections.
The amount of light energy absorbed in the hot portion of the arc space will increase.

This means that the energy of the light emitted by the arc A is eventually absorbed by the gas in the container 3, thereby increasing the temperature of the gas and the pressure of the gas.

Therefore, the premise of this idea is to use a specific material to effectively absorb the light energy, which reaches approximately 70% of the energy injected into the arc. One or two of fibers, nets, and highly porous materials with an apparent porosity of 35% or more that effectively absorb the light emitted by the arc at specific positions that receive the energy of the light.
By selectively arranging more than one type of composite material, a large amount of light within the container is absorbed to lower the temperature of the gas space, thereby lowering the pressure.

In general, the above-mentioned fibers are selected from inorganic, organic, composite materials of inorganic and organic, metals, woven materials, non-woven fabrics, etc.; On top of that, it needs to have thermal strength.

In addition, the mesh may be selected from inorganic, organic, inorganic/organic composite materials, metal, etc., as well as multi-layered thin wire mesh, knitted wire, etc. This net also needs to have thermal strength.

Among the above-mentioned fiber and mesh materials, inorganic materials such as ceramics, carbon, and asbestos are suitable, and metals such as Fe and Cu are most suitable, and materials plated with Zn, Ni, etc. are also applicable.

Porous materials are generally materials with a large number of pores within a solid structure, and exist in a wide range of materials such as metals, inorganics, and organic materials. One type is sintered and solidified at the contact points between solid particles, and the other type is mainly composed of pores and the partition walls forming the pores are made of solid material. In this invention, the term "material" refers to the original material before shape processing, regardless of shape.

Further classification can be divided into those in which the gaps between particles exist as pores, those in which the gaps between particles and the pores within the particles are shared, and those that contain foamable pores inside. Also breathable
It can also be roughly divided into those that have water permeability and those that have independent pores and are not breathable.

The shape of the above-mentioned pores is very complex and is broadly classified into open pores and closed pores, and the structure is expressed by pore volume or porosity, pore diameter and pore diameter distribution, specific surface area, etc.

The true porosity is the ratio of the volume of all open and closed pores contained in a porous material to the total volume (bulk volume) of the material, that is, the true porosity is expressed as a percentage. It can be calculated by a liquid or gas displacement method, an absorption method, etc., but as a simple method, it is calculated as follows, as defined in JISR2614, Method for Measuring Specific Gravity and Porosity of Fireproof Insulating Bricks.

True porosity = (1 - bulk specific gravity / true specific gravity) × 100% In addition, the ratio of the open pore volume to the total volume of the material (bulk volume), which is expressed as a percentage, is the apparent porosity, and JISR2205 As defined in the method for measuring the apparent porosity, absorption rate, and specific gravity of firebrick, it is calculated as follows. Note that the apparent porosity is also referred to as effective porosity.

Apparent porosity = saturated water weight - dry weight / saturated water weight - weight in water x 100% The pore diameter is determined from the measured values of pore volume and specific surface area. Although the interfacial gap ranges from several angstroms to several mm, it is generally defined as the average value of the distribution. In porous materials, the shape, size, and distribution of pores can be measured using a microscope or mercury intrusion method. In general, it is preferable to use a microscope directly in order to accurately understand the complicated shape and distribution of pores.

The BET method, which is determined using adsorption isotherms at various temperatures of various adsorbed gases, is often used to measure the specific surface area, and nitrogen gas is particularly used.

Next, we will explain the absorption of light energy by a specific material and the resulting drop in gas pressure, which is the premise of this invention, using an inorganic highly porous material as an example.

FIG. 6 is a perspective view showing the inorganic highly porous material, and FIG. 7 is a partially enlarged sectional view of FIG. 6. In the figure, 33 indicates a highly porous inorganic material, and 34 indicates an opening leading to the surface of the inorganic material. The pore diameters of the openings 34 vary in size from several μ to several mm.

Now, as shown by R in FIG. 7, when light enters the porous material 33 and enters the aperture 34, the light hits the wall of the inorganic material and is reflected, inside the pore. Multiple reflections and finally on the wall
100% absorbed. That is, the light incident on the apertures 34 is directly absorbed by the surface of the inorganic material and becomes heat within the pores.

FIG. 8 shows a curve diagram of the pressure change inside the model container when the apparent porosity of the inorganic highly porous material is changed in a model container in which the inorganic highly porous material is placed. In FIG. 8, the horizontal axis is the apparent porosity, and the vertical axis is normalized to the pressure of 1 when the inner wall of the container is made of metal such as Cu, Fe, Al, etc. The experimental conditions were as follows: AgW contacts were installed at a constant gap of 10 mm in a cubic sealed container with sides of 10 cm, and a sinusoidal current arc with a peak of 10 KA was applied for 8 mS.
(milliseconds), and the pressure inside the container generated by the energy at this time is measured.

The inorganic highly porous material used in the above examples is porous ceramic made by molding and sintering cordierite ceramic raw material by adding a combustible or foaming agent, etc. to make it porous, and the average pore size is Range 10~300μ, apparent porosity of porous material 20%,
30%, 35%, 40%, 45%, 50%, 60%, 70%, 80
%, 85%, various samples measuring 50 mm x 50 mm x 4 mm were used and placed on the wall of the container so as to cover 50% of the surface area of the inner surface of the container.

Regarding the pore diameter, the issues are the average pore diameter, which slightly exceeds the wavelength range of the absorbed light, and the ratio of the pores to the surface, that is, the specific surface area of the pores. Further, in terms of absorption of light within the pores, deep pores are effective, and continuous pores are preferable. The light generated from arc A in the switch is several hundred angstroms to 10,000 angstroms.
Å (1 μm), so it is suitable to have an average pore diameter that slightly exceeds this, that is, from several thousand Å to several 1000 μm, and the area of the pores on the surface is
A highly porous material with an apparent porosity of 35% or more is suitable for absorbing the light emitted by the arc A. In particular, the upper limit of the pore diameter is in the range of 1000 μm or less, and the larger the specific surface area of the pores, the more effective it is. In the experiment, the average pore size
It was confirmed that the material exhibits good absorption characteristics for light emitted by an arc in the range of 5μ to 1mm. In addition, when the material was glass and the average pore diameter was 5μ or 20μ, good light absorption was observed for the light emitted by the arc.

As can be seen from the characteristic curve a in Figure 8, the pores of the inorganic highly porous material absorb light energy and have the effect of reducing the pressure inside the switch, and this increases as the apparent porosity of the porous material increases. It becomes especially noticeable when the porosity is 35% or more, and 85%
The effect was confirmed over a range of Further increases in porosity require corresponding increases in the thickness of the highly porous material.

However, in terms of the relationship between the apparent porosity and mechanical strength of porous materials, when the porosity increases, the material becomes brittle, its thermal conductivity decreases, and it tends to melt due to high heat. The effect of decompression is weak. Therefore, in practical terms, a highly porous material with an apparent porosity in the range of 40 to 70% is optimal.

The characteristic trends shown in FIG. 8 apply to inorganic porous materials in general, and this can be inferred from the above explanation regarding light absorption.

Some conventional switches use inorganic materials, but their purpose is to protect organic containers from arcs, and their properties include arc resistance, service life, heat conduction, and mechanical properties. physical strength, insulation,
Countermeasures against carbonization are required, and the inorganic materials that meet these requirements are necessarily oriented towards densification, have different purposes, and have an apparent porosity of around 20%.

Highly porous materials include inorganic, metallic, and organic materials, among which inorganic materials are characterized as insulators and high melting point materials. These two properties are
It is an ideal material to be installed inside the switch container, and as it is an electrical insulator, it has little negative effect on shrinkage, and it does not easily melt or release gas even when exposed to high temperatures. It is ideal as a pressure suppressing material.

Porous inorganic materials include porous ceramics, refractories, glass, hardened cement, and the like, and any of them can be used to reduce the pressure of gas in the switch.

Hereinafter, embodiments of this invention will be described based on the drawings.

FIG. 9 is a partially cutaway side view of a circuit breaker according to the first embodiment of the invention, and FIG. 10 is a perspective view of the main parts. In these figures, reference numeral 4 denotes a fixed contact, which is formed by fixing a fixed contact 6 to the upper surface of the tip of a fixed conductor 5. Reference numeral 7 denotes a movable contact, which is formed by fixing a movable contact 9 that comes into contact with and separates from the fixed contact 6 to the lower surface of the tip of the movable conductor 8. 35, 35 are a pair of light absorbers,
It is selected from inorganic materials, organic materials, and composite materials of inorganic and organic materials, and is composed of one or more composite materials of fibers, nets, and porous materials with an apparent porosity of 35% or more. The two light absorbers 35, 35 are arranged so as to sandwich the arc A generated between the movable contact 9 and the fixed contact 6 from both sides when the movable contact 7 is separated from the fixed contact 4. They are arranged on both sides near the contacts 4 and 7 at a predetermined interval. Reference numeral 36 denotes an L-shaped heat absorber, which includes part or all of the upper opening 37a and the rear opening 37b formed between the two light absorbers 35, 35, except for the movement locus of the movable contact 7. It is placed near and opposite to this. Heat absorber 3
6 is an aggregate of fine metal wires made of metals or alloys such as copper, iron, stainless steel, aluminum, and nickel, porous metal, and a composite of one or more of metal plates with many small holes. It is made of wood. The rest of the configuration is the same as the conventional one, so a description thereof will be omitted.

Next, the operation of the above configuration will be explained. When the movable contact 7 is separated from the fixed contact 4, an arc A is generated between the movable contact 9 and the fixed contact 6. Light absorber 3
5 and 35 are located closest to arc A, so even though the contact point is installed on the side, the solid angle that receives the energy of the light emitted by arc A is very large, and the energy of the light, which is the source of pressure generation, is very large. The aforementioned effect of absorption is carried out very efficiently, and the internal pressure of the container at the time of shriveling is significantly reduced. As a result, the conventionally common mold container breakage due to heat or breakage is eliminated, and the mechanical strength of the container 3 consisting of the cover 1 and base 2 can be reduced, and the cover 1 and base 2 can be formed. The cost of the cover 1 and base 2 can be reduced by significantly reducing the amount of molding material and by using cheaper grade materials with lower mechanical strength as materials for the cover 1 and base 2. Furthermore, due to the reduction in the internal pressure of the container, the amount of arc emitted from the container 3 at the time of a power outage is reduced, which prevents secondary disasters such as short circuit accidents on the power supply side at the time of an electrical power outage. As the internal pressure of the container decreases, the arc temperature decreases, and because the arc A is sandwiched between the light absorbers 35 and 35 from both sides, metals and insulators near the arc A are prevented from melting and evaporating, as was the case in the past. The resulting drop in megohms between power loads and between phases is prevented, improving safety and reliability.

Further, the heat absorber 36 is the light absorber 3 as described above.
Since the opening 37a and 35 are disposed opposite to and near the openings 37a and 37b, the opening 37
The molten material of the contacts 6, 9 and the conductors 5, 8 discharged towards a, 37b adheres to the heat absorber 36,
The megohm between contacts and between phases is improved after the shear break.

In addition, since the heat absorber 36 acts on the high temperature gas after passing through the light absorbers 35, 35, the heat absorber 36
It is difficult for the legs of the arc A to be formed directly on the surface of the heat absorber 36, and there are no problems caused by the formation of the legs of the arc, such as a decrease in arc voltage or a decrease in megohm due to melting and evaporation of the heat absorber 36, and the thermal conductivity is The heat absorber 36 with a large surface area compensates for the absorption of light energy and thermal energy that could not be absorbed by the light absorbers 35, 35.
It has the effect of promoting a decrease in the internal pressure of the container.

FIG. 11 shows a second embodiment of this invention, in which a heat absorber 36 is installed only at the back between the light absorbers 35, 35.

Note that if an inorganic porous material containing magnesia or zirconia as a main component is used as the material for the light absorbers 35, 35, the surface of the light absorber will crystallize without becoming vitrified even if it is exposed to the arc and heated to high temperatures. Therefore, during the arc period, the megohm on the surface of the light absorber does not decrease, and good cutting performance can be obtained. Furthermore, if the surface of the inorganic porous material is hardened by heat treatment or if an organic material is suitably combined with the inorganic porous material, the effect of reducing the internal pressure will not be significantly hindered, and the Precipitation of powder from the absorbers 35, 35 can be prevented.

As described above, according to this invention, the switch Because it can effectively reduce the gas temperature and gas pressure inside the container,
It is possible to prevent insulation deterioration inside the container and to prevent short-circuit accidents on the power supply side due to a reduction in the amount of discharge sparks to the outside. In addition, according to this invention, by using the above-mentioned light absorber and heat absorber together, high temperature arc gas can be efficiently cooled, so the effect of extinguishing the arc generated between the contacts is extremely large. Become. Therefore, it is now possible to omit the arc extinguishing device consisting of a plurality of arc extinguishing plates conventionally provided in this type of switch. It also has the effect of significantly reducing costs.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views of conventional circuits and disconnectors, each showing different operating conditions. Figure 4 is an explanatory diagram showing how an arc occurs between the contacts.
Fig. 5 is an explanatory diagram showing how an arc is generated between the contacts in the container, Fig. 6 is a perspective view showing the inorganic highly porous material, Fig. 7 is a partially enlarged sectional view of Fig. 6, and Fig. 8 9 is a curve diagram showing the change in pressure inside the container with respect to the apparent porosity when an arc is generated, FIG. 9 is a partially cutaway side view of the circuit breaker according to the first embodiment of this invention, and FIG. The figure is a perspective view of the main part.
FIG. 1 is a perspective view of essential parts according to the second embodiment. 3... Container, 4, 7... Electric contact, 5, 8...
...Conductor, 6,9...Contact, 35...Light absorber, 3
6... Heat absorber, 37... Opening, A... Arc. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) At least one pair of electrical contacts that are composed of a conductor and a contact fixed thereto and that open and close within a container, and both sides of the electrical contacts in the vicinity thereof. a pair of light absorbers arranged at a predetermined distance from each other and absorbing the optical energy of the arc generated between the contacts; and a pair of light absorbers formed between the two light absorbers except for the movement locus of the electric contact. and a heat absorber disposed near and facing a part or all of the opening to absorb the thermal energy of the arc gas discharged toward the opening, and the light absorber may be inorganic or organic. It is selected from composite materials of inorganic and organic systems, and is composed of one or more composite materials selected from fibers, nets, and porous materials with an apparent porosity of 35% or more. The absorber is a switch made of a composite material of one or more of the following: an aggregate of thin metal wires, a porous metal, and a metal plate with many small holes. (2) The switch according to claim 1, in which the surface of the light absorber is hardened by heat treatment. (3) The switch according to claim 1 or 2, wherein the light absorber is formed mainly of magnesia or zirconia.