JPH0451926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switch. Note that the term "switch" as used in the present invention particularly refers to circuit breakers, current limiters, electromagnetic switches, etc., and usually means a switch that generates an arc within a small container.

The present invention will be explained below using a circuit and a circuit breaker 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. 4 is a fixed contact, which has a fixed conductor 5 and a fixed contact 6 at one end thereof;
The other end is a terminal portion to be connected to an external conductor (not shown). A movable contact 7 has a movable conductor 8 and a movable contact 9 facing the fixed contact 6 at one end thereof. 10 is a movable contact device;
Reference numeral 11 is a movable arm that is fixed to the crossbar 12 and is configured to open and close each pole at the same time. 13 is an arc extinguishing chamber in which an arc extinguishing plate 14 is held by a side plate 15. Reference numeral 16 denotes a toggle link mechanism, which is composed of an upper link 17 and a lower link 18. Top link 17
One end is attached to the cradle 19, and the other end is attached to the lower link 1.
8 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. 2
Reference numeral 2 denotes an up-and-down operation handle, and 23 an operating spring, which connects the shaft 21 of the toggle link mechanism 16 and the operation handle 2.
It is stretched between 2. 24 and 25 are thermal and electromagnetic trip mechanisms, respectively, and when activated, they are a bimetal 26 and a movable iron core 27, respectively.
This allows the trip bar 28 to be rotated counterclockwise. 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. Credle 19 is latch 29
When the operating handle 22 is tilted to the closing position while the handle is locked, the toggle link mechanism 16 extends and 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, when the operation handle 22 is tilted to the open position, the toggle link mechanism 16 is bent to separate the movable contact 9 from the fixed contact 6 and move the movable arm 11 to the cradle shaft 30.
is locked. This state is shown in FIG. Furthermore, if an overcurrent flows through the circuit in the closed state shown in FIG.
As a result, the cradle 19 rotates clockwise about the cradle shaft 30 and is locked to the stopper shaft 31. Since the connecting point between the cradle 19 and the upper link 17 crosses the line of action of the actuating spring 23, the toggle link mechanism 16 is bent by the spring force of the actuating spring 23, and each pole is interlocked by the cross bar 12 to automatically operate. make a decision. This state is the third
It is a diagram.

Next, the behavior of an arc that occurs when a current is interrupted in a circuit or breaker will be explained.

Now, when the movable contact 9 and the fixed contact 6 are in contact, the power is supplied from the power supply side to the load side via the fixed conductor 5, fixed contact 6, movable contact 9, and movable conductor 8 in order. Ru. In this state, when a large current such as a short circuit current flows through this circuit, the thermal tripping mechanism 24 or the electromagnetic tripping mechanism 25 acts to separate the movable contact 9 from the fixed contact 6 as described above. At this time, an arc 32 is generated between the fixed and movable contacts 6 and 9, an arc voltage is generated between the fixed and movable contacts 6 and 9, and the separation distance of the movable contact 9 from the fixed contact 6 increases accordingly. At the same time, the arc 32 is drawn toward the arc-extinguishing plate 14 by the magnetic force and extends, so it 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 injected arc energy eventually becomes thermal energy and completely escapes from the container, but during the transient period up to that point, it increases the temperature of the gas inside the limited container, and will cause the gas pressure to rise rapidly. This resulted in serious drawbacks such as deterioration of the insulation inside the circuit and disconnector, power supply short-circuit accidents due to an increase in the amount of sparks emitted to the outside of the circuit and disconnector, and destruction of the circuit and disconnector itself.

Specifically, the reason for this drawback is related to the energy consumption mechanism of the arc. That is, FIG. 4 shows an arc A occurring between the contacts 4 and 7. In the figure, T indicates the flow of thermal energy conducted from the arc to the contactor, 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. 3, the energy injected into the arc is largely consumed by the three energy flows T, m, and R mentioned above. Of this, heat escapes to the electrode T
is minute, and most of the energy is carried away by m and R.

Conventionally, in the mechanism of arc energy consumption, m in the figure is overwhelming, and R
The energy of R was almost ignored, but recent research by the inventors revealed that the energy of R, that is,
It was found that the energy consumption by light was enormous, reaching about 70% of the energy injected into the arc.

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

Pw=V・I=Pk+Pth+P _R Pk=1/2mv ² +m・Cp・T However, Pw: Instantaneous injection energy V: Arc voltage I: Current V・I: Instantaneous electrical energy injected into the arc Pk: Metal particles Instantaneous energy consumption taken away 1/2 mv ² : Instantaneous energy consumption taken away when mg of metal particles fly away at speed v m・Cp・T: Gas (metal particle gas) with constant pressure specific heat Cp escapes at temperature T Pth: Instantaneous energy consumption that is carried away from the arc space by heat conduction to the electrode P _R : Instantaneous energy consumption that is radiated directly from the arc by light The above consumption depends on the electrode shape and arc length. However, for arcs of 10 to 20 mm, each
Pk=10-20%, Pth=5%, P _R =75-85%.

Next, we will explain the situation when the arc is confined in a container.
As shown in the figure. When the arc is confined in the container, the space inside the container is filled with metal particles of the electrode and becomes hot. In particular, the surrounding gas space Q of the arc positive column A
(Space Q indicated by diagonal lines in the figure) is in the above-mentioned state. Now, the light emitted from the arc 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 electrode 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 Ra→
It is shown as Rb→Rc→Rd.

In the above process, the light emitted from the arc is consumed in the following two ways.

(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. The light emitted from the arc ranges from deep ultraviolet light below 2000Å to 1μm.
over all wavelength ranges up to far infrared,
Consists of continuous spectrum and line spectrum.
Even if the surface of a typical container wall is black, it will only emit odors within the range of 4000Å to 5500Å.
It only has the ability to absorb light; in other areas, it only partially absorbs and reflects most of it. However, absorption in the arc space and surrounding high temperature gas space is as follows.

When a gas space of length L and 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=A・n・LIin...(1) Ia: Absorbed energy by gas A: Absorption probability Iin: Irradiated light energy n: Particle density L: Optical path length through which light passes It shows the amount of absorbed energy versus 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 that is in the same state as the light source gas that emits light (i.e., the type of particles and temperature are the same) for both continuous and line spectra. will have the following. That is, the light emitted from the arc space is most absorbed 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 Figure 5, when the light from the arc space is reflected by the wall surface, L in equation (1) increases by a multiple of the number of reflections, and the light is absorbed in the high temperature part of the arc space. This results in an increase in the amount of light energy used.

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

Therefore, the present invention has been made to solve the above-mentioned drawbacks, and consists of a conductor and a contact fixed to the conductor, and at least one conductor that opens and closes.
In a switch equipped with a pair of electrical contacts, an arc extinguishing plate having a notch for sucking and extinguishing an arc generated during an opening operation, and a container for storing the contacts and the arc extinguishing plate, , a pair of vertical walls made of a composite material of one or more types of netting and porous materials with an apparent porosity of 35% or more are arranged on opposing inner wall surfaces in the notch of the arc-extinguishing plate, respectively. The present invention provides a switch.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the switch according to the present invention may have almost the same configuration as that shown in FIGS. 1 to 3, for example, in the case of a circuit or disconnector, so in the following description, the present invention will be used. Only the main parts that were covered will be explained.

First, in FIGS. 9 and 10, as is well known to those skilled in the art, each arc extinguishing plate 14 is made of a magnetic metal plate and has a substantially U-shaped end face on the rear side in the arc driving direction (direction of arrow F). , or has a U-shaped notch 140. In other words, by providing a notch from one side of the magnetic metal plate, the notch 14
The arc-extinguishing plate 14 includes a pair of leg portions 14a and a bridge portion 14b connecting both leg portions 14a on both sides of the arc-extinguishing plate 14. These arc-extinguishing plates 14 are supported by side plates 15 that form the arc-extinguishing chamber 13 and are separated from each other by a predetermined distance substantially along the moving direction of the movable conductor 8 . (See Figures 1 to 3.) 35, 35 are a pair of vertical walls made of, for example, an inorganic highly porous material, as shown in Figure 9.
The legs 14a are arranged along opposing inner wall surfaces 140a, 140a of each leg 14a facing the notch 140 so that the plane thereof is substantially orthogonal to the plane of each arc-extinguishing plate 14. Since one vertical wall 35 is used for each leg 14a, if arranged as described above, the notch 14
The width of 0 becomes narrower to form a slit.
These vertical walls 35, 35 may be supported by being fixed to the corresponding leg portions 14a in an appropriate manner, or the arc extinguishing chamber 13 may be arranged in a predetermined manner.
It may be supported by the side plate 15 or the wall of the container 3.

With the above configuration, the following effects can be obtained. In other words, the arc extinguishing plate generally attracts (extends) the arc by magnetic action and cools and extinguishes the arc by contacting it, but in some cases, the arc extinguishing plate It sticks to the legs of the arc extinguishing plate without penetrating deep into the notch of the plate. In this case, the arc may not be able to extend sufficiently, and therefore may reach a current zero point without being sufficiently cooled and may not be interrupted. This phenomenon occurs particularly when the magnetic field generated by the arc current locally interacts with a portion of the arc-extinguishing plate, that is, when the applied current is in a relatively small current range.

Furthermore, if a standing wall is simply placed in the cutout and a slit is created in the arc extinguishing plate, even if a large current arc occurs and enters the slit, the arc positive column within the slit will be Rapid temperature rise and
Due to the pressure increase associated with this, the arc does not easily penetrate deep into the slit, even though it is receiving an attractive force from the arc extinguishing plate. Therefore, the suction, elongation, and cooling effects of the arc-extinguishing plate are not sufficient, and the shearing performance is also not sufficient.

From the above, in this invention, each vertical wall 35 is made of a composite material of one or more of fibers, nets, and porous materials with an apparent porosity of 35% or more, thereby solving the above problems. can be resolved. For example, as mentioned above, the standing wall 35,3
5 is made of an inorganic highly porous material, the light energy of the arc A existing in the slit formed between the pair of vertical walls 35 is absorbed by the pores of each vertical wall 35. Therefore, the rise in temperature and pressure of the positive column of the arc A trying to enter the slit is extremely suppressed, and the slit prevents the large current arc from being attracted and driven by the magnetic force of the arc extinguishing plate 14. You will not be harmed.

The above-mentioned fibers are selected from inorganic materials, metals, composite materials, woven materials, non-woven fabrics, etc., but since they are installed in a space exposed to high-temperature arcs, they must have thermal strength.

Further, as the mesh, in addition to inorganic materials, metals, composite materials, etc., a material made of multiple layers of thin wire mesh, a knitted wire, etc. can be selected.
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.

A porous material is a material that generally has a large number of pores within its solid structure, and exists in a wide range of materials such as metals, inorganic materials, and organic materials. One type is sintered and solidified at the points of contact between solid particles, and the other type is mainly composed of pores and the partition walls forming the pores are made of solid material. Note that in this invention, the 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 in which foamed pores are included inside. It can also be roughly divided into those that have air permeability and water permeability, and those that have independent pores and are not breathable.

The shape of the pores mentioned above is very complex and broadly classified into open pores and closed pores, and their structure can be expressed in terms of pore volume or porosity, pore diameter and pore size distribution, specific surface area, etc. .

Porosity includes true porosity and apparent porosity, and 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 is the void ratio, that is, the percentage. The value shown in is the true porosity, and measurement methods include liquid or gas displacement method and absorption method, 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% On the other hand, apparent porosity is the ratio of open pore volume to the total volume of the material (bulk volume), that is, expressed as a percentage. As defined in JISR2205 Method for Measuring 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.

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

Next, the absorption of light energy by a highly porous material and the resulting reduction in gas pressure, which is the premise of this invention, will be explained 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, numeral 33 indicates a highly porous inorganic material, and numeral 34 indicates an opening leading to the surface of the inorganic material. The pore diameters of the openings 34 range from several micrometers to several mm, and exhibit a wide range of sizes.

Now, when light enters the opening 34 of this porous material 33, as shown by R in FIG. is 100% absorbed by the wall. 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 fixed gap of 10 mm in a cubic hermetic container with sides of 10 cm, and an arc with a peak 10 KA sinusoidal current was generated for 8 mS (milliseconds), and the pressure inside the container was generated by the energy generated at this time. are being measured.

The inorganic highly porous material used in the above examples is a porous ceramic made by molding and sintering cordierite ceramic raw material using a method such as adding a combustible or foaming agent to make it porous. The pore diameter
In the range of 10 to 300 μ, the apparent porosity of the porous material is 20%, 30%, 35%, 40%, 45%, 50%, respectively.
60%, 70%, 80%, 85%, 50mm x 50mm x
Various samples of 8 mm ^t 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 axial pores. Furthermore, in terms of absorption of light within the pores, deep pores are effective, and continuous pores are preferable. The light generated from the arc in the switch is several hundred Å to 10,000 Å
(1μm), so slightly exceeding this,
That is, a material with an average pore diameter of several thousand angstroms to several thousand micrometers is suitable, and a highly porous material in which the surface area of the pores has an apparent porosity of 35% or more is suitable for absorbing the light emitted by the arc. In particular, the upper limit of pore size
The larger the specific surface area of the pores in the range of 1000 μm or less, the more effective it is. In the experiment, the average pore size was 5 μ to 1
It was confirmed that if a highly porous material with a diameter of 1 mm is used, it exhibits good absorption characteristics for the light emitted by the arc.
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 FIG. 8, the pores of the inorganic highly porous material absorb light energy and have the effect of reducing the pressure inside the switch. This increases as the apparent porosity of the porous material increases, and becomes especially noticeable when the porosity is 35% or more.
Effectiveness was confirmed up to 85%. 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 becomes large, it becomes brittle and has low thermal conductivity, making it easy to melt due to high heat.On the other hand, when the porosity is small, opening and closing The effect of internal depressurization 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 primarily to protect organic containers from arcing, so when selecting an inorganic material, consider Emphasis is placed on characteristics such as arc resistance, lifespan, heat conduction, mechanical strength, insulation, and countermeasures against carbonization. Inorganic materials that meet these characteristics are necessarily densified and have different purposes, and their apparent porosity is 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 suitable as a material to be installed inside the switch container, and as it is an electrical insulator, it will not have a negative effect on shrinkage, and will not melt or emit gas even if exposed to high temperatures. This makes it ideal as a pressure suppressing material.

Examples of inorganic porous materials include porous ceramics, refractories, glass, hardened cement, and the like, all of which can be used to reduce the pressure of gas within the switch. Note that organic porous materials have problems with heat resistance and gas generation, and metal porous materials have problems with insulation and withstand voltage, so the places where they can be used are limited.

FIG. 11 shows an actual measurement example based on an embodiment of the present invention.

In the figure, the horizontal axis is the apparent porosity, and the vertical axis is the pressure value shown in comparison with the standard value 1, which is the pressure inside the container at the time of arc occurrence in the standard product.

The experimental conditions are as follows.

An actual machine with a 50A frame was used. Internal volume is 2cm
It is a sealed container measuring 9 cm x 5 cm deep, and is made of phenolic resin, which is an organic substance. The contact point in this experiment consists of Agw, which performs the normal opening and closing operation, and the peak value
An arc of 14 KA half-sine current was generated for 8 ms (milliseconds), and the pressure inside the container caused by the energy generated at this time was measured.

The above-mentioned cordierite was used as the inorganic highly porous material constituting the vertical walls 35, 35. Apparent porosity 20%, 30 with average pore size range 10μ~300μ
%, 35%, 40%, 50%, 70%, 10mm x 20
A total of two samples of mm x 3 mm ^t were used, one on each side.

In the figure, curve b is a characteristic curve obtained from actually measured values. The black point a is the same as the measured value a in FIG.

As is clear from the above characteristic curve b, the pair of vertical walls 35, 35 made of an inorganic highly porous material are connected to the opposing inner wall surface 140a of the notch 140 of the arc-extinguishing plate 14,
It can be seen that the internal pressure can be suppressed without deteriorating the shatterability by simply installing each of them in 140a.

By the way, the shape of the vertical wall 35 is not limited to that of the above embodiment, and other shapes can be selected, such as an L-shape as shown in FIG. 12, for example.

Further, in the above embodiment, the vertical walls 35, 35 are made of an inorganic highly porous material with an apparent porosity of 35% or more, but they may be made of a porous material other than an inorganic material, or they may be made of a porous material other than an inorganic material. It can be made of fibers or nets, or it can be made of a composite material of two or more of fibers, nets, and porous materials with a specific porosity.

If the present invention is carried out as described above, a switch with excellent insulation breaking performance from small currents to large currents can be provided, and a vertical wall made of a specific material such as an inorganic highly porous material can be placed in a space close to the arc. Because of this arrangement, the light energy from the arc can be effectively absorbed and the pressure inside the switch can be significantly suppressed.

[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, and FIG. 9 is a top view showing the arc extinguishing plate portion of the circuit breaker to which the switch according to the present invention is applied. , FIG. 10 is a cross-sectional view taken along the line -- in FIG. 9, FIG. 11 is a characteristic diagram obtained from the measured internal pressure of a circuit breaker according to an embodiment of the present invention, and FIG. 12 is an explanation of a modification of the vertical wall. It is a diagram. 3... Container, 4, 7... Electric contact, 5, 8...
...Conductor, 6,9... Contact, 14... Arc-extinguishing plate, 35
... Standing wall, 140 ... Notch, 140a, 140
a... Opposing inner wall surface, A... Arc, F... Drive direction. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 At least one pair of electrical contacts consisting of a conductor and a contact fixed thereto, which open and close within the container, and a notch on the rear end face in the arc driving direction to absorb and extinguish the arc generated during the opening operation. In the switch equipped with the formed arc extinguishing plate, porous pores are arranged along the arc driving direction on the opposing inner wall surface of the notch, and have an apparent porosity of 35% to 70% and an average pore diameter of 5 μ to 1 mm. 1. A switch comprising a pair of vertical walls made of a high quality material and absorbing the optical energy of the arc.