JPH0777101B2 - Contact for vacuum switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a contact for a vacuum valve in a vacuum switch.

(Prior Art) Since the vacuum switch has various excellent features such as small size, light weight, maintenance-free and environmental harmony as compared with other switches, its application range has been gradually expanded in recent years. The vacuum circuit breaker utilizes the arc diffusivity in a vacuum to perform current cutting in a high vacuum, and will be described with reference to FIG. 4 showing a side cross section thereof.

The vacuum breaker has a breaking chamber 1 that is kept vacuum-tight,
This is composed of an insulating container 2 formed of an insulating material in a substantially cylindrical shape, and metallic lids 4a and 4b provided on both ends of the insulating container 2 via sealing metal fittings 3a and 3b.

A pair of fixed electrodes 7 and movable electrodes 8 attached to opposite ends of the conductive rods 5 and 6 are arranged in the interrupting chamber 1. A bellows 9 is attached to the conductive rod 6 of the movable electrode 8 so that the movable electrode 8 moves in the axial direction while maintaining vacuum tightness in the blocking chamber 1. A metal arc shield 10 is provided above the bellows 9 to prevent the bellows 9 from being covered with arc vapor. Similarly metal arc shield 11
Is a fixed electrode 7 and a movable electrode 8 in the shutoff chamber 1.
To prevent the insulating container 2 from being covered with arc vapor. The movable contact 13a is in contact with the fixed contact 13b during energization, and the current is cut off by moving the conductive rod downward and breaking the contact between these two contacts.

Next, with respect to the mutual fixing structure of the conductive rods 5 and 6 and the electrodes 7 and 8 and between the electrodes 7 and 8 and the contacts 13a and 13b, refer to FIG. 5 showing the details around the movable electrode 8 in FIG. explain. Movable electrode 8
Is fixed to the conductive rod 6 by brazing indicated by reference numeral 12 or caulking not shown, and the movable contact 13a is fixed at the movable electrode 8 by brazing indicated by reference numeral 14 or caulking not shown. The same applies to the method of fixing the fixed electrode 7 and the contact 13b on the fixed side.

(Problems to be Solved by the Invention) Requirements for a contact for a vacuum switch are: (1) low weldability, (2) high withstand voltage, (3) excellent wear resistance, 4) The contact resistance is low and stable. In addition to this, expectations for recent vacuum switchgear have further increased, and (5) it has a low surge function,
(6) It is required to have a large current cutoff function,
These two requirements are in conflict.

First, the requirements for having a low surge function will be described. When the current is cut off by an induction circuit such as a motor load, an excessive surge voltage may be generated, and the insulation of the load device may be destroyed. The cause of this abnormal surge voltage is due to the current interruption phenomenon that occurs on the low current side during interruption in vacuum (forced current interruption without waiting for the natural zero point of the AC current waveform). is there. The value of the abnormal surge voltage V _S is represented by the product of the surge impedance Z _{O of the} circuit and the current interruption value I _C , that is, V _S = 2Z _O · I _C , and in order to lower the abnormal surge voltage V _S , That is, in order to have a low surge function, the current threshold value I _C must be reduced. Therefore, at the time of interruption,
A large amount of ions and metal particles evaporate from each surface of the movable contact 13a and the fixed contact 13b by the arc and float between the contacts, so that the arc must be easily connected. Therefore, the contact
The materials used for 13a and 13b are required to have high vapor pressure, which is highly vaporizable, not only when blocking a large current, but also when the switching current is small and the temperature rise of the contact is small.

As a material satisfying such a low surge function, an Ag-WC alloy containing Ag, which is a high vapor pressure material, is known.
The contacts made of this alloy have (1) the interposition of WC facilitates the emission of ions from the contact surface, and (2) the evaporation of metal particles from the contact surface due to the heating of the electrode surface due to the collision of field emission electrons. It has an excellent low surge function by accelerating, (3) Carbide in the contact material is decomposed by an arc to generate a charged body, and the like. In addition to this, as a material having this function, a Cu-Cr alloy containing Cu, which is a high vapor pressure material, a Cu-Bi alloy, and the like are known.

On the other hand, the contacts are required to be made of a material having a low vapor pressure in order to have the large current interruption function which is the other contradictory requirement. When shutting off a large current, the contact surface temperature becomes extremely high, but even in such a case, the amount of evaporation from the contact surface due to the arc is small, and ions and metal particles hardly float between both contacts. If it is not in a state, the cutoff property will be impaired. Therefore, in general, when one of the functions is improved, the other function is deteriorated.

As a means for satisfying these two conflicting requirements, there is one in which the contact is made of two kinds of materials, a high vapor pressure material and a low vapor pressure material. When the contacts that were in contact during energization to separate the current are separated from each other, many ions and metal particles evaporate from the part made of the material with high vapor pressure and float between the contacts, and the arc guides them. It is connected to the high vapor pressure material comrades at both contacts. After a lapse of time necessary for satisfying the low surge function, the arc is moved so that the arc, which was connected to the high vapor pressure material at both contacts, is connected to the low vapor pressure material at both contacts. This is the coil electrode 4 shown in FIG.
4, Ions floating between both contacts by controlling the longitudinal magnetic field H using the spiral electrode 45 shown in FIG.
This can be performed by changing the distribution of the metal particles and forcibly moving the arc.

However, the physical properties of a high vapor pressure material having a low surge function even at low current interruption and the physical properties of a low vapor pressure material having a large current interruption function differ greatly in terms of vapor pressure characteristics. Therefore, even if the distribution of ions and metal particles floating between both contacts is changed by the longitudinal magnetic field, the arc stagnates on the boundary between the part made of high vapor pressure material and the part made of low vapor pressure material, and it is easy to Do not move. Therefore, the low surge function and the large current cutoff function cannot be satisfied at the same time by simply configuring the contact point by simply combining the high vapor pressure material and the low vapor pressure material.

In view of the above-mentioned circumstances, the arc transfer from the high vapor pressure material to the low vapor pressure material at the time of current interruption is easily performed without stagnation, and it has two contradictory functions of low surge function and large current interruption function. An object of the present invention is to provide a contact for a vacuum switch.

[Structure of Invention]

(Means for Solving the Problems) In the vacuum switch contact of the present invention, two alloy regions and a boundary region sandwiched therebetween are concentrically arranged, and each of the alloy regions has a high vapor pressure. It is characterized in that the boundary region is made of a material having different vapor pressure levels continuously in the radial direction.

(Operation) In the vacuum switch contact of the present invention, when the alloy region located on the outer peripheral side is made of a material having a higher vapor pressure than the alloy region located on the inner peripheral side, the boundary region (B ₁ ) The height of the vapor pressure of the material forming the element decreases in the continuous region from the outer peripheral side toward the inner peripheral side in the radial direction. Therefore, the height of the vapor pressure of the material gradually decreases from the alloy region (A ₁ ) to the boundary region (B ₁ ) to the alloy region (A ₂ ). When current is cut off using such a vacuum switch contact for a vacuum switch, when the two contacts that were in contact with each other during energization are separated, the material with the highest vapor pressure in the region that makes up the contact is selected. Many ions and metal particles evaporate from the alloy region located on the outer peripheral side and float between the alloy regions of both contact points, and an arc is guided to this and connected between the two.

After that, when the distribution of ions and metal particles floating between both contacts is changed by controlling the longitudinal magnetic field, the arc is directed from the alloy region located on the outer peripheral side to the boundary region. The height of the vapor pressure of the material gradually decreases from the alloy region on the outer peripheral side to the alloy region on the inner peripheral side through the boundary region to the alloy region on the inner peripheral side, so that the arc easily transitions to the boundary region without stagnation. In this way, by controlling the longitudinal magnetic field, the arc is forcibly moved toward the alloy region on the inner peripheral side. Then, after the time required for satisfying the low surge function, that is, because the arc is connected between both contacts, the vapor pressure is the lowest and the arc moves to the inner alloy region where metal particles do not evaporate. Then, at this moment, the arc connection will be cut off.

On the contrary, when the alloy region located on the inner peripheral side is composed of a material having a higher vapor pressure than the alloy region located on the outer peripheral side, the vapor pressure of the material in the boundary region is high. The depth decreases continuously from the inner circumference side to the outer circumference side in the radial direction. For this reason, the vapor pressure of the material gradually decreases from the alloy region on the inner peripheral side to the alloy region on the outer peripheral side via the boundary region. In this case, the arc is first connected between the alloy areas on the inner circumference side of both contacts, and the arc is transferred to the alloy area on the outer circumference side through the boundary area by the control of the longitudinal magnetic field, and the arc is disconnected. Be drunk

(Example) As an example of the present invention, FIG. 1 is a top view of the contact in the case where the contact is composed of two kinds of alloy regions (A ₁ ) and (A ₂ ) and a boundary region (B ₁ ). It demonstrates using. It differs from the conventional contact shown in FIG. 6 in that an intermediate region (B ₁ ) 22 is arranged between the alloy region (A ₁ ) 21 and the alloy region (A ₂ ) 23. Alloy area (A ₁ ) 21 and alloy area (A ₂ ) 23
And may be made of the same alloy-based material having different contents, or may be made of different alloy-based materials. The alloy-based material of the intermediate area (B ₁ ) 22 is different from both the alloy area (A ₁ ) 21 and the alloy area (A ₂ ) 23, or at least one of the alloy-based materials has a different content. There are cases.

If the alloy region (A ₁ ) 21 and the alloy region (A ₂ ) 23 are made of the same alloy material, for example, Ag-WC alloy, one of the regions has a low surge function. 40Ag-WC-10Co (numerical value shows% by weight; the same applies hereinafter) with a high content of Ag, which is a metal with a high vapor pressure, was used as a material with a large current interruption function in the other alloy region.
30Ag-WC-0.2Co with a low Ag content can be used. In the boundary region in this case, there are cases where an alloy system used for both alloy regions, that is, an alloy system different from the Ag-WC system alloy, and a case where the same alloy system Ag-WC system alloy is used. Also in the above, the composition of the material has a distribution that continuously differs in the radial direction, and thus the height of the vapor pressure of the material continuously differs in the radial direction.

One of the alloy area (A ₁ ) 21 and the alloy area (A ₂ ) 23 is made of a high vapor pressure material and the other is made of a low vapor pressure material, but the alloy area (A ₁ ) 21 is made of a high vapor pressure material. When the material is made of a material, the range of the vapor pressure height value of the material in the intermediate region (B ₁ ) 22 is determined by the vapor pressure height value of the alloy region (A ₁ ) 21 and the alloy region (A ₂ ) 23 of the vapor pressure height value, and the distribution of the vapor pressure height of the material in the radial direction continuously decreases from the outer peripheral side to the inner peripheral side. The opposite is true when the alloy area (A ₁ ) 21 consists of a low vapor pressure material, and the alloy area (A ₂ ) 23 consists of a high vapor pressure material,
The range occupied by the high vapor pressure value in the intermediate region (B ₁ ) 22 is
Value of vapor pressure height of alloy area (A ₁ ) 21 and alloy area (A ₂ )
23 and the vapor pressure height value of 23, and the distribution of the vapor pressure height of the material in the radial direction continuously increases from the outer peripheral side to the inner peripheral side. Any combination of these two ways is possible. The case where the alloy region (A ₂ ) 23 is made of a high vapor pressure material will be described below.

First, an example of a method of manufacturing a contact having such a composition will be shown. As the molding die, the die 31, the first punch 32, the second punch 35, and the die stand 37 shown in FIG. 2 are used.

Remove the first punch 32 from the mold 31 and remove the second punch
35 is installed so that its bottom portion 35a is in contact with the die stand 37. Powder for forming the alloy region (A ₁ ) 21 is mixed and prepared in the space between the die 31 and the second punch 35, and the mixture is pressed by the first punch 32 at the molding pressure P ₁ . Next, the second punch 35 is once pulled out of the mold 31, and the space 38
Powder for forming the alloy region (A ₂ ) 23 is mixed and prepared and filled in, and is pressed with the molding pressure P ₂ by the second punch 35. In this case, when the same alloy system is used in the alloy area (A ₁ ) 21 and the alloy area (A ₂ ) 23, the pressure P ₂ is infiltrated with a large amount of Ag afterwards in the alloy area (A ₂ ) 23. In order to make it so, it is made smaller than P ₁ to increase the proportion of vacancy. When different alloy systems are used for the alloy area (A ₁ ) 21 and the alloy area (A ₂ ) 23, the pressure P ₂ may be the same as P ₁ . The boundary region (B ₁ ) 22 in this case is made by mixing and preparing the same powder as the alloy region (A ₁ ) 21, and the pressure applied by the tapered portion 32b of the first punch 32 is in the radial direction. However, unlike the alloy region (A ₁ ) 21 from the outer peripheral side closer to the alloy region (A ₂ ) 23 to the inner peripheral side, it becomes lower,
The proportion of holes is increased.

When the thus obtained product is shaped into a disc, a molded body 39 showing a cross section in the direction of the central axis in FIG.
To get Further, if this molded body 39 is sintered in a non-oxidizing atmosphere, a skeleton is obtained. On one side of this skeleton
A high vapor pressure material such as Ag or Cu is brought into contact, the skeleton is heated at a temperature equal to or higher than these melting points in a non-oxidizing atmosphere, and Ag or Cu is infiltrated into the pores of the skeleton. According to this method, an alloy region (A ₁ ) 21 made of a low vapor pressure material having a constant composition, an alloy region (A ₂ ) 23 made of a high vapor pressure material having a constant composition, and Ag in the radial direction were used. Alternatively, the Cu content distribution is different, and the Cu content increases from the outer peripheral side toward the inner peripheral side. That is, a contact having a boundary region (B ₁ ) 22 made of a material having a distribution in which the vapor pressure increases toward the inner peripheral side is obtained.

The contact thus obtained has the coil electrode shown in FIG. 7 or the spiral electrode shown in FIG. 8, and the movable contact of the vacuum switchgear shown in FIG. 4 capable of controlling the longitudinal magnetic field. A case of performing current interruption using the 13a and the fixed contact 13b will be described. When the contacts 13a, 13b, which were in contact with each other during energization, separate from each other, many ions from the alloy region (A ₂ ) 23 made of the highest vapor pressure material among the alloy regions forming the contacts 13a, 13b , The metal particles evaporate and float between the contacts, and an arc is guided to connect the alloy regions (A ₂ ) 23 on the contacts.

After that, by controlling the longitudinal magnetic field, the distribution of ions and metal particles floating between both contacts changes, and the arc moves from the alloy area (A ₂ ) 23 to the boundary area (B ₁ ) 22 adjacent to the outer peripheral side. To do. The height of the vapor pressure of the material in the boundary region (B ₁ ) 22 has different distributions in the radial direction, and the vapor pressure of the inner peripheral portion is high in the vapor pressure of the material in the alloy region (A ₂ ) 23. Slightly lower than the outer peripheral side, the vapor pressure of the material in the alloy region (A ₁ ) 21 adjacent to the outer peripheral side is slightly higher than the vapor pressure of the outer peripheral side. high. Therefore, the arc heading from the alloy area (A ₂ ) 23 to the boundary area (B ₁ ) 22 by controlling the longitudinal magnetic field does not stay at the boundary of each area and passes through the boundary area (B ₁ ) 22 and the alloy area ( A ₁ ) Easily move to 21. Here, until the time required to satisfy the low surge function elapses, the vapor pressure of the material is high and many ions and metal particles float between both contacts, and the alloy area or boundary where the arc is connected. An alloy region (A ₁ ) made of a material with the lowest vapor pressure to prevent the ions and metal particles from evaporating so that the arc can be transferred while being connected between the regions, and then the high current cutoff function is satisfied.
When the arc is transferred to 21, the arc connection between both contacts is cut off at that moment.

The case where the contact consists of two kinds of alloy areas (A ₁ ) and (A ₂ ) and a boundary area (B ₁ ) between these areas has been described. When there is a boundary region between the contact points, the change in the distribution of the vapor pressure height in the radial direction of the contact becomes more gradual, so that the arc transition is easier and there is no stagnation. .

Next, the results of test evaluation of the low surge property and the large current interruption property of the contact according to the present invention will be described. In order to compare and contrast the low surge function and large current interruption function of each contact, the contact pressure when both contacts were in contact, the contact opening speed when separating from this state, and the vacuum degree were the same conditions.

The superiority or inferiority of the low surge property can be evaluated by the magnitude of the current interruption value required for the arc to be connected between the separated contacts, and the smaller the value, the better the low surge property. When an AC current of 44 A was applied through the LC circuit, the voltage drop of the coaxial shunt inserted in series with the vacuum breaker was measured with an oscilloscope to calculate the current interruption value.

The superiority or inferiority of the large current cutoff property can be evaluated by the maximum value of the current when an arc that inhibits the cutoff property does not occur immediately after the cutoff, and the larger this value, the better the large current cutoff property. After cleaning the contact surface by baking, voltage aging, etc. to make the conditions constant, measure the maximum value of the current at the cutoff limit while increasing the current by 1 KA at 7.2 KV, 50 Hz, and multiply the specified standard value. It was calculated as the cutoff ratio.

The effect of the contact according to the present invention will be described with reference to Table 1 showing the surge current value and the breaking ratio for each contact. In both Example 1 and Conventional Example 1, 30Ag-WC-0.2Co, which is a low vapor pressure material, is used in the alloy region (A ₁ ), and 40Ag-WC-10Co, which is a high vapor pressure material, is used in the alloy region (A ₂ ). Therefore, only Example 1 has a boundary region (B ₁ ). As a result, at the time of breaking, the arc is first connected to the alloy region (A ₂ ) made of the same material in both Example 1 and Conventional Example 1, so that the current breaking value is the same, There is no difference in surge characteristics. However, unlike Example 1 of the prior art, Example 1 has a boundary region (B ₁ ), so that the arc transfer from the alloy region (A ₂ ) to the alloy region (A ₁ ) can be easily performed without stagnation. Magnification has increased from 1.0 to 1.4. This is because the second embodiment, the second prior art, and the third embodiment.
And the relationship between Conventional Example 3 and Example 4 and Conventional Example 4 are applicable. From the above test results, not only are there two or more alloy regions that use materials with different vapor pressure heights, but the vapor pressure heights between the alloy regions are continuously different in the radial direction. It has been demonstrated that the contact according to the invention with a boundary region with distribution has not only a low surge function, but also a high current interruption function.

[Effects of the Invention] As described above, the contact for a vacuum switch according to the present invention has an alloy region made of a high vapor pressure material having a low surge function and an alloy region made of a low vapor pressure material having a large current interruption function. There are at least two types, and there is a boundary region between the alloy regions in which the distribution of the vapor pressure height in the radial direction is continuously different. Therefore, forcible arc transfer is easily performed by controlling the longitudinal magnetic field from the alloy region made of the high vapor pressure material to the alloy region made of the low vapor pressure material, and it does not stagnate. It is possible to simultaneously satisfy two contradictory requirements of the current cutoff function.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a contact for a vacuum switch of the present invention, FIG. 2 is a diagram showing an example of a die used when manufacturing the contact for a vacuum switch of the present invention, and FIG. 3 is a molded body. FIG. 4 is a view showing a cross section in the direction of the central axis of FIG. 4, FIG. 4 is a view showing a vacuum switch, FIG. 5 is a partially enlarged view showing details around the movable electrode 8 in FIG. 4, and FIG. 6 is a conventional vacuum switch. FIG. 7 is a diagram showing contacts, FIG. 7 is a diagram showing coil electrodes used in a vacuum switch, and FIG. 8 is a diagram showing spiral electrodes used in a vacuum switch. 1 ... Cutoff chamber, 2 ... Insulation container, 3a, 3b ... Sealing metal fittings, 4a, 4b ... Metal lid, 5,6 ... Conductive rod, 7 ... Fixed electrode, 8 ... Movable electrode , 9 ...... Bellows, 10, 11 ...... Arc shield, 12, 14 ...... Brazing, 13a ...... Moving contact, 13
b …… fixed contact, 14 …… brazing part, 21 …… first alloy area (A ₁ ), 22 …… first boundary area (B ₁ ), 23 …… second alloy area (A _2). ), 31 …… Mold, 32 …… First punch, 32
a ...... bottom of first punch, 32b ... tapered portion, 35 ... second punch, 35a ... bottom of second punch, 37 ... mold base, 38 ... space, 39 ... molding Body, 44 ... coil electrode, 45
… Spiral electrode, H… magnetic field.

Claims (1)

[Claims] 1. Two kinds of alloy regions and a boundary region sandwiched between the alloy regions are concentrically arranged, each of the alloy regions is made of a material having a different vapor pressure, and the boundary regions are radially arranged. A contact for a vacuum switch, characterized in that the contact is made of a material having a composition of continuously varying vapor pressures.