JPH0222492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit breaker or breaker, and particularly to a circuit breaker or breaker that has improved current-limiting performance when the breaker is disconnected.

An example of a conventional circuit breaker has a structure as shown in FIG. FIG. 1A is a partially sectional plan view taken along line 1E-1A in FIG. 1, and FIG. That is, in the figure, 1 is an enclosure made of an insulator and forms the outer frame of the circuit or disconnector, 2 is a fixed conductor, and the electrical contact surface of the fixed conductor 2 is provided with a wire as shown in FIG. A fixed contact 3 is attached to. 2 and 3 constitute one of a pair of electrical contacts. In addition, Figure 2 A,
B and C are front and top views of the electrical contact, respectively;
It is a right side view. 4 is a movable conductor, and a movable contact 5 is attached to its electrical contact surface as well, similar to that shown in FIG. 4 and 5 constitute the other of the pair of electrical contacts. Reference numeral 6 indicates an operating mechanism for opening and closing the movable conductor 4, 7 indicates an arc extinguishing plate for cooling the arc 8 generated between the fixed contact 3 and the movable contact 5, and 9 indicates an arc or hot gas extinguishing plate formed in the enclosure 1. It is an outlet.

The conventional circuit breaker is constructed as described above, and its operation will be explained next.

Now, when the movable contact 5 and the fixed contact 3 are in contact, the power is supplied from the power supply side to the load side via the fixed conductor 2, fixed contact 3, movable contact 5, and movable conductor 4 in order. Ru. In this state, when a large current such as a short-circuit current flows through this circuit, the operating mechanism section 6 is activated and the movable contact 5 is connected to the fixed contact 3.
Separate from. At this time, an arc 8 is generated between the fixed and movable contacts 3 and 5, and an arc voltage is generated between the fixed and movable contacts 3 and 5. This arc voltage increases as the separation distance of the movable contact 5 from the fixed contact 3 increases, and at the same time, the arc 8 is attracted and expanded in the direction of the arc extinguishing plate 7 by magnetic force. , further increases. In this way, the arc current reaches a current zero point and the arc 8 is extinguished, completing the shearing. During such closing and disconnecting operations, a large amount of energy is generated between the movable contact 5 and the fixed contact 3 by the arc 8 within a short period of time, that is, several milliseconds, and therefore, a large amount of energy is generated within the enclosure 1. The temperature of the gas rises and the pressure also rises rapidly, but this high temperature and high pressure gas is released into the atmosphere from the exhaust port 9.

The circuit breakers and disconnectors and their internal components operate as described above when disconnecting, but the performance that circuit breakers and breakers that operate in this way should have is as follows:
The arc voltage is high, and depending on the high arc voltage, the arc current that flows during the disconnection operation is suppressed, and the magnitude of the current that flows through the circuit and the disconnector is reduced. . Therefore, circuit breakers and breakers that generate high arc voltages have high protection performance for various electrical equipment, including distribution lines, that are placed in series with the circuit breakers and breakers, and protect circuits that are connected in series with each other. Selective coordination between disconnectors and disconnection areas,
Alternatively, the cutting area will be expanded at the same time.

Conventionally, in this type of circuit breakers, in order to generate a high arc voltage, the movable conductor 5 is opened at high speed, or the arc 8 is extended using magnetic force. However, in these cases, there was a certain limit to the increase in arc voltage, and a drawback was that a satisfactory result could not be obtained.

Here, prior to explaining the switchgear of the present invention, the behavior of arc voltage, etc. between the fixed and movable contacts 3 and 5 will be explained.

Generally, arc resistance has the following relationship.

That is, R=ρl/S where R: arc resistance (Ω) ρ: arc resistivity (Ω・cm) l: arc length (cm) S: arc cross-sectional area (cm ² ) However, generally speaking, For high current and short arc length of 50mm or less,
The arc space is occupied by contact particles, but the ejection of these contact particles occurs in a direction perpendicular to the contact surface, and the ejected particles are caused by the contact metal material at the time of release. It has a temperature close to the boiling point of the arc, and as soon as it is injected between the arcs, it receives electrical energy and becomes high temperature and pressure, becomes conductive, and expands in a direction that follows the pressure distribution in the arc space. It flows away from the contact point at high speed. In this way, the arc resistivity ρ and the arc cross-sectional area S in the arc space are determined by the amount of contact particles generated and their emission direction, and therefore the arc voltage also depends on the behavior of the contact particles. , has been determined.

The behavior of such contact particles or electrode particles will be explained based on conventional circuits and disconnectors. Fig. 3 is a schematic explanatory diagram between the contacts, where 3 indicates a fixed contact and 5 indicates a movable contact, and the , In addition, the Y plane shows a part of the contact surface and the conductor surface other than the facing surface Furthermore, a, b, and c schematically show contact particles emitted from the contact, where a represents the contact particles emitted from near the center of the opposing surface X, and b represents the contact particles emitted from the contact surface and the conductor surface. c is a contact particle emitted from the vicinity of the opposing surface X plane, which is an intermediate position between contact particles a and b, and the path after its release. are indicated by respective streamlines indicated by arrows m, n and o, respectively.

The contact particles emitted from such contacts 3 and 5 range from the boiling point temperature of the contact metal, which is approximately 3000°C, to the temperature at which it becomes conductive, which is 8000°C or higher,
Or, since the temperature is raised to an even higher temperature of about 20,000°C, energy is removed from the arc space, lowering the temperature of the arc space, and as a result, arc resistance occurs. Note that the amount of energy taken away by the contact particles from the arc space is greatly influenced by the degree of temperature rise, and the degree of temperature rise is determined by the position in the arc space of the contact particles emitted from the contact and the emission path. However, in the conventional circuit breaker shown in Fig. 3, the contact particles a emitted from near the center of the opposing surface X take away a large amount of energy from the arc space, but the contact particles The contact particles b emitted from the surface are, compared to the contact particles a,
The amount of energy taken away from the arc space is small,
In addition, contact particles c emitted from the peripheral portion of the opposing surface
This means that only an intermediate amount of energy is removed between the amount of energy removed by contact particles a and b.
That is, in the range where contact particles a flow,
A large amount of energy is taken away to lower the temperature of the arc space, thus increasing the arc resistivity ρ, but in the flow range of contacts b and c, in order not to take away a large amount of energy, the temperature of the arc space is also reduced. Therefore, the arc resistivity ρ cannot be increased, and since the arc is generated from the opposing surface X and the contact surface Y, the arc cross-sectional area also increases, and the arc resistance also decreases.

Since the outflow of energy from the arc space due to such contact particles is balanced with the electrically injected energy, if contact particles generated between the contacts, especially contact particles a and c, are injected into the arc space, It can be seen that by increasing the amount, it is possible to naturally greatly reduce the temperature of the arc space, thereby increasing the arc resistivity and greatly increasing the arc voltage.

Therefore, in the prior art of the present invention, the surface of the electric contact has been developed with the aim of overcoming the limit on the rise in arc voltage in conventional circuit breakers and breakers, and to obtain a circuit breaker that can greatly increase the arc voltage. In order to limit the size of the arc foot generated between the contacts and to increase the amount of contact particles generated between the contacts, especially contact particles a and c, injected into the arc space, on each conductor of a pair of electric contacts. A pressure reflector is formed around the contact point. Furthermore, in this invention, the pressure reflector is made of thermoplastic polyacetal, and based on the temperature rise of the insulator caused by the arc, the arc voltage is further increased by the decomposition gas generated from the insulator. It is an attempt to do so.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 4 shows a fixed electric contact incorporated in the circuit breaker of the present invention, in which A is a front view and B is a plan view. Note that the movable electric contact has the same configuration and will therefore be omitted. A fixed contact 3 is provided on the fixed conductor 2, and a pressure reflection plate 20 made of thermoplastic polyacetal is attached so as to leave a contact surface of the fixed contact 3, cover its periphery, and face the arc space. It is fixed. 2
Reference numeral 2 denotes a groove formed in the pressure reflecting plate 20, which is formed so that the conductor 2 is exposed from the side surface of the contact point 3 in the direction in which the arc travels.

FIG. 5 shows a circuit breaker showing an embodiment of the present invention;
B is a partially sectional side view taken along line 5-5 in A.
FIG. 5 shows a fixed electrical contact provided with the pressure reflecting plate 20 described in FIG. 4, and a movable electrical contact similarly provided with the pressure reflecting plate 21. A groove 23 is formed so that the conductor 4 is exposed from the side surface of the contact 5 in the direction in which the arc travels. By forming the grooves 22 and 23, when the arc is extended, the arc concentrates on the grooves 22 and 23,
It will now move along the groove. Note that this groove 2
It goes without saying that only one of 2 and 23 is sufficient.

The opening/closing operation in Fig. 5 is the same as that of the conventional device, so its explanation will be omitted, but the behavior of contact particles between both contacts is different from that of the conventional device, so
This will be explained next.

Fig. 6 is a schematic explanatory diagram between the contacts, and numerals 3 and 5 are a pair of contacts facing each other, and the fixed conductor 2, movable conductor 2, A pressure reflecting plate 20 on the conductor 4,
21 are provided. Also, in the figure, X, a, c, m
are the same as those shown in Figure 3,
Z' is the outline of the space of the arc 8 contracted by the device of the present invention, O' is also the streamline of the contact particles c flowing by the device of the present invention on a different path from that of the conventional device, and Q is a space indicated by crossed diagonal lines where the pressure generated by the arc 8 is reflected by the pressure reflection plates 20 and 21, increasing the pressure that would have decreased in the conventional type without pressure reflection plates. It shows.

Contact particles between the contacts in such circuit breakers and breakers behave as follows. In other words, the pressure value in the space Q cannot exceed the pressure value in the space of the arc 8 itself, but at least it shows an overwhelmingly higher value than in the case where no pressure reflection plate is provided. , therefore,
The considerably high pressure in the space Q generated by the pressure reflecting plates 20 and 21 becomes a force that suppresses the expansion of the space of the arc 8 and "squeezes" the arc 8 into a narrow space. This means that the streamlines of the contact particles a, c, etc. emitted from the opposing surface X are squeezed into the arc 8 space and confined. Therefore, the contact particles emitted from the opposing surface For this purpose, the arc space is significantly cooled, thus significantly increasing the arc resistivity, ie the arc resistance, and the arc voltage.

The pressure reflector is generally made of a high-resistance material that has a higher resistivity than the material that forms the conductor of the electrical contact, and can be fixed to the electrical contact in the form of a plate or formed into a tape. If possible, cover the electrical contacts with a tape-like material.

In this invention, the pressure reflector is particularly made of thermoplastic polyacetal. The pressure reflector is made of thermoplastic polyacetal.
Because it is an insulator, the legs of the arc that occur between the contacts when the current is cut off cannot spread around the contacts, and in the case of a large current arc, the legs of the arc are shrunk and a large arc voltage is generated. Furthermore, since this pressure reflector is an organic material, the temperature rises due to the arc and decomposition gas is generated. At this time, arc energy is taken away to generate decomposed gas, and the arc is cooled by the decomposed gas. Also, due to the generation of decomposition gas, the pressure on the surface of the pressure reflector increases, promoting the arc squeezing effect, and increasing the pressure applied to the pressure reflector, which is applied to the movable electric contact. , the opening speed can be increased. Therefore, the effect unique to thermoplastic polyacetal is added to the effect of the pressure reflector alone, making it possible to further increase the arc voltage. In other words, a material with excellent mechanical and thermal properties is required for a pressure reflecting plate installed near a contact that receives mechanical shock when the contact opens and closes, and boriacetal meets these requirements. In addition, in the present invention, the pressure reflector has a groove (arc travel path) narrower than the width of the contact point.
has been established. Therefore, in a large current region where current limiting is required, the legs of the arc are large, so the legs of the arc cannot penetrate into the arc travel path and are limited to only above the contact point.

Providing the pressure reflector with an arc travel path having a width narrower than the width of the contact point means that there is a corner at the boundary between the contact portion and the arc travel path portion. Since this corner has a small heat capacity, decomposed gas is violently released due to the heat of the arc, and in a large current region, it effectively prevents the legs of the arc from entering the arc travel path. In a large current region, if the foot is on the contact point, the arc is stretched and interrupted by the pressure gradient caused by the pressure increase in the arc extinguishing chamber due to the energy of the arc itself.

Thermoplastic polyacetal has good moldability.
In addition, since it is light, when it is attached to a movable electric contact, it has little effect on the opening speed. Furthermore, since powder does not easily come out, there is less worry about abnormal temperature rises and poor conduction between the contacts.

In addition, when thermoplastic polyacetal is exposed to an arc and decomposition gas is generated, the components themselves hardly decompose and vaporize in a state close to sublimation, so that almost no carbonaceous layer is deposited on the surface. Therefore, it is very advantageous for pressure reflectors near contacts, and there is no need to worry about insulation failure or insulation deterioration after the fiber breaks.

Furthermore, since it has good mechanical properties, fatigue resistance, and creep resistance, it is very advantageous to attach it to a movable electrical contact that is repeatedly opened and closed.

As explained above, in this invention, since the pressure reflector is made of thermoplastic polyacetal,
Based on the temperature rise of the above insulator due to the arc,
The decomposed gas generated from the insulator allows the arc voltage to be further increased, and therefore a circuit or breaker with high current limiting performance can be obtained.

Furthermore, when thermoplastic polyacetal comes into contact with an arc and generates decomposition gas, the components themselves hardly decompose and almost no carbonaceous layer is deposited on the surface of the equipment, so there is no risk of poor insulation or insulation after the sheath breaks. Less deterioration. Furthermore, since it has good fatigue resistance and creep resistance, it is suitable as a material for pressure reflectors.

[Brief explanation of drawings]

Fig. 1 shows a conventional circuit disconnector, in which A is a partially sectional plan view taken along line 1E-1A in B; Fig. 2 shows a conventional fixed electric contact; A, B, and C are respectively a front view, a top view, and a right side view; Fig. 3 is a schematic explanatory diagram between the contacts of a conventional circuit breaker; FIG. 4 shows a fixed electric contact according to the present invention, A and B show a front view and a plan view, respectively, and FIG. E-
Partial cross-sectional plan view of line 5A, whose line B is 5R-5 of A.
FIG. 6 is a partially cross-sectional side view of the line B, and is a schematic explanatory diagram between the contacts of the circuit and disconnector according to the present invention. In the figure, 2 is a fixed conductor, 3 is a fixed contact, 4 is a movable conductor, 5 is a movable contact, 7 is an arc-extinguishing plate, 20 and 21 are pressure reflectors, and 22 and 23 are grooves. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A pair of electrical contacts consisting of a conductor that carries a circuit current and a contact provided on this conductor, and each of the pair of electrical contacts is provided facing each other, and the surroundings of the contact are A pressure reflector formed on the surrounding conductor and made of thermoplastic polyacetal, at least one pressure reflector having a width smaller than the width of the contact in the direction in which the arc travels from the side of the contact. Circuit breakers and disconnectors with grooves that expose the conductive surface.