JPS5938688B2 - vacuum circuit breaker - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a vacuum circuit breaker, more specifically of the type consisting of a slotted disc-shaped contact which rotates the arc formed during interruption. Regarding large current vacuum circuit breakers.

A contact structure generally having this type is disclosed in U.S. Patent No. 2949.
No. 520.

Each contact in this patent is comprised of a disc-shaped member with a plurality of slots extending both radially and circumferentially of the disc-shaped member.

These slots are used to create an arc rotation effect that forces an arc terminating in the slotted portion of the disc to rotate about the central axis of the disc.

At the center of the disk-shaped member is a button-shaped annular contact, at which an arc is initiated during a circuit breaking operation.

This arc is magnetically driven radially outward from the button-shaped contact, and as it approaches the outer circumference of the disc-shaped member, it is rotated by the arc rotation action generated by the slot in the disc-shaped member. It will be done.

U.S. Patent No. 35 is an improved version of the contact structure of the aforementioned U.S. patent.
No. 22399.

In the contact structure of this patent, each disc-shaped contact is provided with four slots.

Each slot is configured to enter the body of the contact from a starting point on the outer periphery of the contact, following a path generally tangential to the outer periphery of the button-like contact.

At its innermost end, the slot has a portion extending transversely of the tangential portion of the slot to a point spaced radially inwardly from the periphery of the button contact.

Although the contact structure of the U.S. patent listed below is generally very effective in producing the desired arc rotation action, there is one particular circuit breaker in which this structure does not appear to be as effective as desired in this regard. It has several uses.

This application is used in high-current vacuum circuit breakers (i.e., with an asymmetry factor of up to 1.3 and a rated breaking current greater than 160,000 amperes rms) in which an ordinary tubular metal shield surrounding the contacts is separated from the contacts by a short distance. This is the case for circuit breakers with

In this application, it appears that high current arcs tend to melt and burn excessively adjacent shields.

A possible reason for this remarkable tendency is that there is a region on the periphery of the contact where the magnetic force component that drives the arc outward in the radial direction is larger than the magnetic force component that drives the arc circumferentially. This was determined from the inventor's research.

This large force component, acting radially outward, arcs the inner surface of the shield, increasing the force heating and erosion of the shield wall at that location.

The increased pressure due to evaporation of the shield material inhibits circumferential movement of the arc, thereby increasing the rate of heat input to this local area of the shield surface.

This causes the arc to slow down further and the erosion of the shield in this local area to be more severe, so that the heating effect in the local area of the shield increases pyramidally.

SUMMARY OF THE INVENTION It is an object of the present invention to avoid undue interference even with the use of slots of the type described in U.S. Pat. To provide a contact device capable of rotating a large current arc along the periphery of a contact at high speed without stalling.

Another purpose is to provide a solution to the invention, generally referred to in U.S. Pat. No. 35,223'
This is the form described in No. 99, but when interrupting a large current,
The use of contacts is such that the arc energy to the shield is more evenly distributed over the entire circumference of the shield, thus avoiding excessive melting and burnout of the shield.

When implementing this invention in one form, two large current vacuum circuit breakers are used.
It consists of three disc-shaped contacts, each of which has at least 6.
It has four arc rotation slots having a diameter greater than 35 cm (2.5 inches) and each having a shape similar to that described in U.S. Pat. No. 3,522,399, cited above.

Typically, a tubular metal shield, which is not in electrical communication with the contacts, surrounds the contacts through a small space.

The circumferential edges of both contacts are substantially aligned but circumferentially offset from each other such that the starting point of the slot on the circumferential edge of one contact is the same as the starting point of the slot on the circumferential edge of the other contact. 35 from the point
The angle should be between 55° and 55°.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order that the invention may be better understood, it will now be described with reference to the drawings.

In FIG. 1, a vacuum circuit breaker is shown having a sealed envelope 10 evacuated to pressures of 10-' Torr or less.

The jacket 10 consists of a tubular casing 11 of insulating material and a pair of end caps 12 and 13 connected to opposite ends of the casing 11 by suitable vacuum seals 14.

A pair of relatively movable contacts 17 and 1B within the jacket 10
is provided.

These contacts are shown in solid lines in FIG. 1 when in a disconnected or open state.

The upper contact 17 is a fixed contact suitably attached to a conductive rod 17a, and the upper end of the conductive rod 17a is coupled to the upper end cap 12.

The lower contact 18 is a movable contact mounted on a conductive actuation rod 18a, which is suitably mounted for vertical movement.

Movement of the contacts 18 upward from the position shown in solid lines to the position shown in dashed lines engages the contacts and thus closes the circuit breaker, whereas a return movement downward disengages the contacts and opens the circuit breaker.

'The actuation rod 18a extends through an opening in the lower end cap 13, and a flexible metal bellows 20 provides a vacuum connection around the actuation rod 18a, without compromising the vacuum inside the jacket 10. The operating rod 18a is movable in the vertical direction.

As shown in FIG. 1, the metal bellows 20 is fixed to the operating rod 18a and the lower end cover 13 at both ends thereof in a sealed manner.

Each contact 17 and 18 is in the form of a generally circular disc and has one major surface facing the other contact.

Each contact has a centrally located button-like contact portion 25 suitably brazed to the other portions of the contact.

Each button-like contact has a recess 27 in its central position such that contact between the button-like contacts occurs in an annular contact area 30 when the contacts are in the engaged position shown in dashed lines in FIG. It has become.

This annular contact area 30 has a diameter such that the current through the closed contact follows a loop-like path that bends radially outward, as shown in phantom in FIG.

The magnetic effect of the current flowing through this looped path tends to lengthen the loop, as is well known.

As a result, when the contacts are separated and an arc is formed between the areas 30, the magnetic effect of the current through the loop drives the arc radially outward.

In order to make the loop of this loop passage strong enough to obtain the desired strong radially outward force, the outer diameter of the button-shaped contact 25 is greater than half the diameter of the disc-shaped contact.

As the ends of the arc move towards the outer periphery of the discs 17 and 18, the arc is subjected to a magnetic force acting in the circumferential direction, which causes the arc to rotate about the central axis of the discs.

This circumferentially acting magnetic force is generated by four slots 32 provided in each disc and dividing each disc into four fingers 33.

Each slot 32 traces a path from its starting point on the outer periphery of its disk 17 or 18 such that the center line 37 of the slot is approximately tangent to the outer periphery of the button-shaped contact portion 25 to reach the contact point. into the body of.

The slot continues for a length generally tangentially to the button contact 25 beyond the point 34 where the centerline 37 first contacts the periphery of the button contact.

At the innermost end of the tangentially extending portion of the slot is a radially inwardly extending portion 35 which extends transversely to the tangentially extending portion.

This inwardly extending slot portion 35 is the button-shaped contact portion 25.
from the outer periphery of the button contact portion to a point 36 spaced radially inwardly from the outer periphery of the button-like contact portion.

As seen in FIG. 2, a button-like contact crosses or bridges the inwardly extending slot portion 35.

These slots 32 force the current flowing to or from the arc end on the finger 33 to follow a path within the finger that extends circumferentially of the disk in the vicinity of the arc.

For example, if the arc end is at position 40 in FIG. 2, the effective path of current through the fingers 33 to the arc extends circumferentially around the disk, as shown at 41.

This circumferential portion of the current path causes the current flowing in loop L to generate a net force component acting in the circumferential direction that rotates the arc about the central axis of the disk.

This force component acting in the circumferential direction is strong enough to cause each end of the arc to traverse the slot 32 at the free end of the finger 33;
This creates a continuous rotational movement of the arc on the surface of the contact.

This continuous rotational motion of the arc helps interrupt large currents by reducing the amount of metal vapor produced by the arc, thus allowing the metal vapor to condense more completely when the current is zero. Make it.

Suitable vapor condensation shields 50 and 54 are provided to condense the metal vapor generated by the arc.

The main shield 50 is a tubular metal member surrounding the contacts 17 and 18 and is located between the insulating casing 11 and the arc gap between the contacts.

This shield 50 is electrically isolated from the contacts and is preferably maintained at a potential approximately midway between the potentials of the two contacts when the circuit breaker is open.

For this purpose, a shield is provided between the upper and lower halves of the casing 11 by means of a radial flange 55 which passes through the casing 11 in a sealed manner.
Supported by

Tubular auxiliary shields 5 connected to end caps 12 and 13, respectively
4 surrounds both ends of the main shield 50.

This auxiliary shield serves, inter alia, to condense the steam that has bypassed the main shield.

For reasons of compactness and economy, it is desirable for the tubular main shield 50 to have as small a diameter as possible.

At the same time, if the contacts 17 and 18 are to interrupt a certain amount of current, it is necessary that these contacts have a minimum diameter.

When these two conditions are satisfied, the circuit breaker will have only a relatively small gap between the outer periphery of the contact and the inner periphery of the tubular shield.

For example, if the asymmetry coefficient is up to 1.3, the effective value is 20000.
For a circuit breaker rated to interrupt amps of current, 7.30
Contacts with a diameter of n (2 inches) and 10.16 (J
(4 inches) inside diameter, resulting in a contact-to-shield clearance of only 1.43 mm.
It becomes crrL (9/16 inch).

With such a small gap in the contacts of the overall shape and dimensions described above, when interrupting large currents, arcing can cause excessive burnout and melting of the shield in localized areas rather than It was found that there is a strong tendency.

As stated at the beginning of the specification, according to the inventor's research,
A possible cause of this local force heating and melting is that the magnetic force component on the periphery of the contact point that drives the arc outward in the radial direction is stronger than the magnetic force component that drives the arc circumferentially. It turns out that there is an area.

This strong force component acting radially outward causes an arc to be blown against the inner surface of the shield, increasing heating and erosion of the shield wall at this location.

The increased pressure due to evaporation of the shield material impedes the circumferential movement of the arc, so that the rate of heat input to this local area of the face of the shield increases.

This causes the arc to slow down more, resulting in more severe erosion of the shield in this local area and a pyramidal intensification of the heating effect in this local area of the shield.

Considering for the moment a single contact having the shape shown in Figure 2, the location of the arc where the magnetic force acting radially outward on the arc is strongest compared to the force acting circumferentially is This is the region at the root of each finger 33 extending in the circumferential direction.

With an arc such as that shown at 60 in this particular region, the net current path 62 through the contacts to the arc is almost entirely radial, with little or no circumferentially extending component. do not have.

As a result, the primary force exerted on the arc in this region by passing current through passageway 62 is radial rather than circumferential, with the result that the arc in this region There is a strong tendency to blow radially outward.

If the end of the arc moves in the circumferential direction of the contact onto the finger 33, the force component acting on the arc in the circumferential direction becomes progressively larger with respect to the radial force component, and correspondingly , the tendency of the arc to be swept radially outwardly against the shield is reduced.

In order to reduce the tendency of the arc to be blown off against the shield 50 while in the region of the root of any finger 33,
In this invention, two contact points are shifted from each other in the circumferential direction,
The starting point of the slot 32 in one contact is angularly offset from the starting point of the slot in the other contact along the periphery of the contact.

Preferably, this angular deviation is the maximum possible, i.e. 45°.
A deviation of 55° is considered.

A 45° offset is shown in FIG. 3, where the slots 32 in one contact are shown in solid lines and the slots in the other contact are shown in dashed lines.

As a result of this shift, when the fin of one contact is in the area of weak circumferential force at the root of 33, as shown at 70 in FIG. The distal end is at a sufficiently exposed point on the finger 33 of the other contact so that said other contact can generate a strong, driving force acting circumferentially on the arc.

At every point on the circumference of the contacts, one or the other contact can generate a strong force acting circumferentially on the arc, so that as the area on the circumference occupied by the arc, both contacts There are no areas where the force exerts a weak force acting circumferentially and a strong force acting radially outward.

As a result of angularly or circumferentially offsetting the contacts as described above, there are no areas where the arc would have a tendency to stall excessively as it moves along the peripheral area of the contacts.

As a result, the arc travels more smoothly along the periphery of the contact, thus distributing the arc energy more evenly to the shield, making any local area of the shield less susceptible to overheating and excessive evaporation. becomes smaller.

This invention is a high current circuit breaker (i.e., rated to interrupt currents greater than 16,000 amperes with an effective value of up to an asymmetry factor of 13, and having a contact disc diameter of at least 6.35C).
Please note that the circuit breaker is limited to rrL (2.5 inches).

In lower current circuit breakers, such as those described in U.S. Pat. Localized melting of the shield is not appreciably reduced by shifting, and circuit breakers of the type described in the above-cited patent, used commercially, have contact disc diameters of only about 3.49 cWL. (13/8 inch), and the gap between the shield and the contact is approximately 1, o 3 crrL (13/32 inch).
inches), and the interrupting rating is 60,000 amps rms at typical maximum asymmetry factors.

In a preferred form of the invention, each slot 32 is made relatively wide compared to the average width of immediately adjacent fingers 33 to direct the current flowing through the finger to the arc end thereon in a more nearly circumferential direction. oriented path, thus strengthening the circumferentially acting component of the magnetic force generated by the current passing through this path.

Along this line, the average width of the slots is preferably greater than 1/3 of the average width of the fingers, considered in the area where the fingers extend parallel to the circumference of the disc.

These widths are measured from the other contact point as seen in FIG.

While specific embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made within the scope of the invention.

Therefore, all such modifications are deemed to fall within the scope of this invention as long as they are consistent with the scope of the claims.

This invention can take the following embodiments in relation to the claims.

@) The width of the gap measured between the outer circumference of the contact and the inner circumference of the shield is 1.59 cIrL (5/8 inch) or less.

(D) Both disc-shaped contacts have substantially the same diameter and their generally circular peripheries are substantially aligned in the radial direction.

(c) Each contact point has an area on its outer periphery, which can be occupied by an arc end, at the root of a circumferentially extending finger portion;
For said region, current can flow from the central portion of the contact along a path that is substantially entirely radial, with substantially no tangential component, so that as the current passes through said path, said Generating a force acting primarily radially outward on an arc having its terminus in one of the regions.

B) In the above item (C), the area at the root of the finger portion at one contact point is angularly offset by 35 to 55 degrees from the area at the other contact point.

(E) The angular deviation of the contact points is approximately 45°.

(f) Measure the width of each contact when viewed from the other contact,
The average width of the tangential portion of each slot is greater than a percentage of the average width of the finger portions immediately adjacent to the slot.

[Brief explanation of drawings]

FIG. 1 is a side view showing a section of a part of a vacuum circuit breaker implementing one type of the present invention, FIG. 2 is a plan view taken along line 2--2 in FIG. 1, and FIG. 3 is a schematic view of the parts of the circuit breaker viewed in the direction of arrow 3; FIG. Explanation of main symbols, 10: Outer cover, 17, 18: Disc-shaped contact, 25: Homonic contact part, 32: Slot, 33: Finger, 35: Portion extending radially inward, 37: Center line ,
50, 54: Shielding body.

Claims (1)

[Claims] 1 In a vacuum circuit breaker that interrupts a current larger than an effective value of 16,000 amperes with an asymmetry factor of up to 1.3, 10=
a housing evacuated to a pressure below Torr; a pair of relatively movable disc-shaped contacts within the housing; and a pair of disc-shaped contacts surrounding said disc-shaped contacts and when the circuit breaker is open; an electrically isolated tubular metal shield, each contact having a diameter greater than 6,351 (2.5 inches), having a generally circular outer circumference, and facing the other contact; each contact has a contact surface capable of engaging with the other contact, each contact having a button-shaped contact portion on the contact surface having a substantially circular outer periphery substantially concentric with the outer periphery of the disc-shaped contact near the center; The diameter of the button-shaped contacts is larger than half the diameter of the disk-shaped contacts, and the button-shaped contacts contact each other when the circuit breaker is closed, and define an area where an arc is initiated when the circuit breaker is released. Since the disc-shaped contact has a large diameter, it produces a radially outward magnetic force on the arc that drives the arc radially outward from the button-shaped contact portion to the outer periphery of the contact, and then causes the vaginal arc to Acting to spray radially outward toward the shield, each contact has four circumferentially spaced slots, each slot extending from its starting point on the outer periphery of the contact to the slot. has a tangential portion that enters the body of the contact following a path such that the centerline area of the button is generally tangential to the outer periphery of the button-shaped contact, thus forming a circle between the outer periphery of the contact and the tangential portion of the slot. comprising circumferentially extending finger portions, each contact having at its outer periphery, at the root of the circumferentially extending finger portion, an area that can be occupied by an arc end, to which area the current is directed from the central portion of the contact. , can flow along a path that is substantially completely radial without having a substantially tangential component, so that when the current passes through said path,
generating a magnetic force acting primarily radially outward on an arc having its terminus in one of said regions, each slot having a slot at the innermost end of said tangential section, transversely of said tangential section; and a portion extending radially inward of the main body of the contact to a point spaced radially inward from the outer periphery of the button-shaped contact portion, and the inner periphery of the shield has a small annular gap from the outer periphery of the disc-shaped contact. separated by apertures, the starting points of the slots in each contact are substantially equally spaced along the outer circumference of the contacts, and the contacts are angularly offset from each other such that the starting points of the slots in one contact A vacuum circuit breaker in which the starting point is offset from the starting point of the slot of the other contact by 35° to 55° along the periphery of the contact.