US3790911A

US3790911A - Electrical circuit-breaker

Info

Publication number: US3790911A
Application number: US00293453A
Authority: US
Inventors: H Kick; W Schwyn
Original assignee: CMC Carl Maier and Cie AG
Current assignee: Maier C & Cie ch; ABB CMC Carl Meier AG
Priority date: 1971-09-30
Filing date: 1972-09-29
Publication date: 1974-02-05
Anticipated expiration: 1991-02-05
Also published as: DK131527B; SE386304B; DK131527C; AT325704B; JPS4842368A; IT967721B; ATA771372A; ES407278A1; NL7213269A; NL172703C; NL172703B; GB1391222A; DE2158749C3; BE789300A; IL40438A; FR2154628B1; DE2158749A1; JPS5614218B2; IL40438A0; DE2158749B2

Abstract

An electrical circuit-breaker having contacts with double rupturing, comprising two fixed contact members and at least one movable contact member. There is provided mechanism for actuating the movable contact member and including an armature which knocks away the movable contact member in case of short circuit, and two arc quenching chambers each having at least one gas outlet opening. Each quenching chamber is equipped with a U-shaped iron plate, the opening of the U facing towards the mechanism. According to the invention, the two arc quenching chambers are arranged along the two opposite sides of a separating wall of insulating material in a manner that the gas outlet opening of the chambers as well as the fixed contact members are separated mechanically and electrically by the wall, and the wall serves as a support for other structural parts of the breaker.

Description

United States Patent 1191 Kick et al. I [45] ,F b, 5, 1974 ELECTRICAL CIRCUIT-BREAKER 2,687,462 8/1954 Cellerini 200/147 R [75] Inventors: Hennann Kick, Schaffhausen;

Walter Schwyn, Beringen, both of Pnmary bummer-Harold Broome Switzerland Attorney, Agent, or Fzrm-Wemer W. Kleeman [73] Assignee: Carl Maier & Cie, Scliaffhausen, 57 ABSTRACT Swltzerland An electrical circuit-breaker having contacts with [22] Filed: Sept. 29, 1972 double rupturing, comprising two fixed contact mem- I bers and at least one movable contact member. There [21] Appl 293453 is provided mechanism for actuating the movable contact member and including an armature which [30] Foreign Application Priority Data knocks away the movable contact member in case of Sept. 30, 1971 Switzerland 14378/71 Short ci'cuit, and two arc quenching chambers each having at least one gas outlet opening. Each quench- [52] US. Cl. 335/201 ing Chamber is equipped with a P iron Plate, 51 Im. c1. H01h 9/30 the Opening of the U feeihg towards the meehehisme [58] Field of Search..... 335/201; 200/147 R, 144 R, Aeeordihg to the invention, the two are quehehihg 200/147 B chambers are arranged along the two opposite sides of a separating wall of insulating material in a manner 5 References Cited that the gas outlet opening of the chambers as well as UNITED STATES PATENTS the fixed contact members are separated mechanically and electrically by the wall, and the wall serves as a 2: 200/147 B support for other structural parts of the breaker. 1:919:438 7/1933 Lindstrom 200/l47 B 8 Claims, 2 Drawing Figures 1 ELECTRICAL CIRCUIT-BREAKER The tendency of technical evolution of circuitbreakers used for the protection of electrical conductors in buildings goes in the direction, on one hand, to reduce the dimensions, on the other hand, to improve the performance:

to increase the rupturing capacity,

to limit the short-circuit current,

to cut the current very rapidly.

Specially in respect of the last two requirements most of the known small circuit-breakers are still inferior to the cheap and well proven fuses. In spite of the mentioned high requirements, such breakers must be fabricated at a minimum of cost.

The present invention concerns an electrical circuitbreaker of very reduced dimensions and of considerably improved performance. The main object of this invention is to provide an electrical circuit breaker in which the short circuit current is limited by creating an arc voltage higher than the supply voltage.

This limitation of the short circuit currents is important in order to reduce the damage which they might cause, and for such small breakers perhaps more important, to arrive at a certain functional selectivity between different breakers connected in series. For such a current limitation it is known that two conditions have to be fulfilled:

1. The breaker should work very quickly, i.e. when a short circuit occurs, the contacts should open as quickly as possible,

2. The arc voltage between the open contacts should be as high as possible, in any case higher than the supply voltage.

To meet this second condition is a further object of the present invention.

It is known that for a high are voltage it is necessary to lengthen the arc and at the same time to cool-it, for example by metal pieces which are put across the path of the arc. A magnetic field which blows the are between these metal pieces may help to lengthen the arc and also to cool it more efficiently.

The electrical circuit-breaker according to the present invention having contacts with double rupturing, comprises two fixed contact members, at least one movable contact member, a mechanism for actuating the movable contact member and including an armature which knocks away the movable contact member in case of a short-circuit, and two arc quenching chambers having each at least one gas outlet opening and being each equipped with a U-shaped iron plate, the opening of the U facing towards the mechanism of the breaker. This circuit-breaker is characterized by the fact that the two are quenching chambers are arranged at the two opposite sides of a separating wall of isolating material, in a manner that this wall separates mechanically and electrically the gas outlet openings of the chambers as well as the fixed contact members, and that the separating wall serves also as a support for other structural parts of the breaker.

This disposition permits, in spite of the small dimensions of the breaker, to place two quenching chambers of a certain length in it. During assembly all parts essential for the functioning can be mounted to the separating wall, tested and regulated before the two halves of a housing are put over it. I

Preferred embodiments of the circuit-breaker according to the invention may additionally have the following structural features:

The movable contact member may have the form of a fork extending on both sides of the separating wall into the two quenching chambers.

Alternatively, two movable contact members can be used, one on each side of the wall, and both of them being connected to each other by a flexible connexion.

The two quenching chambers can, on the side of the movable contact, be equipped with a common are horn, which is lodged in a curved slit in the separating wall.

Each of the two quenching chambers may be equipped with at least seven arc quenching plates of copper which are put substantially at right angles to the direction of the arc. Copper has the advantage to have a high thermal conductivity and also a good heat capacity per unit of volume, which is important for cooling the arc. Also copper is non magnetic and does not disturb the action of the U-shaped iron plates around the quenching chambers, which sucks the arc into the chamber.

These quenching plates not only cool the arc, in addition there is another effect: When the arc is driven between the plates', it sets foot on the plates and at each point where the arc enters or leaves the metal there is a voltage drop. The sum of all these drops helps also to quenche the arc.

Gas outlet openings of the chambers may be provided with meshed screens or grids made of meshed metal wires in order to prevent that the arc may come out of the breaker housing.

At the separating wall may be mounted the breaker mechanism, an axle for carrying the movable contact member as well as an overload and/or a short-circuit release.

The breaker mechanism together with the movable contact member and a handle for manual operation of the breaker can be mounted and pivoted between preferably two plates which are, together with the short circuit release, fastened to the separating wall.

The combination of all these features, together with an armature knocking away the movable contact member, leads to a circuit-breaker with improved performance when compared to known breakers of the same small size: high are voltage (which limits the current) and quick quenching of the current. Breaking capacity and breaking time are comparable with those of good fuses, for certain current ranges even superior. Nevertheless, the breaker is not larger than known breakers of much lower performance. v

A preferred embodiment of the invention is illustrated, by way of example, in the accompanying drawing in which: v

FIG. 1 is a side elevation view into the circuitbreaker, one halve of the housing taken away;

FIG. 2 is a cross-sectional view of the breaker.

Two are quenching chambers 2 are arranged at the two opposite sides of a separating wall 1 of insulating material. The chambers 2 are electrically connected in series: the incoming connexions going to a pair of fixed contact members 4, the connexion between the chambers going over a movable contact member 5 or through a common arc horn 6, which is placed in a curved slit 7 in wall 1. I

On the left hand side of FIG. 1, the wall 1 extends to the edge of the breaker and separates mechanically and electrically the two fixed contact members 4 as well as two gas outlet openings 3 of the chambers 2.

The movable contact member 5 in form of a fork reaches from upside into the two chambers 2. On the outside the chambers 2 are each covered with a U- shaped iron plate 9, the opening of the U facing towards a mechanism for actuating the circuit-breaker. The magnetic field, created by the arc current in case of a short-circuit, is partially concentrated on one side, through plate 9 and forces on the other side the are against and between arc quenching plates 8 made of copper and arranged within the chambers 2 substantially at right angles to the direction of the arc. Tests have shown that seven plates 8 in each chamber give good results for interrupting 220 V with a single pole breaker, or 380 V with a two or three pole breaker (for 3 phase supply). A higher number of quenching plates (for example nine) does not bring much improvement.

Lattices, screens or

grids

13 and 18 made of meshed metal wires and having a mesh width of eg 0.5 to 0.8 mm are arranged at the

gas outlet openings

3 and 12 for the purpose of preventing the are or fire from coming out of the breaker. The lattices, screens or grids 13 in the opening 3 of the two chambers 2 on the left (of FIG. 1) are separated by the wall 1. There are three lattices, screens or grids 13, on each side of the wall. At the other opening 12, two lattices, screens or grids 18 are common for both halves of the breaker.

The mentioned mechanism for actuating the circuit breaker is arranged as follows:

The movable contact member 5 is carried by an axle l0 turnably supported in a pair of plates 17. The axle further carries a lever 33 which is firmly connected to the movable contact member 5. A pair of levers 11 is pivotably arranged on axle and carry a pivotable pawl 28 capable to be engaged with the free end of lever 33. A handle 15 for manual operation of the circuit-breaker is pivotably mounted between the plates 17 and operatively connected to levers 11. A spring 29 urges the movable contact member 5 into its open or off" position.

The plates 17 carrying the described mechanism are fastened to an electro-magnetical short-circuit release 16 which in turn is fixed on the separating wall 1. The fixed contact members 4 and a bimetallic

thermal overload release

24, 25 as well as connexion terminals (not shown) are also fastened to the wall I. In this way, the whole mechanism of the breaker can be put together and tested, the two quenching chambers 2 added and, to complete the assembly, two halves of a housing 14 fastened.

The

thermal overload release

24, 25 comprises a bimetal strip or blade 24 through which the current flows, and a slider 25 coupling the free end of the strip 24 with the pawl 28. The short-circuit release 16 includes an eIectro magnetic coil 23 through which the current flows, a movable armature 20 slidably arranged in the coil 23, a longitudinally displaceable pin 21 arranged between one end of the armature 20 and the movable contact member 5, as well as a pivotably mounted finger 22 which operatively connects the other end of the armature 20 with the slider 25. The coil 23 and the bimetal strip 24 are connected in series with the

contacts

4, 5.

To bring the described circuit-breaker in closed or on position, handle 15 is manually tilted to the right in FIG. 1. By this, the levers 11 are pulled upwards, which in turn by means of the pawl 28 also pivote the lever 33 in clockwise direction. Consequently, the,

movable contact member 5 is moved toward the fixed contact members 4 and thus the electrical circuit is closed.

At the occurrence of an overload, the

thermal overlod release

24, 25 operates as follows:

From one of the fixed contact members 4 the overload current flows through the bimetal strip or blade 24. When this strip 24 is heated up, it curbs and its upper end moves to the left in FIG. 1. By means of the slider 25 the pawl 28 is also pulled to the left and the lever 33 is freed. Under the influence of the spring 29 the lever 3 pivots in anti-clockwise direction and the lower end of the movable contact member 5 moves to the right. Thus, the circuit-breaker opens and cuts the current.

The current also flows through the coil of the shortcircuit release 16. In case of a short-circuit, the magnetic excitation of the short-circuit release 16 is sufficient to attract the movable armature 20 and to move it to the right in FIG. 1. By this the pivotably arranged finger 22 is turned and pushes, by means of the slider 25, the pawl 28 to the left, which frees the lever' 33 as before. At the same time the axially movable pin 21 at the other end of the armature 20 knocks on the movable contact member 5 and accelerates it much more than the spring 29 could do it alone. Therefore the contact members are separated very quickly from each other and an arc is drawn between each pair of

contact members

4, 11. The U-shaped iron plates 9 of the quenching chambers 2 create an unsymmetry of the magnetic field around the path of the arc .current, which causes the arc to move downwards into the quenching chambers 2 and between the quenching plates 8, where the arc is extinguished as described above.

When the breaker mechanism has been released by disengaging the pawl 28 and provided the handle 15 is not held back by hand, a weak spring (not shown in the drawing) pulls the handle 15 into the open or off position shown in FIG. 1. By this movement the levers 11 are turned downwards and the pawl 28 engages again with lever 33. The circuit-breaker is now ready to be closed or switched on again by manual operation of the handle 15.

What we claim is:

1. An electrical circuit-breaker including at least one pole having contacts with double rupturing, comprising two fixed contact members associated with said at least one pole, at least one movable contact member, a mechanism for actuating the movable contact member and including an armature which knocks away the movable contact member in case of short circuit, and two are quenching chambers having each at least one gas outlet opening, each quenching chamber being equipped with a U-shaped iron plate, the opening of the U facing towards said mechanism, this breaker being characterized by the fact, that the two are quenching chambers (2) are arranged along the two opposite sides of a separating wall (1) of insulating material, in a manner that the gas outlet opening ('3) of the chambers (2) as well as the two fixed contact members (4) associated with said at least one pole are separated mechanically and electrically by said wall; the wall (1) serving as a support for other structural parts of the breaker including the mechanism (11) for actuating the movable contact member, an axle carrying the movable contact member, and a short-circuit release (16).

2. A circuit-breaker according to claim 1, wherein the movable contact member (5) has the form of a fork which extends on both sides of the wall (1) into the chambers (2).

3. A circuit-breaker according to claim 1, comprising two movable contact members, one on each side of the wall (1 the two movable contact members being electrically connected together.

4. A ciruit-breaker according to claim 1, wherein on the side of the movable contact member (5), the two chambers (2) are equipped with one common are horn 5. A circuit-breaker according to claim 4, wherein the separating wall (1) has a curved slit (7) to accomodate the arc horn (6).

6. A circuit-breaker according to claim 1, wherein the chambers (2) are each equipped with at least seven copper are quenching plates (8).

7. A circuit-breaker according to claim 1, wherein the gas outlet openings (15,12) are provided with lattices, screen or grids (l3, 18) of metal wires.

8. A circuit-breaker according to claim 1, wherein the mechanism (11), the axle carrying the movable contact (5), and a handle (15) for manual operation of the breaker are carried by at least one metallic plate (17), the latter, together with the short-circuit release,

being fastened at the wall (1).

Claims

1. An electrical circuit-breaker including at least one pole having contacts with double rupturing, comprising two fixed contact members associated with said at least one pole, at least one movable contact member, a mechanism for actuating the movable contact member and including an armature which knocks away the movable contact member in case of short circuit, and two arc quenching chambers having each at least one gas outlet opening, each quenching chamber being equipped with a U-shaped iron plate, the opening of the U facing towards said mechanism, this breaker being characterized by the fact, that the two arc quenching chambers (2) are arranged along the two opposite sides of a separating wall (1) of insulating material, in a manner that the gas outlet opening (3) of the chambers (2) as well as the two fixed contact members (4) associated with said at least one pole are separated mechanically and electrically by said wall; the wall (1) serving as a support for other structural parts of the breaker including the mechanism (11) for actuating the movable contact member, an axle (10) carrying the movable contact member, and a short-circuit release (16).

3. A circuit-breaker according to claim 1, comprising two movable contact members, one on each side of the wall (1), the two movable contact members being electrically connected together.

4. A ciruit-breaker according to claim 1, wherein on the side of the movable contact member (5), the two chambers (2) are equipped with one common arc horn (6).

5. A circuit-breaker according to claim 4, wherein the separating wall (1) has a curved slit (7) to accomodate the arc horn (6).

6. A circuit-breaker according to claim 1, wherein the chambers (2) are each equipped with at least seven copper arc quenching plates (8).

7. A circuit-breaker according to claim 1, wherein the gas outlet openings (3, 12) are provided with lattices, screen or grids (13, 18) of metal wires.

8. A circuit-breaker according to claim 1, wherein the mechanism (11), the axle carrying the movable contact (5), and a handle (15) for manual operation of the brEaker are carried by at least one metallic plate (17), the latter, together with the short-circuit release, being fastened at the wall (1).