US3789334A

US3789334A - Electric protective switch for protection against fault currents, excess currents and short circuits

Info

Publication number: US3789334A
Application number: US00225226A
Authority: US
Inventors: G Knirsch; R Goehle; W Velten
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Switzerland; BBC Brown Boveri France SA
Priority date: 1971-03-29
Filing date: 1972-02-10
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: RO60757A7; IT952394B; GB1390987A; DK137416C; FR2132129B1; DE2115034B2; AT314021B; DE2115034A1; BG24963A3; BE781285A; FR2132129A1; BR7201778D0; CH535504A; DK137416B; HU163086B; PL83340B1; AR193518A1; CS180579B2

Abstract

The switch comprises an automatic cutout on circuit breaker and a separate fault current responsive part with a suitable cutout actuating element. A disengaging clutch is provided and permits closing of the automatic cutout only in the ready position of the fault current release.

Description

United States Patent 1191 Goehle et a1.

[ Jan. 29, 1974 1 ELECTRIC PROTECTIVE SWITCH FOR PROTECTION AGAINST FAULT CURRENTS, EXCESS CURRENTS AND SHORT CIRCUITS [75 Inventors: Rolf Goehle, Leimen; Walter Velten,

Schwetzingen; Gunther Knirsch, Bretten, all of Germany [73] Assignee: Brown, Boveri & Cie AG,

Mannheim, Germany 22 Filed: Feb. 10, 1972 21 Appl.No.: 225,226

[30] Foreign Application Priority Data Mar. 29, 1971 Germany P 21 15 034.5

[52] us. on...) 335/173, 335/18 51 Int. Cl. H01h 71/12 [58] Field'of Search.... 335/13, 173, 17, 18; 317/58,

[56] References Cited UNITED STATES PATENTS 3,152,287 10/1964 Edmunds 317/58 3,436,695 4/1969 Dessert 335/13 3,256,407 6/1966 Klein 335/173 3,636,482 1/1972 Edmunds 317/18 D Primary Examiner-Haro1d Broome Attorney, Agent, or FirmJohn J. McGlew et al.

[ ABSTRACT The switch comprises an automatic cutout on circuit breaker and a separate fault current responsive part with a suitable cutout actuating element. A disengaging clutch is provided and permits closing of the automatic cutout only in the ready position of the fault current release.

3 Claims, 4 Drawing Figures ELECTRIC PROTECTIVE SWITCH FOR PROTECTION AGAINST FAULT CURRENTS, EXCESS CURRENTS AND SHORT CIRCUITS FIELD OF THE INVENTION This invention relates to protective switches for protection against fault currents, excess currents and short circuits and, more particularly, to such a switch comprising a unipolar or multipolar automatic cutout or circuit breaker with contacts and a part for determining a fault current and releasing or opening the cutout responsive to determination of a fault current.

BACKGROUND OF THE INVENTION For a better understanding of the invention, it is believed that a clear definition of the terms used hereinafter will be helpful. Thus, a self acting or automatic switch designates a switching device which automatically releases or opens, and such a switching device always includes a latching mechanism and a force accumulator which, after latching has been released or unlocked, breaks or opens the contacts of the self acting or automatic switch. A force accumulator is an element, such as a spring, storing mechanical energy. Such a self acting switch or automatic cutout is disclosed, as a representative example, in German Pat. No. 957,321

In principle, an automatic or self acting switch may also be considered as a sort of automatic cutout for a single-pole line. If two or more such automatic switches are united, with the number corresponding to the number of phases of the line to be protected, the unit may be designated as an automatic cutout" or an automatic circuit breaker. There are two types of these automatic switches. The first type is provided with electrically actuated releases for the latching mechanism, such as the automatic switches 1 mentioned hereinafter. The second type does not include a release and is released mechanically by means of other switching devices connected thereto, such as the automatic switch 5 mentioned hereinafter, which has the switching contacts for the central or neutral conductor of a polyphase circuit.

It is known to combine a fault current protective switch with an automatic cutout, to connect the switch and the cutout electrically, and to couple the switch and the cutout mechanically, as disclosed in German Pat. No. 1,280,382. In such protective switches, the locking cams of the various self acting switch poles are so coupled with each other that release of one pole of the automatic cutout effects a disconnection of the adjacent pole or poles and transfers the same. Also, if the fault current protective switch is released by its accumulator, the automatic cutout is disengaged.

The operating elements of the automatic cutout and of the fault current protective switch are coupled with each other in a particular manner, so that the automatic cutout can be closed only together with the fault current protective switch. This forced coupling of the operating elements is necessary because it is only in this way that protection against fault currents is'ensured in such a switch.

The known coupling means for the mutual disconnection of self acting switches are so designed that one coupling part of each of the self acting switch poles changes its position when the switching mechanism is released, for example, by rotating a shaft designed as a coupling part, with this rotation being transmitted to the shafts of the adjacent switch poles. The disconnection must be limited to a certain part of the release procedure in the known self acting switches, which have only two switching positions ON and OFF, because it is necessary that the ratchet parts of the switching mechanism of the automatic cutout resume, already again in the position OFF, the normal position so that the circuit cannot be reclosed. In this position, there must therefore be no mutual disengagement of disconnection. The disengagement, that is the rotation or position change of the coupling parts therefore takes place in the free release position." That is, as long as the operating element is retained in the position ON.

On the basis of these requirements, and with known coupling means, the operating elements of the various self acting switches are therefore so connected or coupled with each other, in the assembly of automatic cutouts and fault current protective switches, that, whenever the line circuit breaker is closed, the fault current circuit breaker is necessarily likewise closed.

These known arrangements, however, have the disadvantage that, during the joint closing operation, several functions must take place in a certain order in the switching mechanism, so that the protection requirements are met positively. Initially, the accumulator of the fault current release must betensioned or loaded and the fault current release must be brought into a ready position before the contacts of the automatic cutout or circuit breakers may close. This is necessary so that the current is immediately interrupted in the case of a leak to ground. The condition requires an exact adaptation of the switching mechanism of the self acting switches and of the automatic cutout or circuit breaker, which can be attained only by precision parts, costly assembly, and frequently only by additional and complicated adjustment.

SUMMARY OF THE INVENTION The present invention is directed to the problem of providing a protective switch, of the above'mentioned type, where the presently required adaptation of the switching mechanism, and the necessary complicated adjustments of the two switching mechanisms, can be eliminated by eliminating the joint closing of the automatic cutout and of the fault current part.

The switch design according to the invention has the effect that the coupling part of the fault current protective switch, provided for the disconnection, assumes, in both the free release position and in the shutoff position of the fault current release, a position necessary for the disconnection of the automatic cutout, and maintains this position during the closing movement of the operating element of the fault current part until the fault current part is ready to close.

Such a switching mechanism is so far unknown. In all known self acting switches, which have only two rest positions, the coupling parts are already, in the OFF position, in a position ready for closing, which permits closing. The disengagement or disconnection takes place only in the free release position so that all operating elements must be connected or coupled mechanically in a certain manner to assure the mutual all-pole opening of the contacts and to prevent positively an inpermissible single-pole closing of an automatic cutout in case of a ground leak.

The present invention avoids the existing disadvantages and permits the use of two parts, which are independent in their operation, for their assembly in such a way that no adjustments or only minor adjustments are necessary, and a simpler design of the switching mechanism is possible. The requirement that the closing of an automatic cutout must be possible only when the device for detecting and releasing a fault current is ready to use is met, despite the separation of the operating elements. Even if the fault current part is shut off by hand, the coupling part thereof, for the disconnection, and thus the ratchets of all the self acting switching mechanisms, are brought into the disconnection position, so that the self acting switch poles are released and no re-closing is possible until the fault current part is in the operative position.

In addition, the invention offers, in a simple manner, the known advantage that it can be recognized whether a release was effected by excess current or by a fault current. In the former case, the operating element of the fault current protective switch remains in the closing position.

A preferred embodiment of a protective switch in accordance with the invention is characterized in that the coupling part, between the fault current part and the automatic cutout, is swingable, in the ready position of the fault current release, but is moved positively into the position necessary for disengagement of the auto matic cutout in the released or shutoff position of the fault current release, by a transmission lever on which an accumulator spring sets. Consequently, a positive coupling takes place only in one direction, namely from the fault current part to the automatic cutout, but not vice versa. This preferred embodiment contains relatively few parts and is simple in its design.

An object of the invention is to provide an improved protective switch of the mentioned type.

Another object of the invention is to provide such a switch where the presently required adaptation of the switching mechanisms and the necessary complicated adjustment thereof can be eliminated.

A further object of the invention is to provide such a switch in which it can be recognized whether a release was effected by excess current or by a fault current.

For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the Drawing:

FIG. 1 somewhat schematically illustrates the functional design of a protective switch embodying the invention;

FIG. 2 is a top view, partially in section, of a particularly preferred embodiment of a switching mechanism for the fault current part, taken along the line IIIIII of FIG. 4;

FIG. 3 is a sectional view taken on the line II of FIG. 2, and illustrating the closing position; and

FIG. 4 is a sectional view on the line IIII of FIG. 2, and illustrating the opening position.

DESCRIPTION OF THE PREFERRED EMBODIMENT The protective switch shown in FIG. 1 includes three unipolar self acting switches 1, each containing a switching mechanism 2, an electrically actuated excess current release 3 and a contact 4. These switches are assembled with a mechanically released self acting switch 5, having the contact 6, for the center or neutal conductor, in an automatic cutout. The respective operating elements 7 are rigidly interconnected by a clamp or handle 8, and the mutual disengagement of the switching mechanism is effected by coupling parts 9 whose direction of action is indicated by arrows.

A fault current part 10 has a fault current release 11, devices, which have not been shown, for detecting fault currents, for example, a summation current transformer, a switching mechanism 12 with a force accumulator and an operating element 13. On switching mechanism 12, there is arranged a coupling part 14 which effects, by its position, the disengagement of the adjacent self acting switch l, in a release or disconnection of current fault part 10. Coupling part 14 is designed so that a position change of the parts takes place only from the fault current part 10 to the adjacent self acting switch 1, but not in the opposite direction. This corresponds essentially to a free wheel coupling. This has the effect that, when the release 3 of the adjacent switch responds to an excess current, switching mechanism 12 and operating element 13 remain in the closed position, so that it can be seen on the switch that the release was not effected by a fault current. As described above, the release of the switching mechanism 12 results, however, in any case in release of self acting switches 1.

The preferred embodiment of the invention, shown in FIGS. 2 through 4, illustrates merely the switching mechanism 12, the operating element 13 and the coupling means 14. Switching mechanism 12 is arranged between a front guide plate 15 and a rear guide plate 16, which are held together by rivet pins (not shown) and by the shaft 17 of operating element 13. By means of a bolt 18, a U-shaped double butt strap 19 is articulated on operating element 13 and is guided by a wire bow 20 in oblong slot 21 of a ratchet lever 22, as best seen in FIGS. 3 and 4.

Closing of the switching mechanism, and locking in the closing position, are effected by turning operating element 13 counterclockwise so that one end of wire bow 20 slides down in oblong-slot 21 until operating element 13 and double butt strap 19 pass the over dead center position. During this closing operation, wire bow 20 is so displaced, in slot 21 that it turns a transmission lever 23, arranged in the guide plates, against the bias of a compression spring 24. Spring 24 is, for example, simultaneously the compression spring for a testing key 25 and an accumulator spring, and is turned counterclockwise into the position shown in FIG. 3. On transmission lever 23, there is arranged an arm 26 which bears on an arm 27, of coupling arm 14, which is under the action of a weak torsion spring 28. I

FIG. 4 shows the position of transmission lever 23 and coupling part 14 wherein the opening or disengagement of the automatic cutout takes place, while FIG. 3 shows the position in which the engagement or closing of the automatic cutout is'not restricted and the circuit can be closed. 7

Release of the switching mechanism is effected by a fault current release of which only a pivot 29 is shown. This pivot turns, through a lever 30, the arm 31 of a ratchet 32. Ratchet 32 is mounted through bearings 33 in guide plates and 16 and forms, with ratchet lever 22, an engagement or contact point 34. During the rotation of pivot 29, the contact at point 34 is eliminated and ratchet lever 22 turns clockwise about its fulcrum which coincides with the center of coupling 14. Wire bow thus is released, with transmission lever 23 moving, under the action of spring 24, out of the position in FIG. 3 into that of FIG. 4. The arm 27 of coupling part 14 is turned down, or counter-clockwise, and assumes the position necessary for disengagement of the adjacent self acting switch 1, as shown in FIG. 4.

As can be seen from the drawings, the position of coupling part 14, shown in FIG. 4, represents both the opening position of the switch mechanism and the free release position thereof. The coupling part 14 assumes the position shown in FIG. 3 only during the course of the closing operation, and the release readiness exists immediately after the start of the closing movement because the engagement at point 34 can also be released, during closing movement of the switching mechanism, by the fault current release.

The return of the switching mechanism after a release is effected by a spring 35 which pulls operating element 13 back into the position of FIG. 4 when the engagement is eliminated and the force for maintaining the over dead center position of the toggle joint, formed by operating element 13 and double butt strap 19, is switched by rotation of ratchet lever 22. During this rotation of operating element 13, ratchet lever 22 and ratchet 32 are pulled back into the starting position necessary for the renewed closing through double butt strap 19 and the end of wire how 20. Arm 31 of ratchet 32 turns rotary lever clockwise so that the armature of the fault current release, which has not been shown, is likewise returned to a position necessary for its release, through pivot 29.

The concentric support of coupling part 14, on one hand, and of ratchet lever 22, on the other hand, is attained by two sheet metal eyelet formations 36 in

guide plates

15 and 16. Coupling part 14 is supported in the resulting bores as a shaft, and ratchet lever 22 rotates on the outer peripheries of the eyelets. The support or ratchet 32, as well as that of transmission lever 23, is provided, in a known manner, in corresponding bores of

guide plates

15 and 16 by metal pins molded on the parts.

While a specific embodiment of the invention has been shown and described in detail to illustrate the ap plication of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a protective switch, for protection against fault currents, excess currents and short circuits, including at least a unipolar automatic cutout with contacts, for releasing excess currents and short circuits, and including a part for detecting and releasing fault currents, the improvement comprising, in combination, all conductors to be monitored extending through respective automatic cutouts; said fault current part including a switching mechanism, having a force accumulator, a separate operating element having two stable end positions, and a fault current release; and a single coupling part mechanically coupling said fault current part to an automatic cutout and providing, only in the releaseready position of said fault current part, for engagement of the automatic cutout and for disengagement of the automatic cutout, responsive to excess currents and short circuits, without effecting release of said fault current part; said single coupling part, responsive to release of said fault current part, positively effecting disengagement of the automatic cutout.

2. In a protective switch, the improvement claimed in claim 1, in which said coupling part is swingable in the ready to release position of said fault current release.

3. In a protective switch, the improvement claimed in claim 2, in which said coupling part is moved positively in the released or disconnected position of said switching mechanism by a transmission lever acted on by an accumulator spring constituting said force accumulator, and into the position necessary for disengaging said automatic cutout.

Claims

1. In a protective switch, for protection against fault currents, excess currents and short circuits, including at least a unipolar automatic cutout with contacts, for releasing excess currents and short circuits, and including a part for detecting and releasing fault currents, the improvement comprising, in combination, all conductors to be monitored extending through respective automatic cutouts; said fault current part including a switching mechanism, having a force accumulator, a separate operating element having two stable end positions, and a fault current release; and a single coupling part mechanically coupling said fault current part to an automatic cutout and providing, only in the release-ready position of said fault current part, for engagement of the automatic cutout and for disengagement of the automatic cutout, responsive to excess currents and short circuits, without effecting release of said fault current part; said single coupling part, responsive to release of said fault current part, positively effecting disengagement of the automatic cutout.