US3092699A - Electrodynamic force-compensation pressure contacts for circuit breakers - Google Patents

Description

June 4, 1963 A. L ELECTRODYNAMIC FORC ATOU R 3,092,699

E-CCMPE ATION Filed Dec. 17, 1959 Fig! Ll L2 4 Sheets-Sheet 1 Fig. 2

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P fikp L\ L-2 l L'\ L2 L L INVENTORI rLLafoa/g ATTORNEYS June 4, 1963 A LATOUR 3,092,699

ELECTRODYNAMIC FBRCE-COMPENSATION PRESSURE CONTACTS FOR CIRCUIT BREAKERS Filed Dec. 17, 1959 4 Sheets-Sheet 2 (NVENTOR A. La/our ATTORNEYS June 4, 1963 A. LATOUR 3,092,699

ELECTRODYNAMIC FORCE-COMPENSATION PRESSURE CONTACTS FOR CIRCUIT BREAKERS Filed Dec. 17, 1959 4 Sheets-Sheet a INVENTOR 4. La/our TTORNEYS June 4, 1963 A LATOUR 3,092,699

ELECTRODYNAMIC FERCE-CCMPENSATION PRESSURE CONTACTS FOR CIRCUIT BREAKERS Flled Dec. 17, 1959 4 Sheets-Sheet 4 INVENTOR 14. Lafow BY MDM ATTORNEYS ELECTRODYNAMIC FORCE-COMPENSATION PRESSURE C ONTA CTS FOR CIRCUIT BREAKERS Andr Latour, Grenoble, France, assignor to Ets Merlin 8: Ger-in, Grenoble, France Filed Dec. 17, 1959, Ser. No. 860,186 Claims priority, application France Dec. 23, 1958 9 Claims. (Cl. 200-87) This invention pertains to electrical contacts arrangements such as are employed in circuit breakers, and especially to improvements in the application of electrodynamic forces as an aid to proper functioning of such contacts.

In my prior US. Patent No. 2,821,594 I have described an electric switch combining a stationary contact and a movable contact, and a stationary and a movable conductor respectively terminating at said contacts and both having substantially rectilinear length portions which extend parallel and adjacent to each other when the switch is closed; said movable conductor constituting the supporting arm of said movable contact and being disposed in a position to react magnetically (in the closed position of the contacts) with said stationary conductor, in such a direction as to urge the movable contact against the stationary contact. In those switches the two conductors, at least upon the initial opening movement of the contacts and during formation of an arc, form (with their ends nearest to the contacts, said contacts, and said are) a loop, whereby the magnetic forces of the current tend to expand said loop and thus to repel the arc.

In FIGURES 14 to 16 and 17 to 19 of the patent, corresponding to the diagram of FIGURE 4 of the patent, I described a device in which a second stationary conductor is connected in series with the first named stationary conductor and extends parallel to the same, and is disposed in a position to react magnetically, in the closed position of the contacts, with said movable conductor to urge the movable contact against the stationary contact.

I have now discovered that this patented device can be greatly improved, by modifications that will be understood from the following.

If we designate by i the current to be switched off, in the most favorable case the currents traversing the movable conductor, and that branch of the stationary conductor in which the current flows in the same direction, are equal to i/ 2, so that the attractive force is proportional to i 4, whereas the repulsive force created by the other branch of the stationary conductor is proportional to i /2; thus, the total force which urges the movable contact against the stationary contact is equal to ai /4+bi /2; a and b being constant parameters.

I have now found that, if we dispose the two parallel stationary conductors electrically, relatively to the contacts, so as to have said two parallel conductors connected in series with the movable conductor, the attractive force as well as the repulsive force are proportional to 1' so that, all other things being equal, the total force which.

urges the movable contact against the fixed contact is equal to ai +bi If we assume that the lengths and the distances of the conductors are the same in the two directions, sothat we may seta=b, we have in the first case, a total force equal to %ai and, in the second case, a total force equal to 2ai an improvement of at least 267%.

The invention will best be understood from consideration of the following detailed specification of certain assassin Patented June 4, 1963 ice I FIGURES 1 and 2 represent schematically and according to a known arrangement, the path of the current in the incoming and outgoing conductors of the contact members.

FIGURES 3 and 4 show schematically the novel arrangement, according to the invention, of the incoming and outgoing conductors.

FIGURES 5 and 6 show schematically another arrangement proceeding from the same inventive idea.

FIGURE 7 shows in side elevation, partly in section, an embodiment according to the schematic arrangement shown in FIGURES 3 and 4.

FIGURE 8 is a plan view of FIGURE 7.

FIGURE 9 represents in side elevation another form of execution of the contact arrangement, still according to the schematic arrangement shown in FIGURES 3 and 4.

FIGURE 10 is a horizontal section view taken along the line 1l lt} of FIGURE 9.

FIGURE 1 is a schematic elevational view of the conductors connected to the contact members, taken in a plane perpendicular to the plane wherein the contacts are moving. 4

FIGURE 2 is a side view of the same conductors, the arrangement as shown by FIGURES l and 2 being already shown in my US. Patent No. 2,821,594. In these figures, P represents, for instance, the surface of the fixed contact member and p that of the movable contact member, L1, L2 the conductors carrying the current to the contact P, 1 the conductor carrying away the current from the contact p. For a better understanding, the movable contact 12 and its conductor 10 are not shown in FIGURE 1. It will be easily appreciated that the conductors L1, L2 form, with the conductor 1, a closed loop, and that the repulsive force which is produced between the conductor 1 and the conductors L1 and L2, by virtue of the current flowing in opposite direction in said conductors, has for a consequence an increase in the contact pressure between P and p. One will be aware,

however, that owing to the fact that the conductors L1 and L2 are not located in the plane wherein the conductor 1 is moving, the forces exerted on this latter by the two conductors L1 and L2 are oblique with respect to the direction of the contact pressure, and that only the resultant force produced by the two oblique repulsive forces is located in the motion plane of contact p; that is, in the desired and useful direction. As these forces are relatively very oblique with respect to the motion plane, the resultant vector force is, of course, very much smaller than the arithmetical sum of the two repulsive forces.

FIGURES 3 and 4 show, with the same reference numerals used in FIGURES 1 and 2, an arrangement according to the invention.

One will observe that, in these figures, a conductor L, carrying a current flowing in the same direction as in the conductor 1, is located behind the conductor 1. These currents create an attractive force having the same direction as the contact pressure, and which adds to the repulsive forces exerted by L1 and L2 on the conductor 1. This arrangement is particularly advantageous, due to the fact that owing to its position, the conductor L may be placed much nearer to the conductor 1 than would be possible for the conductors L1 and L2, and thereby to obtain an attractive force much higher than the repulsive force exerted by said conductors L1 and L2. It will easily be appreciated, in FIGURE 4, that the path described by the current flowing through the contacts P and p has the form of the Greek letter (p.

As shown in FIGURES 5 and 6, it is possible to obtain much greater compensation effects, together with a contact device of much smaller dimensions, by combining in series two arrangements similar to the one shown in FIG- URES 3 and 4. So, thus, in FIGURE 6, the rear conductor L is divided as above into two conductors Ll and LZ which are prolonged by two conductors LL, and return to the contact P by the conductors L1 and L2 placed in close proximity to the conductors L1 and L2.

One obtains, in this way, a kind of coil with two turns wound in parallel, in the middle of which the conductor 1 integral with the contact p may freely move. It is obvious that, if so desired, more turns can be provided in each half of this coil.

In comparison with the known arrangement, the new arrangement of this invention allows not only a multiplication of the forces of compensation, but is particularly advantageous when the two contacts have to withstand a rupturing arc, because in this case, the magnetic field created by the two coils provides an excellent means of obtaining magnetic blow-out.

Although the loops shown in the various figures have a rectangular shape, it is obvious that when the maximum resistance to the electrodynamic forces must be obtained, these coils may readily be given a circular shape.

FIGURE 7 is a schematic elevation and sectional view of the contact arrangement according to FIGURES 3 and 4, and FIGURE 8 is a plan view of FIGURE 7. In these figures, the contact surface of the fixed contact P is obtained by means of two deep-drawn shells I placed face to face. At the contact point, the edges of the shells form a recess into which penetrates the contact surface of the movable contact member 17, in such a manner that at least two contact points are always obtained. Each shell extends towards the bottom by virtue of a jaw 2. The two jaws forms the conductors L1 and L2 in FIGURES 3 and 4. In order to prevent the dispersion of the current in the jaws, and to establish a passage in the peripheral zone situated on the right side of each jaw, one or more slits 3, 4 and 5 are provided in the jaws. The jaws are fixed onto a central piece 6 as by means of the rivets 7, 8, 9 and 10. The rivets 8, 9 and 10 are provided with insulating sleeves and insulating washers so that no current can flow from the piece 6 into the jaw 2 in the region of said rivets 8, 9 and 10. On the contrary, the rivet 7, which exerts a clamping action on the two jaws 2, directly or through a metallic washer, is not insulated. It is only in the neighborhood of the rivet 7 that the current can flow from the piece 6 into the jaws 2.

The left end of the piece 6 is clamped between two flat pieces 11 as by means of the rivets 12, 13 and 14, the fiat pieces I]; being intended to carry the incoming current of the circuit-breaker to the fixed contact at 1. Here again, the rivets l2 and 13 are provided with insulating sleeves and insulating washers so that no current can fiow from the fiat pieces 11 into the piece 6 through these rivets. On the contrary, the rivet 14, which exerts a clamping action between the pieces 11 and 6, is not insulated. Therefore, the current flows from the pieces 11 into the piece 6 only in the neighborhood of the rivet 14. The piece 6 is provided with a certain number of slits 15 and 16 intended to force the current to flow along its right side. It will be appreciated that the current path thus obtained, as shown by the dotted lines, has the shape shown in FIGURES 3 and 4.

The use of slits in pieces of flat shape allows one not only to oblige the current to flow along a predetermined path, but presents particularly interesting advantages from other standpoints, namely:

1) It allows one to obtain, at particular chosen points, a heavy concentration of current which is very favorable for the creation of strong attractive or repulsive forces; and this without reducing the mechanical resistance of this piece in the direction in which these forces are acting.

(2) The cooling surface of these pieces is practically not at all diminished by the slits, so that the heat prod duced in the regions of heavy current concentration can be easily dissipated.

For these reasons, the use of slits or saw-cuts in conducting pieces of flat shape constitutes one feature of the present invention.

The movable contact may be constituted by two U- shaped pieces 17 placed face-to-face and assembled by rivets. At their upper end, these pieces cover a lever 18 preferably made of light metal and fixed at its lower end on an axis 21. In order to oblige the current to flow along the desired path, an insulating cap 19 is provided between the end of the lever 18 and the U-shaped piece 17 whose lower extremity has the form of a fork and is riveted onto the lever 18 as by means of the rivet 20.

The movable lever 18 can be displaced by a device actuated by the control mechanism (not shown) of the circuit-breaker; for instance, by two interrupting levers 23. When the points P and p come into contact, the levers 23 continue their movement towards the left and tension the spring 22 which secures the contact pressure. Continuing their movement towards the left of the figure, the levers 23 may, towards the end of their travel, come into contact with the main contact pieces 24 through which most of the current will then flow. During the reverse movement these contacts (23 and 24) part without forming an are because, at the moment of separation, all the current is directed to the points P and p between which the arc is initiated upon the separation of contacts 1 and 17.

It will be appreciated that in the fixed contact the current can only reach the point P by way of the side walls of the shells 1' which are at a greater distance from the median plane than the point P itself (see FIGURE 8). As a result, the current lines reaching the point P form a bend which has for its effect to drive the roots of the arc, whatever their position, towards the inner edges of the shells, that is to say, towards the median plane itself. In this way, an automatic centering of the arc roots is obtained, by which the functioning of the interrupting device is considerably improved. For this reason, the arrangement as described is also considered as a feature of the invention.

Moreover, it will be seen from FIGURE 8 that the edges of the two shells 1 are not in contact but, on the contrary, are separated by an interval 25 of appropriate width.

This arrangement allows the gases which are produced at the separation of the points P and p, and which may have an explosive force, to be evacuated into the slits 25 without exerting on the arc root-s any action impeding the centering of the same.

As already indicated, the contact pressure can be secured, as shown in FIGURE 7, by a spring 22 exerting a force on the movable contact 17. The contact pressure may, however, be obtained by a spring exerting a force on the fixed contact. An arrangement of this kind is shown in FIGURES 9 and 10. In these figures, the movable contact is shown at 26 as a fiat bar of rectangular section. The slits 27, 28 and 29 oblige the current to flow in the left side of the contact bar 26. The fixed contact is formed by two flat pieces 30 (FIGURE 10) fixed on the axis 31, borne by a piece 32 formed by two bracket pieces, as shown in FIGURE 10. A spring 33 secures, through the intermediary of a rod 34 and a fork 35, the contact pressure between the pieces 30 and the movable contact 26. The travel of the contact pieces is limited by the stops 36 and 37. A saw-cut 38 obliges the current to flow into the extreme right region of the piece 32. Under these conditions, the current is obliged to follow approximately the path as shown in dashed lines, this path corresponding closely to the current path as shown in FIG- URES 3 and 4.

In order to avoid the possibility that the electrodynamic forces may deform the contact 26 in the region weakened by the slits or saw-cuts, the latter may advantageously be filled with a suitable insulating material.

It will be appreciated that this kind of contact may advantageously replace, in FIGURES 7 and 8, the contacts 23 and 24 which would not only obtain a compensation of the forces at the contact points themselves, but also completely protect the control mechanism of the circuit-breaker against the electrodynamic forces developed in the pivoting levers 23 and 18.

What is claimed is:

1. In an electric switch, the combination of a stationary and a movable contact, and of a stationary and a movable conductor respectively ending at said contacts and having respectively substantially rectilinear length portions extending parallel and close to each other when the switch is closed, said movable conductor constituting the carrying arm of said movable contact and being disposed in position to react magnetically in closed position of the contacts with said stationary conductor in a direction to urge said movable contact against said stationary contact, the two conductors, at least upon initial opening movement of the contacts and formation of an arc, forming with their ends, nearest to the contacts, said contacts and said arc, a loop, whereby the magnetic forces of the current tend to expand said loop and thus to repel the arc; at least one of said conductors including serially connected portions leading the current in successively opposite directions on opposite sides of the other conductor to its corresponding contact.

2. In an electric switch, the combination of a stationary and a movable contact, and a stationary and a movable conductor respectively ending at said contacts and both having substantial length portions extending close to each other when the switch is closed, said movable conductor constituting the carrying support of said movable contact and being disposed in position to react magnetically in closed position or" the contacts with said stationary conductor in a direction to urge said movable contact against said stationary contact, the two conductors, upon initial opening movement of the contacts and formation of an arc, forming with their ends nearest to the contacts, said contacts and said arc, a loop, whereby the magnetic forces of the current tend to expand said loop and thus to repel the arc; at least one of said conductors including serially connected portions leading the current in successively opposite directions on opposite sides of the other conductor to its corresponding contact.

3. In an electric switch, the combination of a stationary and a movable contact, and of a stationary and a movable conductor respectively terminating at said contacts and having respectively substantial length portions extending close to each other when the switch is closed, said movable conductor constituting the carrying support of said movable contact and being disposed in position to react magnetically in the closed position of the contacts with said stationary conductor in a direction to urge said movable contact against said stationary contact; at least one of said conductors including serially connected portions leading the current in successively opposite directions on opposite sides of the other conductor to its corresponding contact.

4. The combination of claim 3, in which at least one of the conductors and the associated contact are constituted by the contact member itself, being slotted to isolate the contact into portions, at least one of which portions provides a current path substantially parallel to the conductor associated with the other contact.

5. The combination of claim 3, in which, in closed condition of the contacts, one of said portions is connected electrically in parallel with said movable conductor.

6. The combination of claim 3, in which said at least one of said conductors includes at least four such serially connected portions leading the current in successively opposite directions.

7. In an electric switch, the combination of a stationary and a movable contact,a first conductor constituting the carrying arm of said movable contact and traversed by the sarne current as the movable contact, a second conductor traversed by a current flowing in the same direction as the current flowing in the first conductor and disposed in a position to exert on said first conductor an attractive force tending to maintain said movable contact in closed position, a third conductor traversed by a current flowing in the opposite direction with regard to the direction of current flowing in said first conductor and disposed in a position to exert on said first conductor a repulsive force, tending to maintain said movable contact in closed position, said contacts being connected serially between said first conductor, on the one hand, and said second and third conductors on the other hand, in the closed position of the switch.

8. In an electric switch, the combination of a stationary and a movable contact, a first conductor constituting the carrying arm of said movable contact and traversed by the same current as the movable contact, a second conductor traversed by a current flowing in the same direction as the current flowing in the first conductor and disposed in a position to exert on said first conductor an attractive force tending to maintain said movable contact in closed position, a third conductor traversed by a current flowing in the opposite direction with regard to the direction of the current flowing in said first conductor and disposed in a position to exert on said first conductor a repulsive force, tending to maintain said movable contact in closed position, said first conductor being mounted to travel during its opening movement into a position where said second conductor exerts on said first conductor a repulsive force tending to increase the speed of separation of the contacts.

9. In an electric switch, the combination of a stationary and a movable contact, a first conductor constituting the carrying arm of said movable contact and traversed by the same current as the movable contact, a second conductor traversed by a current flowing in the same direction as the current flowing in the first conductor and disposed in a position to exert on said first conductor an attractive force tending to maintain said movable contact in closed position, a third conductor connected to said stationary contact and traversed by a current flowing in the opposite direction with regard to the direction of the current flowing in said first conductor and disposed in a position to exert on said first conductor a repulsive force tending to maintain said movable contact in closed position, said first conductor forming, immediately after the separation of the contacts and the formation of an arc, with said third conductor, said contacts and said arc, a loop, wherein the magnetic forces of the current tend to expand said loop and thus to repel said arc.

References Cited in the file of this patent UNITED STATES PATENTS 1,754,349 Bruhlmann Apr. 15, 1930 2,732,468 Curtis et a1. Ian. 24, 1956 2,821,594 Latour Jan. 28, 1958 FOREIGN PATENTS 534,048 Belgium Dec. 31, 1954 560,368 Germany Oct. 1, 1932

Claims (1)

1. IN AN ELECTRIC SWITCH, THE COMBINATION OF A STATIONARY AND A MOVABLE CONTACT, AND OF A STATIONARY AND A MOVABLE CONDUCTOR RESPECTIVELY ENDING AT SAID CONTACTS AND HAVING RESPECTIVELY SUBSTANTIALLY RECTILINEAR LENGTH PORTIONS EXTENDING PARALLEL AND CLOSE TO EACH OTHER WHEN THE SWITCH IS CLOSED, SAID MOVABLE CONDUCTOR CONSTITUTING THE CARRYING ARM OF SAID MOVABLE CONTACT AND BEING DISPOSED IN POSITION TO REACT MAGNETICALLY IN CLOSED POSITION OF THE CONTACTS WITH SAID STATIONARY CONDUCTOR IN A DIRECTION TO URGE SAID MOVABLE CONTACT AGAINST SAID STATIONARY CONTACT, THE TWO CONDUCTORS, AT LEAST UPON INITIAL OPENING MOVEMENT OF THE CONTACTS AND FORMATION OF AN ARC, FORMING WITH THEIR ENDS, NEAREST TO THE CONTACTS, SAID CONTACTS AND SAID ARC, A LOOP, WHEREBY THE MAGNETIC FORCES OF THE CURRENT TEND TO EXPAND SAID LOOP AND THUS TO REPEL THE ARC; AT LEAST ONE OF SAID CONDUCTORS INCLUDING SERIALLY CONNECTED PORTIONS LEADING THE CURRENT IN SUC-

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