US2945109A - Circuit breaker - Google Patents

Description

July 12, 1960 H. FEHLING 2,945,109

CIRCUIT BREAKER Filed Sept. 3, 1958 6 Sheets-Sheet 1 PRIOR ART Fig.1

Inventor? HE INZ FEHL/NG BY J/ admin 5% zzTna'n/ A T TOR NE V5 July 12, 1960 H. FEHLING CIRCUIT BREAKER 6 Sheets-Sheet 2 Filed Sept. 3, 1958 Inventor? HE/NZ FEHL/NG BYmZ/L 5% cTmw A TTORNE Y5 July 12, 1960 H. FEHLING 2,945,109

CIRCUIT BREAKER Filed Sept. 3, 1958 6 Sheets-Sheet 3 HE/NZ FEHL/NG BY J. admin whim A TTORNE Y5 July 12, 1960 H. FEHLING CIRCUIT BREAKER 6 Sheets-Sheet 4 Filed Sept. 3, 1958 .bweman' HE/NZ FEHL/NG YJv drain/{Lira to Bridge of r'nsu/af/hg maferia/ B ATTORNEYS July 12,, 1960 H. FEHLING 2,945,109

CIRCUIT BREAKER Filed Sept; 3, 1958 6 Sheets-Sheet 5 A TTORNEYS HE/ NZ FEHLING Fly.8b l

July 12, 1960 FEHUNG 2,945,109

CIRCUIT BREAKER Filed Sept. 3, 1958 6 Sheets-Sheet 6 K 68!. magn am Crass Sad-ion A-A I "'5 060 so o'efe a (we "9 999 Q Q Q Q Q Q I eee 9 :2: e Re/afians/nk befween J 9 f cld +1 Shay field g5, current J and resu/fanf magnet/c [2 a blowing farqe kmqg Fig.9

magnet/c iron care .Sfra mag/relic fie/d m'fnauf nragnnfic Iran 9 Curran! or field diracf/an upward bu! of lane of the paper Currenf or field direction do wn ward info fire paper I plan: Shari Circa/1 Currenf-fime-Diagranr 1-; (I)

cu has, '1 Cir-cuff Breaker Release Dev/a (WIS/lawn) 59- I0 Main Canfacfs open t Auxiliary arcing canfracfs open (The exhncfian of in: are ll: naf

illusfmfed) pernrqnanlsbarf cr'rcu/fcurranf v u U U L/ E Inventor." f i t HE/NZ FEHL/NG Normal [and Currenf ATTORNEYS cmcurr BREAKER Heinz Fehling, Neumunster, Holstein, Germany, assiguor to Licentia Patent-Verwaltungs-G.m,b.H., Hamburg, Germany 4 p Filed Sept. 3, 1958,-'Ser. No.-"758,'814 7 Claims priority, application Germany Sept. 4,919 57 'Claims; tclrzuo m intermediary contact .members'wliichrelieve the current- I conductive contact. However, these" improved "known devices still show certain drawbacks to be explained further below, audit is 'the object ofthe present invention to provide a circuit'breaker of the abovementioned arc-extinguishing type which does not'require States Patti ?,i

inte'nnediary contact members, and has inevertheless a better dynamic" stability than the known circuit breakers.

The drawbacks of theknown circuit breakers provided with intermediary .contact members, and ithe nature and "advantages of the device according'to'my invention will now be explained in detail with the "aid of the 'accompanying drawings in which Figure 1 shows schematically a side vi'ew'ofa circuit breaker of the prior art;

Figure 2a shows schematically "the current flow and are extinguishing means in a first 'embodimentof the circuit breaker according tothe invention in make position;

Figure 2b shows the lower part of Figure 2a, but with the circuit breaker being opened to breakposition;

Figure 3 is a partial schematical View in perspective of the lower portion of the embodiment illustrated in Figures 2a and 2b, but showing more structural details;

Figure 4 is a transverse sectional view in a vertical plane through Figure 3 as indicated by IV-IV 'in the latter figure;

Figure 5 is a partial sectional view of a somewhat different detail in the embodiment as illustrated in Figure 4;

Figure 6 is a transverse sectional view of a circuit breaker according to the invention comprising the feature illustrated in Figure 5; 7

Figure 7 is a schematical perspective view, similar to that of Figure 2b, but of another embodiment of the circuit breaker according to the invention;

Figures 8a, 8b and 8c show different modes of wiring the circuit breaker according to the invention in series or in parallel, adapted for direct current as well as for multiphase alternating current.

Figure 9 illustrates the arc blowing field forces generated in the region of the magnet iron system '12;

Figure 9a illustrates the stray field forces in the same region, but without the provision of a magnet iron system, and

Figure 10 diagrammatically illustrates the flow of a short circuit current dependent on time through a circuit breakeraccording to the invention. I

the circuit breakerof the prior as "illustrated in Figure l, reference numeral 2 1-"designates the main contact bearing, for instance, the usual silver lining, 22 is the auxiliary or arc-forming contact, 23 is the'intermediary contact and 24 is the conventionally used arc-blow 7 2,945,109 Patented July 12, 1960 V 2 out which serves to blowthe are formed between the auxiliary contact member 3 magnetically upwardly into an'arc extinguishing chamber (not shown).

auxiliary contact 22 at which are formation is to occur so that only this contact is subjected to the wear by V burning caused by the arc.

.As the intermediary contact opens this transfer of currentflow is to occur to the still closed auxiliary contact 22. This transfer of current flow, however, cannot be instantaneous, but is somewhat lagging in time since the inductive resistance offered in the new current path viathe auxiliary contact 22 must first be overcome. This usually leads to the formation of a small arc-at the intermediary contact 23 as the latter opens.

When rushes of sudden high short circuit currents occur, it often happensthat the current forcesare so strong as to dynamically open the intermediary contact '23 simultaneously with the main contact 21. Thereby, the

to auxiliary contact 22. However, due to the blow-out coil inductivity, the current cannot flow instantaneously fully. through' the auxiliary contact 22, and an arc is formed at the normally arc-free main contact 21, which arcburns the contact members. The blow-out coil in- 'ductivity often becomes firstetfective after both main' and auxiliary contacts have opened and, in turn, alsocauses a delay incurrent'commutation, whereby strong welding and burning effects may occur at the intermediary contacts 23.

Such faulty operation is completely avoided in the circuit breaker according to my invention which comprises, as a main feature, a contact bridge being the movable main contact member and adapted for cooperation with a plurality of stationary main contactmembers and equal number of stationary auxiliary contact members. i I The division into several main and auxiliary contact members and the .provision of a corresponding number of parallel current paths, for instance as current conductive rails, in the bridge achieve a division ot! the voltage, and thegencral arrangement-of the currentpath throughout 'theentire device is particularly favorable for a rapid andsafe arc extinction.

' Of further advantage-inobtaining the la'ttergoal, is the fact that, due to the division of the voltage and by distributing it over at least two or more contact places,. the conventional large arc-extinguishing chamber can be subdivided, into several, for instance two, threeor four subchambers of correspondingly smaller dimensions. I

The individual arc extinguishing chambers can therefore be'of smaller dimensions. 7 4

In connection herewith, the dynamic contact making pressure of the contact bridge directly against the stationary contact surfaces of the circuit breaker system is increased by having the contact bridge disposed movably within the space defined by the aforesaid current-conducting rails and the stationary main contact members. The contact pressure of the closed circuit breaker is increased whenever a sudden current rush occurs, as shall be explained in greater detail hereinafter. It is advantageous to build the contact pairs from members of the type of multi contactpoint surface contacts, as is achieved by providing at least one of th'ettvo contacting surfaces with a'silveriini'ng or plating. The resulting great number of contact points between the movable contact member of each pair uaranteesa reduction of current density at each point.

' According to another important feature of the invention, the blowing of the arc formed between each auxiliary stationary and movable arc-drawing contact members into the corresponding arc extinguishing chamber is effected bya magnetic circuit closed upon itself instead of the conventional blow-out coils. i

Referring now more in detail to the embodiment of a circuit breaker according to the invention illustrated in Figures 3 and 4, a-casing of insulating material houses the main contact, the stationary element of which is dividedinto two fixed plate members 2 and 2a, connected with the two parallel-bus bars and 25a, respectively (see Figures 2a and 2b).

The movable element is formed by the above-mentioned preferably silver-plated contact bridge 1. The latter is mounted at the lower end of two electrically conductive bridge-bearing arms 3, 3a which are pivotally mounted about an axis of rotation indicated at 4 in the casing 20 by means of a shaft 5 against which they are insulated at 4a.

At one end of shaft 5 there is mounted hand lever St: for operating the circuit breaker.

Arms 3 and 3a form at their upper ends the movable members 11 and 11a of the arc-forming auxiliary contact element of the system. These bear against the stationary contact counter members 6, 6a.

Since the contact bridge 1 and the movable contact members 11, 11a of the auxiliary arc-forming contact are rigidly connected with each other by means of,- arms I .3, 311, it is necessary to devisethe contact members 6 and 6a resiliently, as by means of springs 7 and 7a which rest in the frame 20.

The spring means orother resilient means supporting I with members 2 are conventional and correspond to those establishing contact pressure at the main contact shown in Figure l and designated as 18.

According to a slightly different embodiment illustrated in Figure 5, each of members 6 and 6a has a downwardly extending nose 6n pivotably connected by means of a pin or bolt 9 to the stationary rails 10, 10a.

The stationary support members 10 and 10a carry the fixed plate members 2 and 2a respectively of the main contact.

At the same level as the auxiliary arc-forming contact, there is providedabout each set of stationary and movable contact members, for instance 6 and 11, or 6a and 11a, a blowing magnet system 12, consisting of a laminated magnetic iron core, as illustrated, for instance, in

Figures Za and 2b, whichcomprises and legs 12a and 12b, intermediary legs 12c and 12d, and yokes 12a and 121; e V

Each of the magnetic systems closed upon themselves which are thus formed are so disposed, as illustrated in Figure 2b, that the stray field 13a and 13b, on the one a hand, and 13a and 13d on the other hand, generated by the current flowing through 6 and .11 (or 6:1 and 11a, etc.) respectively, generate in turn magnetic flows having the same directions, respectively in the intermediary legs 12c, 12d of the magnetic system. This is indicated by the arrows at 13a, 13b and 13c, 13d. The resulting electromagnetic blowout field is intensified and concentrated in space by the laminated magnetic iron system 12.

The embodiment of the magnetic circuit shown in Figures 2a and 2b thus resembles the yoke of a three-leg transformer. The combined intermediary, or central legs 12c and 12d (which may also be an integral part) diyide the rectangular magnetic core into two closed units each having a window-like opening in which one auxiliary contact system (6, 11 or 6a, 1111) is arranged.

Above each opening there is mounted one of the partial arc-extinguishing chambers 14, 14a, as shown schematically in Figure 2a.

If there are more auxiliary contacts 16a, 16b, 16c, 16d, as in Figure 7, a corresponding number of magnetic circuits 12 12 12 and .12 and a corresponding number of arc-extinguishing chambers (not shown) are provided for. v

The fixed and movable auxiliary contact members of a subdivided system are connected in series as shown by arrows from main terminal to terminal in Figure 2b. The signs of these terminals may indicatedirect current, but multi-phase alternating current may also be controlled with the circuit breakers according to the invention. 1

By this type of series connection current flow between one pair of auxiliary partial contacts, for instance 6 and 11, is opposite in direction to current flow between the other pair formed by members 6a and 11a. This. is also illustrated by. the arrows in the respective arcs 17 and.17a shown in Figure 2b.

When the'circuit breaker is opened, as by swivelling lever -5a from the position shownin full lines in Figure 4, to the position shown'thereinin dashed lines, the oppositely directed magnetic strayfieldsllia and. 13b'at one end, and 13c and 13d on the other end will so influence the oppositely directed arcs 17 and 17a that both arcs are driven-into their respective arc-extinguishing chambers 14 and Ida. L]. The arrangement of the current paths as shown in Figures 2a and 2b, and also in Figu're7, provides for a very favorable blowing of the formed arcs. .Due to: the

voltage 'division at'the auxiliary contacts, each partial extinguishingchamber need only be dimensioned for half the total voltage,.and the entire circuit breaker can be built smaller.

In Figure 7, the contact bridge comprises a bar 10 of insulating material and on the latter two contact sections 1a and 1b forming together the movable member of the main contact. The fixed element of the main contact is subdivided into four contact plates 2 and 2 connected to terminal 19, and 2a and 2a connected to terminal 19a.

The above-mentioned auxiliary arc-forming contacts 16a, 16b, 16c and 16d consist of movable members 11a, 11b, 11c, 11d, and stationary resiliently mounted members 6a, 6b, 6c and 6d. These members are connected with eachother in two parallel series in the following order:

easily understood from Figure 7, according to the following scheme:

circuit breakers in a combined system are illustrated in Figures 8a, 8b and 8c.

Thus, Figure 8a shows the three circuit breakers I, II and III connected in parallel to three direct current sources. Figure 8b shows the same three devices connected in series to a single direct current source, and Figure 8c shows the three devices connected to a threephase alternating current source.

The magnetical and electrical forces occurring during the operation of the circuit breaker according to the invention shall be explained further with the aid of Figures 2a, 2b, 7, 9, 9a and 10.

Due to the inertia of the masses of its contact system, a conventional power circuit breaker is not adapted for having its contacts open during the occurrence of the first half-wave of an eventual short-circuit current.

The time elapsing between the reaction of the excess current breaker releasing. device (conventional and not shown in the drawings) but acting on shaft 4 replacing the hand lever 5a actuating the circuit breaker and the actual separation of the contact members from each other is in the order of 20 to 40 milliseconds, or about 2 to 4 half waves in the case of 50 cycle or 60 cycle alternating currents.

Since the short circuit current usually starts in the form of a current rush, which then changes to the permanent short circuit current of lesser intensity (Figure strong dynamic current forces occur in particular in the first few half waves of the short circuit current, and tend to open the contacts of the circuit breaker.

It is, therefore, a particularly advantageous feature, mentioned further above, that the dynamic forces occurring in the circuit breaker according to the invention during the initial half waves of a short circuit current tend to increase rather than decrease contact pressure in the breaker.

This state is illustrated in Figure 2a, in which the circuit breaker according to the invention is shown with its main and auxiliary arcing contacts in closed or make position.

In this position, the arrangements of a U-shaped pivotably mounted bridge 1 in combination with two separate series-connected separable contacts results in a current flow via closed arcing contacts 6, 11 the closed main contacts 1, 2 and the parallel bus bars 25 and 25a. As these elements form a U-shaped configuration there is formed a current loop. Now, it is well known that a current loop tends to widen the two parallel legs of the U-shaped configuration due to the repelling forces of the magnetic fields established by the current flow through the loop. The resultant of these loop-widening forces is a dynamic force Kdyn, which increases the pressure of contact bridge 1 against contact members 2 and 2a (see Figures 2a and 2b) With the increased intensity of a short circuit current rush, the contact bridge is therefore pressed especially strongly against the stationary main contact members.

Only after the breaker releasing device has been actuated, do the mechanical spring forces designated by Kmech, in Figure 2b come into play and open the contacts in such a manner that the main contacts are broken first, and become as quickly currentless as possible to avoid burning of the contact surfaces and guarantee un- 6 objectionable contact making and breaking over a long life time of the device.

The current then flows entirely via the still closed auxiliary arcing contacts, opening of which is briefly delayed due to the resilient nature of the stationary arcing contact members 6, 6a etc.

The formation of the electromagnetic fields in the magnetic system according to the invention are illustrated further in Figures 9 and 9a.

What I claim is:

1. In a circuit breaker system for electrical currents, having main contact means, an auxiliary arc-forming contact means, and magnetic arc-blowing means, the arrangement comprising two main current conducting elements, a plurality of stationary main contact members and a movable contact bridge for making contact therewith and forming therewith said main contact means, at least two partial movable auxiliary contact members conductively connected to said contact bridge, and a corresponding number of stationary auxiliary contact members adapted for forming arcs with said movable auxiliary contact members, when said bridge is displaced to break contact with said stationary main contact members, said bridge and movable auxiliary contact members being arranged on a substantially U-shaped member with said bridge being in the region of the base of said U-shaped member and said movable auxiliary contact members being in the regions of the free ends of the legs of said U-shaped member, said U-shaped member being pivotable relative to said stationary main and auxiliary contact members in such manner that said bridge moves in a space confined between said main currentconducting elements and said stationary main and auxiliary contact members, thereby ensuring a complete dynamic stability of the system.

2. The arrangement as described in claim 1, further comprising a magnetic circuit closed upon itself which provides for stray fields across the opening enclosed by the circuit, in which stray fields said auxiliary stationary and movable contact members are located, said magnetic circuit replacing the conventional blow-out coil means.

3. The arrangement as described in claim 1, further comprising parallel carrier arms at one end of which said contact bridge is fastened and a shaft on which said carrier arms are spacedly and insulatedly mounted for pivotable movement thereabout.

4. The arrangement as described in claim 1, further comprising a plurality of separate arc-extinguishing chambers each of which is associated with one of the auxiliary contacts formed by one stationary and the corresponding movable auxiliary arc-forming contact.

5. The arrangement as described in claim 1, further characterized in that said stationary main contact members, on the one hand, and said contact bridge, on the other hand, are adapted to effect electrical multi-point surface contact with each other.

References Cited in the file of this patent UNITED STATES PATENTS 2,025,386 Graves Dec. 24, 1935 2,101,783 Leyhausen Dec. 7, 1937 2,871,320 Bardorf Jan. 27, 1959

Images