US1340917A - Overload-circuit-breaking apparatus - Google Patents

Description

E. O. SCHWEITZER. OVERLOAD CIRCUIT BREAK ING APPARATUS.

APPLICATION FILED JAN. 10, i9l9 Patented. May 25, 192% 3 SHILETS-SHEET 2 0 SW A 2 3 v m v 1 Il I'llll'lllll Ill .iiniiiiiiiiusiiiii..iiiia ai 352i??? -E. O. SCHWEITZER.

OVERLOAD CIRCUIT BREAKI NG APPARATUS.

APPLICATION FILED JAN. 10. 1919.

went e6 May 25, 192$ 3 SHEETSSHEET 3.

UNITED/STATES PATENT oF IcE.

EDMUND O. SCHWEITZER, OF CHICAGO, ILLINOIS.

OVERLOAD-CIRCUIT-BREAKING APPARATUS.

Specification of Letters Patent.

Patented May 25, 1975i).

Application filed January 10, 1919, Serial No. 270,488.

tomeans for interrupting current flow at high tension.

The object of my invention is to provide a novel method of and means for switching and particularly for interrupting the flow of high tension current with simple and inexpensive apparatus. Other and subsidiary obj eets will be apparent from the following specification.

The switching or interrupting of current flow on circuits operating on high tension.

is in general a difficult and dangerous matter. When a line bears a heavy flow of current at a high voltage, physical separation of the conductors is followed by an are which tends to persist to adegree depending upon'the resistance and inductance of the circuit, the capacity of the generating systern back of it, and the voltage on the conductors.

In practice previous to my invention, the only feasible way to switch such current flow was by oil switches, but oil switches are very expensive in cost and upkeep and in large sizes are slow to operate. The use of an break switches for such service has been wholly unpracticable heretofore. The reason for this is that the are which is formed dest roys the switch contact. Particularly upon a shorted or overloaded line an air break switch is useless because when the blade is opened, the arc follpws thefull movement of the blade and continues even after the switch is fully opened. The result is the prompt destruction of the switch. This isreadily understood whenit is considered that on a short-circuitedline substantially is concentrated upon the production of heat, andas the break at the switch constitutes the major part of the resistance of the circuit, an enormous amount of heat may be liberated at the switch.

The provision of oil switches. at various .points on a line or system where it is de- .sirable to have means for opening the cii=- the entire capacity of the system cuit, is not feasible, because of first cost and further because of the inability to give them proper attention for maintenance. As

a result, most lines are inadequately provided with circuit breakers.

The statements above made with respect to an air break switch also holds true of any type of switch, the voltage interrupting capacity of which is below that of the circuit upon which it is to be used, whether of a1r break switch, oil switches or any OthGPtYPB.

According to my invention I provide a switch which, of itself, is incapable of satisfactorily interrupting the flow of current/ at the voltage at which the line is operated and by means of a fuse of special character in shunt with the switch I am able to take from the'switch the actual duty of interrupting the current fiow and place it upon I the fuse, which fuse is of such character and construction as to be capable of interrupting the flow of current at the voltage to which the line is subjected.

In the preferred form of my invention 1-80v employ an air break switch of relatively inexpensive construction and ofa'voltage interrupting capacity lower than that required to break a heavy flow of current on the line,

and place inshunt of this switch a fusible 35 circuit break ng device of high voltage interrupting capacity but of small current carrying capacity. The fusible circuit breaking *device which I employ is preferably of the type shown in the patent to myself and Mr. Conrad, No. 1,135,548,altl 1ough any fuse of similar characteristics and ability to positively interrupt the circuit may be employed instead. This type of fuse is particularly valuable becauseof being surrounded by liquid. It is capable of carrying a large overload current for a very short period of time without fusing, thus permitting the switch to open far enough to prevent reformation of theharc at the contact '100 of the switch, and also because of the ability to positively interrupt the flow of current at this fuse.

The fuse may be connected normally in circuit in shunt with the switch, or. it may be connected in a shunt which is closed only when the switch opens with a certain time lag intervening. In the latter construction the fuse will be kept out of the normal flow of current and will be relatively cold so that will not blow immediately, but will per- 'mit the switch to move to open position so J that after blowingof the fuse, the voltage of the line will not be able to reestablish the arc.

In this particular embodiment, the fuse terrupting the are at the fuse by interposition of a dieletric .medium of great strength.

In the accompanying drawings:

Figure l is a diagrammatic view of high tension three phase power or lighting circuit provided with over-load circuit breaking apparatus embodying my invention;

Figs. 2 and 3 are views of the preferred and modified form of my apparatus, respectively Fig. 4 is a longitudinal section of the fuse in normal condition, which fuse is employed by my invention;

Fig. 5 is a similar view of the fuse in operation;

Figs. 6, 7 and 8 are transverse sections taken on corresponding sections indicated in Fig. at; I

Fig. 9 is a front elevation of a modified form of switch embodying my invention:

Fig. 10 is a side elevation of the same; and I Fig. 11 is a fragmentary planview of the same.

In the drawings I have shown the line conductors 1, 2 and. 3, representing the three high tension lines or conductors of a threephase system supplied by dynamo or gen e'ators l. The conductors 5, (l and T are other line com'luctors leading off from the conductors l. 2 and 3. the conductors 5. (S and 7 being understood to run through some suitable transmission device or other apparatus requiring overload current protection. Each of the lines 5. (3 and T lshow equipped with automatic overload circuit breaking apparatus involving my present invention. I show in connection with line or conductor 5,

for example. the fuse S which of very low carrying capacity. preferably a very small percent. for IHSUUKQOIIO percent, of the entire carrying capacity or load carried by I conductor 5.

I also show a circuit breaker 9 which may be any suitable or desirable type of automatic commercial circuit breaker preferably of the air break'type. The contacts 1()10 of thiscircuit breaker are connected by wires ll and 12 with the line 5 so that the fuse S is in shunt of the circuit breaker. The operating solenoid 14; of the circuit hr aker is coni ected in series with the line conductor 5 this solenoid 1 f acting upon tripping mechanism 15 to operate the circuit bro: ker when a predetermined overload traverses the conductor 5. Thus it will be seen that when-- ever a predetermined or sullicient overload passes in the line 5 the solenoid ill will actuate the circuit breaker 9 and thereby open line 5. It will be seen that reliability, certainty and quickness of action are secured. the circuit breaker operating quickly when a predetermined overload is reached and then the fuse operating. Thus; with a low voltage circuit breaker of small and cheap design and a low capacity fuse of high voltage, a very rapid operating mechanism is olb tained with reliability of action and low maintenance cost. it will be seen atthe same time that the arcing effect is taken care of by the character of the arrangement oli circuit breaker and fuse, and protection for the translating apparatus on the line is thereby insured for the circuit breaker with its tripping coil in the primary circuit is more responsive and will. operate more. quickly than the usual oil switch and tripping mechanism at the generating stations. This permits the circuit breaker out at the consumeus premises to open the line before. the main oil circuit breakers at the central station are tripped. llettcr operating of the entire system is thereby secured.

ll hen desired. the circuit breaker may be immersed in oil. although as agencral rule this is not necessary because there is no little are. With the arrangement as shown in my invention, it is easy and inexpensive to replace the fuse since it is contained in a removable cartridge as will be explained later.

in Fig. 9 l have shown the preferred form of'apparatus which employ. 'lhis enibodies a swinging knife blade switch l1") piw oted at IT to a post 18 secured to an upright support if). The blade ll) has an extension 20 to which is secured a spring '31. also fastened to the support 19. said spring tending todraw said extension 20 toward the support 19. 'l l s upright support is made of insulation. Spring contact jaws are also mounted upon the upright support; If) and are arranged to cooperate with the blade i and other contact jaws 2 1 also inounl'ed on the support 19 are arral'iged to cooperate with the extension 20. These contacts are suitably insulated from each other. An elccpivotally connected at its lower end to a support 26 and at its upper end constituting a support for the links 27 and. 28 whichare pivotally connected to one another, by fric- I tionally engaging the under sides of the links at their pivotal point to retain the links in the position disclosed in Fig. 2, it being understood that the-link 27 is in the form of a hook or catch to engage the end of the switch blade 16. A spring 29 acts upon the catch 27 tending tohold the same in engage mentwith the switch blade16. Thus, the

bladej1 6 is normally. held closed in the contact 22 by the catch 27 but when the solenoid 24 is actuated and the armature 25 attracted the catch 27 being shifted due to the action of the spring member 29 so as to disengage the blade 16, thereby permitting the spring 21 to. actuate .the same and separate the blade 16 from the contact 22 and cause extensions 20 to connect withthe contact jaws 23, the

' links 27 and 28v having a loose connection with one another and with the. armature 25 with sufficient loose motion to permit a slight buckling of the links 27 and 28 so as to cause a'r'elease or trip of the blade 16.

On the eother side of the upright 19 are mounted a pair of posts BOand 31 which support-an inclosed fuse 32, the construction of which is shown in-Figs. 4 to 8 and will be described later. The arrangement is so connected that; the solenoid 24 is included in the circuit as shown in Fig. 1, and when and the connection of the fuse in shunt. llnthe solenoid is energized by an overload current and the blade 16 released, the circuit through the blade 16 by way of contact jaws 22 is opened and thefuse 32 is connectedin shunt by: the extension 20 meeting the spring jaws 23, the connection to-the swinging blade 16'. and extension 20 being by way of metal rods to posts 18.

- In this embod ment of the invention, the

fuse 32 is not normally in circuit, and hence is not sub ect to being heated by current flowing during 'normal operation. A further advantage'of this form lies in the lag between the opening movement of the switch less the resistance and circuit carrying capacity of the fuse are carefully proportioned to coiiperate with the voltage and opening action of the fuse, there is a tendency when the fuse is permanently in shunt for the fuse to blow before the switch is far enough opened to prevent the arc being re-formed at the switch.

overcomes this tendency to blow immediately, to a noticeable extent and is an important feature of the invention. ln the preferred form of'Fig. 2 the switch gets an In the form of apparatus which I employ the liquid submerged fusematerial 40 having brass ferrules 41 and 42 at top and bottom. which ferrules are cemented in place on the sleeve. A fusible element 43 inclosed in a cork barrier 44 is connected to. a removable vent or disk\45 by a link 46. .The vent or disk 45 is soldered on the upper ferrule and is adapted to be 7 blown off in the case of vigorous blowing of the fuse. The lower end of the fusible element 43 is connected by a link 47 to acrossbar 48, which cross bar is mechanically connected to the wooden liquid director 49. A

link 50 connects the cross-ba'rto a helical spring 51, the lower end of which is connected to the lower ferrule 42. A flexible cable 52 is connected in shunt of the spring 51 to preventoverheating and destruction of the temper of the spring. The entire sleeve is filled with carbon tetrachlorid or other similar suitable insulating material. \Vhen the element 43 is fused the spring draws the terminal or link 47 down into the sleeve and at the same-time the liquid is projected in a stream by the liquid director 49, asshown inFig. 5, thus positively interrupting the flow of current. The fusible .element 43 is made of a small percent. of the carrying capacity of the main switch to which it is connected in shunt. The resistance is also preferably made sufficiently high so that if the element is normally connected in shunt of the switch, the flow of current through it will be small enough not to blow the fuse under all conditions of current flow to which it is subjected when the switch blade is still closed. The submergence of the fuse also gives it a greater heatabsorbing ability so that actual blowing is,

delayed until the movable blade has had an opportunity to leave the stationary contact. This is highly beneficial in that it permits the switch to move farther toward the open position and thus get farther out of range of the fixed contact before the fuse actually blows. After the fuse once blows the are which is caused by such blowing. is cX-' .tinguished almost instantaneously.

Operation of the complete device. shown in Fig. 3 and diagrammatically indicated in reached a predetermined.position the rear end of the blade connects with the fuse 32 in shunt of the break at the switch contact and the current how is established through the fuse. The fuse then blows and positively stops the flow of current by interposing the arc extinguishing liquid which is a medium of high dielectric strength between the separated terminals of the fuse:

The fuse and switch are scpa ated by in sulating barriers consisting of the insulating support 19 and also the sleeve 40 to prevent mutual interaction between the fusible element and the switch, and particularly to prevent the are at the fuse from reestabhshi the are through the switch.

In l 3 I have shown an arrangement very similar to that of Fig. 2, but instead having three posts on the upright 19 have shown in Fig. 3 only two posts, namely the spring jaws E22 and the post 18 to which the switch blade 16 is pivoted. The fuse is connected with the posts 30, as in Fig. 2 and also with the posts 31, being a rear extension of the post 1 Thus a fuse 32 is normally connected in shunt with the circuit breaker or switch instead of being thrown higs. 9 and 10 I have illustrated a modiacation of my invention suitable for use in connection with certain well known indoor disconnecting switches. The switch shown comprises the upper terminal 60 and the lower terminal (31, consisting of a metal head having a screw threaded shank adapted to be secured in a suitable partition or mountin as is customary indoor inclosed switches of this character. The hear. has a plurality of fins or plates (36 secured thereto, these plates forming the hinge for the movable blade members 67, which in this case are shown as three in number. The up per block 6% has a plurality of similar fins or plates 68 secured thereto for making contact with the free ends of the switch blades A hinge pin or bolt is passed through the hinge plates 66 and through the lower ends of the blades G7 to form the pivots for the mo 'able blades. The movable blades .are thus gripped between pairs of the hinge plates and held in place yieldingly by means of the spring washers and the bolts 69.

The blades are provided with a suitable eye or other engaging portion by which the switch may be manually opened or closed. I connect the fuse 72 in parallel with the switch. The upper ferrulefTZB of the fuse 72 is mounted in a suitable contact clipi i which in turn is supported from a bar of insulation 75 which holds the upper contact clip i i and connected parts at a suitable distance and in suitable alinement with respect to the lower contact clip 76. The lower contact clip 76 which engages the fuse ferrule 7T mounted upon a suitable bracket '78 i which connects electrically with the pivot plate 66 through the bent or U-shap ed connecting member 79, which has its outer end bolted to the bracket 78 by means of the bolt 80. The inner end of the U-shaped member if) is fastened under the adjacent spring washer and is pivoted upon the bolt (39. ii similar ii-shaped member 81 is connected at the upper end of the bar of insulation and the clip iiis connected to said U-shaped member 81 by thedn'acket and the bolt b3. The inner end of the U-shaped member 81 forms a movable switch contact element which engages between the outermost plate or iin (S8 and an added plate or lin 81 which is bolted to the side of the block (it. A suitable eye is bolted to the U-shaped member 81 by the bolt 86 so that the insulating bar I?) with its attached part may be swung about the pivot pin (3!).

The fuse T2 is of the type and character illustrated in the previous figures. mounted on a swinging blade of insulation 72 so that the upper end of the mounting may be disconnected from the upper terminal (30 which preferably is the live. terminal so that the fuse may be withdrawn and replaced without'incurring the danger of contact with live parts.

The operation of follows: smiling and th a s the fuse is this form of device is as that the switch is closed plished by inserting a hook in the hole in the eye Tl and pulling the switch blades 67 outwardly into the position shown in Fig. 10. The 'i'urrent is diverted to the fuse T2 and for an appreciable period of time the current shunted through said fuse so that very little arc occurs at the separation of the blades 67 from thecontact (5S, and after the blades have been moved outward far enough so that the voltage will not reestablish the arc the fuse 72 blows, positively interrupting the connection between the switch terminals. The operating hook may then be inserted in the eye 35 to disconnect the terminals of the fuse so that the fuse may be withdrawn and replaced with a. fuse in the set condition.

it will be apparent from the above description and from the drawings that this form of construction permits the addition of certain parts to standard switches so that my invention may be applied to switches already in use.

it will beunderstood that changes and modifications may be made without departing from the spirit of the invention.

What I claim is:

l. The method of interrupting a How of current in a conductor whichcomprises mechanically breaking the conductor, conducting the current flow wholly through a fusibleelement independent of the break, fusing it is connected. in place, inter- .ruption of the flow of current is accomflow of current at said fusible element by inter-posing a fluid dielectric of greater strength than that prevailing at the mechanical break.

2. The method of interrupting the flow; of current in a conductor which comprises Inechanically breaking the conductor, conducting the current flow wholly through a fusible element independent of the break, fusing the tusibleiclement a short interval of time after the opening of the switch, and promptly interrupting the flow of current at said fusible element by interposing a dielectric of greater strength than that prevailing at the mechanical break.

3. The method of interrupting the tlow of current in a conductor which comprises mechanically breaking the conductor, conducting the current flow wholly through a fusible elementindependent of the break, cooling the fusible element with a liquid dielectric to delay theoperation ot the same, then tusing the fusible element and interrupting the flow (if-current at said "fusible element by inter-posing said liquid dielectric.

4. In combination, [ill'fiil' break switch having means for opening the same, a fusile element, means for connecting the fusible element across I the terminals of the s itch when the switch is opened, a barrier of insulation between the fusible element and the switch to prevent mutualinteraction between the fusible element and the switch, and means for interposing'a dielectric medium of greater strength than air between the terminals of the fuse after the same closes.

in a device for interrupting current flow at high voltage, a-switch of less interrupting capacity than that required to break the flow of current at said voltage, a fusible element and means for connecting the fusible element across the terminals of the switch, said fusible element being submerged in a liquid of relatively great dielectric strength to permit a. slight delay in the l'using of the element and to positively extinguish the are at the fuse. I

6. ln combination, an break switch, a fusible element connected in shunt of the air break switch, and a liquid dielectric surrounding the fusible element for initially cooling the same when the switch is opened and to extinguish the are when the fusible element is fused.

7. in a device for inte flow at high voltage, a sw c h inherently unable to break the full load flow of current the desired voltage, nsible ele 'ient in shunt of the switch, sait ing or a current condr I a small percentage of 11A; of the current carrying capacityei the switch and being ipting a current of a voltage interrupting capacity in excess of the voltage impressed upon the switch and a liquid for. cooling the fuse to permit a slight delay in the operation of the same. ,8. In combination, a switch, a fuse and means for connecting the fuse across the terminals of the switch, said fuse having means to delay the blowing of the same until after the switch is opened a substantial distance. p

9. ln combination, a pair of stationary terminals, a switch blade pivoted on one of the terminals, the other of said terminals having contacts for engaging the switch blade, a pair of terminal clips, a fuse mounted in said clips, a non-conducting member connecting said clips and means for connecting the clips to said terminals.

10. In combination, a pair of stationaryterminals, a switch blade pivoted on one of the terminals, the other of said terminals havlng contacts tor engaging the switch blade, a pair of terminal clips, a fusemounted in said clips, a non-conducting member connecting said clips, a pair of connecting members for connecting said clips to said terminals, one of said members being pivoted on one of said terminals and the other of said connecting members being adapted to engage and disengage electrically the other terminal.

l ain combination, a pair of terminals, a switch blade mounted on one of said terminals, a contact mounted on the other terminal, a bar ct insulation pivotally mounted on the same axis as the switch blade, :t'use mounted on said bar or insulation and means for connecting thefuse in parallel with the switch,

12. in combination, a pairot terminals, a switch blade mounted on one of said termials. a contact on the other terminal for engaging the switch blade, a first member nected said ruse clips and adapted to be con e ed in parallel with the switch across said combf ration, a pair 0" .r

' ivot" on one "\rnnna time iectcd to s adapted to e con-act jaws on or e other 1 ar tact L cans being connected {0 e 'ininal the fuse.

. In c nibinaticn. a pair 0" v i pivot" 'f aninal ha-.'ing contact pivotally mounted on the one terminal llllt having means for engaging the contact jaws on the other terminal to place the fuse in parallel with the switch.

15. In combination, a pair of terminals a switch blade pivotally mounted on one 01 said terminals, a fuse also pivotally mounted on-sairl. one terminal, eontaet jaws on the other terminal, a eontaet member on the fuse for engaging said contact jaws and for placing the fuse in parallel with the switch. In witness whereof .l hereunto suhseriho my name this 7th (lay of January, 19M).

EDMUND SUllll llll'lZllR.

Images