US2590989A - Circuit breaker - Google Patents

Description

Ap 1, 1952 G. A. MATTHEWS CIRCUIT BREAKER Original Filed April 18, 1942 r A. y i.. 2..: n

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Patented Apr. 1, 1952 UNITED STATES PATENT OFFICE:

CIRCUIT BREAKER George Augustus Matthews, Detroit, Miclp, as-

signor to The Detroit Edison Company, Detroit, Mich., a corporation of New York 2. Claims- This invention relates to circuit breakers and particularly to single-pole circuit breakers capable of a quick interruption of relatively heavy currents.

This application is a division of my copending application Serial No. 439,576, filed April 18, 1942, Circuit Breakers, which matured into Patent No. 2,443,260 on June 29, 1948, which application was a division of application Serial No. 333,875, iiled May 7, 1941, Apparatus for Protecting Power Lines, which matured into Patent No. 2,352,556 on June 27, 1944, and was re-issued under No. 22,872 on April 29, 1947. As stated in the earlier patent, serious damage or complete burn-off of overhead insulated conductors occurs even in the case of transient faults when the protective switch gear is of the prior commercially available types which cannot open the line in less than about V6 second. The present invention contemplates a reclosing circuit breaker having an initial opening time substantially lower than that attained or contemplated by the prior workers in this eld.

An object of the invention is to provide a single-pole circuit breaker in which insulating material forms a cylindrical arc-,extinguishing lchamber of restricted annular cross-section in which an arc is drawn upon the separation of the breaker contacts, the movable contact being carried by an operating rod which moves axially in they chamber to open and to close the circuit breaker. A further object is to provide a circuit breaker having the characteristics stated, and which includes an arc-spinning coil for establishing a magneticr field within the arc-extinguishing chamber uponk the opening of the breaker contacts, thereby to move the terminals of the arc around on the arcing contacts, thus minimizing the loss of arcing contact metal by not excessively heating the arcing contact metal at any one spot.

'Thesev and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawings inwhich:

Eig. lis a central section through a` single-pole, oil insulated circuit breaker embodying the invention;

Fig. 2 is a schematic diagram of the same; and

Fig. 3 is an enlarged fragmentary view of the circuit breaker contacts. K

The circuit breakers contemplated by this invention, as employed for the protection of the conventional three-phase electrical distribution systems, are light weight, fully automatic, singlepole circuit breakers that each includes its own mechanical timing equipment and requires no auxiliary circuits, or devices for full automatic operation. As shown in Figs, 1u and 2J the circuit breaker includes., a Control coil and,v operating coil 8| in, series between terminals 82 83, the operating coil 8| being normally shunted by the switch 84 that4 is opened by the control coil 80 against a spring 84. This switch and the main breaker switch are of the reciprocating rod type as described and claimed in my prior Patent No.

2,167,665, granted August 1, 1939, Circuit Breaker, in which an annular arc-extinguishing chamber is formed by horn ber or other organic material,

The core or plunger 85 of coil 8| is secured` to a metal rod B6 which carries the movable contact 81 of the circuit breaker and terminates inarod 88 of' horn ber, or the like. The stationary breaker contacts include a main contact 89 that is normally engaged by the rod 86 or its movable Contact 87,A and an arcing contact 80 above and spaced from the main contacts. The arcing contact 90 is connectedY to the main contact B9 through a spiral coil 9| coaxial with the rod 86 and the contacts. The function of the coil 9| is to rotatethe arc that is drawn between the moving contact 8l and the arcing contact 90 when the breaker opens, and the coil is wound in the sense opposite that of the operating coil 8|. The shunt or control switch 84 is of simpler design as the arc drawn across its contacts can be extinguished without the aid of` an arc-spinning coil.

Timing mechanism 92 is provided to delay the second and subsequent openings of the breaker, but the ii-rst openingY takes place with no delay. The timing mechanism is indicated generally by the block-'diagram overlying-the. junction of' the operatingv lever* 93 of switch t4 and the link 94 that connects leverv 93 to the. armature. 95 ofthe trip coil 80. Any desired type of mechanism may be employed to delay the opening of the shunt; switch 84 for intervals of 60 cycles or upward when the fault is still on the line at the first or subsequent closures of the breaker. The detailed construction lis not illustrated since it forms no partl of the present invention,

The breaker is housed within a chamber comarising a hollow insulator 96 and end. closures 91. 98V of metal that'carry the terminals 82, l83respectively. The insulator is provided with metal sleeves 99 to which thel closures are bolted, and is recessed to receive amounting bracket |00. A plate Ilil extends across the upper end of the insulator 96v and constitutes the support for the control. switch. and the breaker a,Ss e1fr 1b.1y. and

the control mechanism is located in the domed closure 97 above the plate MDI. The insulator 9S is preferably filled with oil to approximately the lower face of the plate IBI which supports all of the switch and control mechanism.

The framework of the breaker assembly includes a series of rods IGZ, a metal plate M33 on which the coil El rests, and a plurality of horn fiber plates or disks EM. Insulating rods IE5 are threaded upon rods HB2 to secure the plate 63 against spacing sleeves Edt' on rods M92, and rods I02 are threaded upon the rods .HB5 to carry the disks IM. A dashpot for arresting the opening movement of the breaker is formed by the enlarged lower end 85 of the core t5 and a cylinder |05 that is mounted between the plate Iil and the upper disk iEM. The top portion of the cylinder flares inwardly above vent openings that permit a free escape of oil from within the cylinder during the major part of the opening movement of the rod 85.

The two intermediate plates Itl are separated slightly and are recessed to receive small horn fiber disks IEM' that form the outer wall of the arc-suppressing chamber. The small plates may be replaced when the diameter of the chamber has been appreciably increased by the erosion of the horn ber. The arc-spinning coil QI is mounted between the two lower disks Ica, and connected between arcing contact il@ that is recessed into the lower face of the upper disk of this pair and a flanged brass tube tilt' that is bolted to the bottom disk I to support the main contact assembly. The main contact 89 includes a plurality of arcuate segments secured to the upper ends of the several sections of a longitudinally slotted tube I of resilient metal. The flanged lower end I lll of the tube Idd is electrically connected to a disk HI by a jumper H2, and the disk I I I is pressed against -a boss on the lower closure 88 by springs IIS coiled about guide rods that extend through the flange l It.

The breaker opens against a spring iid, and displaces a ratchet bar I I5 into engagement with the wheel I I6 of an escapernent mechanism. The

spring I I4 tends to reclose the breaker as soon as the circuit opens but the downward motion of the switch rod 86 is delayed bythe escapement mechanism. The escapement may be of known types, including means for locking the breaker in open position after a predetermined number of reclosures if the fault is still on the line and means for resetting from any point in the schedule of reclosures when the breaker closes on a sound line. The time-delay may be of the customary order of from 30 to 60 cycles, but the specific design of the escapement mechanism is not an essential feature of this invention.

The method of operation of the circuit breaker will be apparent from the foregoing description. In the case of a single phase line, a circuit breaker is connected in series with one side of the line at the terminals 32, 33. An ungrounded threephase rcircuit' can be protected by locating circ-uit breakers in two of the line conductors.

The tripping value of the circuit breaker may be adjusted as desired but will usually be set up to 200% or more of the rated current capacity of Y the breaker. The tripping current is determined by the design of the coil 89 and the adjustment of the reclosing spring 84 of the shunting switch 84. l The line current does not flow through the operating winding under normal operating conditions, and a heavy and sudden current surge flows through the operating winding 8i when the sh-unting switch 84 opens. The operating winding 8I may therefore be designed to develop a heavy force for displacing the movable Contact fil at high speed.

The invention is distinguished from prior circuit breakers of the series operating winding type in that the load current is normally by-passed around the operating winding. The prior circuit breakers have been open to the objections of serious overheating and coil damage due to the continuous iiow through the operating winding of load currents approximating but somewhat less than the tripping value. This overheating under overloads short of tripping value is eliminated by the present invention as te control coil til need develop only a relatively small force to open the shunting switch 85. It is therefore possible, and entirely practical, to design the coil SI to develop suicient force for an exceedingly high speed opening of the breaker as the winding SI is subjected only to a momentary current surge of high magnitude. The reciprocating rod and arcextinguishing chamber construction also contribute to high speed operations as a l to 2 inch movement of the rod, which movement is sufiicient to separate the breaker contacts and suppress the arc, is obtained in about 2 to 3 cycles with operating coils SI of practical design.

The initial opening of the breaker takes place within an interval that depends upon the magnitude of the fault current, as shown graphically by curve B of Fig. 1 of Reissue Patent No. 22,872, but the subsequent openings are delayed by the timing mechanism 92 to supply current to a persistent fault for periods of about 30 cycles and upward at an inverse rate parallel to that for' blowing of fuses, thereby to blow sectionalizing fuses or to burn the conductors down if there are no sectionalizing fuses, in the case of a persistent fault or to lock-out the breaker in the open position, if the persistent fault cannot be otherwise cleared from the system.

Time values are stated in cycles on a 60 cycles per second basis since it is the usual practice in this art to measure the operating times of protective switchgear with oscillographs that generate a timing wave of the frequency of the electrical distribution system. The novel apparatus has been tested and used on lines supplied with alternating current of a frequency of 60 cycles per second but the protective methods and apparatus may be used on direct current lines or on alternating current lines energized at 25 cycles per second or at other frequencies.

The quick acting circuit breakers are particularly useful in protective systems, as described in the reissue patent, which include line shorting contactors for a substantially instantaneous suppression of fault currents, but may be used to advantage in any protective system where high operating speed is desirable. The high opening speeds of the new circuit breakers are attained by making the operating coil 8| a series element in the line to be protected, whereby a sudden and heavy current surge traverses the coil Si upon the opening of the control switch 84 which normally by-passes the line current around the operating coil 8 t The term operating coil is employed in the following claims to identify the element which functions, upon energization as just stated, to operate the circuit breaker to open-circuit condition against the closing force developed by the spring H4. The heavy power surge for effecting a quick opening of the circuit breaker is developed by an operating coil in series with the line but there is no overheating of the breaker assembly when the line current is maintained for long periods at approximately the preselected breaker-opening value, since the line current is cy-passed around the operating coil 8| until the line current reaches that value at which the control coil Si) opens the by-pass switch 84.

It is to be understood that the invention is not restricted to the particular embodiment herein illustrated and described, and that various changes that may occur to those familiar' with the design and construction of circuit breakers fall Within the spirit of my invention as set forth in the following claims.

I claim:

1. A circuit breaker comprising an axially movable rod carrying a contact, cooperating contact means including a power contact and an arcing Contact, means including an operating coil to move said rod to separate the Contact thereof from said contact means, insulating material surrounding said rod and dening a cylindrical chamber in which said rod reciprocates upon the opening and closing of the circuit breaker, said insulating material comprising a plurality of disks, each of said disks having a central opening of a diameter just suciently larger in diameter than said rod to provide mechanical clearance therefor, a pair of adjacent disks being spaced from each other and a cylindrical extension of insulating material on said rod and movable thereby into said chamber upon an opening movement of the rod, said insulating materials having the property of evolving an arc-extinguishing gas when contacted by an arc, said movable rod, said movable contact and said cylindrical insulating material having the same cross-sectional area and being in axial alignment with each other.

2. In a circuit breaker, stationary contact means including a main contact and an arcing contact, movable contact means including an axially movable metal rod engageable with said stationary contact, means including an operating coil for moving said rod to separate said movable contacts from said stationary contacts, an arc-spinning coil connected between said main contact and arcing contact, insulating means enclosing said contacts, said insulating means comprising a plurality of insulating discs, each of said discs having a central opening of a diameter just sufhciently larger in diameter than said rod to provide mechanical clearance therefor, means for spacing adjacent discs from each other, a rod of insulating material secured to said metal rod and movable therewith into the bore or said insulating means upon an opening movement of said rod, said plurality of superposed discs of insulating material being recessed, and removable discs of insulating material mounted in the recess of each of said insulating discs to denne an arc-extinguishing chamber, said arcspinning coil being mounted between two of said discs, said movable rod, said movable Contact and said rod insulating material having the same cross-sectional area and being in axial alignment with each other.

GEORGE AUGUSTUS MATTHEWS.

REFERENCES CTEB The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,441,193 Wyman Jan. 2, 1923 1,883,766 Cox et al Oct. 18, 1932 2,112,033 Lingal Mar. 22, 1938 2,140,378 Biermanns Dec. 13, 1938 2,192,045 Linde Feb. 27, 1940 2,231,576 Grosse Feb. 11, 1941 2,365,509 Baker Dec. 19, 1944

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