US940578A - Protective device for electric circuits. - Google Patents

Description

@ M MQQ' Y by S. R. BERGMAN. PROTEGTIVE DEVICE FOR ELECTRIC GIBGUITS. APPLIGATION FILED OCT. 13, 1905.

940,578. Patented Nov. 16, 1909.

2 SHEETS-SHEET l.

//IIIIIIIITIIIIIIIIIIIIIIIJ II/IIII/II/I Invent or Sven R. Bergman,

Witnesses:

S. R. BERGMAN.

PROTECTIVE DBVIOE FOR ELECTRIC 011mm.

APPLICATION FILED 0GT.13, 1905.

Inventor Sven R. Bergm an Mann 2. GRAHAM c0v PHOYQLITNOGRAPHUKS. msnmm'ou, a c.

Patented Nov. 16, 1909.

tlNlTE STTES 'ATENT QFIQGEO SVEN R. BERGILVIAN, OF LYNN, MASSACHUSETTS, ASSIGNOR, TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS.

To all whom it may concern:

Be it known that I, Sven R. BERGMAN, a subject of the King of Sweden, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Protective Devices for Electric Circuits, of which the following is a specification.

Electrical distribution circuits are often subjected to abnormal potentials caused by lightning or other atmospheric disturbances or by resonance or other abnormal conditions on the line. A lightning arrester or other protective device for such circuits must provide a ready path for the removal of this abnormal potential without subjecting the distribution line to an abnormal rush of current or to other disturbing influences.

Various lightning arr-esters have heretofore been designed in which a spark gap is included in the path over which the discharge or current passes, the spark gap being so ad justed that it does not break down under the normal potential of the line, but nevertheless permits a current of abnormal voltage to pass. Unless special precautions are taken there is danger that the line current will follow across the gap on the arc established by the high voltage discharge, and will thus short-circuit the line or at least produce a violent disturbance.

According to my present invention a spark gap is used in the path of the high voltage current, but the apparatus is provided with novel means for preventing any appreciable quantity of line current from following through on the high potential discharge.

The details of my invention will be better understood by reference to the following description taken in connection with the accompanying drawings, in which Figure 1 is a sectional elevation on the line 11, Fig. 2, showing the details of one modification of my improved protective device; Fig. 2 is a transverse sect-ion on the line 2-2 of Fig. 1, showing the parts as seen from beneath; Fig. 3 is an elevation of a second modification with parts shown in section on the line 3-3 of Fig. 1; and Fig. 4 is an end elevation of the apparatus shown in Fig. 3.

Referring to Fig. 1, an oil-tight compart- V ment 1 of metal or other suitable material Specification of Letters Patent.

Application filed. October 13, 1905.

Patented Nov. 16, 1909.

Serial No. 282,583.

is provided with a cover 2 through which is inserted a shaft 3 carrying an insulating hub 4-, and a plurality of metal plates 5 and 6, clamped together by bolts 7 passing through the outer rim of the insulating hub 4. Each of these plates is provided with four radial arms and the plates are so arranged that the arms of plate 5 are directly below the arms of plate (3, as shown in Fig. 2, in which one of the arms of plate 5 is broken away to show the corresponding arm of plate (5. These plates may be made of steel, and while electrically connected by the bolts 7, are nevertheless insulated from the shaft 3 by the insulating hub at. Shaft 3 carries a pulley 8, and is provided with a suitable thrust bearing 9 supported by cover 2, so that the shaft and metal plates carried thereby may be conveniently rotated at a high speed.

Projecting through the metal cover 2 are three brass studs 10, 11 and 12 each of which carries at its lower end what I choose to designate as a contact plate or shoe. These contact shoes 13, 1 1 and 15 have their inner edges cut in the shape of an arc, and are so placed as to be on the same horizontal level as the rotating plate 5, and so arranged that the arms of this plate are separated from the curved surface of the shoes by a gap of a predetermined length. ,This gap constitutes one of the spark gaps in the path of the high potential discharge. Cover 2 also carries three heavy insulating bushings which support at their lower ends three contact slices 16, 17 and 18. These shoes are on the same horizontal level as the rotating plate 6, and are separated from the arms of plate 6 by a suitable air gap. This air gap may be adjusted throughout a definite range by unclamping the nuts which hold the shoes on their corresponding rods, and slipping the shoes so that the supporting studs move for ward or backward in the slots 19, 20 and 21. The shoes 16, 17 and 18 are electrically con nected by an insulated cable 22, so that the stud 23 which passes upward through bushing 24 is permanently connected to all three of the shoes. When the apparatus is in operation stud 23 may be connected through a resistance 25 to a line 26 to be protected. Contact shoes 13, 1a and 15 are electrically connected to the cover 2 by their support ing studs, and this cover is grounded in any suitable manner, as for instance by a conductor 21. When the apparatus is installed the pulley S is belted to any suitable source of power so that the metal plates 5 and 6 may be rotated at a relatively high speed.

lVith the a 'iparatus arranged. as above described an abnormal potential on line 20 will break down the spark gap between one of the contact shoes 16, 17 or 18, and one of the contact arms of plate 6 and the discharge current will pass through the bolts 7 to the lower plate and outto one ot the grounded shoes 153, H or 15, and thus to ground. its will be seen from the drawing the angular width of the contact shoes is such that there is always one arm of plate (3 at the proper sparking distance from one of the three shoe. connected to line, so that no matter how rapidly the high potential strains may tollow each other there is always a suitable path to ground. This feature of my device I consider of importance.

It the line current tends to follow across the spark gap on the high potential dis charge the movement Oil the rotating arm away from the shoe immediately ruptures the circuit and prevents any substantial rush 01 current through the ground connection. By arranging the grounded shoes in a different plane from that of the shoes connected to lines there is no danger that an are drawn out from a line shoe will be carried over by the rotating arms to the succeeding grounded shoe. I prefer to immerse the revolving plates and the contact shoes in a body of oil 28 as .1 find that; the arcs are more easily ruptured under oil and that the rupture occurs at the zero point of the electromotive force wave, so that oscillations or surges are not produced. in. the line.

Figs. 3 and t show a modification of my invention adapted more particularly for use on circuits of relatively low voltage. lhe apparatus comprises suitable standards 30 and 31 supporting a shaitt 32 on which is mounted a pulley 33 by which the shaft may be rotated. Two wheels Set and 35 of wood, fiber or other suitable insulating material are rigidly secured to shaft 32, and carry in their periphery a plurality of radial. arms. llaeh wheel is provided with eight arms arranged equidistant about the periphery but so staggered that :tour of the arms are in. one plane near one edge of the wheel, and the remaining four are in an other plane near the opposite edge ot the wheel. This staggered relation of the arms, while not absolutely necessary, is nevertheless of value in preventing the possibility of an are generated by one arm from jumping over to the arm which immediately follows, as it will be seen that by the staggered relation the distance between arms is doubled so far as this jumping action of the arc is concerned. A wooden framework 36 rig idly mounted on the metal standards it) and 31 is provided with six cross-bars 3T, :38, 3t), lt), 11 and 42. Each of these cross-bars supports two contact shoes bolted thereto and insulated therefrom in any suitable manner. These shoes are arranged in pairs on the cross-bars and are staggered with respect to the rotating wheels so that three alternate pairs L3, l l and 15 cooperate with wheel 34, while the other pairs 46, 4t? and 41*) cooperate with wheel All the arms of wheel 35 are electrically connected by metal bands a9 and 50, and these bands are both electrically connected to the annular llange 51 mounted on wheel 35, and separated by a spark gap from a metal plate 52 electrically connected with. the metal standard 51, or otherwise suitably grounded. The arms of wheel 84 are connected together in a similar manner and are provided with a spark gap similar in all respects to that formed by the annular flanges 51 and 52 of the other wheel. Conductors 53 and 54L connect the studs on one wheel to those of the other.

.111 connecting up the apparatus for operation, I connect the three pairs o'l shoes 43, 141; and 15 to one line, and the remaining three pairs 16, 4:7 and 48 to the other line of the circuit to be protected. in case of an abnormal voltage between the two line conductors a discharge will take place from one shoe to the arm which happens to be near it, and then across through the wire connections to the other wheel and back to the other side of the line through a second air gap. Thus for instance, a. discharge might take place from shoe 15 to the arm i=5, and then across to the other wheel 35 and out to contact shoe l7. ll the abnormal strain between one line and grouml the discharge will take place from one shoe to the rotating arm and then across the air gap between flange 51 and plate and then to ground. By making the angular width ot the contact shoes equal to or grei'lter than 15 there will. always be one arm 01'' each wheel at proper sparking distance from one of the contact shoes, so that no matter when the high voltage is developed in the distribution circuit there will be a suitable patl to ground. The rapid rotation of the wheels and the quick break at the cont act shoes prevents any abnormal llow of line current across the gaps.

Vhat I claim as new, and desire to secure by Letters Patent 01 the United States, is,

1. in a lightning arrester, a rotary member having a plurality of conducting arms, a plurality of contact plates in proximity to said arms but each having an angular width less than the angular distance between adjacent conducting arms, a second rotary member having conducting arms, a second set.- ot contact plates cooperating therewith, means for continuously moving said rotary members, and means for permanently connecting one set of said contact plates to the line to be protected.

2. In a lightning arrester, a rotary memher having arms, a plurality of contact plates arranged about said rotary member and cooperating therewith to term spark gaps, said rotary member having spaces between arms so proportioned with respect to the angular width of said contact plates that a constant sparking distance to said rotary member is insured while the sparking distance to any particular arm periodically increases and decreases as the rotary member is revolved.

3. The combination with a 11110 conductor to be protected, of a rotary member having projecting arms, segmental contacts disposed about said rotary member, said contacts each having an angular width sutlicient to permit high potential currents to discharge through said line to said projecting arms at any instant but insuiticient to bridge across from one projecting arm to the next, and means for moving said rotary member.

l The combination with a line conductor to be protected, of a conducting plate forming one side of a spark gap, a rotary mem ber comprising a hub and radial arms, said member being movable with respect to said plate and separated therefrom by a gap which periodically increases in length, and other conducting plates cooperating with said rotary member to maintain a constant discharge path to said rotary member.

In a lightning arrester, a plurality of conductive plates connected together, a 1'0- tary member having radial arms cooperating with said plates to form spark gaps, the angular width of each of said arms being substantially less than the angular distance between adjacent plates, and means for moving said rotary member.

(3. In a lightning arrester, a plurality of conductive plates spaced about a rotary member, and radial arms on said rotary member some one of which is at any instant within sparking distance of a plate, each of said plates having an angular width such that each of sale radial arms passes out of sparking distance with one plate before coming into sparking distance with another plate.

7. In a lightning arrester, the combination or a plurality oi conductive plates electrically connected and spaced about a rotary member, arms on said rotary member at least one of which is always within sparking distance of one of said conductive plates, and cut-away portions between said arms for periodically varying the sparking distance from said rotary member to any one of said plates.

8. In a lightning arrester, a plurality of conductive plates connected together and grouped about a rotary member, and arms on said rotary member differing in number from the conductive plates, said plates having such angular width that a spark gap path to said rotary member is present at all times.

9. In a lightning arrester, a. rotary member carrying two sets of conducting arms, a plurality of conductive plates cooperating with each or said arms to "form a discharge path including a plurality of spark gaps.

10. In a lightning arrester, a plurality of conductive plates connected to line, a rotary member having arms which periodically come within sparking distance of each of said plates, and means between said rotary arms and ground for forming a discharge path including a spark gap, the opposing conductors of which are in relative motion.

11. In a lightning arrester, a rotary memher having a plurality of radial arms, conductive plates disposed about said member and forming a discharge path to one or another of said arms at any instant, a second set of rotary arms connected with said first set, and conductive plates cooperating with said se ond set of arms to form discharge path therefrom at any instant.

12. In a lightning arrester, the combination of a plurality of conductive plates connected together, a rotary member cooperating therewith and having an irregular periphery to periodically vary the sparking distance between each conductive plate and said rotary member, and a plurality of paths for discharges from said rotary member, said paths being established progressively by movement of said member.

In witness whereof, I have hereunto set my hand this eleventh day of October, 1905.

SVEN R. BERGWAN.

Witnesses JOHN A. MoMANUs, Jr., HENRY O. Wns'rENDARr.

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