US 1936469 A
Description (OCR text may contain errors)
Nov. 21, 1933.V
c. H. HILL PRIMARY DSCONNECTING DEVICE Filed June 50, 1950 oc/Zm His Attov'h eg.
u mmii [all i Ihventor'; Y Chcl'rles H. Hill,
Patented Nov. 2l, 1933 PATENT OFFICEV PRIMARY DISCONNECTIN G DEVICE Charles ll. Bill, Drexel Hill, Pa., assignor to General Electric Company, a corporation of New York Application June 30, 1930. Serial No. 464,758
My invention relates to primary disconnecting devices, more particularly to disconnecting devices used in connection with the so-called trucktype or metal clad switchgear wherein a circuit 5 breaker unit is bodily movable for connecting and disconnecting the same with respect to main and auxiliary busses.
In switchgear of the character above described, it is customary to trip the oil circuit breaker unit and to thereafter move the unit bodily for effecting the disconnecting or isolating operation. Accordingly, the primary disconnecting device, so called, must be designed to carry the n normal rated current of the breaker without overheating.
In disconnecting devices heretofore used difflculty has been encountered in carrying the rated current without excessive temperature rise at the disconnect contact surfaces. This excess heating is due to high contact resistance and may be caused by too low contact pressure and/or by high resistance oxides formed on the contacting surfaces.
It is a principal object of my invention to provide an-improved primary disconnecting device which shall have high current-carrying capacity without excess heating and be simple and rugged in construction.
.It is a further object of my invention to provide animproved primary disconnecting device of the plug and socket type having coacting contact surfaces composed of metal having low resistance under all conditions of operation so arranged that the coacting contact surfaces in the closed circuit position engage in substantially circular line contact.
My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claim annexed to and forming a part of this specification.
Referring to the drawing, Fig. 1 is a fragmentary elevational view of metal clad switchgear embodying my invention and Fig. 2 is an elevational view, partly in section, of my improved primary disconnecting device in the open circuit or isolating position thereof.
In Fig. 1 there is illustrated metal clad switchgear of the elevated type comprising a frame 1 with respect'to which an oil circuit breaker unit 2 is mounted for vertical movement for connecting and disconnecting the circuit breaker with respect to the busses (not shown) which are oilv immersed and mounted within the metallic housings 3 forming the superstructure on the frame 1. Suitable means (not shown) are provided for raising and-lowering the circuit breaker 2 and the breaker is controlled by operating mechanism generally indicated at 4 which may com- 60 prise well known mechanism as tripping and interlocking means so that the opening and closing of the breaker and its vertical movement with respect to the busses must be in the desired sequence.
For the purpose of electrically connecting the breaker 2 to the busses above referred to, primary disconnecting devices 5 are employed comprising a stationary contact 6 and a movable contact 7 secured to the breaker unit. The sta- 70 tionary or plug contact 6 is mounted within a suitable insulating bushing 8 and is connected in any suitable manner to its corresponding bus inthe superstructure.4 The movable or socket contact 'l comprises in fact a terminal of the 75 circuit breaker and is suitably mounted within an insulating bushing 9 extending through the breaker cover. It will be apparent from the foregoing description that raising and lowering of the circuit breaker 2 effects connection and discon- 80 nection of the alined plug and socket contacts 6 and 7 comprising the disconnecting device and that the current traversing the breaker when in operative position likewise ows through the coacting plug and contact surfaces of the disconnecting device.
In plug and socket disconnecting contacts of the character so far described, the contacting surfaces which are generally of copper may have poor contacting engagement due to slight mis- 9o alinement of the contacts and due to the cylindrical contact surfaces which may not bear evenly against each other throughout their length. Accordingly, the contacting engagement is uncertain and the difliculties cannot be over- 95 come by simply increasing the pressure on the plug contact. Moreover, the oxide of copper has comparatively high resistance and is a common cause of heating at contacting surfaces.
For the purpose of insuring uniform contact- 10o ing engagement and high unit pressure at the contacting surfaces, the stationary contact 6, which comprises a rod-like member of conducting material as copper having a blunt or rounded end, is provided with a ring or band 10 having 105 a curved or convex contact surface 10'- so that the contact 6 when in engagementwith its coacting tubular socket contact 'l makes line contact therewith regardless of whether the contactsare vin exact alinement. In other words, 11o
the curved contact surface 10u provides line contaeting ent, which may be either circular or elliptical in shape, depending on the relative positions of the longitudinal axes of the coacting contacts. The socket contact 'I comprises a tubular member of conducting material as copper having a ared upper edge at 11 for receiving the stationary contact 6 and provided with slots 12 extending from the open end of the contact for permitting expansion of the tubular `member during engagement of the contacts.
`contactface14,andhighcurrentsmaytraverse the contact surfaces without causing excessive rise in temperature.
It shall be understood that my invention is not limited to speciiic details of construction and arrangement thereof herein illustrated. and that changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.
WhatIclaimasnewanddesiretosecureby Letters Patent of the United States is:
A primary disconnecting device for carrying large power currents comprising relativeLv movable piug and socket contacts composed of copper or the like, the plug contact provided at its contact end with a silver contact band and the socket contact also provided at its inner contact surface with a silver contact band, one of said silver bands having a convex contact surfacewithrespecttothecoactingnirfaceofthe otherbandsothatsaidbandsenslgeinw stantially line contact in the closed circuit position of the disconnecting device.