US3118995A - Eddy-current heater for compressedgas circuit interrupters - Google Patents

Description

Jan. 21, 1964 R. G. coLcLAsER, JR., ETAL 3,118,995

EDDY-CURRENT HEATER FOR COMPRESSED-GAS CIRCUIT INTERRUPTERS Filed April 2o', 1961, s sheets-sheet 1 ATTORNEY Russell N. Yeckley BY W Jan. 2l, 1964 R. G. cOLcLAsER, JR., ETAL 3,118,995

EDDY-CURRENT HEATER FOR COMPRESSED-GAS CIRCUU.` INTERRUPTERS Filed April 2o, 1961 s sheets-sheet 2 Jan- 21, 1964 R. G. coLcLAsER, JR., ETAL 3,118,995

EDDY-CURRENT HEATER FOR COMPRESSED-GAS CIRCUIT INTERRUPTERS Filed April 20, 1961 5 Sheets-Shea*l 5 Fig. 5

United States Patent O 3,118,995 EDDY-CURRENT HEATER EUR CUMPRESSED- GAS CHtCUlT INTERRUPTERS Robert G. Colelaser, lr., Belmont, and Russell N. Yeclrley, Murrysville, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 2i), 1961, Ser. No. 104,355 Claims. (Cl. Zitti-148) This invention relates to eddy-current heaters for cornpressed-gas circuit interrupters and, more particularly, to an `eddy-current heater for maintaining the temperature of the high-pressure gas above its liquefaction point.

A general object of the present invention is to provide an improved and economical compressed-gas circuit interrupter utilizing an eddy-current heater for preventing the temperature of the high-pressure gas from going below its liquefaction point.

Still a further object of the present invention is to provide an improved compressed-gas circuit interrupter of the dead-tank type in which the magnetic losses are deliberately diverted to bring about eddy-current heating loss within the high-pressure tank to maintain the temperature of the compressed-gas above its liquefaction point.

`In compressed-gas circuit interrupters, particularly of the type employing an extremely eilicient arc-extinguishing yand dielectric gas, such as sultur-hexaiiuoiide (SFG) gas, it is necessary to maintain the temperature of the high-pressure gas above its liquefaction point. A drop of temperature means la drop in the eile-otive vapor pressure, and, for effective gas-blast interruption necessarily the igas pressure of .the high-pressure reservoir must not -fall too low. It has been customary to utilize heaters, energized from an independent source of supply, to maintain the temperature of the high-pressure gas, such as sulfur-hexalluoride (SFS), gas, at .a predetermined highpressure level. Accordingly, it is a fmther object of the present invention -to eliminate as far as possible such auxiliary heating supply Land to utilize eddy-current heating losses by means of closed-turn magnetic straps, or diverting the magnetic flux into the walls lof the high pressure tank to ensure that the temperature and hence the pressure of the high-pressure gas supply will be adequate for its intended interruption purposes.

Further objects and advantages will readily become apparent upon reading the following speciiication, taken in conjunction with the drawings, in which:

FIGURE 1 is a `fragments-.ry side elevational View of a portion of a oompressedagas circuit interrupter embodying the principles of the present invention;

FIGURE 2 is a sectional end view of the compressedgas circuit interrupter pictured in FIGURE l;

FIGURE 3 is a vertical sectional view taken longitudinally through the compressed-gas circuit interruptor olf FIGURE 1 illustrating the contact assemblage .at `an intermediate poiint inthe opening operation;

FIGURE 4 illustrates a modified type of tank construction;

FIGURE 5 is a Vertical sectional view taken substantially along the line V-V of the modiiied tank construction of FIGURE 4; and,

Patented Jan. 21, 1964 lCC FIGURE 6 illustrates a side elevational view of the bridging arc-entinguishing assemblage of FlGURE 3, but showing a modified closed magnetic strap construction.

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral l generally designates a compressed-gas circuit interrupter. Generally, the compressed-gas ycircuit interrupter 1 'includes a longitudiallly-extending grounded tank Z having disposed adjacent its outer ends opstanding cylindrical supports 3, 4 for supporting in a xed operative position terminal bushings 5', 6.

Disposed interiorly of the tank structure 2 and extending longitudinally thereof is an arc-extinguishing assemblage, generally designated by the reference numeral 7, and more clearly illustrated in FIGURES 3 and 6 of the drawings. As shown in FIGURE 3, the arc-extinguishing assemblage 7 includes a high-pressure reservoir tank 8, a main blast valve 9 and a plurality of serially-related orifice-type interrupting units l0. A generally laddershaped movable Contact assemblage 1l, comprising a pair of longitudinal, `spaced operating rods 11a (FIG. 6), bridged by transverse bridging members 12 and centrallysecured movable contacts 13 (FIG. 3), moves as a unit, being biased in a leftward opening direction, as viewed in FIGURE 3, by an opening accelerating spring 14.

During the `closing operation, a suitable mechanism, not shown, is operative to rotate an internally-disposed crank-arm 1S in a countenclockwise direction and move, under tensile stress, an insulating operating rod t6 to `force the ladder-like movable contact assemblage 1l toward the right and effect compression of the accelerating spring la. The movable contact assemblage is latched in the fully closed-circuit position, in which the movable contacts 13 engage relatively stationary contacts 17, by a suitable latch mechanism associated with the operating mechanism 18.

During the opening operation, the latching mechanism, associated with the `operating mechanism 18, is unlatched; and the accelerating spring 14 serves to bias, in a leftward opening direction, the movable Contact assemblage 1l, thereby causing a separation between the movable contacts 13 and the relatively stationary contacts 17. A plurali-ty of serially-related arcs 19 are consequently drawn. Simultaneously with the leftward opening movement of the movable Contact assemblage vl1, the blastvalve mechanism Ztl is operated to open the blast valve 9 and permit the blasting of high-pressure gas from the high-pressure reservoir tank 3 through suitable blast tubes 21-23 toward the orilioe structures Z4 to eect extinction of the several serially-related arcs 19.

Reference may be had to United States patent application led October 7, 1960, Serial No. 61,284, by Robent G. Colclaser, lr., and Russell N. Yeckley and assigned to the assignee of the instant application for a detailed and minute description ot the operation of the circuit interrupter l.

The blast valve mechanism 2li is set forth and claimed in United States patent application tiled January 23, 1959, Serial No. 788,668, now United States Patent 3,057,983, issued October 9, 1962, to Russell N. Yeckley, Joseph Sucha and Benjamin l. Baker and Yassigned to the assignee of the instant application.

The high-pressure gas, such as sulfur-hexafluoride (SFG) gas 4d, which is stored in the high-pressure reservoir chamber t8, -is fed thereinto by an insulating feed tube 25 which connects with an auxiliary high-pressure rese Voir tank 26.

As shown more clearly in FIGS. l and 2 of the drawings, the auxiliary high-pressure reservoir tank 26 comprises a semi-circular section 27 and a pair of end plates 2S, which may serve as suitable supports for the cornpressed-gas circuit interruptor l.

A non-magnetic strip 29 and welds Sti and 3l extend lengthwise of the tank structure 2, and force the magnetic circuit to pass through the walls of the auxiliary highpressu-re tank 26 in a manner indicated by the arrows 32.

As well known by those skilled in the art, in the closedcircuit position of the circuit interruptor ll, relatively heavy loa-d currents pass through the arc-extinguishing assemblage 7. This passage of current is accompanied by an associated magnetic field, which, due to the nonmagnetic strip 2% and welds 3i), 3d, is forced to pass through the lower-disposed auxiliary high-pressure reservoir tank 26 in the manner illustrated by the arrows 32 of FIGURE 2.

The passage of such a magnetic ux through the steel walls of the auxiliary tank 26 sets up eddy-current losses within the metallic walls of the Itank 26, and brings about a heating effect. This is very desirable inasmuch as at the 260 pound pressure, which the SFG gas has attained within the tanks 8, 26, the SFS gas will liquefy at a 42 F. temperature. Heat must, therefore, be supplied When temperatures go below this value. It has been previously proposed that heater units be inserted into the auxiliary high-pressure reservoir tanks to meet this problem. In addition, insulation to provide a thermal lag in the event of heater failure is placed around the auxiliary rese-rvoir tanks as shown in FIG. 2. Additionally, it has been proposed to provide two heaters in each auxiliary high pressure tank energized from separate sources `for the ultimate in reliability.

The present invention is particularly concerned with a means of utilizing eddy currents, produced in the walls of the high-pressure lreservoir tanks by the normal load currents of the breaker, to provide the necessary heating effect to prevent the SFS gas pressure from dropping to too low values. -It is this source of heat which can be used to increase the reliability of the interruptor 1. As illustrated in FlGURES l and 2, there is incorporated in the present invention the Walls of the high-pressure auxiliary reservoir tank 26 in the magnetic circuit of the interruptor. The high-pressure reservoir tank 2.6 is formed by the semi-circular section 27 and the two straight end plates 28. The plates 28 serve as heads on the ends of the auxiliary tank 2d. Additionally, braces 35 may be used to strengthen the sides and also the main tank 2. A non-magnetic strip 29 is used in the main tank 2 to force the magnetic ilux into the high-pressure resenvoir tank 26. The ribs 35 also act as radiator strips. An electric heater element 36 is also shown. This is a supplementary heat source `when the breaker is closed and may be necessary during cold weather when the breaker is open.

Associated in heat-transmitting relationship with the high potential high-pressure reservoir tank S of FIGURE 3 is a closed strap 33 of magnetic material, such as iron or steel, to convey the heat set up therein by eddy-current losses to the walls of the tank 8. The closed magnetic strap 33 encircles the load current passing through the extinguishing assemblage 7 and thus has magnetic flux induced therein. This induced magnetic liux results in the establishment of eddy currents in the strap 33 leading to 'heating thereof. This heat, in turn, is transmitted to the tank S. This assists in maintaining the temperature of the high-pressure gas within tank d at the desired high level value and prevents liquefaction thereof.

With reference to FIGURE 6 of the drawings, it will be noted that a modified closed magnetic strap 33a is employed. The action is the same as in the strap 33 of FiGURE 3. Heat from the modied closed magnetic strap 33a is `transmitted to the high-pressure tank 8.

FIGURES 4 and 5 show a modified tank construction in which the high-pressure auxiliary tank 26a encircles the centrally disposed exhaust tank 2. Again eddy-current losses heat the 'central portion 2a of the tank 2, which constitutes the inner wall of the outer encircling tank 26a. ln addition, there may occur some eddycurrent heating of the outer wall 34 of the modified auxiliary tank 26a.

From .the foregoing description it will be apparent that there has been disclosed la novel utilization of eddycurrent heating losses to effect the maintenance of the temperature of the high-pressure tank above that of the liquefaction point. This is done by utilizing the normal load current passing through the circuit interrupter and consequently is very economical.

From the foregoing description, it will also be apparent that there are utilized eddy-currents induced in the walls of the high-pressure tank 26 to supply the heat necessary to prevent liquefaction of the sulfur-hexai'luoride (SP6) gas or other gas, the lione-faction of which it is desired to prevent. The closed breaker will be supplied with heat, and the use off the auxiliary heater 36 will be kept to a minimum, thus greatly increasing the reliability of the circuit interrupter l.

Although there have been illustrate-d and described specific structures, it is to be clearly understood that the same are merely l:for the purpose of illustration, and that changes and modiications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

We claim as our invention:

l. The combination in a compressed-gas circuit interruptor of Kan exhaust tank, a high-pressure auxiliary tank dispose-d outside the normal magnetic flux path of the exhaust tank and connected to the exhaust tank, an are extinguishing assemblage disposed interiorly of said exhaust tank for carrying load current, the exhaust tank and the high-pressure auxiliary tank collectively forming a magnetic circuit which encircles the normal current path through lthe circuit interruptor, and means for divert-ing magnetic liux in the exhaust tank through the walls of the high-pressure auxiliary reservoir tank to bring about eddy-current heating losses to prevent liquefaction of the high-pressure gas.

2. The combination as set forth in claim 1, wherein the gas comprises sulfur-hexafluoride (SFG).

3. The combination in a compressed-gas circuit interrupter `of an elongated grounded generally horizontallydisposed exhaust tank, an underslung high-pressure auxiliary tank composed of magnetic material disposed outside the normal magnetic flux path of the exhaust tank and connected to the exhaust tank, an arc-extinguishing assemblage disposed interiorly of said exhaust -t-ank for carrying load current, the exhaust tank and the highpressure auxiliary tank collectively forming a magnetic circuit which encircles the normal current path through the circuit internupter, and means including a non-magnetic strip extending longitudinally ot said exhaust tank for diverting magnetic ux in the exhaust tank through the =walls of the high-pressure auxiliary reservoir tank to bring about eddy-current heating losses to prevent liquefaction of the high-pressure gas.

4. A compressed-gas circuit interruptor including a metallic tank, a pair of terminal bushings extending within said tank, an arc-extinguishing assemblage including separable contact means bridging the interior ends of said terminal bushings, said arc-extinguishing assemblage also including a high-pressure chamber, magnetic closed strap means surrounding the normal current path, said high-pressure chzrmowr having said magneiic @inscri strap References Cite in the file of this patent means in heabtifansmiitting relationship therewith for as- FOREIGN Av/TENTS sising in maintaining he temperature of the [gas within n. said high-pressure chamber at the desired temperature greafibmam 2mg 21% level by eddy-current heating losses generated in said 5 rance a magnetic closed strap means. OTHER REFERENCES 5. The COmbirla'tOn 3S Set Orh in Claim 4, wherein The Electric Ioninai, V01. 25, March 1928, pp. 133435. the hghPFeSSUTe @as COUPFSS Sulfufhexaufde The Electric Journal, Vol. 26, No. 6, June 1928, pp.

(SFS). 312-313.

Claims (1)

1. THE COMBINATION IN A COMPRESSED-GAS CIRCUIT INTERRUPTER OF AN EXHAUST TANK, A HIGH-PRESSURE AUXILIARY TANK DISPOSED OUTSIDE THE NORMAL MAGNETIC FLUX PATH OF THE EXHAUST TANK AND CONNECTED TO THE EXHAUST TANK, AN ARC EXTINGUISHING ASSEMBLAGE DISPOSED INTERIORLY OF SAID EXHAUST TANK FOR CARRYING LOAD CURRENT, THE EXHAUST TANK AND THE HIGH-PRESSURE AUXILIARY TANK COLLECTIVELY FORMING A MAGNETIC CIRCUIT WHICH ENCIRCLES THE NORMAL CURRENT PATH THROUGH THE CIRCUIT INTERRUPTER, AND MEANS FOR DIVERTING MAGNETIC FLUX IN THE EXHAUST TANK THROUGH THE WALLS OF THE HIGH-PRESSURE AUXILIARY RESERVOIR TANK TO BRING ABOUT EDDY-CURRENT HEATING LOSSES TO PREVENT LIQUEFACTION OF THE HIGH-PRESSURE GAS.

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