US2333598A

US2333598A - Circuit interrupter

Info

Publication number: US2333598A
Application number: US373852A
Authority: US
Inventors: Albert P Strom
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1941-01-09
Filing date: 1941-01-09
Publication date: 1943-11-02
Anticipated expiration: 1960-11-02
Also published as: GB549763A

Description

Patented Nov. 2, 1943 cmcurr INTERRUPTER Albert P. Strom, Forest Hills, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 9, 1941, Serial No. 373,852

7 Claims.

This invention relates to improvements in circuit interrupters of the fluid-blast type and, particularly, to circuit interrupters utilizing compressed air as an arc-extinguishing medium.

Heretofore circuit interrupters have been developed which bring about arc-extinction by subjecting a substantially stationary arc to a blast of compressed gas. have shown remarkable performance in extinguishing high power arcs, some difliculty has been encountered, particularly at the higher current ranges. At the higher current values rapid destruction by burning of the contacts and any adjacent insulating material takes place. In addition to the erosive effect caused by the stationary arc terminals a large volume of hot ionized gas, produced during the high current portion of a half cycle is permitted to remain in and about the arc path which interferes with the interrupting process at current zero.

It is an object of my invention to overcome the foregoing difiiculties in circuit interrupters of the fluid-blast type so as to improve the current interrupting capacity thereof. My invention contemplates avoiding excessive burning at the contacts and of the adjacent insulating material by the provision of arc terminal paths for the terminal ends of the are which will permit rapid movement of the are over the arc terminal surfaces. An annular or recurrent arc path is preferred since this form of path lends itself admirably to achieving both high speed are movement and eflicient removal of the ionized arc gases from the arc path.

A further object of the invention resides in the provision of a circuit interrupter of high efficiency wherein arc length and are energy are maintained at a low value.

It is also an object of my invention to obtain eflicient circuit interruption in interrupters of the gas-blast type by the use of gas-blast pressures considerably lower than those generally used in prior art devices. This has been made possible in part by a more effectiv removal of the hot ionized gas particles from the arc stream and by subjecting the arc to mild blasts of gas formed by the action of the are upon gas-forming material.

Other objects and advantages will become apparent in the following description when read in connection with the accompanying drawings, in which:

Figure 1 is an elevation view partially in section 01' a circuit interrupter embodying my invention;

Fig. 2 is a sectional view of a circuit interrupt- Although these interrupters I ing unit which illustrates a further embodiment of the invention;

Fig. 3 is a sectional view of a circuit interrupt ing unit of still another form which illustrates the principles of my invention; and

Fig. 4 is a sectional view through the device of Fig. 3 taken on the line IVIV.

Referring to the drawings and particularly to Figure 1, the reference numeral 5 designates a tank for storing gas, such as air, under pressure. Disposed upon the tank 5 is a supporting framework 1 which carries a tubular insulator 9. The insulator 9 has a plurality of partitions, in this instance, four, designated as H, l3, l5 and iii, extending thereacross to divide the interior of the insulator 9 into a number of chambers. An annular spacing member I9 is disposed between the partition members II and I3, whereas a imilar spacing member 2| separates the partitions i5 and I1. An annular spacing member 23 separates the partitions i3 and 15 to provide an arc chamber 25. Each of the partition members ii to ii has openings therethrough, as shown, for the reception of a pair of tubular contact members 2'! and 29. Contact 21, in this instance, may be stationary, and may be screw threaded into the partition member I! as shown. The contact member 29 is movable through the apertures in the partition members H and I3 so as to make contacting engagement with the stationary contact 21.

A field coil Si is disposed in the annular space between partition members l5 and I 1 in surrounding relation with respect to the tubular contact 21 and may, for example, be series connected with respect to the contact 21. More specifically one end of the coil may be connected to the tubular contact, as shown at 33, and the other end may be connected by a suitable connection 35 to a terminal plate 31 carried by the upper end of the insulator 9. A second field coil 39 is disposed in the annular space between the partition members II and i3 in surrounding relation with respect to the movable contact 29 and ma also be series connected with respect to the movable contact 29. One end of the coil 39 is electrically connected by means of a flexible connection M to the movable contact 29 and. has its other end Joined with a conductor 43 which terminates at a line terminal 45. A second line terminal 41 is provided which makes electrical connection with the terminal plate 31. Thus, when the

contacts

21 and 29 are in engagement, a circuit is completed through the interrupter from the line terminal 41 to the terminal plate 31, conductor 35,

ner in which they function will appear more fully hereinafter as the description proceeds.

Movement .of the movable contact 29 to open and closed circuit positions may be accomplished 'by a fluid actuated driving means, generally indicated at 49. The driving means 49 comprises a cylinder 5| having a piston 53 operative therein which is coupled by an insulating operating rod 55 to the lower end of the movable contact 29. Compressed gas from the storage tank 5 controlled by an electromagnetically actuated valve 51 is admitted to the lower side of the piston 53 so as to move the piston and the movable contact 29 to the closed circuit position. Movement of the movable contact 29 to the open circuit position is accomplished by admitting compressed gas from the tank 5 to the upper side of the piston 53 through the electromagnetically controlled valve 59. The operating solenoids of the valves 51 and 59 may be connected to a suitable source of potential and controlled by manually operated switches as is well known in the art, and, in addition, the energization of the solenoid of the opening electromagnetic valve 59 may be controlled in accordance with the current conditions in the circuit in which the interrupter is connected. which control is also well known in the art and need not be further described.

Provision is also made by means of conduit 51 for conducting compressed gas from the storage tank 5 to the arc chamber 25. The flow of gas through the conduit 5| may be controlled by an electromagnetically actuated valve 53. The control of valve 53, for example, may be effected jointly with the control of valve 59 so that upon actuation of the movable contact 29 to the open circuit position, the valve 53 is opened to admit a blast of gas from the storage tank 5 through the conduit 51 into the arc chamber 25. In practice, it is desirable to provide a control for opening valve 53 slightly in advance of valve 59 so that fluid pressure will be available in the arc chamber 25 when the

contacts

21 and 29 separate.

If the movable contact 29 is actuated to the open circuit position while the interrupter is carrying current, either as a result of a manual energization of the valve 59 or by automatic actuation thereof, an arc will be drawn between the annular contact surfaces formed on the faces of the

tubular contacts

21 and 29. An are formed at any point along the annular arc terminal path will then be subjected to a blast of compressed gas flowing from the chamber 25 through the annular space between the contacts. Inasmuch as the flow of gas is radially inward with respect to the

tubular contacts

21 and 29, gas flow is established axially of the tubular contacts in the direction shown by the arrows. Thus, arc gases are driven from the region of the arc and caused to discharge through the passages provided by the tubular contacts. Due to the fact that field coils 3| and 39 are respectively serially connected to the

contacts

21 and 29, these coils will be energized to establish a radial magnetic field across the arc gap between the contacts which is proportional to the intensity of the arc current. The fleld coils 3| and 39 are connected in opposition so as to produce a radial magnetic field with respect to the annular arc terminal path. The are is thus caused to move rapidly over the annular terminal surfaces and at such a rate which prevents the formation of a hot cathode arc and, conse quently, avoids burning of the arc terminal surfaces. In practice, I have found that are velocities upwards of 1,000 feet per second may be obtained with an arrangement, as shown. If electrodes are employed having a mean diameter of approximately 2 inches it will thus be apparent that quite a large number of revolutions of the are per half cycle may be obtained.

Under the conditions here present the gas Dressure in the chamber 25 need only be high enough to carry away the hot ionized arc gases from I the annular arcing space with sufflcient rapidity so that the arc is rotated in a substantially unionized atmosphere of gas. As the current approaches zero, the arc decreases in cross section, and the rate of ionization of the gases also decreases so that at current zero the annular arcing space is substantially swept free of hot ionized gases produced during the high current portion of the half cycle. It, therefore, requires only a very low velocity flow of gas to finally bring about are extinction at a current zero.

The

contacts

21 and 29 are preferably lined with

tubular members

55 and 55 of insulating material for the purpose of preventing the blast of gas traversing the are from moving the. arc inwardly from its annular arc terminal path. The insulating members and 55 also prevent elongation of the arc along the inner surfaces of the

tubular contacts

21 and 29 as a result of the blast action traversing the arc.

two inches and a contact separation of substan-.

ti-ally inch, interruption of 5000 amps. R. M. 8. at 2300 volts R. M. S. on a circuit of 40,000 cycles natural frequency could be obtained with 50 pounds per square inch and less gas pressure. whereas in gas blast interrupters which maintain the are substantially stationary, gas blast pressures upwards of 100 pounds per square inch are required.

Eventhough the field coils 3| and 39 are shown connected in series with their

respective contacts

21 and 29 so that the coils are energized in accordance with the current flowing in the circuit, it should be understood that other methods of connecting these coils may be employed. For example, main current carrying contacts could be used in conjunction with arcing contacts as is well known in the art, andarranged so that when the main contacts are closed, the fleld coils are short circuited but upon separation of the contact structure and transfer of the current to the arcing contacts the field coils are connected in circuit and become energized.

In Fig. 2 a circuit interrupting unit of somewhat different form is shown. In this

arrangement partition members

61, 59, 1i and 13 are separated, respectively, by

annular spacing members

15, 11 and 19 so as to form in the order named a gas-receiving chamber 9!, an arc chamber 93, and a second gas-receiving chamber 35. Each of the partition members 59 and 1| have openings therethrough for receiving stationary tubular arcing contacts 91. A field coil 89 may be serially connected to each tubular arcing contact and to a pair of line terminals 9| and 93, so as to provide a radial magnetic field between the arcing contacts 81 in a manner similar to that described in connection with Fig. 1. The fleld coils 89, in this instance, are protected and partially supported by a pair of annular insulating members which are disposed adjacent to the contact terminal paths on the tubular arcing contacts 91 and extend radially outwardly from these arcing contacts. The opposed surfaces of the annular members 95 are preferably convex with respect to each other so as to provide an annular nozzle for the control of gas flow with respect to the arc. The circuit is established between the stationary arcing contacts 81 by means of a tubular movable bridging member 91 slidably engaging the inner surfaces of the arcing contacts 81. The movable bridging member 91 may, in this instance, be actuated to the open and closed circuit positions by an insulating operating rod 55 forming part of the fluid-pres sure driven mechanism 49 previously described.

As in the interrupter shown in Fig. 1, compressed gas may be supplied to the interrupter through the supply line BI leading from the storage tank and controlled by the electromagnetically actuated valve 63. In this instance, however, gas under pressure is conducted from the valve 63 through a conduit 99 to the chamber BI, and through a second conduit IM to the chamber 85. The chamber 85 is in direct communication with the upper tubular arcing contact 81, whereas the chamber BI communicates with the lower arcing contact 81 through an opening I03 provided in the tubular bridging member 91. Thus, upon movement of the bridging member 91 to the open circuit position as shown in Fig. 2, at a time when the interrupting unit is carrying current, an arc will be established in the annular arcing space between the arcing contacts 81. Field coils 89 will produce a radial magnetic field across the annular arcing space for rotating the are at high speed therearound. Compressed gas from the chambers 8| and 85 will flow through the tubular arcing contacts 81, as indicated by the arrows in the drawings, to traverse the rotating arc, and thereby carry the hot ionized arc gases from the annular arcing space through the annular nozzle formed by the opposed annular members 95 of insulating material. The hot ionized arc gases discharged into the arcing chamber 83 may be permitted to vent therefrom through openings I05 provided in the spacing member 11.

The annular nozzle produced by the members 95 of insulating material serves to maintain the proper pressure conditions within the annular arcing space so as to maintain efficient arcextinguishing conditions.

Improved circuit interrupting performance has also been obtained by making the annular members 95 of a material which gives off gas when acted upon by an arc, as, for example, horn fiber. The improved performance is believed to be due to the fact that as the arc impinges upon the insulating surface, the surface emits a gas which reacts with the hot ionized gas particles in the arc stream and sets up a turbulence to a degree which permits the blast of extinguishing gas to penetrate the arc stream and thereby rapidly deionize the arc. In the absence of gas-producing material, there is a tendency to the formation of a layer of ionized gas adjacent the insulating surface which is substantially immovable and which cannot be penetrated by the arc-extinguishing blast of gas. Thus, higher arc-extinguishing blast pressures are needed to bring about arc-extinction where non-gas-forming materials are used adjacent the arc path than where gas-forming insulating materials are used. Gas evolving material is also believed to be better than refractory materials because the surface decomposition by the action of an are on the former keeps the surface cool so that it continues to have a good surface breakdown characteristic. Keeping the surface cool also avoids possible thermionic emission from the surface which would render arc extinction more difficult.

In Fig. 3 a further form of circuit interrupter is shown which is substantially the same as that shown in Fig. 2 with the exception that the arcing contacts 81 are spaced further apart. This permits the use of a plurality of, in this instance, two, annularly-shaped arc splitting members I01 of insulating material to be inserted therebetween and in the space surrounding the annular arcing space. The arc splitting members I01 may be flat and of uniform thickness or have at least a narrow portion adjacent their inner edge of thickness somewhat greater than their remaining portions. If enlarged portions are provided, they are preferably of elliptical cross section, as shown, so as to provide a series of annular nozzles, respectively, between the insulatingmembers 95 and the arc splitting members I01. These annular nozzles, as described in connection with-Fig. 2, also serve to control the flow of gas from the annular arcing space between the arcing contacts 81, and thereby maintain the pressure in the arcing space at the desired value. The are splitting plates I01 are preferably held in spaced relation with respect to each other and with respect to the annular members 95 by insulating spacer members I09 of segmental form, the latter having dimensions such as to further control the area of the gas discharge passages between the arc splitter members I01 and the annular members 95 as more clearly shown in Figure 4.

Movement of the conducting bridging member 91, as previously described, will establish an are between the arc-ing contacts 81 which rotates about its annular arcing space between these contacts as a result of the radial magnetic field established by the coils 89. As previously described, compressed gas is admitted to the chambers 8| and 85 which flows through the tubular arcing contacts 81 transversely of the annular arcing space and also traverses the are so as to move the same against the edges of the splitter plates I01 and, in effect, tends to split the are into a plurality of serially related sections. Although the arc, in this instance, is drawn to a somewhat greater length than in the interrupter shown in Fig. 2, a higher deionizing effect is made possible due to the action of the splitter members I01 tending to sectionalize the arc, and thereby hastening its deionization. By making the insulating splitter plates I01 of material which gives off gas when acted upon by an arc, the deionizing action is materially enhanced and considerably higher currrents may be interrupted without increasing the blast pressure.

Although I have shown specific forms of circuit interrupting devices, it is to be understood that the same are for the purpose of illustration and that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a gas blast circuit interrupter, an arc chamber with insulating walls and having a pair of openings disposed in opposite sides thereof, a pair of tubular arcing contacts extending through said openings and arranged to provide an annular arc gap of predetermined length therebetween at least when the interrupter is in the open circuit position, means for establishing an arc between said arcing contacts, a fleld coil surrounding at least one of said tubular arcing contacts, said coil being arranged to be energized to produce a radial magnetic fleld across said annular arc gap between said arcing contacts for rotating said are therearound, means for projecting a blast of gas under pressure into one said tubular contacts, out through said annular arc gap, and into said are chamber, and,means ior ventingthe ionized arc gases from said are chamber.

2. In a fluid blast circuit interrupter, a pair of ring-shaped arcing contacts arranged to provide an annular arc gap therebetween at least one of said arcing contacts being tubular, means for establishing an are between said arcing contacts, means for rotating said are around said annular arc gap, means of insulating material disposed about said arcing contacts and arranged to provide an annular discharge nozzle adjacent said annular arc gap, and means for projecting a blast of fluid into saidtubular contact to cause a flow of fluid radially outwardly through said are gap and said annular discharge nozzle, said annular nozzle controlling the rate of fluid discharge and confining said are to substantially the annular arc gap between said arcing contacts.

3. In a circuit interrupter of the fluid blast type, a pair of contacts arranged to provide an annular arcing gap therebetween, at least one oi said contacts being hollow, means for establishing an are between said contacts, means for rotating said are around said annular arcing gap, means for introducing a fluid under pressure into said hollow contact to establish a radial outward blast of fluid across said arcing gap and transversely of said are as the latter is rotated, and at least one barrier member of insulating material disposed in surrounding relation about said annular arcing gap, said radial outward blast of fluid moving the arc laterally against said barrier member to split the arc gases into a plurality of sections.

4. In a circuit interrupter of the fluid blast type, a pair of contacts arranged to provide an annular arcing gap therebetween, at least one of said contacts being hollow, means for establishing an arc between said contacts, means for rotating said are around said annular arcing gap, means for introducing a fluid under pressure asaasoa into said hollow contact to establish a radial outward blast of fluid across said arcing gap and transversely of said are as the latter is rotated, and a plurality of insulating annular are as splitters disposed about said annular arcing gap and against which said are is blown, the inner edges of said insulating annular splitters being shaped to provide a plurality of annular fluid discharge nozzles for controlling the drop in pressure of said fluid blast in the region oi! said arcing gap.

5. In a gas blast circuit interrupter, a pair oi. arc terminal members between which an arc may be established, means for rotating said arc between said are terminal members, at least one oi said are terminal members being tubular, means for causing a blast of gas to flow through the tubular arc terminal member and radially outwardly between the pair 01 are terminal members to extinguish the rotating arc, and an annular member of insulating material covering part of said tubular arc terminal member adjacent the end thereof to limitthe area on which the arc may play and direct the flow of said gas adjacent the end of the tubular arc terminal member.

6. In a circuit interrupter, a pair of arcing contacts, at least one of the contacts being tubular, means for establishing an arc between said contacts, means for rotating said arc around said contacts, and means for projecting a blast of gas under pressure into the tubular contact and radially outwardly across the region between said contacts to extinguish the arc.

7. In a circuit interrupter, a pair of relatively thin ring-shaped arcing contacts, one of said contacts being tubular, means for establishing an are between said arcing contacts, means for rotating the arc around said relatively thin ringshaped contacts, annular means oi insulating material disposed around both arcing contacts to provide an annular discharge nozzle adjacent the opposed inner ends of said contacts, and means for projecting a blast of fluid into the tubular contact to cause a radial outward blast of fluid between the contacts, the nozzle conflning the terminal ends of the arc to the contacts and also raising the pressure and hence the dielectric strength adjacent the arc.

ALBERT P. STROM.