US1955212A - Circuit breaker - Google Patents

Description

April 17, 1934- w. B. WHITNEY El AL CIRCUIT BREAKER Filed March 4, 1932 2 Sheets-Sheet l m E/ym/Ps jog/k7 I 4770/?A/EKS April 17, 1934. w. B. WHITNEY Er AL C IRCUIT BREAKER Filed March 4, 1932 2 Sheets-Sheet 2 Fig. Z

a cylinder and current UNITED This invention relates STATE S PATENT-OFFICE CIRCUIT BREAKER Willis Bevan Whitney and Edmund Basil Wedmore, London, ish Electrical England, assignors to The Britand Allied Industries Research Association, London, England, a British com- Application March 4, 1932, Serial No. 596,853 In Great Britain March 18, 1931 14 Claims.

to alternating current electric switches or circuit breakers and particularly to fluid blast switches in which an arc is formed between adjacent electrodes when they 5 are separated at the instant of opening the switch and is caused to move in a particular direction by the application of fluid in motion, the force of which may be utilized to overcome any electromagnetic force which may tend to cause the arc to move in an opposite direction in such a way as to prevent the switch or circuit breaker from functioning.

The object of the present invention is to provide a construction which ensures that the elec tromagnetic forces set up are such as to assist the return of an arc root to a region swept by I the blast, should it tend to wander from that region.

In circuit breakers dealing with large amounts of power, it is generally provision that the arc is kept relatively short whilst the current is heavy and this is ensured in designs of the type in advantageous to make question by a relatively small separation of the electrodes in the first instants when the arc is drawn so that the arc roots are retained within a region scoured by a highly intense blast of fluid. Now, in providing means according to this invention to prevent the are being forced electromagnetically againstthe fluid stream, it is also arranged that there shall be no considerable electromagnetic force tending to extend the arc in the neighbourhood where it is first formed, or to move the blast away from the the root or roots with region where the fiuid blast washing the-root or roots is of a given degree of intensity.

When the arc is rooted on the surface of a conductor extending in opposite directions and the current travels in one direction along the conductor, a magnetic field is set up which tends to cause the arc root to move along the surface towards the part carrying 1:0 current, and we utilize such force for our purpose. If, for example, an arc strikes t he inner surface of a is conveyed from one end,

the current at a particular pointtends to be distributed equally around the cylinder tending to create no internal field but where current concentrates towards the arc root, a local field is set up. This effect can be increased when denarrow segments or strip To ensure, therefore,

that the arc shall be that upon movement of the arc, current from one or other end is increased so as to oppose the mo- 9 tion. This .may be ensured by leading current into the conductor at two points on either side of the are or by returning one end of the conductor upon itself so that when the arc travels on to that return portion the direction of the concen- 5 trated current flow is reversed.

In order that the invention may be clearly understood and readily carried into efiect, some constructions of gas blast switches in accord ance therewith will now be described more fully 7 by way of example with reference to the accompanying drawings, wherein'.-

Figure 1 is a diagrammatic central vertical section of the upper part of one construction of switch;

Figures 2 and 3 are similar views of alternative constructions;

Figure 4 is an assembly view; and Figure 5 is a central vertical section similar to Figure 1 showing yet another alternative con- 30 struction;

Figure 6 shows yet a accordance with the invention;

Figure 7 is a cross section on in Figure 6.

In these drawings various constructions in acfurther construction in and the line VIL-VII cordance with the invention are shown for the upper part of the switch casing and these con structions may be employed as modifications of the top part of a switch such as shown and described in our United States Patent application Serial No. 180,204 filed 1st April, 1927.

In the construction shown in Figure 1, the usual nozzle contact 1 has screwed into its lower edge a turned up part 2 which reaches practically to the restricted throat 3 of the contact 1. The current connection 4 is shown in this figure, at the'top of the contact 1 so that when the switch is opened as shown in the figure, current flows down from the lead-in 4 to the restricted throat 3 and then dlrectly through the arc to the contact pin 5. The latter is shown resilient with its end formed with a slit 6 to enable it to enter the throat 3 of the rigid outer contact. Under the conditions set forth, the current distribution is such that there is a slight te==-2ncy to blow the root of the arc downwards by the magnetic field set up by the current flowing down in the contact 1. However, any bowing of the arc between the central pin 5 and the side wall of the contact 1 may tend to no cause upward movement of the are due to the greater general concentration of current in the contact pin 5. If, in spite of this, the arc crosses the gap and becomes rooted on the upper edge of the inner lining member 2, the current then has to flow from the lead-in 4 to the bottom of the nozzle contact 1 andthenup the inner lining 2 to the arc and thence to the contact pin 5. The cur rent flowing up in the inner upturned part 2 has a more vigorous magnetic action than that in the outer shell of the contact 1 and acts immediately to blow the are up again into its original position on the inner wall of the contact 1. The action may be made more intense by providing the inner upturned portion 2 with longitudinal slits, indicated at 2a by the dotted lines, so that when the arc jumps on to the edge of the member 2, the

' current is confined to one of its segments and almost up to the therefore has a more concentrated action. Slots or holes as indicated at 3a by the dotted lines may also be provided in the lower part ofthe outer shell 3 to give access to the back of the parts 2 to provide an inward scouring blast across the upper edges of 2 to prevent the are from getting to the back of that part.

In the form of construction illustrated in Figure 2, the nozzle contact 1 is made in one piece, secured to the top of the switch casing 7 to which the pressure gas is supplied. At the throat 3, therefore, there is an internal projecting arcing surface at about the middle height of the contact 1. The latter has parallel leads-in at 4 and 8 respectively at the top and bottom of the contact so that the switch current flows from the top and from the bottom so as to unite at about the throat 3 and to flow into the arc and thence to the moving central switch pin 5. It will be seen that if the arc becomes displaced either upwardly or downwardly there is an unbalanced magnetic force due to the current flowing in the nozzle contact 1 which tends to move the are back to its original position. In this case also the member 1 may be formed of a number of segments to concentrate current and magnetic action in the region of the are root.

In the form of construction shown in Figure 3, the nozzle contact 1 is substantially a cylindrical body, but with an inward downwardly-turned member 9 screwed into the upper part and formed with the throat 3. The effect is improved again if the member 9 is slit in the same way as described for the member 2 in Figure 1. Asillustrated the lead-in 4 is in this case at the baseof the contact 1. If the arc tends to move downwards and crosses the gap between the bottom edge of the inturned member 9 and the inner wall of the lower part of the outer'cylindrical contact 1, the current has a tendency for blowing the are up from below. The lower part of the memberl may also be slit netic effect and the annular gap between the flanged entrance to the bottom of the member 9 and the lower inner wall of the cylinder 1 fitted with a packing of insulating material 1a.

It is of course, perfectly feasible to have a noz zle contact with turn-in portions both at the top and bottom. Thus-in Figures 4 and 5 the main body of the contact 1 has a central waist at the throat 3 at which the inner moving contact pin 5 makes contact- An internal slit piece 2 similar in shape to that shown in Figure 1 is screwed in at the bottom of the contact 1 so as to extend waist and a shorter slit piece 9 similar to that shown in Figure 3 is screwed in at the top. The contact 1 is rigid at the waist and are first 'moves to produce a concentrated mag' therefore it is desirable, in this case, for the moving contact pin 5 to be slit at 6 so as to make satisfactory contact at the waist. The lead-in connection 4 for the current is at the foot of the nozzle contact 1. In this case, when the arc lies between the moving contact pin 5 and the throat 3 of the contact 1, the current flowing upwardly in the outer shell of the contact 1 tends to move it in the direction of the fiow of the gas blast. If, however, in spite of this the arc does strike-across the gap to the edge of the lower internal piece 2, current will flow upwardly in the latter and its magnetic action will be to blow the arc upwards again into its original position as would also be the action if it struck the lower part of the member 1, but in this case it would be weaker unless the lower portion of 1 is slit. 0n the other hand, if the arc travels upwards and crosses the gap to the edge of the upper internal slit piece 9 current will flow right to the top of the contact 1 and down the prongs of the piece 9 and the current in the latter will again blow the are down into its original position. It will be noted that the member 2 is perforated to allow of the escape of gas into the annular space surrounding it. Furthermore, the slits between the prongs of the member 9 are filled with strips of soft iron 11 meeting in the lower ring 12 in order to cause'the electromagnetic action on the arc root to be intensified. Figure 4 illustrates the assembly of this embodiment, the switch casing constituting a pressure-retaining vessel being indicated at 15 and having an inlet pipe 16 for the gas which is to produce the blast. The operating mechanism for the moving switch pin 5 is of the usual kind including a cross bar 1'7, a guided operating rod 18 encircled by an operating spring 19, the whole being mounted on a base or framework 20.

In the construction shown in Figures 6 and 7, the construction of Figure 5 is modified by extending the inner it with a waist 3 so that it forms in effect the nozzle contact itself. As it is slit and resilient at the waist the moving contact pin 5 may be nonresilient. When the arc is struck in this case, current flows upwardly from the lead-in conductor 4 through the -internal piece 2 and the up slightly, then any upward or downward movement of the arc will vary the path of the current so that appropriate magnetic restoring forces come into play. Thus, if the arc crosses the gap to the lower edge of the upper internal piece 9 the current will again flow up through the outer shell 1 to the top and then down through the prongs of the'upper internal piece 9 as in rated to provide some escape for the hot expanding gases which have passed the arc. It will be noted that the segments of the member 2 are carried by laminated plates 13 which are carried within a ring 14 screwed in the lower end of the shell 1 so as to increase the yielding action of the member 2 when the contact'pin 5 enters the constricted portion of the member 2.

In any of the forms of construction described above the action may be intensified by providing slit portions of the members with iron strips'as at 11 and 12 which in Figures 5 and 6, extend along the edges of the upper internal piece 9. In Figures 5, 6 and '7 iron may be placed behind the copper electrode rial may be provided between the slit strips and the outer conducting cylinder. l

or a cylinder of magnetic matethe leading-in conductor may It will be understood that the forms of construction shown in Figures 1, 4, 5 and 6 are not only suitable for use in cases in which a sudden pressure of fluid is applied at the time of arcing, but also in cases in which fluid is stored under pressure in the arcing cylinder for some time before it is required for use in extinguishing the are, as especially in the latter cases, a valvecan be easily mounted on the top of the outer shell or on an extension pipe from the shell so that owing to the continuous or solid nature of the outer shell, fluid can be retained under pressure in and around the slit parts of the electrode. The same result can be attained with the forms of construction shown in Figures 2 and 3 by mounting them in an outer shell. It will be understood from the description given above in regard to the functions of the various members and their configurations that the point of attachment of the leading-in conductor may be altered somewhat, without departing from the scope of the present invention. For example, it is clear from the configuration of the current carrying parts in the forms of construction illustrated in Figures 5, 6 and 7, that the position of the attachment of be altered to any other point on the shell 1, above that shown in the drawings, without altering the correct functioning of the members 2 and 9.

We claim:-

1. An alternating current circuit breaker comprising in combination a casing, apair of relatively movable electrodes mounted therein, means for supplying a blast of fluid to the arcing surfaces of said electrodes, and to said electrodes, one of said electrodes being so shaped and having a current connection at such a point that upon a root of the are formed on opening the circuit breaker becoming displaced from its normal position in an intermediate region on the surface of that electrode in a direction substantially parallel to the direction of flow of the fluid, the eifective direction of flow of current to that are root is such as to create a magnetic field tending to return said are root to said intermediate region on the surface of said electrode.

2. An alternating current circuit breaker, comprising in combinationa casing, a fixed electrode mounted therein, a movable electrode mounted to co-operate with said fixed electrode, operating mechanism for said moving contact, means for supplying a blast of fluid to the arcing surfaces of said electrodes and current connections to said electrodes, said fixed electrode being so shaped and a current connection being attached to it at such a point that upon a root of the are formed on opening the circuit breaker becoming displaced from the normal position in an intermediate region on the surface of said fixed electrode in a direction substantially parallel to the direction of flow of the fluid, the effective direction of flow of the current into that are root is such as to set upa magnetic field tending to return said are root to said intermediate region on the surface of said nxed electrode.

3. An alternating current circuit breaker, com prising in combination a casing, adjacent relatively movable electrodes mounted therein, means for supplying a blast of fluid to the arcing sur faces of said electrodes, one of said electrodes being shaped to form a hollow passageway for the blast fluid and comprising a number of segments held resiliently together and a current supply conductor connected to said segments so that current connections current reaches the arc root from the same gen eral direction as the said blast fluid.

4. An alternating current circuit breaker, comprising in combination, a casing, a pair of relatively movable electrodes mounted therein, means for supplying a blast of fluid to the arcing surfaces of said electrodes; and current connections to said electrodes, the current connections to one of said electrodes being arranged to lead current into said electrode at points spaced apart in a direction substantially parallel to the direction of flow of the fluid, on either side of the are formed on opening the circuit breaker.

5. An alternating current electric circuit breaker, comprising in combination, a casing, a pair of relatively movable electrodes mounted therein, means for supplying a blast of fluid to the arcing surfaces of said electrodes, and current connections to said electrodes, one of said electrodes being shaped to constitute a hollow passageway for said blast of fluid and with a reentrant portion with its edge directed towards the are formed on opening the circuit breaker so that when said are moves between the inner wall of said lastmentioned contact and its re-entrant portionthe distribution of current in said re-entrant portion is altered so as to set up a magnetic force tending to restore the arc to its original position.

6. An alternating current electric circuit breaker comprising in combination a casing, a hollow electrode mounted therein and formed with a constricted threat, a eo-operating electrode mounted to move relatively to said hollow electrode so as to make contact with said hollow electrode at the throat thereof and current connections to said electrodes, said hollow electrode being formed with re-entrant portions, one on either side of said throat.

'7; An alternating current electric circuit breaker comprising in combination, a casing, a pair of relatively movable electrodes mounted therein, means for supplying a blast of fluid to the arcing surfaces of said electrodes, and current connec tions to said electrodes, one of said electrodes being so shaped and having a current connection to it at such a point that upon the root of the are formed on opening the circuit breaker becoming displaced from its normal position in an intermediate region on the surface of that electrode, the effective direction of flow of current into that are root is such as to create a magnetic field tending to return said are root to said intermediate region on the surface of said electrode in a direction substantially parallel to the direction of flow of the liquid and said last-mentioned being slit over the portion aiong which the are root is moved in the general direction in which the arc root is moved so as to concentrate the current flowing to the are when the latter moves on to a part of said electrode between the slits.

8. An alternating current electric circuit breaker comprising in combination a casing, a pair of relatively movable electrodes mounted therein, means for supplying a blast of fluid to the arcing surfaces of said electrodes and current connections to said electrodes, the current connection to one of said electrodes being arranged to lead current to said electrode at points spaced apart in a direction substantially parallel to the direction of flow of the fluid, on either side of the are formed on opening the circuit breaker, said lastmentioned electrode being slit in the general direction in which the arc root is moved over the portion along which the arc root is moved, in

order to concentrate the current flowing to the are when the latter moves on to the electrode between the slits.

9. An alternating current circuit breaker comprising in combination, a pressure retaining vessel, a hollow electrode mounted on said pressure retaining vessel, a casing surrounding said hollow electrode, means for supplying a blast of fluid to said hollow electrode, a movable electrode mounted to co-operate with said hollow electrode a current connection to said movable electrode and a current connection to such a point in said hollow electrode that upon a root of the are formed on opening the circuit breaker becoming displaced along the inner surface of said hollow electrode from its normal intermediate position on that surface, the eifective direction of flow of current to that are root in said hollow electrode is such as to create a magnetic field tending to return said are root to said intermediate region on the surface of said hollow electrode, the walls of said hollow electrode being provided with slits which open into said casing.

10. An alternating current circuit breaker comprising in combination, a pressure retaining vessel, a pair of relatively movable electrodes one mounted on said pressure retaining vessel, a casing surrounding said last-mentioned electrode, means for supplying a blast of fluid to the arcing surfaces of said electrodes and current connections to said electrodes, one of said electrodes being so shaped and having its current connection at such a point that upon a root of the are formed on opening the circuit breaker becoming displaced from its normal position in an intermediate region on the surface of that electrode in a direction substantially parallel to the direction of flow of the fluid and one of said electrodes being formed with slits in the general direction in which the arc root is moved over the portion along which the arc root is moved so as to concentrate the current flowing to the are when the arc moves on to the part of that electrode between the slits, said slits opening into said casing.

11. An alternating current circuit breaker comprising in combination, a casing, a pair of relatively movable electrodes mounted therein, means for supplying a blast of fluid to the arcing surfaces of said electrodes, current connections to said electrodes and magnetic material located behind one of said electrodes in order to intensify the action of said magnetic field, one of said electrodes being so shaped and having a current connection at such a point that upon a root of the are formed on opening the circuit breaker becoming displaced from its normal position in an intermediate region on the surface of that electrode in a direction substantially parallel to the direction of flow of the liquid, the effective direction of flow of current into that are root is such as to create a magnetic field tending to return said are root to said intermediate region on the surface of said electrode.

' 12. An alternating current circuit breaker comprising in combination a casing, a pair of relatively movable electrodes mounted therein, one being formed with slit walls, means for supplying a blast of fluid to the arcing surface of said slit electrode, current connections to said electrodes and magnetic material located along the edges of a slit portion of said last named electrode to intensify the electromagnetic action on the arc root of the current flowing in said electrode, said slit electrode being shaped to provide a hollow passageway for said blast fluid.

13. An alternating current circuit breaker comprising in combination a casing, a hollow electrode mounted therein, means for supplying a blast of fluid to said hollow electrode, a co-oper-' ating electrode mounted to move relatively to said hollow electrode a current connection to said cooperating electrode and a current connection at such a point in said hollow electrode that upon a root of the are formed on opening the circuit breaker becoming displaced from its normal intermediate position on the surface of said hollow electrode the effective direction of flow of the current into that are root is such as to set up a magnetic field tending to return said arc rootto the intermediate region on the surface of said hollow electrode, the wall of said hollow electrode being provided with a plurality of perforations connecting together the spaces on both sides of the said wall to allow of the passage of the blast fluid.

14. An alternating current circuit breaker comprising in combination a casing, a pair of relatively movable electrodes mounted therein, one being hollow and having its wall perforated, means for supplying a blast of fluid to the passageway in said hollow electrode and current connections to said electrodes, said hollow electrode being so shaped and having a current connection at such a point that upon a root of the arc formed on opening the circuit breaker becoming displaced from its normal position in an intermediate region on the surface of that electrode, 1 5 the effective direction of flow of current to that are root is such as to create a magnetic field tending to return said are root to said inter mediate region on the surface of said electrode.

WILLIS BEVAN WHITNEY. 13 0 EDMUND BASIL WEDMORE.

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