US2262505A - Electric converting apparatus - Google Patents

Description

Nov. 11, 1941. A, J LARRECQ ELECTRIQ CONVERTING APPARATUS Filed Sept. 22, 1939 .n. M M

Inventor:

His Attorney.

c e r r a L J W O m n A Patented Nov. 11, 1941 2,262,505 ELECTRIC CONVERTING APPARATUS Anthony J. Larrecq,

New York Beach Bluflf, Mass, assignor to General Electric Company,

a corporation of Application September 22, 1939, Serial No. 296,076

15 Claims.

My invention relates to electric valves and electric converting apparatus, and more particularly to those types of valves in which an arc is periodically ignited and extinguished between a plurality of electrodes and a continuous flow of some fluid medium is maintained between the electrodes.

Electric converting apparatus of the kind referred to have been described in a book by Erwin Marx, entitled "Lichtbogenstromrichter, published in Berlin in 1932, and in United States Letters Patent No. 2,074,930, granted March 23, 1937, upon an application of Erwin Marx. In such apparatus it has been customary to provide a continuous flow of gas, such as air, within the gaps between the electrodes. However, due to the action of oxygen in the air the main electrodes of the prior art devices are subject to considerable deterioration and therefore it has been proposed to use a relatively inert gas instead of air. However, even with the use of such inert gas deterioration of the electrodes is considerable and hence it would be desirable to provide a valve of the gas cooled arc type wherein less burning and deterioration of the electrodes occur. In the arrangements of the prior art it has been necessary to provide an auxiliary electrode which serves as a starting or ignition electrode. In order that this auxiliary electrode may cause the arc discharge to start between the main electrodes considerable auxiliary equipment is necessary. It would be desirable to provide a valve of the gas cooled arc type wherein the auxiliary equipment heretofore required for igniting the arc discharge may be dispensed with along with the'difiiculties encountered in the operation of such auxiliary equipment. Also in some of the arrangements of the gas cooled arc type of electric valves difficulties have been incurred in extinguishing the arc at the end of the conducting period, i. e., at current zero. In accordance with my invention therefore, I provide an arrangement wherein heretofore necessary auxiliary equipment may be dispensed with, wherein a minimum deterioration of the electrodes occurs, and wherein the extinguishment of the are at the proper tim is much more positive and satisfactory than with apparatus heretofore used.

It is an object of my invention to overcome the disadvantages above noted in connection with valves of the gas cooled arc type and to provide a more efficient and more positive valve for use in connection with electric converting apparatus.

It is another object of my invention to provide a new and improved electric valve for use in connection with an electric converting apparatus.

Still another object of my invention is to provide an electric valve apparatus including valves of the gas cooled arc type wherein less deteriora tion of the electrodes occurs and whereby more efiicient and more stable operation is obtained.

It is a further object of my invention to provide an electric valve converting apparatus including valves of the gas cooled arc type wherein complicated auxiliary apparatus for initiating the arc discharge at periodic intervals is eliminated and wherein suitable means are provided for extinguishing the are at the end of the conducting period.

In accordance with the illustrated embodiment of my invention I provide for an electric converting apparatus an electric valve or electric valves of the gas cooled arc type comprising a plurality of stationary segmental electrodes annularly arranged, connected to the respective phases of the alternating current circuit, while an annular collector ring is suitably spaced from said segmental electrodes so as to produce an arc discharge gap therebetween. A segmental conducting member is rotated in synchronism with the alternating current circuit in the arc discharge gap, so reducing this gap that an arc discharge may readily be initiated between one of the segmental electrodes and the collector ring. The rotating conducting member is so dimensioned as to reduce the arc gap only between one segmental electrode at a time and current flowing through the arc discharge is caused to commutate from one segmental electrode to another by the great increase in the arc gap as well as by cooperation of a gas blast which sweeps past the segmental faces causing the arc to move thereacross and to commutate from segment to segment at the proper'time. This gas blast is produced by fan means mounted on the rotating member.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, Will best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a cross sectional view of one form of my gas cooled arc type of valve; Fig. 2 discloses the stationary segmental electrodes shown in cross section in Fig. l; 3 illustrates the rotating member and fan blades shown in cross section in Fig. 1; Fig. 4 discloses the stationary annular direct current collector ring shown in cross section in Fig. 1, and Fig. bis 9. diagrammatical representation of one form of converting apparatus employing my new gas cooled arc type of valve. Referring to the drawing I have shown in Fig. 1 one form of my gas cooled arc typeof valve l including a sealed casing ll mounted on a suitable support l2 which should preferably be constructed of insulating material so that the apparatus may be used for high voltage installations. Mounted within the sealed casing I l are a plurality of segmental electrodes l3 annularly arranged as best shown in Fig. 2 and lodged in a suitable dielectric or insulating material l4 in such a manner that the segmental faces are flush with the surface of the dielectric l4 so as to permit a smooth path for cooling medium as will be described hereinafter. Although I have shown in Fig. 2 six segmental faces it will be understood by those skilled in the art that there should be as many segmental faces as there are alternating current phases in the converting system with which this electric valve is to be used. The segmental electrodes l3 and dielectric l4 are fixedly supported within the sealed casing H by means of an annular support l5. Similarly mounted in the opposite end of sealed casing H is a direct current collector ring or electrode l'6 of annular shape also suitably lodged in a dielectric or insulating material I! so that the collectorring I6 is flush with the surfaces of, the insulating material thereby to provide a smooth path for the cooling medium as will be described hereinafter. The direct current collector ring I6 is best shown in Fig. 4. This collector ring l6 and insulating material I! are fixedly supported within casing II by means of annular support ill in such a manner as to provide a relatively large gap or space between segmental electrodes l3 and collector ring l6, and a rotor l9, shown also in Fig. 3, is mounted so as to rotate within the gap formed therebetween. The rotor I9 is integrally mounted or otherwise suitably secured upon a hollow shaft and adapted to rotate with the shaft 20 which is provided with suitable bearings 2| and 22. A synchronous motor 23 drivingly connected to shaft 20 and rotor I9 is preferably mounted directly to casing ll so as to form an integral unit therewith. Rotor I9 is provided with an enlarged segmental portion 24 of approximately the same circumferential dimensions as segmental electrodes l3 so as to reduce the gap between successive segmental electrodes l3 and collector ring It to a minimum. Segmental electrodes I 3, enlarged portion 24 of rotor l9 and collector ring l6 are constructed of any suitable conducting material, although in order to reduce deterioration I prefer to use electrodes constructed of a eutectic silver-copper alloy' to which has been added a small amount of thorium or barium similar to the electrodes disclosed and broadly claimed in U. S. Letters Patent No. 2,151,567, granted March 21, 1939, upon an application of Hugo J. Seemann, and assigned to the assignee of the present application. Enlarged segmental portion 24 thus produces two relatively short gaps and 26, gap 25 being formed between one of segmentalelectrodes l3 and enlarged segment 24 of rotor l9 and gap 26 being formed between collector ring l6 and en larged segment 24 of rotor l9. Gaps 25 and 26 are sufliciently small so that an arc discharge mayreadily be initiated thereacross and further the arc losses are reduced to a minimum by constructing gaps 25 and 26 as small as possible determined by the necessary minimum running clearance. The remaining portion of rotor l9 to rotate.

has a very narrow cross section so that the gap between the remaining segmental electrodes I 3, not adjacent enlarged portion 24 of rotor l9, and collector ring [6 is suiiiciently large to prevent an arc discharge from being initiated thereacross and hence also reducing the likelihood of arc backs. By means of synchronous motor 23 rotor I9 is rotated atsynchronous speed in the gap between segmental electrodes l3 and collector ring l6 and the enlarged segment 24 is always opposite the particular segmental electrode l'3 through which current is to be conducted, by means of arc discharges in gaps 25 and 26, at that particular instant. This current is commutated from one segmental electrode l3 to another as the enlarged portion 24 of rotor l9 continues Although I have illustrated segmental electrodes I 3, and collector ring [6 .as fixedly mounted while member 19 is rotatable, it will be understood by those skilled in the art that all that is necessary is a relative movement between these members and it is immaterial as far as my invention is concerned as to how this relative movement is obtained. A plurality of fan blades 21 are provided on rotor l9 so as to circulate a cooling medium through gaps 25 and 26 as well as through the relatively large gap formed between segmental electrodes l3 and collector ring Hi. This cooling medium not only cools the electrodes but also serves to move the arc foot-point diagonally across the segmental faces of electrodes I3. The clearance between fan blades 21 and insulating members l4 and I! should be' reduced to a minimum and it may be preferable to employ labyrinth packing arrangements similar to those used for interstage turbine packing. A plurality of heat transfer surfaces or cooling tubes 28 are provided to cool the fluid medium which leaves the arc discharge gaps 25 and 26. The fluid medium may be continuously recirculated in a closed system by passing through openings 29 and 30 in annular supporting members f5 and I 3, respectively. If a closed system is employed the fluid cooling medium will be continually recirculated and cooled by contact with heat transfer members 28. It will, of course, be understood by those skilled in the art, that the pressure of the fluid cooling medium may be suitably chosen as well as the particular type of medium. The particular fluid medium used and the pressure thereof are not critical so far as my invention is concerned and any suitable medium such as air or nitrogen may be used, although I would prefer to use one of the inert gases such as argon in case a closed system is employed. In Fig. 1, however, I have shown an arrangement wherein a cooling fluid circulating system is not completely enclosed in casing II, but where an additional supply of cooling medium is provided through hollow shaft 20 and openings 3| therein. The pressure of this cooling, medium may be controlled by any suitable means (not shown). It will, of course, be understood by those skilled in the art, that if openings 3| in hollow shaft 29 were eliminated then the closed type of system would be provided. Heat transfer members 28 may have any suitable cooling fluid circulated therethrough such as water or air and in certain cases a suitable refrigerant might even be used.

In Fig. 5 I have diagrammatically shown my gas cooled arc type of valve as applied to an electric converting apparatus. It will be understood that my invention is applicable to any electric converting system well known in the art and it is equally adapted to rectification of alternating current or inversion of direct current. For simplicity of disclosure I have shown in Fig. 5 my invention as employed in connection with a six-phase rectifier circuit wherein electrical energy is transmitted from a three-phase alternating current circuit 33 to direct current circuit 34. A transformer 35 is provided having a delta connected primary winding 36 associated with alternating current circuit 33 and a six-phase star connected secondary winding 31, the respective phases of which are directely connected to one of the segmental electrodes l3. The neutral terminal of star connected secondary winding 31 is connected to the negative terminal of the direct current circuit, while the positive terminal of the direct current circuit is connected to collector ring IS.

The operation of the illustrated embodiment of my invention will best be understood by reference to Fig. 5. Rotor I9 is rotated by means of synchronous motor 23 in synchronism with and in proper phase relationship to alternating current circuit 33 from which synchronous motor 23 is preferably energized. Enlarged section 24 of rotor I9 is so adjusted as to come opposite successive segmental electrodes l3 which have for the particular instant a positive potential applied thereto from alternating current; circuit 33 of such a value as to exceed the threshold value of voltage required to initiate an arc discharge across gaps 25 and 26. Each segmental electrode l3 conducts current for substantially sixty electrical degrees after which the succeeding electrode becomes conductive. This happens when the next successive segmental electrode has a sufiiciently positive potential applied thereto to exceed the threshold voltage required to initiate an arc discharge across gaps 25 and 26 for at this instant enlarged portion 24 of rotor I9 has L reached a position such that its leading edge just overlaps the end of the succeeding electrode. Hence the arc discharge is caused to commutate from one segmental electrode l3 to another partly by the large increase in arc gap which obtains as soon as the trailing edge of enlarged segment 24 has passed the end of the particular segmental electrode which was conducting current and also because of the blast of cooling medium produced by fan blades 21 which causes the arc foot-points 5 to move diagonally across the segmental faces of electrodes l3. Of course, due to the relative movement of the stationary and rotating segmental electrode the arc foot-points naturally tend to move over the face of the same. The large increase in gap is such as to practically eliminate the possibility of arc backs when the high inverse voltage appears across the particular segmental electrode which has just become nonconductive. Furthermore the potential of the segmental electrode [3 which is conducting ourrent varies during the arc discharge so as to produce a minimum potential difference at the instant the arc is being extinguished. The proper phase relationship of rotor l9 and the alternating potentials impressed on segmental electrodes I3 is maintained by suitable adjustment of the synchronous motor field, this adjustment being such that the enlarged segment 24 comes opposite the proper segmental electrode 13 when the potential of the associated alternating current phase exceeds the threshold value of potential required to initiate the arc which passes cur rent from that particular electrode to the direct current collector ring Hi. It will be understood by those skilled in the art that my proposed arrangement is in some respects analogous to the multi-anode, single-cathode electric discharge valves known to the prior art.

While I have described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

' 1. In combination a supply circuit, a load circuit, one of said circuits being an alternating current circuit, a transformer and a converting apparatus interconnecting said circuits, said transformer having one winding connected to said alternating current circuit, and a plurality of phase windings inductively associated therewith, said converting apparatus comprising a plurality of angularly spaced electrodes associated with said phase windings, other electrode means mounted in spaced relationship with each of said plurality of electrodes so as to provide a uniform gap therebetween throughout the angular extent of said plurality of electrodes, and means for transmitting electrical energy between successive ones of said plurality of electrodes and said other electrode means comprising a member rotated in said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said other electrode means so as to initiate an arc discharge between said other electrode means and each of said plurality of electrodes in succession, said member having an extent greater than the distance between adjacent ones of said plurality of electrodes so that the arc discharge is readily transferred from one of said plurality of electrodes to the next as said member is rotated.

2. In combination a supply circuit, a load circuit, one of said circuits being an alternating current circuit, a transformer and a converting apparatus interconnecting said circuits, said transformer having one winding connected to said alternating current circuit, and a plurality of phase windings inductively associated therewith, said converting apparatus comprising a plurality of electrodes associated with said phase windings, other electrode means mounted in spaced relationship with each of said plurality of electrodes so as to provide a uniform gap therebetween, and means for transmitting electrical energy between successive ones of said plurality of electrodes and said other electrode means comprising a member rotated in said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said other electrode so as to initiate an arc discharge therebetween, and means for commutating said are discharge between said plurality of electrodes.

3. In combination an alternating current supply circuit, a direct current load circuit, a transformer and a converting apparatus interconnecting said circuits, said transformer having a primary winding connected to said supply circuit and a polyphase secondary winding, a plurality of stationary electrodes each connected to one of the phases of said secondary winding, a collector ring connected to said direct current circuit and positioned in spaced relation to said plurality of electrodes and a rotary member including a conducting element mounted between said first mentioned electrodes and said collector ring, and means for driving said rotary member in synchronism with said alternating current supply circuit so that an electrical discharge is produced successively between each of said plurality of stationary electrodes, said conducting element and said collector ring, said conducting element having an extent in the direction of the rotation greater than the distance between adjacent ones of said plurality of electrodes to provide an overlap between said conducting element and adjacent ones of said electrodes as said member is rotated thereby to facilitate the transfer of the are between said plurality of electrodes.

4. In combination an alternating current supply circuit, a direct current load circuit, a transformer and a converting apparatus interconnecting said circuits, said transformer having a primary Winding connected to said supply circuit and a polyphase secondary winding, a plurality of stationary electrodes each connected to one of the phases of said secondary winding, a collector ring connected to said direct current circuit and a rotary member mounted between said first mentioned electrodes and said collector ring, means for driving said rotary member in synchronism with said alternating current supply circuit so that an electrical discharge may be produced successively between said plurality of stationary electrodes and said collector ring, and means for causing a gaseous fluid to cool said arc, driving it across the faces of said electrodes and successively forcing it to transfer from one of said plurality of electrodes to another.

5. An electric valve of the gas cooled arc type for transmitting energy between direct and alternating current circuits comprising a plurality of segmental electrodes and a direct current collector ring so constructed and arranged as to provide a uniform gap therebetween, means for transmitting electrical energy between successive ones of said plurality of electrodes and said collector ring comprising a conducting member rotated in said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said collector ring so as to initiate an arc discharge therebetween and means for causing a gaseous fluid to flow through said gap to aid in the transfer of said are discharge from one of said plurality of electrodes to another.

6. An electric valve of the gas cooled arc type for transmitting energy between direct and alternating current circuits comprising a plurality of segmental electrodes and a direct current collector ring so constructed and arranged as to provide a uniform gap therebetween, means for transmitting electrical energy between successive ones of said plurality of electrodes and said collector ring comprising a member rotated in said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said collector ring so as to initiate an arc discharge therebetween, and means for commutating said are discharge between said plurality of electrodes.

7. An electric valve of the gas cooled arc type for transmitting energy between direct and alternating current circuits comprising a plurality of segmental electrodes mounted within a' casing and insulated therefrom, a collector ring mounted within said casing and insulated therefrom, said collector ring being so constructed and arranged with respect to said electrodes as to provide a uniform gap therebetween, means for transmitting electrical energy between successive ones of said segmental electrodes and said collector ring comprising a member rotated within said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said collector ring so as to initiate an arc discharge therebetween, and means for commutating said arc discharge between said plurality of electrodesby increasing said are gap when commutation is to take place.

8. An electric valve of the gas cooled arc type for transmitting energy between direct and alternating current circuits comprising a plurality of segmental electrodes mounted within a casing and insulated therefrom, a collector ring mounted within said casing and insulated therefrom, said collector ring being so constructed and arranged with respect to said electrodes as to provide a uniform gap therebetween, means for transmitting electrical energy between successive ones of said segmental electrodes and said collector ring comprising a member rotated within said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said collector ring so as to initiate an arc discharge therebetween, means for commutating said are discharge between said plurality of electrodes by increasing said are gap when commutation is to take place, and means for producing a flow of gaseous medium for cooling said are discharge and aiding the commutation from one electrode to another.

9. An electric valve of the gas cooled arc type for transmitting energy between a direct and an alternating current circuit comprising a plurality of electrodes and a direct current collector ring so constructed and arranged as to provide a uniform gap therebetween, means for' transmitting electrical energy between successive ones of said plurality of electrodes and said collector ring comprising a member'rotated in said gap in synchronism with the alternating current of said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said collector ring so as to initiate an arc discharge therebetween, and a plurality of fan blades mounted on said member for producing a flow of fluid medium to cool said are discharge and cause it to commutate between said plurality of electrodes.

10. An electric valve of the gas cooled arc type for transmitting energy between direct and alternating current circuits comprising a plurality of segmental electrodes mounted within a casing and insulated therefrom, a collector ring mounted within said casing and insulated therefrom, said collector ring being so constructed and arranged with respect to said electrodes as to provide a uniform gap therebetween, means for transmitting electrical energy between successive ones of said segmental electrodes and said collector ring comprising a member rotated within said gap in synchronism with said alternating current circuit said member successively reducing the gap between each of said plurality of electrodes and said collector ring so as successively to initiate an arc discharge therebetween,

for transmitting energy between a direct and an alternating current circuit comprising a plurality of electrodes and a direct current collector so constructed and arranged as to provide a uniform gap between said electrodes and said collector,

means for transmitting electrical energy between 1 successive ones of said plurality of electrodes and said collector comprising a member rotated in said gap in synchronism with the alternating current of said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said collector so as to initiate an electrical discharge therebetween, means for producing a flow of fluid medium to cool said are discharge and cause it to commutate between said plurality of electrodes, 1;

and heat transfer means in the path of said fluid medium to cool said fluid medium after it has been heated by said are discharge.

12. An electric valve of the gas cooled arc type for transmitting energy between direct and alternating current circuits comprising a casing, a plurality of electrodes and a direct current collector insulatingly mounted therein, said collector being so arranged in said casing with respect to said plurality of electrodes as to provide a uniform gap therebetween, means for transmitting electrical energy between successive ones of said electrodes and said collector comprising a member arranged to be rotated within said gap, a synchronous motor mounted on said casing drivingly connected to said member and rotating it within said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said collector so as to successively initiate an arc discharge therebetween, and means for commutating said are discharge between said plurality of electrodes by increasing said electric gap when commutation is to take place.

13, In combination, a supply circuit, a load circuit, one of said circuits being an alternating current circuit provided with a plurality of phase terminals, a converting apparatus interconnecting said phase terminals and said other circuit,

said converting apparatus comprising a plurality of electrodes mounted in electrically insulated and closely spaced circumferential relation associated with said phase terminals, other electrode means mounted in spaced relationship with each of said plurality of electrodes so as to provide a uniform gap therebetween, and means for transmitting electrical energy between successive ones of said plurality of electrodes and said other electrode means comprising a member rotated in said gap in synchronism with said alternating current circuit, said member successively reducing the gap between each of said plurality of electrodes and said other electrode means so as to initiate an arc discharge therebetween, said member being dimensioned to overlap portions of successive ones of said plurality of electrodes as the member is rotated to thereby facilitate the commutation of current from one of said pluralities of electrodes to the next.

14. An electric valve of the gas cooled arc type for transmitting energy between a load circuit and a supply circuit, one of said circuits being an alternating current circuit, comprising a plurality of electrodes and a direct current collector ring so constructed and arranged as to provide a uniform gap therebetween, and means for transmitting electrical energy between successive ones of said plurality of electrodes and said collector ring comprising a conducting member mounted so as to be relatively rotatable with respect to said plurality of electrodes, said relative rotation being in synchronism with said alternating current circuit thereby successively reducing the gap between each of said plurality of electrodes and said collector ring to initiate an arc discharge therebetween and means for directing a flow of gaseous fluid across said gap for aiding the commutation of said are discharge from one of said pluralities of electrodes to another as said conducting member is rotated.

15. In combination, a supply circuit, a load circuit, one of said circuits being an alternating current circuit, a transformer and a converting apparatus interconnecting said circuits, said transformer having one Winding connected to said alternating current circuit and a plurality of phase windings inductively associated therewith, said converting apparatus comprising a plurality of electrodes associated wtih said phase windings and mounted in electrically insulated and closely spaced circumferential relation, other electrode means mounted in spaced relationship with each of said plurality of electrodes so as to provide a uniform gap therebetween, and means for transmitting electrical energy between successive ones of said plurality of electrodes and said other electrode means comprising a conducting member mounted in said gap so as to be relatively rotatable with respect to said plurality of electrodes, said relative rotation being in synchronism with said alternating current circuit thereby successively reducing the gap between each of said plurality of electrodes and said other electrode means so as to initiate an arc discharge therebetween, said member having sufficient extent in the direction of rotation thereof to overlap successive ones of said electrodes to thereby facilitate the commutation of said arc discharge between successive electrodes.

ANTHONY J. LARRECQ.

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