US2125131A - Metallic vapor discharge apparatus for high voltages - Google Patents

Description

A. SIEMENS 2,125,13l

METALLIC VAPOR DISCHARGE APPARATUS FOR HIGHv VOLTAGES Jly 26, 1938.

Fild Aug. 17, 1956 2 Sheets-Sheet 1 lNvEN'foR f v Alfred Siemens.

AfslEMr-:Ns 2,125,131v

' 2 Sheets-Sheet 2 Filed Aug. 1v, 4195s lNvENToR ATTORNEY METALLIC VAPOR DISCHARGE APPARATUS FOR HIGH voLTAGEs vllv Jury 2 6, 193.8.

Alfred Siemens.

Patented July Z6, 1938 UNITED STTES ATENT GFFICE Alfred Siemens, Berlin,

Germany, assigner to Siemens-Schuckertwerke Aktiengesellschaft, Berlin-Siemensstadt, Germany, a corporation of Germany Application August 17, 1936, Serial No. 96,521

In Germany 7 Claims.

My invention relates to metallic Vapor discharge apparatus for high voltages, and more particularly to steel-tank mercury arc rectiers.

The construction of high-voltage rectiers is 5 closely connected with the control of the high field intensities occurringin such apparatus. Besides the difculties hithertoI encountered in the high-voltage practice and already partly overcome, such as electrical stress on material, design of bushings etc., also the diiiiculties presented in metallic vapor vacuum apparatus and caused by the ionization of the discharge path during the active period must also be taken into consideration. In this case operating conditions of a greatly diierent character occur owing to the periodical alternation of the active and inactive period; that is, in the active period the discharge is practically without an electric eld but strongly ionized, whereas in the inactive period a strong electric eld is set up between the anode and cathode which causes disturbances and backres as a result of the excessive acceleration of the residual charges or of the creation ofV unclesirable glow discharges.

It the case of the mercury arc discharger apparatus for high voltages hitherto employed the known construction of high-voltage rectiers has been in principle followed. In these apparatus the anodes are located in the interior of the vacuum discharge tank by means of insulated bushings of ceramic material passing through the cover of the vacuum tank, which bushings are dimensioned and extended according to the necessary drops of voltages. Endeavors have been made to split up the Voltage drop between the anode and the vapor space surrounding the anode and having a cathode potential by various means, for instance, by telescopically arranged cylindrical shields which cause a splitting up of the voltage drop as a result of their capacity both with respect to the anode and cathode and with respect to one another.

However, in this connection it has been found that the voltages may be only controlled within 45 certain limits, since an absolute control of the distribution of the electric fields is not possible. Measurements of the eld distribution in the vacuum tank are practically impossible and it is diiicult to effect changes in capacities. ther diiiiculty in the high-voltage practice is presented by the bushings which require in most cases considerable costs for the construction of the same.

The following considerations show a method how the above-mentioned diiiiculties may be re- A fur- August 17, 1935 (Cl. Z50-27.5)

moved and, therefore, how the reliability of discharge apparatus may be enhanced to any desirable extent.

If the simplest arrangement of the arc path is considered in a discharge device controlled by a grid the path may be subdivided into two part paths which from an electrical point of view behave in a substantially different manner, i. e., into the part path: cathode-control grid and into the part path: control grid-anode. As reference potential the potential of the cathode is chosen. Referred to the cathode potential the potential of the control grid fluctuates only by relatively small amounts, as are entailed by the construction of the discharge apparatus, that is to say, in the positive direction during the active period of the anode and in the negative direction during the inactive period of the anode. According to the order of magnitude these values amount, for instance, at most to i200 volts and are so chosen that they do not cause a disturbance or an unfavorable influence of the operation of the electric discharge apparatus. The electric eld produced by the same is too weak in the inactive period of the anode to produce an 1:

ionization by impact when accelerating the electrons and in the active period of the anode any substantial potential diiierences do not exist at all events.

.The conditions in the path: control gridanode are quite diierent. It is true that also in this case a conductive connection is established in the active period of the anode by the arc but in the inactive period the anode has a higher negative Voltage with respect to the cathode and,

therefore, also with respect to the control grid. The voltage in the case of a six-phase operation is two times the direct voltage produced. Particularly in the case of high voltages the strength of the field produced in this case is by orders of magnitude greater than the eld between cathode and control grid. This strong field causes the known disturbances.

According to the present invention both paths which behave electrically in a quite different manner are not inserted one in the other as has hitherto been the case but are in spaced relation with one another. The anodes are arranged according to the invention in such a manner outside the main tank which encloses the cathode and the condensation chamber and is impressed with the cathode potential that the planes of equal potential formed between the counterelectrodes are practically uniform outside the main tank. In this case the upper wall of the .f

El l) Cfl main tank and the anode surfaces are given forms as are usual for adjacent electrodes in the high-voltage practice; i. e., they are designed as plate-sphere, sphere-sphere, concentric sphere or plate-plate. It is essential that also the condensation chamber does not extend beyond the wall of the main tank, for the condensation chamber, the walls of which possess also cathode potential, would lead to a disturbance of the planes of equal potential so that they would not be uniform. Consequently, according to the invention the portion of the space containing the cathode and which serves above all to produce vapor and has substantially constant cathode potential, i. e., the cathode space, is separated from those portions of the space in which alternating fields occur (anode spaces).

The anode spaces lie preferably outside the portion of the tank containing the cathode chamber and are separated from said portion by control grids. It is preferable to insulate the portion of the tank enclosing the anode chamber from the portion of the tank containing the cathode chamber. The portion of the tank enclosing the anode chamber may be made of insulating material; for instance porcelain, ceramic or the like and, if desired, be provided with conducting coatings. The portion of the tank enclosing the anode chamber is preferably curved in the neighborhood of the anode head so as to conform therewith. It may be, for instance, designed in the form of a sphere. Conducting surfaces or coatings concentrically arranged, screens disposed outside the tank portion enclosing the anode chamber and/or grid bodies disposed inside the tank portion enclosing the anode chamber may be allotted to the anodes. The conductive parts lying inside and/or outside the tank portion enclosing the anode chamber may be designed as control bodies and be impressed with graded potentials. It is preferable to arrange the control bodies in the surfaces of the screen or to dispose them in such a manner as to form extensions thereof. The electrodes and, if desired, also the conducting surfaces are preferably designed as sphere-plate, concentrical sphere or the like. The conducting surfaces, for instance, also the control bodies may form at the same time cooling surfaces. To this end, the cooling surfaces may be under the influence of cooling agents.

Since both above-mentioned discharge charnbers are arranged in spaced relation the advantage is obtained in that it is possible to attain maximum voltages, particularly when employing approximately the most simple electrode arrangements and forms (plates arranged in parallel relation, sphere-sphere, sphere-plate or concentric cylinders). In this case, the field distribution may be so influenced by outside means as is required for the high voltages and is most favorable for the corresponding operating conditions. The electrode surfaces, particularly the anode surfaces, are as far as possible concentrically arranged with respect to screens which extend to the space parts to be homogenized. The electrode surfaces and the screens are preferably designed as concentric spherical surfaces and the control or neutralization bodies placed in the space parts to be homogenized are so arranged that they lie in the surfaces of the screen (spherical surfaces) serving to effect the homogenization. Besides, in the novel high-voltage discharge apparatus all high-tension bushings are dispensed with, which from an electrical and economical point of View presents a further great advantage. Furthermore, the difliculties present in the known apparatus owing to the mutual inuence of the anodes are removed. This influence does not only entail the disturbances of the fields lying in the neighborhood of the anodes but also very high local eld intensities which lead to lateral discharges such as, for instance, leakage discharges or the like. In multiphase discharge apparatus as a matter of fact not only an electric eld is present between the anode and the cathode but also a mutual influence of the anodes takes place which in accordance with the multiphase cycle are impressed with differently high voltages. The cross fields deflect particularly the charge carriers in the discharge path so that the insulating material may be even punctured. These difficulties are overcome according to the invention by designing the abovementioned shield plates, surrounding the anode chambers and serving to control the cross and longitudinal elds, in such a manner that the shield plates in the form of bell-like bodies having a predetermined potential, for instance cathode potential, allot a well-defined cross field to each anode and thus prevent a mutual influence.

In controllable discharge apparatus in which control grids and deionizing grids are arranged in a shield the above phenomena impair the controllability. The reliability and accuracy of the control leave in many cases so much to be desired that they do not correspond to the present daypractice. Endeavors have been made to remove these difliculties by alloting to the anodes which were located in the inner space of the discharge apparatus, several concentrical shields, the openings of which facing the cathode were, if desired, provided with grids. But also apparatus designed in such a manner proved to be disadvantageous in that the heating of the electrode chamber caused by the arc led to overheatings. The dissipation of heat from the anode parts in such arrangements'is very deficient, insofar as the heat is rather stored up than dissipated, since the heat is retained by the shields surrounding the anodes. v

In the accompanying drawings some embodiments of my invention are shown in diagrammatic form.

Fig. l is a vertical sectional view of a multiphase high power mercury vapor discharge apparatus.

Fig. 2 is an enlarged vertical sectional view of an anode part of a steel tank discharge apparatus.

Fig. 3 illustrates diagrammatically how the anodes of a six-phase discharge apparatus may be mutually influenced.

Figs. 4, and 6 show modified forms of the anodes and the anode parts.

In Fig. l, i denotes the steel tank of the discharge apparatus. The insulated cathode 2 is arranged at the bottom of the tank l and the anodes 3 on the top thereof. The anodes 3 are arranged in a spherical chamber which forms the closed end of the shield 4 designed as arm. The chamber 3 either forms the anode or encloses, if desired, concentrically an anode, the center of which is the center of the spherical anode arm part and of the screens 5 and 6. The screens 5 and 6 serve to influence th fields surrounding the anode.

, According to Fig. 2 the anode tube 'l designed as arm consists of insulating material and enters the tank El as indicated at 8 at which point it is provided with a vacuum-tight joint. The tank 9 has cathode potential. The closed end of the tube 'I has also a spherical shape and, if desired, a metallic coating and encloses a spherical anode I0, the center of which is the center of the spherical anode arm` end and of the likewise spherical screens Il, I2 and I3. The upper sides of the grid bodies I4, I and I6 which are either insulatedly embedded in the anode tube 'I or, when impressed with a voltage, may be designed as control members are adjacent to the curved surfaces of the screens Il, I2 and I3.

As will be apparent from Fig. 3 each anode I1, I8, I9, 25, 2l and 22 is under the influence of the five adjacent anodes. This influence may as above-mentioned be of such nature that serious disturbances may occur in the operation of the discharge apparatus. 'I'hese disturbances are practically prevented from occurring by the use of the screens and globes surrounding the anodes, if desired concentrically.

As will be seen from Fig. 4 theanode 23 may also be arranged eccentrically within the closed spherical anode tube end 24. According to these embodiments it is preferable to arrange the screens 25, 2li, 21 in such a manner that the front surface of the spherical anode 23 Contacts with the spherical surface of the screen 25. A metallic cap 29 having a beaded edge 30 may be directly placed over the anode arm end 28 as shown in Fig. 5.

In the modification shown in Fig. 6 the anode 3l eccentrically arranged in the screen 32 has a beaded edge.

I claim as my invention:

1. A high voltage vapor electric device comprising a metallic chamber enclosing the cathode, a plurality of anode tubes connected to said chamber, said tubes being composed of insulating material, an anode in each of said tubes adjacent the outer extremity thereof, a plurality of conducting shields respectively secured to said anode tubes external to said device, said shields being substantially spherical sectors so as to control the electric eld between said anode and said cham- 1 ber and the field between said anodes.

2. A high voltage vapor electric device comprising a metallic chamber enclosing the cathode, a plurality of anode tubes connected to said chamber, said tubes being composed of insulating "g material, an anode in each of said tubes adjacent the outer extremity thereof, a plurality of conducting shields respectively secured to said anode tubes external of said chamber and said tubes, said shields being curved so that all points on said shield are substantially equidistant from said anode so as to control the electric field between said anode and said chamber and the field between said anodes, and grids in said anode tubes,

said grids being shaped to form a continuation of the shield surface.

3. A high voltage vapor electric device comprising a metallic chamber enclosing the cath- 0de, a plurality of anode tubes connected to said chamber, said tubes being composed of insulating material, an anode in each of said tubes adjacent the outer extremity thereof, a plurality of conducting shields respectively secured to said anode tubes exterior of said chamber, said shields being substantially semispherical in shape and concentric with respect to said anode so as to control the stress field applied to said anode.

4. A vapor-electric-device comprising a metallic chamber enclosing the cathode space, a plurality of substantially tubular arms secured in vacuum tight relation to openings in said chamber, said arms being composed of vacuum tight insulating material, said arms ending in a substantially spherical anode chamber, and anode in each of said anode chambers, a cathode in said cathode chamber, a plurality of substantially semi-spherical conducting shields secured to the outside of said tubular arms exterior to said cathode chamber and said anode chamber, said shields being intermediate the anode chamber and the cathode chamber.

5. A vapor-electric-device comprising a metallic chamber enclosing the cathode space, a plurality of substantially tubular arms secured in vacuum tight relation to openings in said chamber, said arms being composed of Vacuum tight insulating material, each of said arms ending in a substantially spherical anode chamber, an anode in each of said anode chambers, a cathode in said cathode chamber, a plurality of curved conducting shields secured to the outside of each of said tubular arms intermediate the anode chamber and said cathode chamber, said shields being exterior of said anode chamber and said cathode chamber, and grids in said arms forming a continuation of said shields.

6. A vapor-electric device comprising a metallic chamber enclosing a cathode space, an anode chamber enclosing a single anode space, a plurality of conducting shields of substantially spherical section secured to said anode chamber between said anode and said cathode chamber and exterior to said cathode chamber, for controlling the potential gradient between the anode and the metallic cathode chamber.

7. A vapor-electric device comprising a metallic cathode chamber enclosing a cathode space, a plurality of anode chambers opening into said cathode chamber, each anode chamber enclosing a single anode space, a plurality of individual conducting shields secured to the outside of each of the anode chambers between the anode and the metallic cathode chamber and exterior to the cathode chamber for controlling the potential gradient between the anode and the metallic cathode chamber, said conducting shields being semi-spherical bodies concentric with the anodes.

ALFRED SIEMENS.

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