US2479853A - Current converter - Google Patents

Description

Aug. 23, 1949. M. MEUNIER CURRENT CONVERTER Filed Nov. 15, 1946 Q Inventor Marcel Meunier Patented Aug. 23, 1949 CURRENT CONVERTER Marcel Meunier, Cuesmes, Belgium, assignor to Ateliers de Constructions Electriques de Charleroi, Brussels, Belgium,

anonyme a Belgian socit Application November 13, 1946, Serial No. 709,582 In France December 17, 1945 7 Claims.

This invention relates to gas or vapor filled current converters and in particular to mercury vapor rectifiers or converters having metallic tanks.

In current rectifiers or converters of the monoanodic type, it is desirable, by a judicious arrangement of the electrodes, to provide as short as possible a discharge path, so that the voltage drop in the corresponding arc shall have a very low Value.

It has already been proposed for this purpose to arrange the anode and cathode in one and the same compartment, as close as possible to one another. In particular, in monoanodic converters having metallic tanks, it is possible to place the anode and cathode on the same vertical axis, at a relatively small distance from one another. In this way the length of the discharge space or path is diminished to the maximum extent; there is therefore obtained a specially low value of the voltage drop in the arc.

However, and mainly in the case of monoanodic mercury vapor rectifiers or converters having a liquid cathode, both in those having permanent excitation and in those with periodic ignition, this arrangement has the grave drawback of provoking numerous failures of the valve effect of the converter, in the shape of back fires, even under low voltage.

In fact, the anode, by its arrangement immediately in the vicinity of the cathode, is subjected directly to the bombardment of the electrons emitted freely by the cathode spot as well as to the projection of mercury vapor originating from the cathode, these two phenomena being the root cause of the back fires.

In order to ensure satisfactory operation of monoanodic converters, it has been found desirable to arrange between the anode and cathode deviating screens of which the shape and position allow of withdrawing the anode from the electronic radiation of the cathode spot and from the projection of mercury vapor from the cathode. These screens, however, become the path of the discharge and possess the drawback of lengthening the discharge space. This results in a corresponding increase in the value of the voltage drop in the are.

More particularly when the monoanodic converter has to include a control grid, the above drawback is further intensified. In fact, the deviating screens of the discharge space cannot function as control grid, having regard to their wide opening relative to the passage of the arc. Similarly, the control grid placed immediately in proximity to the anode cannot play the part of deviating screens, having regard to the imperfect protection which it furnishes to the anode. Moreover, it would itself be exposed directly to the electronic radiation and to the projection of vapor. It is therefore necessary to provide for the simultaneous presence of deviating screens, between anode and cathode, and of the control grid. The anticipated benefit of the low value of the voltage drop in the are, due to the fundamental arrangement of the monoanodic converter, is therefore lost in part in the control grid and in the deviating screens.

The present invention has for its main object to provide an improved arrangement for current converters, with gas or vapor filling and with liquid cathode, in particular mercury vapor current rectifiers or converters, of the monoanodic type, both with permanent excitation and with periodic ignition, which allows, while ensuring an efi'icacious protection of the converter operation against back fires, of obtaining a very low value of the voltage drop in the arc. 7

Another object of the invention is to provide an improved arrangement of a monoanodic rectifier or converter having a metallic tank, utilizing a circular anode shaped as a crown or annulus, with the object of eliminating the aboveindicated drawbacks of monoanodic rectifiers or converters of the usual construction, while ensuring a low value of the voltage drop in the arc.

A further object of the present invention is to provide a monoanodic rectifier or converter in which the cathode and anode are disposed on the same vertical axis in one and the same metallic tank, the anode being in the shape of a circular crown or annulus and therefore surrounding the central vertical cylinder delimited by the cathode.

The improved rectifier or converter is further characterized in that the crown-shaped anode is contained in a circular chamber likewise closed on all sides and open only towards the interior of the converter tank. This open portion of the chamber containing the anode is closed by a series of screens such as, for example, in Fig. 1, which have for object to protect the anode against electronic radiation from the cathode spot and against projection of mercury vapor from the cathode. There can be employed for this purpose any kind of screens adapted to fulfil this role.

A still further object of the invention is to provide a rectifier or converter in which the closed chamber containing the crown-shaped anode is freely suspended from the converter cover and is itself contained in the interior of the tank, thus leaving between it and the tank wall a 4 ments, the main advantage that, in spite of the small distance which separates the anode a from the cathode 70, there is only a single member g disposed in the discharge space and playing at pace allowing fr e passage of the mercury 5 the same time the part of protective screen ensed upon heiatera wa f t e tank, back against-electronic radiation from the cathode towards the cathode. spot andagainst the projection of mercury vapor The invention is hereinafter described wi from the cathode, and also the part of control reference to the accompanying drawing repregrid senting by way of indication and not oflimita- Itwill be readily understood that, beside obtion an example of construction of a monoanodic taming a hot and uncooled anode chamber farectifier or converter accord tot e invention "vorable-to satisfactory operation of the converter, In this drawing, wherein all detail not indis- -the inventionnlocates the anode a in immediate pensable to the clear understanding of the invenproximity to the cathode is. The length of the tion has been voluntarily neglect d Figs. 1 and discharge space or path is therefore very small 2 represent respectively an elevation and a half '1. and thet-coresponding value of the voltage drop plan, in section on the line AB of F 1, of a the arcis not materially increased. monoanodic converter in accordance with the in- The latter is therefore maintained at a low vention. value and the fundamental advantage of the V Asshown in the drawing, the converter is conmonoanodic converter is thus secured more comstituted by '"ametallic tank 0 having a cover a, pletely. :the' tank beingcooled for example by iron or On the other hand, thisarrangement of monocopper fins r exposed to an air blast; the tank anodicconverterwithcrown-shaped anode precarries at its lower part a container k for the sents the great advantage that the mercury con- ,'liquid 'cathod it; this container being insulated 5 densed upon' the cold lateral walls of the metallic *"from therbase of the tank at n and the active tank a can return'freely to the cathode without surfaceof the-cathode being limited by a quartz being -exposed'--directly to-the action of the dis- ;ring q resting 0n-the'bottom of the container lc'. charge." In fact, the' closed chamber containing Thegconverteris provided with a crown-shaped the crown-shaped anode a affords between its "anode-a consisting ofxa continuous ring enclosed external cylindrical wall and the internal wall in a chamberh likewise of annular shape. The of the metallictank, an annular space which alannular chamber h is freely'suspended from the lows the passage of the droplets of condensed tank cover a by'means of three metal tubes w, w, mercury. These latter,"returning to the cathode, the upper ends of these tubes being fixed to rings are shielded from the action of the discharge, y, y restingv upon tubular insulators m, m. The thus preventing the formation of excess pressure annular anode a is likewise suspended by means of mercury vapor due to the volatilization of of three conductor rods 11, v, concentric with the mercury dripping back suddenly .into the hot tubes w, w, the upper ends of these rods being zone Of'th'e discharge.

, screwed into discs 1:, x resting upon tubular in- What Iclaim is:

"sulators l', Z,1,above the rings y, y. The three 40 1. ma currentconvertercomprising a cathode discs :r,.a:' are connected to th current supply by and a singleanode' enclosed in one and the same {means of a common ring b, and one of the rings container; an anode arranged in the form of a y, y is connected to a source of grid potential by circular crownabove and coaxial with said cath- .means of a binding screw d. Thus the insulaode, in combination with a chamber containing tion of the anode chamber h is provided at m, m, said anode, said 'chamberbeing closed on all sides, the anode a. being further insulated at Z, Z, and and'screeningmeans'forming the closure on the the cathode is is'insulatedfrom the tank base by inner side of"said"chamber,said screening means insulation n. I being adapted to'protect' said anode against radi- The annular or crown shaped anode a is pro ation and projectionfrom said cathode. tected as regards the direct electronic radiation 2. In acurrent'converter comprising a cathand the projections of mercury vapor from the ode and a single anode enclosed in a metallic 'j' cathode is by screens 9. which form the internal tank, an anode'arranged in the form of a circuwall of the anode chamber h, the top and botlar crown above and coaxial with said cathode, in tom of this chamber and its external wall 2' being combination with an inner chamber containing imperforate. In the present instance, where said anode, said chamber being open only towards these screens g are required to perform the ofiice the interior of said tank anda series of screens of control grid, it is necessary to insulate them .closing' the" open portion of said chamber, said (and, in the construction illustrated, the whole "screens being adapted to' protect said anode anode chamber h) in relation to the container against radiation and projection from said cathcover a, such insulation being efiected in imme-. ode. diate proximity to the latter by the insulators m, 3; In a current converter comprising a cathm', so that the tubes w, w supporting the anode ode and a single anode enclosed in a metallic chamber 71. can be raised to the potential of the tank, an anodearranged in the form of a circuscreens 9 performing the oilice of control grid. larcrovvn above and-coaxial with said cathode, Suitable known means can b utilized in ord in combination with an inner chamber containto obviate too great inactive surface of this con- 7 ing said' anode, said chamber being suspended trol grid; in particular, a covering with insulafrom-the top of said tank'and spaced from its tion having an enamel base may be provided for p p al wall by a distance suificient for free any metallic part which is not intended to act passage of condensation liquid on the inner surdirectly upon the discharge space. The are path face of said wall.

- is shown in dotted lines in Fig. 1, extending up 4. A current-converter comprising a cathode from the cathode R: to pass through slots in the e and a single anode enclosed in one and the same screensg and thus reach the anode a. container, a closed inner chamber for said an- This-novel arrangement of monoanodic conode,-and a'series of screens'forming the closure '--verter-presents, inrelation tothe usual arrange- 'for'saidcham'ber towards the'int'erior of said container, said chamber being insulated electrically from the remainder of said converter and being raised to a suitable potential for said screens to function as a control grid for said anode.

5. A current converter comprising a cathode and a single anode enclosed in a metallic tank includin a cover, a closed inner chamber for said anode, said chamber being suspended from said cover, and a series of screens forming the closure for said chamber towards the interior of said tank, said cover being insulated electrically from the remainder of said tank, and said cover and chamber being raised to a suitable potential for said screens to function as a control grid for said anode.

6. A mercury vapor rectifier comprising a mercury cathode and a single anode enclosed in a metallic tank, a closed inner chamber for said anode, said anode and chamber being of annular shape and surrounding a vertical cylindrical space above and coaxial with said cathode, and a series of screens forming the closure for said chamber towards said cylindrical space.

MARCEL MEUNIER.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Country Date Germany Jan. 7, 1913 Number

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