US2221615A

US2221615A - Single anode hg arc rectifier

Info

Publication number: US2221615A
Application number: US283471A
Authority: US
Inventors: Slepian Joseph
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1939-07-08
Filing date: 1939-07-08
Publication date: 1940-11-12
Anticipated expiration: 1957-11-12

Description

Nov" 12 1940' J. @LEMAN ZJZZ'LE SINGLE ANODE HG ARC RECTFIER wlTNEssEs; M3' INVENTOR M, Jse/D/Q Sig/Diaz?. l BY W 5 K m/ 1l 2 l 9 e N 1 e w .fw Nvu .R 2 h E O s V 2, N .U 2 0/ d A e m e s S 2 .0. J 7 m I fw w @7W W9 M9 N l C n EGW LH u @QEJ md m JN e Al l F E m 5 N I s 7 ,4

Patented Nov. l2, 1940 UNITED STATES lPATENT OFFICE SINGLE ANODE HGARC RECTIFIEB vania Application July 8, 1939, Serial No. 283,471

11 Claims. (Cl. F75-354i My invention relates to electric y discharge valves and has particular relation to electric discharge devices of the pool type.

In pool electric discharge valves of certain 5 types, a continuous condition of ionization is maintained by a keep-alive discharge. The discharge passes between the pool which functions as the cathode of the valve and a keep-alive electrode disposed adjacent to the cathode. The in- 1u tensity of the keep-alive discharge governs the ionization within the valve and, therefore, fletermines the facility with which an are is ignited between the anode and the cathode.

Because of the ionization maintained in the valve by the keep-alive discharge, the possibility of frequent backfire is considerably increased. To suppress the tendency to backfire, the discharge valve is customarily provided with shields which are disposed. adjacent to the anode. The electrostatic eiect proclucerl my the shields decreases the number of hacklres, lout the same time, it also increases the catho'e reluctance of the valve and the valve often fails to lire in the forward direction when it should. An increase in the keep-alive discharge ciment suppresses the failure to fire in 'the forward. clirection, but it enhances the tendency to ham i'ire. Additional shielding which decreases tendency to hmkre again increases the uncertainty of the firing in the orwarc direction. The advantages ci shielding and increasing the keepalive discharge are thus counteractecl comitant disadvantages so that e. satis'actory valve cannot be attained ley mere-hf relying en the improvements introduced hy chang-i1 g these features.

lt is, accordingly, an object of my invention to provide a discharge valve of 'the keep-alive type in which there shall he no uncertainty 40 the firing oi the forward arc while the tendency to backfire shall be soppresse Another object of my invention is to provide an electric discharge valve oi the keep-alive type, having sufficient shielding to prevent hach'ire, that shall, without fail, re in the torwarol clirection when expected to do so.

An ancillary object of my invention is to provide an arrangement for maintaining a discharge in an electric discharge valve of the keep-alive type in which the power consumed in the keepalive circuit shall be a minimum.

More concisely stated, it is an object of my invention to provide a keep-alive circuit lor an electric discharge valve that shall assure the proper ignition of a main arc in the valve.

In accordance with my invention, the current flow through the keep-alive discharge is responsive to the potential impressed between the anode and the cathode of the valve. The relationship between the keep-alive current and the anode-cathode potential is such that the keepalive current is increased when the forward iiring is to take place and decreased when backiire may occur.

The novel features that I consider characteristie of my invention are set iorth with particulai-ity in the appended claims. The invention itself, however, hoth as to its organization and its method of operation, together with additional objects and advantages thereof, will best be untierstcocl from the following description 01"' the specific embodiments when read in connection the accompanying drawings, in which: i gui'e l is a diagrammatic view showing a preferred embodiment of my invention,

2 diagrammatic view showing modifications of my invention, and

3 a diagrammatic view showing the structure the tube of Figs. l and 2 in larger e apparatus shown in Fig. l

.'i comprises an ric discharge valve through which a load general is supplied from alter- The line con-- electors l may energized from the usual com- G -cycle generator (not shown) large valve il comprises a hol- Q of steel o1' other suitable le lower which a metallic plate f" in such manner that the joint between the plete ano. the cylinder is gas-tight. pool bly ol mercury, rests on the tions as the cathode of the valve, l meta -c ring [l5 is securely fastened to the :lange lll the cylinder. on. a robber gasket l@ and when the bolts 2l securing the ag 'to the flange are tightened, the junction region between the ll and the ring it is gas-tight. An elongated porceelec lain sleeve 23 passes through the opening in g the ring l and extends well within the cylinoler t. The sleeve is provided with a shoulder t5 near its central portion and is supported on a flanged annular bracket 2l which is L-olted to the ring and. on the central portion ci which the shoulder rests.. The ring has an inner shoulder 2Q which tightly abuts the upper surtace of the central shoulder 25 on the sleeve 23 with a gasket 3l of rubber or other suitable material interposed between the two surfaces.

The ring rests g 10 sleeve.

2 y anuncis Near its center the ring I3 has a groove 33 in which the flange 3l of a metallic sleeve 31 soldered to the porcelain sleeve 23 engages. The metallic sleeve 31 is soldered to the ring I3 with- 3 in the groove 33.

The anode stem 33 which is in the form of a metallic rod to the end of' which the anode 4| is secured, passes through the porcelain sleeve 23 and extends into the cylinder 3 below the The upper end 43 of the stem 39 is threaded and a plurality of terminal washers 43 for clamping the anode supply lead are in engagement with the thread. Below the upper threaded portion 43 there is a threaded region l5 41 of increased diameter. A flanged nut 49 is screwed on the latter thread 41 in such manner that its flange 3|, which is turned over, engages the upper rim of the porcelain sleeve 23. Below the threaded portion 41 the stem 33 has a shoulder 33 which abuts a gasket 33 disposed on the upper end of the insulator 23. The nut 49 is tightly screwed on the stem and the Junction between the flange 3| and the insulator 23 is soldered so that the joint is completely gas-tight.

To further seal the arrangement, the stem 39 is provided with another shoulder 31 below the one adjacent to the thread 41. The latter tightly engages an inwardly extending shoulder 39 of the insulator 23 and a gasket 3| is interposed between the two.

'Ihe anode shield 33 is of composite structure. It comprises a hollow metal cylinder 33 from the lower rim of which a metallic screenv 31 in the form of a segment of a sphere is suspended. The

35 segment 31 screens the lower surface of the anode 4| entirely from the mercury I3. A short cylinder 39 of metal is welded along the upper end of the first cylinder 35, and to the former a metal ring 1I in the form oi' an open truncated cone is 43 welded. The two cylinders 33 and 69 are welded at their upper ends to a flanged ring 13. The ring 13 is provided with a short central portion 13 which is round along the inner edge and extends downwardly to `engage a trough-shaped 45 shoulder. 11 near the lower end of the insulating sleeve 23. A spring washer 19 is disposed between the upper rim of the flanged ring 13 and a downwardly extending shoulder 3| on the insulator 23 and holds the shield 33 firmly in engagement with the insulator. The inner cylinder 33 of the shield 33 extends to a point just below the lower end of the insulator 23 and the truncated conical ring 1I is disposed between the insulator 23 and the upper rim of the anode 4|.

Near its lower end, the enclosing cylinder 9 is provided with an opening from which a sl'ort flanged cylindrical stem 33 extends. The stem 33 may be integral with the cylinder 9 or may be welded or soldered thereto. A flanged porcelain tube 33 is bolted tightly between the flange 31 of the stem 33 and a disc 39 parallel to the flange. The outer surface of the flange 31 and the inner surface of the disc 39 are grooved and the flange 9| of the tube 33 is disposed in the grooves with 55 rubber gaskets 93 interposed on each side between the porcelain and the adjacent surface. 'I'he central portion 93 of the tube 33 extends for a short distance along the stem 33.

A metallic rod 91 which is bent over at right 0 angles at its free end and carries a graphite tip 99 extends horizontally from the disc-39. The rod 91 is insulated from the stem 33 by the flanged porcelain cylinder 33. It is protected against the discharge heat and the mercury vapor by a sleeve 73 |3| of quartz which extends from the disc 39 t0 the tip33. Thetip33isonlyashortdistance abovethe mercury I3 andarod |33 ofboron carbide, silicon carbide, or a similar substance is secured to the graphite tip 33 and dips into the mercury. The rod |33 functions as a make-alive 3 electrode and the tip 39 as a keep-alive electrode. When sufficient current flows through the rod |33, a discharge ls ignited between the tip 99 and the mercury I3. The discharge short-circuits the current flow through the rod |33 and if it is enerl0 gized from a direct current source, it continues to supply ions for the main discharge in the valve 3.

The valve 3 may be completely sealed of! against the outside atmosphere. In many cases, it is l5 maintained evacuated by a pump system which is in communication with the interior of the valve. The make-alive electrode need not, of course, be a rod |33 as described hereinabove.

It may be of any type now well know in the art; 20 i'or example, a magnetically operated plunger which producesmercury spray in the region of the keep-alive electrode 99 may be used.

The make-alive current is supplied and the keep-alive discharge is sustained from a full-wave 25 rectier |33 energized from the main line conductors 1. 'I'he positive terminal |31 of the rectifier is connected to the disc 39 through a suitable current limiting resistor |39 and its negative terminal ||I is connected to the lower plate I| 30 on which the mercury pool I3 is disposed. Normally, the make-alive discharge current is maintained at a value such as to preclude the possibility of backfire between the anode 4| and the cathode I3. Discharge current of this magnitude 35 is, however, not suflicient to, at all times, assure the ignition of a forward arc. In accordance with my invention, the discharge is enhanced from the main line conductors 1 when the polarity of the anode-cathode potential is proper for ignition. 40

The increase in the keep-alive discharge current is attained by connecting a half-wave rectifier I|3 of any suitable type between the anode 4| and the keep-alive electrode 99. The anode I|3 of the rectifier is connected to the anode 4| 45 of the main valve and the cathode II1 to the keep-alive electrode. When the anode-cathode potential impressed on the valve 3 is negative, the current flowing in the keep-alive discharge is supplied only through the full-wave rectifier 50 |33 and, therefore, is relatively small. Under such circumstances, backfire does not occur. When the anode-cathode potential of the main discharge valve I3 becomes positive, current first flows through the half-wave rectifier I I3 and be- 33 tween the keep-alive electrode 99 and the cathode I3. 'I'he keep-alive discharge current is thus increased to a sufllcient value to assure the ignition of a forward discharge. When the forward arc is ignited, the current flow through the 30 rectifier ||3 is materially reduced because the potential drop across the main discharge is relatively small.

The half-wave rectier I|3 may be of any general type. Where the additional current required 63 is not excessive, a dry rectifier or a high-vacuum rectifier may be used. Where the additional keep-alive current is relatively large, the rectifier should be of the arc-like type.

In the modification shown in Fig. 2, the increase in keep-alive current is produced by short-circuiting a portion ||9 of the resistor |39 in the keepalive circuit at the instant when the polarity of the anode-cathode potential is proper for ignition. An auxiliary electric discharge valve |2| of the 73 type having a control electrode |22 is connected across the portion ||9 of the resistor |09 which is to be short-circuited. The anode |23 oi' the auxiliary valve 2| is connected to the positive terminal |01 of the full wave rectifier |05 and its cathode |24 to an intermediate tap |25 of the resistor |09. A voltage divider |28 of relatively high resistance is connected between the'anode 4| and cathode |3 of the main discharge valve 3. The control electrode |23 of the auxiliary discharge device is connected to the intermediate tap |21 of the voltage divider. Where the auxiliary valve is of the arc-like type as is, in general, the case, it is desirable that the anodecathode potential supplied thereto shall fall to zero periodically. For this reason, the filter |29 utilized in connection with a full-wave rectiiler |05 is interposed between the keep-alive electrode 99 and the resistor 09 and not between the rectier |05 and the resistor |09 as in the Fig. 1 system.

The anode-cathode potential which is normally impressed on the auxiliary discharge valve |2| is the potential drop across the portion ||9 of the current limiting resistor |09Which arises by reason of the keep-alive current now produced by the rectifier |05. The potential impressed between tne control electrode |22 and the cathode |24 of the auxiliary valve consists of a negative component produced by the potential drop across the portion of the resistor |09 between the intermediate tap |25 and the keep-alive electrode f 99 and a component of changing polarity impressed by the portion of the voltage divider |26 between the cathode |3 of the main valve 3 and the tap 21 to which the control electrode |22 is connected. When the anode-cathode potential impressed on the main valve 3 is negative, its

. cathode I3 is at a positive polarity relative to its anode 4| and the keep-alive electrode 99 is, therefore, more positive than the intermediate tap |21 of the divider |26. The potential impressed between the control electrode |22 and the cathode |24 of the auxiliary valve |2| from the divider |26 is, therefore, at this time, negative and the auxiliary valve is non-conductive. When the anode-cathode potential impressed on the main valve 3 becomes positive, the potential supplied by the voltage divider reverses in polarity and the auxiliary valve |2| becomes conductive and short-circuits the portion 9 of the current limiting resistor |09 so that the additional current is supplied in the keep-alive circuit. The auxiliary valve is rendered non-conductive at the end of every half-cycle during which it conducts current because its anode-cathode potential falls to zero. 'g

Although I have shown and described certain specic embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination, an electric discharge valve having a cathode of the pool type, a keep-alive electrode cooperative with said cathode and a charge-collecting electrode, means for continuously maintaining current flow of a substantial magnitude between said keep-alive electrode and said cathode, means for impressing a potential between said charge-collecting electrode and cathode and means responsive to said potential for varying the current flow between said keepalive electrode and said cathode.

2. In combination, an electric discharge valve having a cathode of the pool type, a keep-alive electrode cooperative with said cathode and a charge-collecting electrode, means for continuously maintaining current flow of a substantialmagnitude between said keep-alive electrode and said cathode, means for impressing a potential between said charge-collecting electrode and cathode and means responsive to said potential for increasing the current flow between said keep-alive electrode and said cathode to a magnitudesuch as to expedite ignition of an arc between said collecting electrode and said cathode when said potential attains the proper magnitude for the ignition of such an arc.

3. In combination an electric discharge valve having a cathode of the pool type, a keep-alive electrode cooperative with said cathode and a charge-collecting electrode, means for continuously maintaining current flow of a substantial magnitude between said keep-alive electrode and said cathode, means for impressing alternating potential. between said charge-collecting electrode and cathode and means responsive to said potential for increasing the current flow between said keep-alive electrode and said cathode to a magnitude such as to expedite ignition of an arc between said collecting electrode and said cathode when said potential attains the proper polarity forthe ignition of such an arc.

4. In combination an electric discharge valve having a cathode of the pool type, a keep-alive electrode cooperative with said cathode, a chargecollecting electrode, and shielding means cooperative with said collecting electrode for preventing inverse current between said collecting electrode and' said cathode, means for continu,

ously maintaining current flow of a substantial magnitude between said'keep-alive electrode and said cathode, said shielding means functioning to decrease the tendency to ignite an arc between said collecting electrode and cathode for agiven keep-alive current, means for impressing a potential kbetween said charge collecting electrode and cathode and means responsive to said potential for increasing the current iiow between said keep-alive electrode and said cathode to a magnitude such as to expedite ignition of an arc between said collecting electrode and said cathode when said potential attains the proper magnitude for the ignition of such an arc.

5. In combination, an electric'discharge valve having a cathode of the pool type, a keep-alive electrode cooperative with said cathode, a chargecollecting electrode and shielding means cooperative with said collecting electrode for preventing inverse current flow between said collecting electrode and said cathode, means for continuously maintaining current flow oi' a substantial magnitude between said keep-alive electrode and said cathode, means for impressing a potential between said charge-collecting electrode and cathode, said shielding means functioning to decrease the tendency to ignite an arc between said collecting electrode and said cathode for a given potential when the keep-alive current has a predetermined magnitude, and means responsive to said potential for compensating for said decrease in the tendency to ignite an are.

6. In combination, an electric discharge valve having a cathode of the pool type, a keep-alive electrode cooperative with said cathode, a charge collecting electrode and shielding means cooperative with said collecting electrode for preventing inverse current ilow between said collecting electrode and said cathode, means ior continuously maintaining current ow oi a substantial magnitude between said keep-alive electrode and said cathode, means for impressing a potential between said charge-collecting electrode and cathode, said shielding means functioning to decrease the tendency to ignite an arc between said collecting electrode and said cathode for a given potential when the keepalive current has a predetermined magnitude, and means responsive to said potential for increasing the keep-alive current flow to compensate for said decrease in the tendency to ignite an arc.

7. In combination an electric discharge valve having a cathode o! the pool type, a keep-alive electrode cooperative with said cathode and a charge-collecting electrode, means for continuously maintaining current ilow of a substantial magnitude between said keep-alive electrode and said cathode, means for impressing a potential between said charge-collecting electrode and cathode, and auxiliary electric discharge valve means interposed between said collecting electrode and said make-alive electrode for varying the current ilow between said keep-alive electrode and said cathode.

8. In combination, an electric discharge valve having a cathode of the pool type,- a keep-alive electrode cooperative with said cathode and a charge-collecting electrode, means for maintaining current ilow of a predetermined magnitude between said keep-alive electrode and said cathode, means for impressing a potential between said charge-collecting electrode and cathode, and current rectiiying means interposed between said collecting electrode and said make-alive elec-y trode, in such a manner as to conduct current in the same direction as the normal current now between said anode and cathode, i'or varying the current ow between said keep-alive electrode and said cathode.

9. In combination. an electric discharge valve having a cathode o! the pool type. a keep-alive electrode cooperative with said cathode, a chargecollecting electrode and shielding means cooperative with said collecting electrode for preventing inverse current tlow between said oollecting electrode and said cathode. means for maintaining current ilow of a predetermined magnitude between said keep-alive electrode and said cathode, means for impressing a potential between -said charge-collecting electrode and cathode, said shielding means functioning to decrease the tendency to ignite an arc between said collecting electrode and said cathode for a given potential when the keep-alive current has a predetermined magnitude, and means including a rectiiier having an anode connected to said collecting-electrode and a cathode connected to said keep-alive electrode for compensating for said decrease in the tendency to ignite.

10. In combination, an electric discharge valve having a cathode of the pool type, a keep-alive electrode cooperative with said cathode, a chargecollecting electrode and shielding means cooperative .with said collecting electrode for pre,

venting inverse current now between said collecting electrode and said cathode, means ior continuously maintaining current ilow of a substantial magnitude between said keep-alive electrode and said cathode, means, for impressing alternating potential between said charge-collecting electrode and cathode, said shielding means functioning to decrease the tendency to ignite an arc between said collecting electrode and said cathode i'or a given potential when the keep-alive current has a predetermined magnitude, and means responsive to said potential for compensating for said decrease in the tendency to ignite an arc.

11. In an electric discharge valve having a cathode o! the pool type. a keep-alive electrode and means for transmitting through said electrode current varying periodically between a maximum value and a maximum value which is substantially greater than zero.

JOSEPH SLEPIAN.