US2379620A - Mercury vapor discharge device - Google Patents

Description

July 3, 1945.

A. F. BOWLES ETA L MERCURY VAPOR DISCHARGE DEVICE Filed March 12, 1942 abcdefgh'hgfed 'INVENTORS HARRY M. LIPSIUS BAYLBYERT FRANK BOW\ ES 1L; ATTORNEY Patented July 3, 1945 I MERCURY VAPOR DISCHARGE DEVICE 7 Albert Frank Bowles and Harry M. Lipsius,

Philadelphia, Pa.

" Application March 12, 1942, Serial No. 434,934

4 Claims. (01. 250-215) The present invention relates to mercury vapor discharge devices and, more particularly, to a mercury arc rectifier provided with novel ignition means.

One object of our invention is to provide a mercury vapor arc rectifier of high ambient current, temperature maintained through an electron flow from electrodes to vapor and vapor to electrodes through -a primary ionization of the mercury vapor when the starting switch is thrown to the on position and maintained constantly until the operating switch or circuit breaker is thrownto the off position. Since it is well known that mercury vapor will not carry an electric current unless ionized, we have provided auxiliary mercury pools with a special wiring system as well as an electron filament at the top of the rectifier tube Whereby the mercury in the auxiliary pools are first vaporized and while in the vapor phase the electron fiow between the filaments and s'pecialheater elements bombard the mercury vapor and produce a high state of ionization andthereby produces a current flow between the anode elements of the rectifier and the cathode element supplyizer and starting electrodes. operated at 5Q"'C. and 96 percent transformer efiiciencyr' Table I :Dist'ance Potential drop across the I OVEN-11,; between potent al electrodes Anode Cathode Spark-gap I 55 2. O 3. O 2. O i 7. (l a .It willbe observed" that the potential loss tween electrodes and spark gap is'controllable 'by means of the adjustable 'anode's and themain mercury pool to an overall potential loss of less :than 10v percent of the operating load.

These and other objects which willappear more clearly as the specification proceeds, are 'accoming the positive electrical charge'jo the electrolytic cell or other apparatus requiring'a controlled voltage and current in the output stage from the rectifier element.

A stillfurther object of our invention is to provide a mercury vapor Iarc rectifier tube, embodying several features not heretofore embodied in any type of electric generator or rectifier heretofore known.

given current is applied to the electrodes of a mercury vapor rectifier, there is a voltage drop It is well known that when a given voltage under a pressure of any .plishedaccording to our invention, by means'of the combination of elements set forth and claimed hereinafter.

Atypical installation according to ourinvention is set forth in the following detailed'description, defined in the appended clai'msyand illustratively exemplified in the accompanying drawing in which:

The single figure is a diagrammatic andschematic view of a mercury vapor rectifier 'unit,

or loss depending upon thetype of material used in the electrodes, the distance between theanode and cathode elements, ambienttemperature. at which the rectifier is operated. ments have proven that by producing a high electron bombardment of the vaporized mercury, whereby the mercuryis ionized toa very high 'Our. experidegree, thereby giving a cathode ray effect to the vaporized mercury, we have been able to reduce the operating losses to a large extent, as will be found in the following data tables, setting forth the voltage and current losses under various conditions of operation of our mercury vapor rectifier.

Potential drop or loss with operating characteristics of our mercury vapor arc rectifier with electron filament and auxiliary pool vapor- 'or cycles to give a line equivalent to duced'by' a motor generator set.

showing the electrode system, transformer "and reactance system for straightening the sinecurv'e that pro- Referring now to' the drawing, themercury vaporrectifier iscomposed of the tank or tube 28, which may be off'an'y .desired size "from 3 to twenty four inches in diameter and fromfi to thirty inches deep or high. This shell for the mercury vapor rectifier may be manufactured from a special heat resistance glass such as pyrex, lpyrex-quart'z'mixture or quartz; 'ora glass lined metal shell. The water jacket sg'proviqes a cooling systemby which the ambient tempera ture within the rectifier shell can be maintained at any desired degree. In current 'of from'0 to 1500 amperes the rate at which water is delivered to and taken from the rectifier shllwill approximate 3 gallons'per'minuteg 'At currents offrom 1600 to'5,000' amperes the rate 'o'fwater passedthrough thecoolingjacket or coilsfwill "amount to 5gallons per minute. Higher currents -T6--'" and 68, 10, 681, 101.

will reduire a slight increase in water passage for cooling purposes. The transformer 63 is composed of a number of sections of laminated steel sheets of transformer grade 29 gauge number .0141. The amount of the iron in the transformer depends upon the voltage and current desired in the secondary leads. It is pointed, out that several taps a--h are taken from the secondary coil of the transformer 63 by which, through the conductors 65, 66, any desired alternating current may be taken across the reactance coils II, 12, 13 and I4. transformer winding for a step down type, we impress a voltage of 440 A. C. volts across the transformer 63 through primary winding of the transformer. Using 1 volt per turn of the winding, and allowing additional copper or turns for normal loss, we take a total of 450 turns onthe secondary Side of the transformer 800 amperes. v

When alternating current is supplied to the transformer 63 through the leads 63a, a heating current is delivered through the leads 68, I and 681, 101 to the heating coils 65d, 69m arranged to heat the auxiliary mercury pools 69, 691 at the bottom of the rectifier tube 28, and through leads 16, T1 to the special filament 84 at the top of the rectifier tube. The special filament 84 is arranged in front of a reflector 84a forcing theelectrons given ofi to'fiow toward the opposite end of the tube 28. When the heater circuit is established the small auxiliary pools of mercury 69, 591 are quickly vaporized. The filament 8:! immediately begins throwing off electrons which bombard the mercury vapor evaporated from thepools in 69, 691 and this vapor becomes heavily ionized. -When this mercury vapor becomes ionized it'then makes contact between the cathode 82 disposed in the main mercury pool 8| and the anodes 78'l8. When such electric contact is made with the consequent fiow of current be tween the anodes 18-48 and the cathode 82, a: relay-81' operates which opens the heater circuit thereby cutting off the current flow in Water is then introduced through 85 and 83 at such rate thatthe temperature within the jacket is maintained between 50 C. and 75 C. depending upon distance between the'e'lectrodes 18 and 8 I. By raising and lowering-the anodes Ill-J8 the voltage drop between-the anodes l8 and cathode B2 is increased or decreased in direct proportion to the mean distance between the spark gap. In practice it is well known that the voltage drop across the cathode varies between 9 and 6'. volts.

Thevoltage drop across the anodes varies between are gap have been determined for the conventional type of mercury vapor rectifier where the contact between the mercury andelectrodes isbrought about in the shaker type of rectifier.

.Our experiments have shown that where the mercury vapor within the rectifier shell is highly ionized. that thevoltage drop across the anodes .--:=md;cathodes varies directly as the square of the As an example of the.

distance between the electrodes and directly with the electrode materials used. The following table shows the voltage drops plotted for the various materials which we have used in constructing the anodes and cathodes in our mercury vapor rectifier:

' The electrodes were all highly polished, and of inch diameter and from 4 to 6 inches long. The spark gap between apex of anode and cathode was maintained at 60 mm. From this we were able to determine the exact voltage drop between the anodes and cathodes by raising and lowering the distance from anode to cathode.

After the water has been introduced as a coolant through the water jacket 83 of the rectifier shell 28, and the current fiow between anodes 18 and cathode 82 has been established the field rheostat 81 of the dual plate type to which the leads and 6B are attached before passingthrough the rectifier 28, is then adjusted by means of the hand operated knobs 88 so that the voltage across the rectifier plus the drop-will be between 4.5 and 3.56 volts, while the current delivered will vary between 600 and 2000 amperes, as desired.

The electrodes 18-18 are adjustable so that they may be raised or lowered to give any desired drop across the terminals 1'8 and 8f of the rectifier.

We have found that by providing two auxiliary pools at 69, 691 the menisci of the mercury contained in the auxiliary wells will make a contact with the meniscus of the main mercury pool in 82 holding the cathode element of the rectifier, so that when current is supplied to the transformer, the mercury in the auxiliary pools 69, 691 is vaporized, while the electron filament 84 begins throwing off electrons and a bombardment of the mercury vapor takes place. This electron bombardment produces a highly ionized mercury which is capable of carrying current and thereby completes the circuit between the anodes l8 and the cathode 82 of the rectifier system, with the smallest possible voltage drop or loss between the electrodes. The energized vapor establishes a physical contact between the electrodes 18 and the auxiliary pools 69, 691. Since the auxiliary pools 69, 691 make physical contact with the main pool 8! through the mercury menisci of the auxiliary pools an electric current and voltage flow is set up between the electrodes 18 and 82 by means of the ionized mercury vapor, this voltage fiow between the anodes 18 and cathode 82 operating the relay 61 to throw the heating filaments out of circuit.

We claim:

l. A mercury vapor discharge device comprising a sealed bulb, an anode projecting into said bulb, a mercury pool cathode disposed in said bulb opposite said anode at a distance therefrom sufficient to prevent arcback, means to connect said anode and cathode, respectively, to opposite terminals of a source of high potential current, an auxiliary relatively small mercury pool adjacent the mercury pool cathode, means for heatelectron emitting element disposed at the anode end of the bulb and consisting ofa coil of wire made of an alloy capable of emitting electrons at high temperatures, means for connecting said electron emitting coil across a source of high intensity low voltage current, and means for breaking the circuit through said electron emitting coil as Soon as a current flows from the anode to the cathode.

2. A mercury vapor discharge device, as claimed in claim 1, including a reflector arranged behind said electron emitting coil to concentrate the electrons emitted therefrom upon the mercury vapors produced from the mercury in said auxiliary pool.

3. A mercury vapor discharge device, as claimed in claim 1, in which said heatingmeans for the mercury in said auxiliary pool includes a heating coil, means to connect said heating coil across a, source of high intensity low voltage current, and means for breaking the circuit through said heating coil, as soon as a current flows from the anode to the cathode.

4. A mercury vapor arc rectifier, comprising a sealed bulb, a pair of anodes projecting into saidbulb from one end thereof, a mercury pool cathode disposed in said bulb opposite said anodes at a distance therefrom sufiicient to prevent arcback, means to connect said anodes, re-

spectively, to opposite terminals of a source of high potential alternating current, means to connect said cathode over a load to the zero .point of said source of high potential alternatsource of high intensity low voltage current, and

means for breaking the circuit through said electron emitting coil as soon as a current flows from the anodes to. the cathode.

ALBERT FRANK BOWLES. HARRY LIPSIUS.

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