US2165075A - Flat rectifier and circuit - Google Patents

Description

July 4, 1939. J. SLEPIAN ET AL 2,165,075

FLAT RECTIFIER AND CIRCUIT Filed May 25, 1957 WITNESSES: INVENTORS 4 a W If) 15 /09 Joseph S/ep/an &

' Leo/7 R Ludw/ MM BY ATTORN Y Patented July 4, 1 939 PATENT OFFICE FLAT RECTIFIER AND CIRCUIT Joseph Slepian, Pittsburgh, and Leon R. Ludwig,

Forest Hills, Pa., assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 25, 1937, Serial No. 144,754

13 Claims. (01. PIE-354) Our invention relates to electric discharge apparatus and has particular relation to electric discharge devices of the type incorporating an ignition electrode.

The discharge device to which our invention particularly relates in general comprises a. cathode composedof mercury, lead, cadmium, or some other suitable metal, an anode to cooperate with the cathode and an ignition electrode associated with the cathode. When a current is transmitted between the ignition electrode and the cathode, a discharge is initiated between the anode and the cathode.

In the following discussion and in the claims, we shall refer to an electrode of the mercury pool type. This expression shall be taken to include not only a cathode composed of mercury, but also cathodes of other suitable materials which function in substantially the same manner as mercury.

The ignition electrode associated with the oathode may be disposed either within or without the container in which the anode and cathode are located. If it is within the container its tip may be a short distance from the cathode so that during the ignition period a spark is produced between-the ignition electrode and the cathode, or it may be in contact with the cathode. In the latter case, the ignition electrode is composed of a highly resistant material, suchas silicon carbide, boron carbide, silicon, boron, or a number of other suitable materials, and to initiate a discharge, a current is transmitted through the ignition electrode and the electrode in contact therewith,

When we refer herein to an ignition electrode,

we mean thereby an ignition electrode of any general type including those located within or without the container that do not make contact with the cathode as well as those that do make contact with the cathode. An ignition electrode of the latter type we shall specifically designate herein as an electrode of the silicon carbide device of this type, a spotis formed on the surface of the cathode, and the discharge is tr tted between the spot and the anode. As th discharge passes the spot spreads and forms a number of spots all of which are located in the region of the ignition electrode. We have found an 5 arrangement of this type to operate satisfactorily for load requirements of moderate magnitude for currents less than 1000 amperes, for example. However, where the current drawn by the load is very large, the region of the spots on the surface of the cathode since it is comparatively small becomes excessively heated, and the excessive vapor produced during the non-arcin Period results in backflres and other di'fiiculties. This dimculty, while principally arising in discharge devices in which the ignition electrode is of the silicon carbide type, is, of course, also involved although to a lesser extent, in discharge devices of I other types.

It is accordingly an object of our invention to provide a discharge device particularly adapted for the transmission of high currents of the order of 1000 amperes or more, wherein the cathodeshall not become excessively heated.

Another object of our invention is to provide an are discharge device particularly adapted to the transformation or control of high currents.

More specifically stated, it is an object of our invention to provide a discharge device of the type having an ignition electrode that shall transform or control heavy currents without difliculty.

In accordance with our invention, we provide a discharge device in which the single ignition electrode is replaced by a plurality of such electrodes so that for heavy currents a plurality of spot 85 regions are formedon the surface of the cathode. The ignition electrodes are supplied in parallel from a suitable source. On the application of potential to the ignition electrodes simultaneously one of the electrodes will in general effect the striking of an are before the others. If the ignition electrodes are merely connected directly in parallel, the potential drop between the other ignition electrodes and the catholic will be reduced u when this occurs' To make certain that the other ignition electrodes continue to operate, we provide coupling means. preferably coupling coils, between the ignition electrodes which when one of the electrodes has become eflcctive, operate to impress an additional potential on the other electrodes so that they also become effective. To prevent the striking of an arc between the spot formed by one ignition electrode and the top or head of another ignition electrode (as anode), II

Y independently of each other in initiating dis-L barriers are inserted between the ignition elec-' trodes.

The novel features that we consider characteristic of our invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its methodof operation, together with. additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic view showing embodiment of our invention;

Fig. 2 is a diagrammatic view showing a modification of our invention;

Fig. 3 is a diagrammatic view showing a further modification of our invention; and

Pig. 4 is a view in section showing a discharge device constructed in accordance with our invention.

The apparatus shown in Fig. 1 comprises a flat rectifier 5. The rectifier 5 consists of an evacuated container I having an insulating cylindrical wall 9 to the upper and lower edges of which metallic discs II and i3 are sealed and thus form the bases of a hollow cylinder. A mercury pool I5 isdisposed in the bottom of the container and forms the cathode of the rectifier 5, while the upper disc'll forms the anode.

are provided into which insulating plugs l1 and I9 of circular section carrying ignition electrodes 2| and 23 of the silicon carbide type are sealed. When the plugs l1 and I8 are in place, the igni-. tion electrodes 2| and 23 dip intothe mercury l5. So that the ignition electrodes shall operate charges and forming pot regions on the surface of the mercury, any i sulating barrier 25 is provided which extends from the lower base I3 to a point a short distance from the anode II. The barrier 25 is equipped with a small opening 21 through which the mercury may flow from one side thereof to the other.

While the fiat rectifier 5 described herein has general applicability, itis shown as utilized to supply half-wave direct current from, an alternating source 29. The load 3| to be supplied other hand.:

' is adjustable.

is connected betweenone terminal of the secondary 33 of a supply transformer 35 and the anode The other terminal of the secondary 33 isconnected directly to the cathode l5 through the lower base l3. The ignition electrodes 2| and 23 are suppliedin parallel from a separate source 31 through a suitable transformer 39, the secondary ll of which is connected to the primary 43 of a saturable transformer 45. The secondary 41 of the saturable transformer 45 is connected to the mid-tap 49 of a balance transformer 5| through an auxiliary rectifier 53 on the one hand and to the cathode l5 of the fiat rectifier 5 on the The terminal taps 55 and 51 of the balance transformer 5| are connected to the ignition electrodes 2| and 23. I

The source 31, whereby the ignition electrodes 2| and 2'3 are supplied may be of any general type and may have any general frequency. How- In the upper disc II, a pair of small openings transformer 45.

23 are positive and the cathode I5 is negative are transmitted through the auxiliary rectifier 53. The impulses are impressed between the ignition electrodes and the cathode l5, and current flows between theseelectrodes and the cathode. In 5 general, an arc is ignited first between the anode II and the portion of the mercury l5 associated wlthone or the other of the ignition electrodes 2| or 23. On the striking of this arc, an additional potential is impressed between the other 10 ignition electrode and the mercury, and the latter continues to operate in spite of the fact that an arc has been struck first in the region of the former electrode; Immediately after the striking of an are at the first ignition electrode 2i or 23, an 15 are is, therefore, also struck at the second elec- .trode. The discharge device now continues to opcrate with two spot regions and to supply rectified wave form of the impulse may be broadened by properly selecting the dimensions of the saturable v It is to be noted, moreover, that while our invention is shown in the Fig. 1 embodiment as applied to supply half-wave current to a load, it

may equally as well beapplied for full-wave rectification and for inversion or conversion of any general character. The number of discharge de vices or sets of anodes, cathodes and ignitio electrodes will depend on the particular requirements of each case.

In the modification shown in Fig. 2, our invention is shown as, applied to a system in which the load-is so large that two ignition electrodes do' not provide satisfactory operation. In the modification shown in Fig. 2, a discharge device 59 equipped with three ignition electrodes GI, 63 and 65 is utilized. Here again the electrodes BI,

63 and 65 are carried by insulating plugs 61; 69 and II which are inserted in the anode II in such manner that the electrodes dip in the cathode: I5. In lieu of a singlebarrier, two barriers l3 and 15 are now provided between the central ignition electrode 93 and the other two, GI and 65.

The three ignition electrodes 6|, 63 and are now again supplied in parallel, but the balance transformer 5| is now replaced by three pairs 55 of balance coils ll, 19 and 8L One coil 83, 85 or 81 of each pair is in series with a corresponding ignition electrode SI, 83 or 65. The remaining coils 89, 9| and 93 of the pairs are connected in series with each other. The individual coils 83 so and 89, 85 and 9|, and 81 and 93 are in inductive relation with each other, and on the striking of an arc in the region of any one of the ignition electrodes .GI, 63 or 65, current flows through the corresponding series connected coil 35 83, 85 or 81 and a potential is induced in the other coil 89, 9| or 93 of the pair. The induced potential causes current to fiow through all of the coils 89, 9| and 93 connected in series with each other and the necessary additional potentials are induced in the coils 83, or 81 connected in series with the ignition electrodes 6|, 93 or 95 in the region of which an arc is not struck at first.

The modification shown in Fig.3 is particularly 1;

adapted for use in a system inwhich the load requirements are variable over a wide range. When light loads are supplied, it is undesirable that more than one ignition electrode should operate. Accordingly, we provide a relay 9!, the exciting coil 91 of which is connected in the load circuit. When the load current is low, the relay 95 is deenergized and maintains the supply circuit of one or the ignition electrodes, say 23, open. When the load rises above a predetermined value, the relay 85 is operated and the supply circuit of the ignition electrode 23 is closed so that the two electrodes 2| and 23 operate in parallel as in the modification shown in Fig. l. The modification shown in Fig. 3 is as applicable to a system incorporating a discharge device with more than two ignition electrodes as 59, for example, as it is to a system incorporating a discharge device such as 5.

In Fig. 4, a discharge device 98 particularly adapted for the practice of our invention is shown. The device comprises a container having an insulating cylindrical wall llll which maybe composed of a ceramic material or such a material as glass. The upper edge of the wall I! is secured to the flange I03 of a flanged circular metallic disc llliwhich may function as an anode. To the lower edge a flange ill! of a flanged cupshape metallic element N19 is secured. The cupshaped element I09 carries the liquid mercury l5, forming the cathode oi the discharge device. The ignition electrodes III and H3 are carried by lead-in wires I I5 and I H, which in turn are sealed through the cylindrical wall IM. A barrier H9 is supported along the center of the cathode cup I09 and extends upwardly into a groove |2l cut into the anode disc Hi5. It is provided with the customary opening I23 through which the mercury l5 may flow from one side to the other.

It is to be noted that while the multiple spot region discharge device is generally highly evacuated, it may also be filled with an inert gas at a low pressure or even-at a pressure of several atmospheres.

Although we have shown and described certain specific embodiments of our invention, we are fully aware that many modifications are possible. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim as our invention:

1. A discharge device comprising an electrode of the mercury pool type, another electrode to cooperate with said mercury pool electrode, and means for producing a plurality of emissive spot regions on the surface of said mercury pool electrode, said other electrode being so arranged with respect to said emissive regions as to cause discharges to pass simultaneously between said plurality of spot regions and said other electrode.

2. A discharge device comprising an electrode of the mercury pool type, another electrode to cooperate with said mercury pool electrode, and a plurality of ignition electrodes associated with spaced regions of the surface of said mercury pool electrode, said other electrode being so arranged with respect to said spaced regions'as to cause discharges to pass simultaneously between said spaced regions and said other electrode.

, 3. A discharge device comprising an electrode of the mercury pool type, another electrode to cooperate with said mercury pool electrode, and a plurality of ignition electrodes of the silicon carbide type in contact with spaced regions of the surface of said mercury pool electrode.

4. 'A discharge device comprising an electrode or the mercury pool type, another electrode to cooperate with'said mercury pool electrode, a plurality of ignition electrodes of the silicon carbide type in contact with spaced regions of the suriace oi'said mercury pool electrode, and-barriers extending between said mercury pool electrode and said other electrode for separating saidspaced regions. a

5. In combination, a discharge device comprising an electrode of the mercury pool type, another'electrode to cooperate with said mercury pool electrode, a plurality of ignition electrodes associated with spaced regions, of the surface of said mercury pool electrode, and coupling means between said ignition electrodes which, when current flows between one of said ignition electrodes and said mercury pool electrode, operates to increase the potential diiference between the other ignition electrodes and the mercury pool electrode.

6. In combination, a discharge device comprising an electrode of themercury pool type, another electrode to cooperate with said mercury pool electrode, a plurality of ignition electrodes of the silicon carbide type in contact with spaced regions, of the surface 01' said mercury pool electrode, and coupling means between said ignition electrodes which, when current flows between one of said ignition electrodes and said mercury pool i electrode, operates to increase the potential dif ference between the other ignition electrodes and the mercury pool electrode.

'7. In combination, a discharge device compristion electrodes and the mercury pool electrode.

8. In combination, a discharge device comprise ing an electrode of the mercury pool type, an-

other electrode to cooperate with said mercury pool electrode and means for producing a plurality of emissive spot regions on the surface of said mercury pool electrode, and means for preventing the formation of one of said spots so long as the discharge current between said mercury pool electrode and said other electrode is below a predetermined value. I I

9. In combination, a discharge device comprising an electrode of the mercury pool type, another electrode to cooperate with said mercury pool electrode, and a plurality of ignition elec trodes associated with spaced regions oithe surface of said mercury pool electrode, and means for impressing potential simultaneously on said ignition electrodes to produce current flow between said ignition electrodes and said mercury pool electrode, said other electrode being so disposed relative to said spaced regions that a discharge passes. to it from all said spaced regions when said current flow takes place.

10.In coinbinaiton, a discharge device comprising an electrode of the mercury pool type, another electrode to cooperate with said mercury pool electrode, and a plurality 'oi ignition electrodes associated with spaced regionslot the sur- .face of said mercury spool electrode, means for impressing a periodically pulsatingpotential between said other electrode and said mercury pool electrode, and means for impressing potential pulses having a substantial value only for ,a time interval that is short compared to the trodes associated with spaced regions of the surface ofsaid mercury pool electrode, means for impressing potential of peaked wave form simultaneously on said ignition electrodes to produce current flow between saidiignition electrodes and said mercury pool electrode, and coupling means between said ignition electrodes,

which, when current is transmitted between one of said ignition electrodes and said mercury pool electrodes, operates to increase the potential be--- tween the other ignition electrodes and said mercury pool electrode.

12. In combination, a discharge device comprising an electrode of the mercury pool type,

V another electrode to cooperate-with said mercury pool electrode, and a plurality of ignition electrodes associated with spaced regions of the surface of said mercury pool electrode, and means for impressing potential simultaneously on said ignition electrodes to produce simultaneous current flow between said ignition electrodes and said mercury .pool electrode, said other electrode being so disposed relative to'said spaced regions that a discharge passes'between all said spaced regions and said other electrode when said current flow is produced.

13. In combination, a discharge device compris a ing an electrode of the mercury pool type, an-

other electrode to cooperate with said mercury poolelectrode, and a plurality of ignition-elecface of said mercury pool electrode, means for impressing a. periodically pulsating potential between said other electrode andsaid mercury pool,

and means for impressing potential pulses hav- .ing a substantial value-only during a time interval that is short compared to the period of said pulsating potential simultaneously on said ignition electrodes to produce simultaneous current flow between said ignition electrodes and said mercury pool electrode. I

' JOSEPH SLEPIAN.

LEON R. LUDWIG.

is trodes associated with spaced regions of the sur-

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