US1657574A - Method and apparatus for converting electric power - Google Patents

Description

Jan. 31, 1928-.

L. A. HAZELTINE METHOD AND APPARATUS FOR CONVERTING'ELECTRIC POWER 2 Sheets-Sheet l Filed July 28 1325 l l l I l l l l l l Ill l lllllill Fas. h5

INVENTOR Jan. 3'1, 1928. 1,657,574

L. A. HAzELTlNE METHOD AND APPARATUS FOR CONVERTING ELECTRIC POWER Filed July 28. 1925 2 Sheets-Sheet 2 FIG. 2c

FIG. ZA

s QQ@ k x ////I\ INVENTOR ATTORNEYS Patented Jan. 3l, 1928.'

LOUIS A. HAZELTINE, OF HOBOKEN, NEW JERSEY.

METHOD AND APPARATUS FOR CONVERTING ELECTRIC POWER.

Application filed July 28, 1925. Serial No. 46,528.

This invention relates to an electrostatically controlled magnetically guided valve converter and constitutes an improvement over the form of valve converter described 5 in my pending application for Letters Patent, Serial- No. 649,536, filed July 5, 1928..

Therprincipal object of this invention is to provide more certain and reliable means for preventing electronic currents from l" flowing in undesired paths and thereby causing losses.

A second object of this invention is to 'provide a valve structure which is .mechanically strong and rigid, with a minimum of external supports and of electrlcal connectors.

A third object of the invention is to provide a form of magnetic core which minimizes stray magnetic fields and which is of such open construction as to leave a maxlmum space for bringing out the leads `from the valves. l

In the valve converter whose structure is illustrated in Figs. 58a to 59 of my patent application above referred to, electron emission occurs from certain portions of the sur-` faces of the main electrodes, but not from the remaining portions nor from the surfaces of the control electrodes. Such selective emission is secured by coating portions of the main electrode surfaces with an electron-emissive material, such as calcium oxide, and employing for the remaining surfaces a highly non-emissive material, such as uncoated tungsten. Unless means are provided for maintaining differencesl in temperature, it may be difficult to prevent 'sublimation of the emissive coating from one portion of the surface to another, with consequent undesired emission. This difficulty is avoided in the present invention byarranging the electrode surfaces so as to eliminate Vall undesired electron paths between exposed portions of the surfaces, and by placing barriers i'n the paths that must exist for structural reasons between surfaces that do not need to be exposed. These ends are attained by arranging the electrodes so that, when their outlines are projected into a planev perpendicular to the magnetic fiux, the projections of the ex-l .posed portions of the main electrodes will not overlap the projections vof the exposed portions of the control electrodes, and by interposing barriers of insulating material in places Where the projections of the remaining portions of the electrodes overlap. The result is that it is unnecessary to depend on selective emission from the different electrodes or portions thereof.

Referring to the drawings:

Fig. 1a shows an elevation in section of a valve converter arranged in accordance with this invention. Fig. l" shows a plan in section corresponding to Fig. la.

Figs. 2a, 2b and 2 show oblique projections of the structures of the control electrodes, the low-frequency electrodes and the high-frequency electrodes, respectively.

Fig. 3 shows a side view' of one valve structure with the containing vessel removed.v t Fig. 4 shows a detail of the valve strucure.

AThe valve converter illustrated in the accompanying drawings has the following features in common with that illustrated in Figs. 58a to 59 of my prior-application above referred to. It has a number of separate valve structures (l, 2, 3 and 4) each placed between the poles (l1) of an electromagnet (l2) excited by direct current (in the coils 8, 9 and 10). Each valve structure consists of a highly evacuated vessel inside of which are reflectors consisting of concentric metal shells (13), preferably polished, for the purpose of retaining the heat developed by the losses in the valves and so maintaining the main electrodes at the proper temperature for electron emission. Within the reflectors are the valves proper, each consisting of a control electrode (5), and two main electrodes (6 and 7).

During a portion of each control cycle, the control electrode 5 is highly positive rela- 95 tive to the main electrodes and causes electrons to flow from one main electrode to the other as illustrated by the dots and arrows in Fig. 4. These electrons are drawn from whichever of the main electrodes 6 or 7 100 happens to be the cathode and are rapidly accelerated to high velocity. It is well known that in a magnetic field an electron initially moving obliquely to the lines of magnetic flux will describe a path of a heli- 105 cal character having a line of magnetic flux for an axis. If the magnetic field is intense, the path will at all points be so close to its axis that the latter may roughly represent the actual path. This effect has been u motion after they pass the point of maXi-' mum potential midway between the main electrodes, and are retarded so that they strike the anode with a low velocity. Some 'of the electrons which happen to have a slightly lower longitudinal velocity than the others will not quite reach the anode and will return towards the cathode, oscillating back and forth throughout the interval when the control electrode is positive. During the remaining portion of the control cycle the control electrode will be highly negative with respect to both main electrodes and will prevent the flow of electronic current. At the beginning of this interval all electrons present in thespace will be drawn to the main electrodes. Y

The specific valve converter illustrated in the drawings may be associated with the circuits illustrated in Figs. 54, 56, 57n and 57b of my prior application above referred to, and therefore includes 12 direct-current valves and 18 alternating-current valves, each valve having a separate control electrode.

The valve converter illustrated herewith diifers from that of my prior application in ythe following respects. First, the directcurrent valve structure is made in two parts 1 and 2, and the alternating-current-valve structure is also made in two parts, 3 and 4. Secondly, the individual valves of each valve structure, instead of being placed side by side in the direction of the magnetic flux lines, are placed in the same plane perpendicular to the magnetic flux and in a rectangular arrangement (as illustrated in Fig. 3) with as many valves in one direction as there are output leads 21 from that structure and as many valves in the other direction as there are input leads 22, with the result that input and output electrodes may each be made common to several valves. Thirdly, the active portions of the main electrodes consist of parallel tubes (or rods or strips) 25 and 27 displaced from one another in the direction of the magnetic flux lines; and the active portion of the control electrode consists of plates 23 parallel to the magnetic flux lines and to the main electrodes. The active portions of each electrode are firmly held in posi-l tion by metal end plates 24, 26, 28. Around these end plates are interposed barriers 29, 3031 of insulating material to prevent the tlow pf electrons.

The splitting of the direct-current valve tages.

structure and the alternating-current valve structure into two parts has several advan- First, it brings all of the large exposed. ironsurtaces (at each side and at the bottoni of Fig. 1) to the same magnetic potential, thus minimizing thetendency for magnetic flux to pass to an enclosing tank. Secondly, it leaves the top and both ends of each .valve structure exposed for bringing out leads. Most conveniently the control leads 20 arc brought out at the front of Fig. 1. the high-frequency leads 22 at the rear, and the direct-current and low-frequency leads 2l at the top. Thirdly, the number of leads to be brought out from one vessel is much less (2l3+6=1l, as against 2-I6+12=20, for the direct-current valves, and 3+3+9=15, as against fitti-18 :27, for the alternatingcurrent valves), with only a slight increase in the total number of leads to be brought out (11 2=22, as against 20, for the directf current valves and l5 2="0, as against 27, for the lalternating-current valves), thus simplifying the arrangement of the insulating seals 19. Fourthly, the smaller -number of valves results in a more rigid and stronger mechanical structure. Fifthly, the three dimensions of the complete structure are not far from equal, making the arrangement more compact.

This structure is particularly suitable for large power ratings, such as several hundred kilowatts. For smaller power ratings it might be preferable to use a smaller number of valve structures, even going as far as putting all valves in a singlestructure, associated with a single magnetic field.

The arrangement of all of the valves of each valve structure in a single plane, as described above, avoids all special connectors between main electrodes in any circuit-closing valve converter connected in accordance with the scheme of Fig. 37 of my prior application above referred to. For example, referring to an alternating-current valve structure h/aving m high-frequency electrodes an/ n low-frequency electrodes giving mn valves altogether, each with a separate control electrode, m valves may be placed one above the other and n' valves end to end, in a rectangular arrangement, as shown in Fig. 3. The on valves lone above the other may have the tubes 25 forming the low-frequency electrodes connected between two parallel metal plates 26, as shown in Fig. 2b, making a very rigid structure which is thc primary support for the remaining electrodes. The n valves associated with one high-frequency electrode may be placed end to end, the high-frequency electrodes consist. ing of tubes 27 extending through all of these valves, as illustrated in Fig. 2. These tubes will pass through insulating bushings 32 in the end plates 26 of the low-frequency electrodes, as shown in Fig. 2b, which serve as mechanical supports. The control electrodes are fixedv relative to the low-frequency electrodes by the insulating pieces 30, which serve also as barriers to electron flow between the end plates 24 of the control electrode and the main electrodes.

Insulating barriers 29 are placed over thc I end plates 24 of the control electrodes to revent electrons from being emitted by t ese end plates. For the same purpose insulating barriers 31 are placed at each side of the exposed end connections of each valve, as shown in Fig. 1b. In general, such insulating barriers should be interposed wherever magnetic flux lines extend from one conducting surface to another, one of -which is emissive.

The motion of the electrons between the main electrodes has a component parallel to the electrodes, which may be referred to as a drift, and which carries the electrons erpendicularly to both the magnetic flux lines and the dielectric flux lines. When this drift carries the electrons to the end of the active space of a valve, the electrons will curve around the edges of the control electrode, still moving perpendicularly to the dielectric flux lines. The result is that any electron which is oscillating back and forth between the main electrodes without reaching them will experience a drift that will carry it completely around one of the lates of the control electrode. No barrier s ould be interposed in the path, as such a barrier would accumulate a negative electric charge from the electrons and would impair the action of the valve.

When the control electrodes are negative a cloud' of electrons will form over their surfaces. The electrons in this cloud will also experience a similar drift to that described above, which for the same reason should not be interrupted by barriers. The clearances around the surfaces of the control electrodes are chosen with respect to the voltages and to the strength of the magnetic field so that this electron cloud does not extend to the main electrodes nor to the other control electrodes.

During motion from one main electrodek to another, the electrons are subjected by the control electrode to a varying transverse force. In general electrons moving in a magnetic field have a certain natural period of rotary motion. If this period of rotary motion should happen to lie close to the time` taken by an electron to traverse the space between the main electrodes, then those electrons which are oscillating back and forth between electrodes may build up relatively high transverse velocities, which ultimately may carry them to the surface of the control electrode. The same will be true, but toa less degree, if the natural period of rotation corresponds to some har- .in the control electrode circuit.

inc nc component of the transverse force.v This effect is obviated by the cooperation of rtwo means: first, ythe transverse force is made Aelectrodes gives a com aratively uniform transverse eld and it 1s preferred to the use Vof flat strips. 'Ihe -round electrodes also are simpler structurally and provide a greater emissive surface than would flat strips.

I claim:

1. An electrostatically controlled valve comprising an evacuatedvessel, two main electrodes and a control electrode, and means for maintaining a constant magnetic flux for guiding the electrons between said main electrodes, the lines of said magnetic flux extending from one main electrode to the other main electrodes, and the projections of the control electrodeA not overlapping the projections of the main electrodes when the outlines o f the exposed portions of the electrodes are projected on a plane perpendicular to the lines of magnetic flux.

2. An .electrostatically controlled valve comprising an exacuated vessel, two main electrodes therein whose active surfaces have the form of parallel cylinders, a control electrode whose active portion has the form of plates parallel to the plane including the axes of said main electrodes, means to maintain a constant magnetic field passing through .the valve in the plane including the axes of the main electrodes and pendicular to said axes, and insulating rie-rs interposed in all paths where inactive metallic surfaces would otherwise face one another along lines of magnetic flux, whereby no electron paths along lines of magnetic flux exist between electrodes eX- cept the desired paths between the active surfaces of said main electrons.

3. In a magnetically guided electrostatically controlled valve converter having a certain number fm, input leads, a certain number n output leads, and mn valves arranged to connect each input lead with each output lead, the rectangular arrangement of the 'um valves in a single plane perpendicular to the magnetic flux, with m valves in one direction and ln, valves in the other, and with the input and output electrodes each structurally common-to a'number of ralves,

' whereby'the required number fof electrical *connectors and mechanical'supports for said valves is minimized.

' 4. In a magnetically-guided eleetrostatie vcally controlled -valve converter, the combination Iof a 'magnetic core h'aYing an oddnumber of poles symmetrically arranged and proceeding from a common yoke, exciting coils wound o nvsaid poles-except the .two end poles whereby external magnetic' j fields are minimized, and a symmetrical arrangementof -valve structures placed lietween sai-d poles, with the result that three sides of each valve-structure are vavailable for bringing out leads.

- 5. A magnetically guided electrostatically controlled valve as claimed in claim 2,

raten; NQ. 1,657,574.

which includes free paths around the ends of the plates of the control electrodes-@icing '2o lwhich paths electrons' drift perpendic'ztlarly vto the magnetic llux and tothe dielectric` flux existing between electrodes thereof'.

6. In an electrostatical-ly controlled valveV converter, the method of minimizing `the current to the control electrode which consists in employing a magnetic field to guide l I vtaken by an electronv in vtraveling :fromI one main electrode to another, 'nor-fa submul- `tiple of thistiine'. 'l In testimony whereof I aliixmy signature.

' LOUIS-A. rnlznn'rirrE.A

esgrime-Arcor' u isherby cerfif'iedi'tht 'rrer'a'ppr's in the l f Printed s cifrcatwn of.-

above numberedzpatent requiring orrecton. as fol lows; Pe. `the the misspelled werd "exacuated" read""evacuated"-, and line .120, 'last werd-0f f claim', f for "electrons" read"cl'ectrodes";f and thatthe said 4Letters'IP-tuent' Y- should he yread wi(h1these-:corrections therein that the sameniay eonformjmf the record `of Vthe fcaseiu lthe Patent Office.

l y v Signed and sealed this 21st day of` Februaryg` A. D. l

Sealy.A l

M.' Moore "j Acting Commissioner of Patents.,

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