US1909737A - System of rectification - Google Patents

Description

y 1933- c. s. WEYANDT 1,909,737

SYSTEM OF RECTIFICATION Filed May 2, 1930 4 Sheets-Sheet 1 a &

May 1 9 c. s. WEYANDT SYSTEM OF RECTIFICATION Filed May 2, 1930 4 Sheets-Sheet 2 May 16, 1933. 3 s w T 1,909,737

SYSTEM OF RECTIFICATION Filed May 2, 1950 4 Sheets-Sheet 4 Patented May 16, 1933 PATENT OFFICE CARL B. WEYANDT, OF PITTSBURGH, PENNSYLVANIA SYSTEM OF BECTIFICATION Application fled Kay 8, 1980, Serial No. 449,834, and in R'uuia December 14, 1828.

My invention relates to electrical systems and circuits utilizing prcponderatingly unidirectional current derived from a source of alternating current through electric valves,

particularly of that type which is not perfectly asymmetrically conducting, but which allows substantial inverse current.

It is the object of my invention to provide in such circuits and systems, arrangemeuts, combinations of elements and devices,

and particularly proportions which minimize the size and number of electric valves and which prevent undue temperature rise and prolong the life of the valves.

In accordance with my invention the number of imperfect valves in series, either one or more, is such in relation to the impressed alternating electro-motive-force that substantial inverse current would flow, except 2 for the fact that there is effective in the valve circuit inductive reactance of such magnitude that the inverse current is controlled or determined thereby, and is less than that which would flow in the absence of the inductive 2 reactance or upon substitution therefor of a substantially equal non-inductive resistance, and in some cases the inductive reactance may be of such magnitude that the inverse current is reduced or limited to substantially negligible value. From the combination of inductive reactance, suitably related in magnitude to the circuit and the purposes for which the rectified current is utilized, with slnall or reduced number of imperfect valves in series, as aforesaid, arise advantages, among which are the following:

(a) The electrical losses in the valve structure itself are materially reduced, thereby enhancing the efficiency of the system.

(b) For a given number of valves in series, either one or more, a higher impressed alternating electro-motive-force may be employed, or for a given impressed electro-motiveforce fewer valves in series may be utilized, maintaining adequate rectification, and without overheating or rapid deterioration of the valve structure.

(0) Without overheating or rapid deterioration of the valve structure it may be small- 50 er for a given load current, or for a valve structure of a given size, greater load current may be passed therethrough, and in either case the current passed by the-valve structure may be reater per unit of area of its rectifying sur ace.

(d) Without overheating or rapid deterioration of valve structure of given size, it will pass a greater amount of electrical energy or power; or for passing electrical power or energy of certain magnitude smaller valve structure may be utilized.

(0) Notwithstanding the smaller number of valves in series the rectification is adequate because the ratio of the direct or preponderating current impulses are suitably large in comparison with the inverse current impulses, the ratio of the direct or forward current to the inverse current being of any suitable magnitude, generally at least two, and, in most cases, several or many times that figure.

(f) Notwithstanding the small number of valves in series, the inverse current may be made substantially negligible by the effect of the inductive reactance, so that, as regards 7t very small magnitude of inverse current there may be procured by the combination of inductance with small number of valves in series practically the same condition or result obtaining when so great a number of valves in series is employed that the inverse current is negligible solely by the action of the valve structure itself, it being then a matter of indifl'erence whether or not inductance be present, since the valve structure has of itself 5 already greatly reduced or substantially eliminated inverse current.

(g) The ratio of the reactance to resistance of the valve circuit, and more particularly the ratio of the reactance to the resist ance external to the valve structure, may be less than, equal to or greater than unity, depending upon circumstances and upon the uses to which the valve circuit is put.

(h) The voltage drop across the valve structure, for a given load current, is materially reduced, and generally that voltage drop is materially less than the voltage drop across the remaining impedance of the circuit. The fall of potential across the imdance external to the valve structure ma 8: less than, equal to or greater than the fa l of potential across the valve structure itself, but generally, and for high efliciency, the fall of otential across the im edance external to the valvestructure is at east four, and preferably more than four, times the fall of potential across the valve structure itself.

(11) When the valve structure is of that character in which the inverse current rapidl increases with small'increase of inverse vo tage, the inductive reactance may be of such magnitude as to limit the inverse current to a value below that at which it so rapidly increases, preventing undue temperature rise or rapid deterioration, and reducing inverse current losses otherwise occurring.

(j) The cost of the valve structure and the space occupied thereby are materially reduced for a given duty, or for the same electric power, energy or current transmitted therethrough.

Further in accordance with my invention the inductance, whose reactance is effective as aforesaid in the valve circuit, may be either wholly or in part either a worklng or.an idle inductance, in the sense that it may be either inductance of or occasioned b electromagnetic structure utilized to per oi'm mechanical work, or an inductance which itself performs no mechanical work but nevertheless modifies, limits or controls the current transmitted by the valve. structure to the actual or useful load. The resistance component of the circuit impedance, of which the inductive reactance is the other component, may be constituted largely or substantially entirely by the ohmic resistance of the inductance winding, or may be some other resistance in the circuit, for example, that of a non-inductive load.

In accordance with one of the aforesaid aspects of my invention, and in contrast with pr1or practice, the ratio of the impressed electro-motive-force to the number of valves in series in the circuit is materially increased, in some cases as many as from five to ten times; and as the ratio of reactance to resist ance increases, this figure of comparison increases.

Further in accordance with my invention the valve structure is or may be subject to artificial or forced cooling materially to increase the current, power or energy transmitted by the valve structure, all without overheating or rapid deterioration of the valve structure, or materially to increase the current per unit area of rectifying surface.

This application is a continuation in part of my application Serial No. 290,668, filed July 5, 1928.

My invention resides in a method and features of structure, arran ement, combination and proportionment of t e character hereinafter described and claimed.

For an understanding of my invention and for an illustration of some of the various forms it may take, reference is had to the accompanying drawings, in which:

F g. 1 is a diagram of a circuit arrangement illustrative of one of the embodiments of my invention, characterized by the fact that the magnetic field of the inductance performs mechanical work.

Fig. 1a is a diagram of a modified circuit arrangement illustrating alternately energized inductances operating upon a movable core.

Fig. 2 is a diagram of a circuit arrangement illustrative of another embodiment of my invention, characterized by the fast that the inductance is idle, as regards performance of mechanical work and in which the useful load is an arc, resistance of other type of load. I

Fig. 3 is a diagram of a circuit arrangement illustrative of another embodiment of my invention, characterized by the fact that the inductance is idle, as regards performance of mechanical work, and the load is non-inductive, and capable of exerting a counter electro-motive force, such for example as a storage battery to be charged.

Fig. 4 is a diagram of a circuit arrangement for a vibratory signal embodying my invention.

Fig. 5 is a characteristic curve of a cuprous oxide valve or rectifier cell.

Fig. 6 is a characteristic curve of a series of cuprous oxide valves or rectifier cells.

Fig. 7 is a characteristic curve of a solid electrolytic valve.

Fig. 8 comprises a plurality of curves illustrative of electrical characteristics of my invention.

Fig. 9 is an oscillogram illustrative of the gppgcatirn of the characteristics illustrated Fig. 10 is a comparative oscillogram.

Referring to Fig. 1, A represents a source of alternating current which term herein includes both current and voltage of simple sine wave form, or of any complex form having numerous sine wave components of different amplitudes and frequencies.

In circuit with the source A is an inductance L such as a winding of an electromagnet, solenoid or other electromagnetic structure having a magnetizable core or other element C moved or actuated by the current through L to perform useful mechanical work; inductance L is connected in series with one, or a number of serially connected, electric 'valve or valves V, of suitable type.

In parallel with the valves V are similar valves V1, serially connected with each other and in series with inductance L, the parallel relation being employed to effect a suitable current density per unit of area of rectifying surface, to maintain suitably low the temlmlflllll't' rise. of the valves upon which their action, particularly when of the cuprous oxide type, de wnds.

It shall he und rstood that the valves contcmplatcd by my invention may he of any of the following t. 'pes, havmg lll common the charm-terislic of permitting substantial in-.

verse current llow Typo in, comprisingacouple-formcd 0f a metal and an oxide thereof; which ty eineludes Others, having substantially similar, characteristics; for exam lc, landip referably, j copper and enprous oxir e,- generally 4 of the;

character disclosed in Letters Patentl No. 1,640,335, (irom l ahl. Valves of this type, and their.- upiivalents, exhibit little or ,no. polarization, in contrast with elcctrolytic valves, .and have a current conduct ng characteristic similarto that of simpleresistancc, andwin some cases at least decrease in resistance with rise in temperature. It is a further characteristic of the copper-cuprous oxide recti-J licl'. that, itv deteriorates or ages, the more rapidly the higher its temperature, with-resultant lossof its property of asymmetrical conductivity or rectifying action.v

Type 1), solid or dry electrolytic recti tiers, such for example as marketed by Bennwood-Linze Company; and ty e c-, electr0- lytic rectifiers whose electro yte .is liquid,

such as a solution of sulphuric acid, with which areassociated electrodes of suitable. materials, generally dissimilar. Both SOlld;

and wet electrolytic rcctifiers exhibit polarization. v r

Type (1 valves comprising silicon-carbonor equivalent couples, or couples of the character described in Patents 1,751,360 to 1.751,363 an d 1,751,460, or their equivalents.

The following description will be, for the sake of brevity, largely in connection with type a rectifiers, which-is at present the preferred type for the purposes of m present invention, andis the type illustrate in Figs. 1 to 4 inclusive.

Returning to Fig. 1, it will be understood that the reactance of the inductance L and of any other inductance in circuit is in magnitude suitably related to the number. of valves in series, to the resistance of the circuit external to the valves, and .in general to the characteristics of the circuit, to procure the performance and effects herein described;

It will ofcoursc be understood that where the operation of the device is intermittent or not prolonged, forced cooling may be omitted, as jitsmay also unglefi all circumstances when thecurrent densit peraunit area (if-rectifying surface is tlti-Slliflll low. To obtain low current density per unit area of -rectifying surface, valves may be connccted in parallel as imlicatcd in Fig. 1 or the. rectifying areas, of the individual valves .may bcniadecorrespondingly larger.

lti'errin toliig. 1a, the arrangement is generally tie same except that two induc- .tanocs .L-and Liam-employed to move the core C'in oppositedirectiongasfor exam le .1" a reciprocatingelcctricimotor genera ly of the type illustrated inLmy-prior Letters -1atcnt .No.-,1,637 717,.August 2,1927.- Dif- 4 f valves are associated re-I ,spectively with the coils or-inductances L fcrent groups :o

andLl, and are'reversel related in their connections to the source whereby prepon- :(leratin or core-actuating impulses are alter- :nately clivercd to the-coils Land L1.

In arrangements of the general character of F igsi 1 andrla the. number-of valves in series, either one or more, is such that in the absence of the inductance a substantial inversecurrcnt would'flow.

As contrasted with cases where the number;

of valves in series is such that without in-.

ductance, and by .the valves themselves, little or no inverse current would flow, my arrangement dispenses with a considerable portion of the.. valves in series and substitutes therefor inductance, which by its reactive effect determines what shall be the magnitude of the inverse current, imparting thereto a suitable magnitude which will not cause overheating of the-valves and their rapid deterioration. The inductance serves the purpose also of permitting greater current to be transmitted through the valves without overheatin for example, .4 amperev per square in of rectifying surface when the valves, type a, are cooled by convection, as by contact of the air with the valve disks themselves or with radiatingfins attached.

to or comprising a part of the valve structures. With artificial 'or forced cooling this current density may be readily doubled, and in general, the greater the artificial cooling the higher the current density.- Either with .or without forced cooling the temperature should preferably not exceed 140 F.

It is preferable in an arran ement of this character also that the ratio 0 the inductive reactance to the resistance of the circuit external tothe valve structure be greater than unity and in fact in some instances as high as 20, though it will be understood that-the ratio of umty or even less than unity may, accordin to circumstances, be utilized.

By utilizing inductance, as described, with a reduced number of valves in series, the

losses in the valve' structure are materially reduced, with consequent increase in the efficiency of the system. .Generall and preferably in an arrangement *of this character the fa l of potential across that portion of the circuit external to the valve structure is greater than unity, and preferably several times that figure. In addition, the ratio of the direct or forward'current to the inverse current, is greater than 2'and'generally several times-that figure. In the case of reciprocating motors, such as shown in Figs.

"- 1 and 1a, and in some other relations, it is 1 desirable that the inverse current be notmduccd to too small a magnitude, buton'the contrary that it be large enough to perform a useful function such as dema etization, of parts previously magnetized b; the forward current or pre onderatin impulses.

In Fig. 2 a stepown trans ormer T intervenes between the source A of alternating current and the circuit 'including'the group of valves V in parallel with the group of valves V1. In series'with the'valves is anidle inductance L, and the useful load has the characteristic of'a resistance and as specifically indicated is an area, such for example as may be utilized in weldin and utilizing for example 200 amperes. fn this case the inductance L performs no mechani cal work but imparts to the valve circuit a characteristic essential in accordancewith my invention. The magnetic circuit of the inductance L may be complete or closed, or as indicated may have a series air gap. or the purpose of my invention the material for the magnetic core of the inductance L is preferably one having high magnetic retentivity, characteristic of some steels or alloys thereof, and particularl high carbon steel, or tungsten 'alloy 'stee and equivalents. Such core material may be used for any of the inductances contemplated by my invention when it is particularly desired that the persistence of the direct or forward current wave through the valves shall have particularly long time duration. It will of course be understood that double wave rectification may be applied in Fig. 2 by using another group of valves reversely connected with relation to the current supply and the load.

The inductance in the arrangement of Fig. 2 is again of a magnitude which determines or controls the magnitude of inverse current, when in series with a number of valves such that, in the absence of the inductance, substantial inverse current would flow. The impressed voltage, that delivered by the secondary of the transformer T, is such that the voltage per valve, or impressed voltage divided by the number of valves in series, is higher than in prior practice. While the transformer T may be used, as described, it should be understood that it is not essential and may be omitted, though the number of valves in series .will be greater because of the {greater impressed voltage, though the num- K3! in series will still be such that the inductance determines the magnitude of inverse current. In an arc circuit the inverse current may be reduced by the effect of the inductance to vary small magnitude, which implies a relatively high inductive -reactance.

Here again the cooling of the valves may be forced, as indicated, though it should be understood that forced or artificial cooling is not essential. By recourse-to forced cooling however,thepermissihle current density =-n1ay'he materially increased, as hereinbefore described, the temperature in any event being restrained substantially below 140 F. for type a valves. 1

In this circuit arrangement again the elec trical loss in the valves themselves is smaller alone, in thea sence of inductance, restricts the inverse current to lnsubstantlal or neglihigher as permitted by employment'of inductance,"nevertheless the number of valves in series in the. arc circuit is generally not so much reduced as in circuit arrangements such as those shown'in Figs. 1 and 1a, and others herein described. Nevertheless, particularly where large currents are involved, as of the order of 200 amperes, requiring very large valves or a large'number of small valves in parallel, the saving of onl one or two in series, by recourseto the inductance, is of great advantage in reducing the total size and cost of the valve structure.

In Fig. 3 there are again shown two groups of valves V and V1 in parallel and in series with an inductance L, which ma be of the character of the inductance L with its core, described in connection with Fi 2, utilized for charging a storage battery or'for supplying current to any other device having both a resistance'characteristic and exhibiting counter electro-motive-force. For example A may deliver alternating current at 60 cycles and at a pressure of 110 volts. The storage battery-S of three cells may then be suitably charged by the utilization of about. three types a valves in series. In this case the impressed'voltage; per valve is approximately 33, under which circumstance, withe inductance L, the. inverse current would be large indeed, and the heating efl'ect disastrous to the valves themselves. In this instance. the. inductance L is a substitute for a considerable number of extra valves in series that would be necessary suitably to limit the inverse current, in the absence of inductance. As in all other cases herein described, artificial or forced cooling of the valves may be resorted to. In this case, and the others described, and in general, the effect of the "gible magnitude. While theimpressed voltage per valve is in this circuit arrangement inductance operates cumulatively with the cooling medium to maintain the temperature of the valves within their safe working limits,

giving them prolonged life, the inductance in addition permitting larger load currents for a given size of valve structure and permitting a greater impressed voltage per valve than in prior practice.

Referring to Fig. 4, there is illustrated an electric trembler or vibrator bell, buzzer or equivalent signaling instrument comprising the gong 3 struck by clapper 4 carried by the armature 5, biased toward stop 50, of the electromagnet whose core 6 is provided with the magnet windings 7, 7 in series with WhlCh across the terminals of the source A is a valve V and control switch or push button I). When the inductance of the windings 7, 7 is sufliciently high, the bell or signal may be operated with a single valve V, or a few valves V in series, of type a from a source A delivering current at a pressure of 110 volts. Here again the number of valves in series is small, as permitted by the inductance, of the windings 7, 7, which determines and controls the inverse current. A device of this character operates intermittently or infrequently, and accordingly forced or artificial cooling is rarely if ever necessary; and, insofar as concerns heating effect, the relation of inductance to number of valves in series, their size, and the current transmitted by them, need not be so carefully or nicely related as in the case where the apparatus operates for long periods or continuously, though in, no event should the inverse current or heating effects be so large during the short periods of operation that the valve structure deteriorates or ages at a too rapid rate.

Vibratory structure of this general character may also be utilized for massage implements, on a larger scale where the electromagnetic system is employed to operate screens of sieves, or to tap foundry molds, either when the operation is intermittent or prolonged.

ere use is continuous or prolonged artificial or forced cooling may be resorted to, though not essential.

The voltage-current characteristic of a type a rectifier, particularly the copper-cuprous oxide rectifier, such as now known to the trade as Rectox or Kuprox, is indicated in Fig. 5 wherein ordinates are current magnitudes in amperes and abscissae are electro-mot'iveforces in volts. Through a single disk or valve was passed, in a non-reactive circuit, current from a direct current source. The portion of the characteristic curve extending from the origin 0 upwardly to the right, represents the relations of current to voltage across the terminals of the cell or disk for conduction from the oxide to the copper, and is the current of that direction which gives the largely predominating current in circuits of the character hereinbefore referred to. It

is noted that the resistance to flow of current from oxide to copper indicated by this portion of the characteristic, is represented at every point thereof by the quotient of the voltage divided by the current. The resistance to current flow in this direction is low and, except for temperature effects, is fairly constant. The temperature coeflicient is up to' a certain point negative, the resistance falling slightly with temperature rise; beyond that point, where the current density and heating effects are of certain magnitudes, the valve has a positive temperature coefiicient of resistance. The portion of the characteristic to the left of the origin 0 and below the horizontal axis indicates a high resistance to conductivity or current flow in the inverse or reverse direction from zero to two or three volts, with a rapidly decreasing resistance however thereafter, due to the temperature rise caused by the losses of electric power, represented by the product of the resistance into the square of the current. The characteristic shows that because of the negative temperature coefficient of resistance, the inverse current rapidly increases with small increases in the impressed voltage, tending to agggavate the condition of temperature rise. ecause of the great difference in the resistances for the positive and inverse directions of conduction, and particularly from zero to two or three volts applied in the inverse direction, the watt losses due to the large and preponderating direct or positive current impulses are not great because the resistance for conduction in the positive or direct sense is low while for relatively smaller inverse currents the watt losses are greater than for the relatively great current passed in the positive or low resistance direction. In the example illustrated this high wattage loss begins to occur from upwards of three or four volts inverse, and it is therefore desirable to maintain conditions that will restrain the inverse current and voltages to magnitudes of the order of one tenth of an ampere and two or three volts, for the particular cell, disk or valve in question which had a rectifying surface of about three and one-half square inches, as represented by an oxide covered disk or plate about two inches square. The characteristic indicates that for the currents corresponding to inverse voltages of about 4.8 and 5.3 the disk or valve partook of temperatures of 127 and 158 degrees Fahrenheit, respectively. At least the higher of these temperatures was for this particular valve too high and caused its rapid deterioration or aging, causing it soon to lose its rectifying power or valve action. In general for type a valves, without forced cooling, the temperature should not, for steady use and long life, exceed about 140 F.

By way of example merely as capable of illustration by Fig. 5, it is desirable to keep the inverse current below magnitudes corresponding with inverse voltages of about five volts, and generally less. It Wlll be understood however that this will depend upon the excellence of the valve as manufactured and in some cases this permissible inverse voltage may materially exceed five volts. In

neral it is desirable to operate below such lnverse current values as corres end with a rapidly increasing current wit crease of inverse voltage, and this 1s efiected by the inductance, in circuit with the valve or valves, which limits and determines the inverse current.

In Fig. 6 is given a characteristic taken under similar conditions for three of the copper-cuprous oxide disks or cells in series with each other. The characteristic to the right and above the origin is generally similar to that of Fig.6 and that below and to the left of the origin 0 is also generally similar to that of Fig. 5, except that it is not carried to the above mentioned extreme or undesirable conditions. This characteristic, for conduction in inverse or reverse direction indicates that for three cells in series the voltage applied in inverse direction should not materially exceed about 15 volts, to mamtam suitable and desirable temperature condi tions.

Fig. 7 is a generally similar characteristic curve of a. Bennwcod-Linze dry electrolytic valve, two cells in series, non-inductive circuit, alternating current source. To the right and above the origin 0 the characteristic 8, in solid line, for the building current, current increasing. from zero to a ositive maximum, and the characteristic 9, 1n dotted line, for the decaying current, diminishing from the positive maximum to zero, are both generally similar to the characteristic to the right an above the origin 0 in Figs. 5 and 6, indicating relatively low resistance for conductivity in the direct or positive sense. To the 1e and below the origin 0 the building current, or current increasing from zero to a maximum in the negative or inverse direction, is indicated by the solid line curve and the decaying inverse current is shown by the dotted curve 11. These two also are generally similar to the inverse current characteristic of Figs. 5 and 6; and as in the case of the copper-cuprous oxide type of valve it is desirable to keep the inverse current within suitably small limits to prevent excessive losses and tem rature rise.

With lmperfect valves in general, and particularly those of the types hereinbefore referred to, and especially type a, there is used. in substitution for a part of the whole number of valves in series necessary, for a given impressed voltage, to limit the inverse current to insubstantial or negligible magnitude, an inductance which determines, controls or limits the inverse current to a magsniall innitude which may bev insubstantial or negligible or which may be substantial, but in all cases less than that obtaining when the inductance is absent, or when for the inductive re-- actance there is substituted an equivalent noninductive resistance.

When so utilizin fewer valves in series, either one or more, t e inductance may be of such magnitude as to procure a desired ratio of forward or direct current to inverse current (root means square values, such as measured, for example, by an ammeter of the electro-dynamometer type) to cause the fall of potential across the impedance of the circuit external to the valve structure, greater than, equal to or less than the fall of potential across the valve structure; to control the magnitude of losses in the valve structure; to effect a ratio of reactance to resistance in the circuit external to the valve circuit, greater than, equal to or less than unity; to increase the current density in the valve structure without overheating; to permit transmission of greater power, energy or current through a valve structure of a given size without undue heating; and in general to prevent undue temperature or rapid deterioration of the valve structure.

The aforesaid ratio of reactance to resistance of the circuit external to the valve structure may in many cases be substantially greater than unity, as, for example, from 5 to or more. In cases such as generally illustrated by Figs. 1, 1a and 4, this high value of. the ratio may obtain. Ratios materially greater than unity and of the order of 10 or 20 may be utilized also in the case of charging storage batteries in a circuit arrangement generally illustrated by Fig. 3. In the case of battery charging the inductance or reacd tor has the further function of suitably limiting or regulating the charging rate of the battery. In the case of are or arc welding circuits, such as generally illustrated by Fig. 2, and in which generally the current is of high magnitude, the ratio of reactance to resistance, external to the valve structure, may be approximately unity, and in some cases less than unity.

In general where the inductance is a working inductance, illustrated generally by Figs. 1, 1a and 4, this ratio of reactance to resistance is generally at least unity and generally and preferably many times unity. In general, in the case where the inductance is idle, or not a working inductance, and the load has relatively high ohmic resistance, for highest efliciency the ratio of reactance to resistance will generally be less than or approximately unity.

The ratio of the root means square forwarded direct current to root mean square inverse current is generally greater than 2 and may be 4 to 6, or higher.

The efliciency of operation is the higher as the ratio of the fall of potential across the im dance external to the valve structure is igher; and this ratio in some instances may range upwardly to a magnitude of the order of 10.

Fig. 8 com rises characteristic curves illustrative of t e choices of relations of circuit factors and conditions which may be resorted to to effect the results contemplated by my invention.

Ordinatesare magnitudes of the ratio of positive or direct current, root mean square value, to negative or inverse current, root mean square value; and abscissae are magnitudes of the expression or ratio as X in which R is the non-inductive resistance of the circuit external to the valve or valves; X is the total inductive reactance of the cir cuit; and K is the voltage drop (root mean square values, both direct and inverse) across the impedance external to the valve or valves, divided by the number of cells or valves in series. If however K represents line voltage divided by the number of cells or valves in series, each characteristic curve will be of the same type, to wit, in a broad sense hyperbolic, but will be displaced somewhat from the corresponding curve of Fig. 8. Furthermore in the foregoing expression K is itself proportional to Of Fig. 8 the curve 12 applies to a coppercuprous oxide valve or several of them in series, of the present Rectox or Kuprox type manufactured respectively by the Westinghouse Electric & Manufacturing Company and by Kodel Manufacturing Company, Cincinnati, Ohio.

Curves 13 and 14 apply, respectively, to wet electrolytic and dry electrolytic rectifiers.

Referring to curve 12, and assuming a ratio of direct to inverse current of 7, the corresponding value of is 3.5, which, for an assumed value of equal to 0.1, gives a value for K equal to 35 which is the number of volts per cell or valve found by dividing the voltage drop across the impedance external to the valve or valves by the number of valves in series. Assuming a certain efiiciency, in terms of voltage drop, and assuming a line voltage of 110 volts, the voltage drop across the load or impedance external to the valve or valves is 0.9 times 110 or 99 volts which, divided by 35, gives roughly a value of K corresponding with three valves or cells in series. If the individual valves be of large enough surface as regards active rectifying area, for the magnitude of the load current, i. e. root mean square value of both positive and inverse currents, paralleling of the valves will be unnecessary. This is the case for example for Rectox and Kuprox valves operated at a current density of about of an ampere per square inch of rectifying area, at which current density without forced ventilation or cooling, the temperature attained will be within desired limits. For example if the individual valves have one square inch of rectifying area, and the load current, aforesaid, shall be one ampere, the rectifying valve system will 'comprlse 9 cells or valves, 3 in parallel and 3 in series.

Each of the curves 12, 13 and 14 is exressible in an algebraic formula which may be utilized in lieu of the curves themselves in the manner above indicated. The equation will be of the general form of in which Z is a constant depending upon the characteristics of the valve and which, for copper-cuprous oxide valves is of the order of 250, for wet electrolytic valves is approximately 800, and for dry electrolytic valves is of the order of 100 to 125; y represents ratio of root means square values of direct to inverse current; :1: represents the aforesaid relation and n is an exponent of a magnitude depending upon the characteristics of the valve, and for copper-cuprous oxide valves has been found in some instances at least to be greater than 2 and of the order of 2.2, and approximately 1.2 and 4 for wet and dry electrolytic valves, respectively. However the characteristic curves of Fig. 8 suflice as a means for determining the magnitude of various essential circuit factors.

The point on any of the curves of Fig. 8 selected for operation depends upon the desired ratio of forward or positive current to inverse current. If that ratio is first chosen, then the corresponding point on any of the curves will give by reading downwardly to the axis of abscissae the corresponding approximate value of and the several factors of this expression may then further be selected or chosen, particularly R and X, suited to the particular purpose for which the valve of selected type is to be used. Conversely, with BE X chosen, the resultant ratio of forward to inverse current will be approximately indicated.

Fig. 9 comprises oscillograms of a circuit operated from a 110 volt 60 cycle supply, containing 20 ohms inductive reactance, 2 ohms non-inductive resistance external to the valves, 3 Kuprox valves in series, 6 in parallel, each having a rectifier plate or disk about 2 inches square, with an effective rectifying surface of about 3 square inches. Ordinates are magnitudes of voltage and curlent, and abscissae represent time interva The curve F represents the sinusoidal impressed or line voltage; I+ represents the current in the direct or positive sense, having a duration, in practice, of from about 27 to about 290 electrical degrees; I-- represents the inverse current; E+ represents the positive fall of potential across the impedance external to the valves; E- represents the negative fall of potential across the terminals of the impedance external to the valves; 0+ represents the positive fall of potential across the terminals of the valves in series; and ethe negative fall of potential across the terminals of the series of valves. These oscillograms are not to scale, but are approximately correct and illustrate the reactions and effective proportions of circuits embodying my invention.

Fig. 10 comprises curves relating to the same circuit described in connection with Fig. 9. In it the curve having the positive and negative components, respectively, 1+ and I- is for one coil of an electric hammer or reciprocating motor having the aforesaid reactance of ohms, with the core reciprocating in synchronism with the line current. The curve iis that of the inverse current when the core of the hammer was held in fixed position corresponding with minimum magnetic circuit reluctance, the component I+ being substantially the same for both conditions of core reciprocating or fixed. Comparison of I-*. with 5- shows the influence of movement, of any portion of the magnetic circuit of an inductive reactor, upon, generally in reducing, the inverse current. The dotted curve whose positive and negative components are indicated at n+ and,n, respectively, represents the current magnitudes when for the reciprocating motor or hammer winding is substituted a non-inductive resistance or non-reactive load of substantially the same number of ohms as the impedance of the hammer winding, the valve structure being the same as before. This dotted line curve shows first that the current is strictly in phase with the electro-motive-force and secondly that the of 76% of the peak value of the positive current wave represented by 10+, and the root means s uare negative or inverse current is many times larger than the root mean square inverse or negative current I or z'-. Furthermore the peak value of the current 13-, corresponding to an idle inductance in the circuit, is about 24% of the peak value of the current 1+, and the peak value of the curve I-, for a working inductance, is about 16% of 1+. Obviously the heating efiect of either current I or i is small compared to nand hence the aging efiect upon the valve is.enormously reduced b the employment of inductance with smal number of valves in series, and in addition the ratio of the positive or direct to the inverse current is many times greater for 1+ than for n+.

By way of example of proportions falling within my invention, and more particularly relating to a two coil reciprocating motor-or hammer, as illustrated in Fig. 1a, each of the hammer windings or inductances L had a reactance, at cycles, of 44.9 ohms; the resistance of each coil circuit external to the valves, of the copper-cuprous oxide type, was 2 ohms, corresponding to a ratio of reactance to resistance of about 22.5. The root mean square current in the positive or direct sense was 1.9 amperes through each coil or inductance; the root mean square negative or inverse current was 0.27 ampere. There were 2 valves V and VI in series with each coil, 2 valves in parallel. Each individual valve had an efiective rectifying surface of about 3.5 s uare inches. The current density of recti ying surface was of the order of A; ampere per square inch, with a line voltage of 110 volts. The temperature of the valves remained sufliciently low, well below 140 F., without air blast or other artificial cooling. The hammer or reciprocating motor was utilized to drill holes in concrete or stone and to chip or cut concrete metal or stone, at or higher than its usua rated capacity when previously used in connection with thermionic valves.

I have also operated the same reciprocating motor or hammer, from a 60 cycle 110 volt circuit, with 10 copper-cuprous oxide valves in series, reactance 90 ohms, resistance 8 ohms external to valves. This relation also is within my invention.

A single copper-cuprous oxide valve in series with each coil of a two coil reciprocating motor or electrical percussive tool of the same type has also been used by me on a 110 volt alternating current circuit. This also is within my invention.

The reduction in number of valves in series with the windings of reciprocating motors, such as described in the fore oing examples, increases the efliciency of e valves and of the circuit or system, and in fact increases the mechanical output of the motor, for a given amount of electric energy consumed, over my prior practice in which thermionic valves were utilized. Furthermore, with reciprocating motors of the character specified in the foregoing examples, the elliciency was reduced, as mm a mt 15')?- to 20%, when the number of valves in series was increased to that number which by the valve action itself and without substantial benefit from inductance, the inverse current was small or insubstantial.

For an electric bell system such as shown in Fig. 4, I have operated the same from a 60 cycle 110 volt circuit through 2 valves V in series of the cop r-cuprous oxide type, eaeh havin a rectifying surface of about 2 square inc 10s. The magnet winding had a reactance of 1090 ohms at 60 c cles, and the resistance of the circuit externalto the valves was 50 ohms, giving a reactance to resistance ratio of about 22. I have also utilized, at 10 volts, and briefly at 110 volts, one coppercuprous oxide valve in series with a bell winding 7, 7 whose reactance at 60 cycles was 15.2 ohms and the resistance 1.4 ohms, giving a reactance to resistance ratio of about 11, the valve having a rectifying surface of about 2 square inches. This combination also is within the scope of my invention.

It will be understood that such a valveinductance relation as'indicated in Fig. 4 has wide application. For example it may be used for high power systems as when the electromagnet 7 is utilized to vibrate a screen or sieve, to tap a foundry mould etc.

In circuits of the characters described, in which the inductance may be in whole or in part a working inductance, and of the general character of Figs. 1, 1a and 4, in general the ratio of the inductance'to resistance of the circuit, or the ratio of the inductive reactance to resistance of the circuit external to the valve structure, may be anything suitable or desirable, but is enerally greater than unity, and may be as high as 20 or more, the number of valves in series being that generally herein described. When the circuit is not operating continuously, but only infrequently or intermittently, and where considerations of efliciency are not important, or where only low power is involved, the aforesaid ratio may have a magnitude lying within the lower ran e of values, and yet only a low number 0 valves in series need be used.

An arc circuit, generically indicated in Fi 2, is generally itself a low voltage circuit,-

inc uding the case of arc welding where very large current at low voltage is utilized. For

1 this purpose a step-down transformer T may be utilized, serving merely to procure a magnitude of voltage impressed upon the arc circuit which is suited thereto; the transformer T may be omitted however with the employment of more valves in series, though still reduced in number when compared with the voltage of the circuit A. Notwithstanding the employment of the transformer T, the number of valves in series is small compared to the voltage delivered by the transformer secondary.

Where the are a is used for welding, the current may have a magnitude of 200 amperes or more, requiring for each valve in series, a great number, as one hundred or more in parallel, particularly when of the cuprous oxide type of usual size.

ln such a circuit, enerically represented by Fig. 2 the voltage drop across the welding are itselfjs low, but nevertheless this voltage drop is generally substantially the entire or a very large portion of the entire voltage drop in the circuit external to the valve structure, and the voltage drop across the are or external circuit may sometimes be less than the drop of voltage across the valve structure itself, comprising a number of valves in series with a great number in parallel. In general, however, the voltage dro across the valve structure is about equa to or less than the voltage drop across the are or circuit external to the valve structure.

In the case of an arc welder, it is from some standpoints desirable to have a high ratio of reactance to resistance external to the valve structure. On the other hand, in the case of arc welders or other circuits where the current involved is of a high order of magnitude, impl ing a great number of valves in parallel or w at may be termed large valve structure, this ratio of reactance to resistance may be considerably smaller, as of the order of unity, or even less than unity, to permit further reduction of the number of valves in series, because for each valve in series that may be dispensed with, there may be a saving of one hundred or more valves in parallel, particularly in the case of cuprous oxide valves. Presence of inverse current under such circumstances is not altogether disadvantageous, and generally the saving in cost of valve structure is more important.

In charging storage batteries, generically indicated by Fig. 3, it is preferable that, with the low or reduced number of valves in series,

as herein described, the inductance be great rectification, that double wave rectification may'be utilized. However, single wave rectification generally sufiices, particularlywhere so high inductance is used, with reduced number of valves in series, that the inverse current is insubstantial or negligibly small.

By way of example, ina system of the general character illustrated by Fig. 3, where the battery S is a so-called 6-volt battery, and

circuit external to the valve structure 1.8

ohms, giving a ratio of reactance to resistance of about 19, the current being about 2.5 amperes with three valves of the cuprous-oxide type in series, and a suitable number in ar- N allel to carry the current in question wit out overheating or deterioration. In such a case, the inverse current is insubstantial, the cost of the inductive reactor, as L, under these circumstances would be less than half the cost of the transformer necessary to step 'down the line voltage; and because of the few valves in series, the cost of the valve structure is of the order of half that of systems commonly emloyed. For purposes of comparison it may be stated, that in one instance of common practice, -utilizing cuprous-oxide valves, for charging a 6-volt storage battery, charging current 1 am re, there has been utilized a transformer or stepping down the line voltage to a secondary pressureof 6 volts, with 4 valves in series 2 in parallel in each side or branch of a double wave recti g system, requiring a total of 16 valves; w ereas, the maximum number of valves required in accordance with my invention, would be 8. In another instance, for charging a 6-volt storage battery at 4 amperes charging rate, with 0. ate down transformer, 4 cu rous-oxide va ves were utilized in series, wit 4 in multiple in each branch or side of the full wave rectifying system.

In general, in battery charging, the ratio of reactance to resistance is preferably high, as, for exam le, from about 15 to about 20,

articularly 1n the case of single wave rectication.

In the case of cuprous-oxide valves, such as the Reetox and Ku rox hereinbefore referred to, the current ensity, by recourse to my invention, may be one-third of an ampere or hi her, as .4 ampere, per square inch of reetig'ing surface, without artificial or forced cooling; i. e., when the valves are either supplied with radiating fins, as in the 60 case of Rectox, or themselves are in the form of discs or fins, as in the case of Kuprox, the valves being assembled in reasonably compact groups, side by side. As commonly now produced, the valves are assembled as close together as possible, and in consequence the heat from one valve affects the temperature of the adjacent valve, causing greater temperature rise for a given current density than would otherwise be the case if there were fewer valves within the same space, or if the valves were further apart. In consequence, where fewer valves in series are employed in accordance with my invention, the greater will be the current carrying capacity per square inch of rectifying surface without undue heating or deterioration.

In accordance with my invention, as stated. upwards of one-third of an ampere (total root means square value of both forward and inverse current) per square inch of rectifying surface is 'ood practice without artificial coolin ithout overheating or deterioration, t 1e current density is increased in accordance with my invention about 15 to 20%. While it has been common to utilize that number of cuprous oxide valves in series,

corresponding with about 4 volts impressed voltage per valve, and generally about 3 volts per valve, in accordance with my invention the impressed line voltage per valve is materially greater, in many cases as much as eight times that aforesaid. In the case of arc welders, however, the impressed voltage per valve is about five volts, which too is substantially greater than prior practice above mentioned.

B forced or artificial cooling of cuprousoxi e valves, particularly when assembled as customary,and as above referred to, the current density may be materially increased and easily doubled, as when the cooling medium is air whose velocity is about 1000 feet per minute, in which case with a room or ambient temperature of 80 degrees F., the valves will operate safely below deteriorating temperature and continuously for-thousands of ours and practically indefinitely. I

In the case of an arc welder system, in accordance with my invention, for 200 amperes,

with the valves arranged fairly uniformly over an area of about 254 square inches, with three stacks or tiers of valves each occupying such area and with about 4 inch space between stacks, sufiicient cooling is obtained vif there is passed through the valve assembly 1750 cubic feet of air per minute, the velocity above mentioned being that of the air as it left the stackof valves furthest from the blower or fan, the entire valve assembly being about 6 inches deep and the blower or fan disposed about 5 inches from the nearest stack or tier.

The reactance X hereinbefore referred to and the non-inductive resistance of the circuit external to the valve are the components of an impedance which is the quotient of the root mean square value of the impressed sinusoidal electro-motive force divided by the root mean square (positive and inverse) current. The non-inductive resistance of the circuit being known or readily determ ned, the reactance is determinable since the aforesaid quotient or impedance has become known.

The root mean square values of current and/or electro-motive-force hereinbefore referred to are those which are measured by two coil ammeters or two coil volt-meters, of the electro-dynamometer ty of which it is characteristic that the stationary field producing coil is in series with the deflecting or moving coil.

For measuring the ratios of root mean square values of positive or direct current impulses to root mean square values of negative or inverse current impulses, the ratios of these direct and inverse currents being ordinates in Fig. 8, the positive or direct and inverse or negative current impulses are isolated from each other in ditlerent circuit branches by recourse to use of perfect valves, such as thermionic valves, connected in reverse senses in branches in parallel with each other, with an ammeter in series with each, these parallel branches being connected in series with the valve whose direct and inverse currents are to be measured, as well understood in the art.

It shall be understood that my invention is not limited to circuits or systems utilizing small amounts of electrical power, but is utilizable as well, by recourse to generally the relations and proportions described, where large amounts of electric power are to be utilized and controlled, as for driving electric cars, trains, locomotives, or other loads, by motors, of the direct currenttype, between which and an alternating current su ply intervenes valve structure of the c aracter herein described, a reduced or low number of valves in series being utilizable when having the benefit, as herein described, of associated inductance. Similarly, the same relations may be utilized in any other high power circuit for any purpose, and, whether the load be inductive or non-inductive, the circuit will contain sufiicient inductance to make possible the aforesaid reduced number of valves in series, and to make possible in addition any one or more of the advantages herein described.

From the foregoing it will appear that in general, in accor ance with my invention, inductance is utilized in substituton for a art of that number of valves in series w ich would be necessary to reduce the inverse current to an insubstantial or negligible magnitude, the magnitude of the inductance being such as to determine the magnitude of the inverse current, allowing it in some instances to be substantial and for other purposes restricting it to insubstantial or negligible magnitude. It is further apparent that notwithstandin the reduction of number of valves in series, overheating or deterioration is prevented, even when the current rating of the valve structure is increased as it may be, and, in addition, higher electrical conversion or etliciency and other advantages are obtainable; and that, in general, the cost of the valve structure and the space occupied by it are materially reduced for a given duty.

For an imp alternati' electro-motive force of given magnitude, t e impedance of the circuit, inclu the inductive reactance, atlects or determines the magnitude of current passed by the valve structure, and the inductive reactance is of such magnitude and so operates in association with other impedance, including resistance, of the valve circuit that, without overheating or rapid deterioration of the valve structure, it may be materiall less costly for the same duty than hereto ore realized; and it is smaller, for a given eti'ect orduty,thanheretofore re'alized, either as regards the size of an individual valve or individual valves, or as regards the number of valves in series, or in parallel, or both. It is smaller as regards the number of valves in series when that number is less than the normal number of valves in series, that is, such that the inverse current is small or negligible without the use of inductance for determinin the inverse current.

For brevity in the appended claims the term valve structure comprehends either one or more valves in series, and any number in parallel; the term imperfect as applied to a valve or valve structure designates a valve or valve structure havi the characteristic of permitting substantia inverse current, and excludes thermionic and similar substantially rfect valves which permit ractically no inverse current; the term 01:- ide as applied to a valve or valve structure refers to type a valves, particularly copper-cuprous oxide valves; and the term overheating as related to the valve structure refers to that degree of heating which, in continuous intermittent or infrequent operation, would cause rapid deterioration of the. valve structure, as within about 500 to 1000 hours total use, or, in the case of coppercuprous oxide valves a temperature thereof in excess of about 140 F.

What I claim is:

1. In the art of rectification by impressingan alternating electro-motive-force upon a circuit including a load and imperfect valve structure, the method of reducing the size of the valve structure for a given dut which comprises utilizing such number 0 imperfect valves in series that there tends to flow an inverse current of a magnitude to cause overheating of the valve structure, and rendering the circuit inductive to a degree which limits the inverse current to a lesser ma itude which prevents overheating of the va ve structure.

2. In the art of rectification by impression of an alternating electro-motive-foree upon a circuit including a load and imperfect valve structure, the method of increasing the caacity of the valve structure without everiieating which comprises utilizin in series such number of imperfect valves t at the inversecurrent tending to flow is of a magnitude to cause overheating, and rendering effective in the circuit inductance of a magnitude to limit the inverse current to a lesser magnitude which prevents overheating of the valve structure. 1

3. In a method of rectification by imperfect valve structure in a circuit including a load and a source of alternating clectro-motive force, the number of valves in series being such that the inverse current tending to flow is of' a magnitude adapted to cause sub stantial deterioration of the valve structure, the step which consists inrendering elfective in the circuit an inductance of a niagntude to limit the inverse current to a lesser magnitude and to efieet passage of greater load current, without substantial deterioration of the valve structure.

4. In the art of rectification, the method which comprises impressing an alternating electro-motlve-force upon a c'trcuit including im rfect valve structure and a load, utilizing such number'of imperfect valves in series that there tends to flow an inverse current whose heating effect with that of the forward current is excessive, and by inductive reactance limiting the inverse current to a lesser magnitude such that with the corresponding forward current overheating-cf the valve structure is prevented.

5. In the art of rectification, the method which comprises impressing an alternating electro-motive-force upon. a circuit includ in imperfect valve structure and a load, and

re ucing the losses in the valve structure by utilizing such number of imperfect valves in series that inverse current of a magnitude which would cause substantial deterioration tends to flow, andlimiting the inverse current by inductive reactance in the circuit to such lesser value that overheating and substantial deterioration of the valve structure is prevented.

7. In the art of rectification, the method which comprises impressing an alternating electro-motive-force upon a circuit includin imperfect valve structure and a load, an

increasing the impressed voltage fper valve by utilizing such number of imper ect valves in series that an inverse current of excessive heating efl'ect tends to flow, and by inductive reactance limiting the inverse current to a lesser value' to prevent overheating of the a valve structure. v

8. In the art of rectification, the method which comprises impressing an alternating electro-motive-force upon a circuit including imperfect valve structure and a load,.and increasing the current density. without overelectro-motive-force upon a circuit including imperfect valve structure and a load, and in creasing the electrical power transmitted through said valve structure to said load without overheatin of said valve structure by utilizing in series such number of imperfect valves that there tends to flow an inverse current of excessive heating effect, and by inductive reactance limiting the inverse current to lesser magnitude that overheating of the valve structure is revented.

10. In the art of recti cation by im rfect valve structure in circuit with a 10a and a source of alternating electro-motive-force, the method which comprises utilizin such number of imperfectvalves in seriest at an inverse current of excessive heating effect tends to flow,and imparting to the circuit an inductive reactance of such magnitude that the. inverse current is limited to a magnitude which is less than half the magnitude of the forward current-and which prevents overheatin of the valve structure.

11. the art of rectification by im erfect valve structure in circuit with a 10a and a source of alternating eleetro-motiveforce,

the method which comprises'utilizing such number of imperfect valves in series that an inverse current of excessive heating effect tends to flow, and imparting to the circuit inductive reaetanee of such magnitude that the inverse current is limited to a lesser magnitude which prevents overheating of the valve structure while the voltage drop across the valve structure does not exceed the voltage drop across the impedance of the circuit external to the valve structure.

12. In the art of rectification by imperfect 4 number of imperfect valves in series that an valve structure in circuit with a load and a source of alternating electro motive-force, the method which comprises utilizin number of imperfect valves in series t at an inverse current of excessive heating. effect tends to flow, the valve structure being of that character in which the inverse current rapidly increases with small increase of inverse voltage, and im arting to the circuit inductive reactance 0 that magnitude which limits the inverse current'to a value below that at which it rapidly increases with small increase of inverse voltage.

14. In the art of rectification, the method which comprises impressing an alternating electro-motive-force upon a circuit includin imperfect valve structure and a loa utilizing such number of imperfect valves in series that there tends to flow an inverse current whose heatin effect is excessive, artifically cooling t e valve structure, and by inductive reactance limiting the inverse current to a lesser magnitude such that with said cooling ov'erheating of the valve structure is prevented.

15. In the art of rectification, the method which comprises impressing an alternating electro-motive-force upon a circuit including a load and imperfect valve structure of the copper-cuprous oxide t utilizing in series such number of said imperfect valves that there tends to flow an inverse current of excessive heating effect, and effecting a current density of at least ampere per square inch without overheating of the valve structure by inductive reactance of a magnitude which limits the inverse current to a lesser value to prevent'overheating of the valve structure.

16. In the art of rectification, the method which comprises impressing an alternating electro-motive-force upon a circuit including a load and imperfect valve structure of the copper-cuprous oxide type, utilizing in series such number of said imperfect valves that there tends to flow an inverse current of excessive heating efl'ect, effecting a current density of at-least /3 am ere per square inch without overheating o the valve structure by inductive reactance of a magnitude which limits the inverse current to a lesser value to prevent overheating of the valve structure, and artificially cooling the valve structure for materially increasing said current density while preventing overheating of the valve structure.

17. In the art of rectification by imperfect such valve structure in circuit with a load and a source of a1 electro-motive-foree, the method which comprises I u such nnmber ofim ectvalvesinseries tthe-impressed ectro-motive-force per valve is at easttwice the im electro-motive-foree per valve when e number in series is such that there is insubstantial inverse current, and by inductance limiting the inverse current to a lesser-magnitude such as to prevent overheating of the valve structure.

18. In a rectifying system, a sourceof-altemating electro-motive-force and an asso ciated load circuit inclu solid .imperfect valve structure exhibit l ttle or no ization, the number of v ves in series ing such that there tends to flow an inverse current of excessive heating efiect, andinductance in said circuit of a magnitude which.

limits the inverse current to a lesser magmtude which prevents overheating of the valve structure.

19. In a rectifying ternating electro-motive-force and an'associated load circuit inclu solid imperfect valve structure exhibitin little or no larization, the numberof v ves in series ing such that there tends to flow an inverse current of excessive heating effect, inductance of such magnitude in said circuit that the inverse current is limited to a substantially lesser ma I itude, and means for artificiall cooling said valve structure cooperating wi said inductance in preventing excessive heating thereof. f

20. In a rectifying system, a source of alternating electro-motive-force and'an associated load circuit including solid imperfect valve structure exhibiting little or no polarization, the number of valves in series being such that there tends to flow an inverse current of excessive heating efiect, inductance in said circuit of a magnitude which limits the inverse current to a lesser magnitude which prevents overheating of the valve structure, and an element actuated by the magnetic field of at least a portion of the inductance of said circuit.

21. In a rectifying system, a source of alternating electro-motive-force and an associated load circuit including solid imperfect valve structure exhibiti little or no olarization, the number of va ves in series eing such that there tends to flow an inverse current of excessive heating effect, and inductance in said circuit of a magnitude which limits the inverse current to a lesser magnitude which prevents overheating of the valve structure, the impedance of said circuit being of such magnitude that the -.current density is increased without overheating of the valve structure by the co-action of said inductance.

22. In a rectifying system, a source of alternating electro-motive force and an. associated load circuit including solid imperfect larsystem, a source of al-- zation, the number of va ves in series being such'that the impressed electro-motive-force per valve is substantially greater than the impressed electromotive-force per .valve when the number in series is such that insub-' sta'ntial inverse current flows, and inductance in said circuit of a magnitude to limit theinverse current to a value which heating of the valve structure.

23. In a rectifying system, a source of alternating electro-motive-force and an associated load circuit including solid imperfect valve structure exhibiting little or no polarization, the number of valves in series being such that the impressed electro-motive-force per valve is substantially greater than the impressed electro-motive-force per valve when the number in series is such that insubstantial inverse current flows, and inductance in said circuit of a magnitude to limit the inverse current to a value which prevents overheating of the valve structure, the ratio of reactance to resistance external to the valve structure being at least unity.

24. In a rectifying system, a source of alternating electro-motive-force and an associated load circuit including solid imperfect valve structure exhibiting little or no po larization, the number of valves in series being such that the impremed electro-motiveforce per valve is substantially greater than the impressed electro-motive-force per valve when the number in series is such that insubstantial inverse currentflows, and inductance in said circuit of a magnitude to limit the inverse current to a value which prevents overheating of the valve structure, the fall of potenital across the impedance external to the valve structure being at least as great as the fall of potential across -the valve structure.

25. In a rectifying system, a source of alternating electro-rnotive-force and an associated load circuit including solid imperfect valve structure exhibiting little or no polarization, the number of valves in series being such that the impressed electro-motive-force per valve is substantially greater than the impressed electro-motive-force per valve when the number in series is such that insubstantial inverse current flows, inductance in said circuit of a magnitude to limit the inverse current to avalue which prevents overheating of the valve structure, and an element actuated by the magnetic field of at least a portion of the inductance of --said circuit, the ratio'of reactance to resistance external to the valve structure being at least five.

26. In a rectifying system, a source of al ternating electro-motive-force and an associated load circuit including solid imperfect valve structure exhibiting little or no polarization, the number of valves in series being such that the impressed electro-motive-force per valve is substantially greater than the valve structure exhibitin little or no polariprevents over-- impressed electro-motive-force per valve when thenumber in series is such that. insubstantial inverse current flows, and inductance in-said circuit of a magnitude to limit the inverse current to a value which prevents overheating of the valve structure, and which effects a ratio of forward to inverse current of at least two. 7

27. In a rectifying system, a source of alternating electro motive-force and an associated load circuit including valve-structure of the copper-cuprous' oxide t pe, thenumber of valves in series being .suc that there tends to flow-an inverse current of excessive heating effect, and inductance in said circuit of a magnitude which limits the inverse current to a lesser magnitude which prevents overheatin of the valve structure.

28. n a rectifying system, a source of alternatin electro-motive-force and an associated load circuit includingvalve structure of the copper-cu prous oxide t pe, the number of valves in series being suc that there tends to flow an inverse current of excessive heating effect, and inductance in said circuit of a magnitude which limits the inverse current to a substantially lesser magnitude and permits a current density of at least ,4; ampere per square inch of rectifying surface without overheating of the valve structure.

29. In a rectifying system, a source of a1- ternating electro-motive-force and an associated load circuit including valve structure of the copper-cuprous, oxide type, the number of valves in series being such that there tends to flow an inverse current of excessive heating efl'ect, inductance in said circuit of a ma nitude which limits the inverse current to a esser magnitude which prevents overheating of the valve structure, and means for artificially cooling the valve structure to effect materially greater current density without overheating of the valve structure.

30. In a rectifying system, a source of alternating electro-motive-force and an associated load circuit'including solid imperfect valvestructure, said valve structure being further of the character that the inverse current rapidly increases with small increase of inverse volta e, the number of valves in series being such t at' the-inverse current is of a magnitude rapidly increasing to a value adapted to cause substantial deterioration of the valve structure with small increase of inverse voltage, and inductance in said circuit of a magnitude which limits the inverse voltage to a magnitude below. that at which the inverse current ra idly increases as aforesaid, to prevent su stantial deterioration of the valve structure.

31. The combinationwith a source of alternating current of a load circuit, solid imperfect valve structure exhibiting little or no olarization included in said circuit, the numr of valves in series being less than the number of valvesin series a sea insubstantial inverse current, and inductance effective in said circuit ofa ma tude for maintaining the temperature of f e valve structure below that at which it rapidly deteriorates while permitting said valve structure to conduct greater load currentthan permissible'without overheat 32. The com ination with a source of alternating current, of a'load circuit, solid imperfect valve structure exhibiting littleor no larization included in said circuit, and inuctive reactance associated with said valve structure, the number of valves in series being such that in the absence of said reactanee inverse current of excessive heating efiect flows, said reactance having such ma tude that the inverse current is of a magmtude to rmit said valve structure to pass greater oad current than otherwise permissible with out overheatin 33. The com ination with 'a source of alternating current, of a load circuit, solid imperfect valve structure exhibiting little or no polarization includedin said circuit, means for artificially cooling said valve structure, and inductive reactance associated with said valve structure, the number of valves in series being such that in the absence of said reac'tance inverse current of excessive heating effect flows, said reactance having such magnitude that the inverse current is of a magnitude to permit said valve structure, when cooled by said cooling means, to pass greater load current than otherwise permissible with-, out overheatin 34. The com ination with a source of alternatin current, of imperfect valve structure, an inductive reactance and resistance in series therewith, said reactance having such great magnitude with respect to said resistance that the ratio of direct to inverse current is at least two, and said ratio, resistance, reactance, and number of valves in series hav ing the relation wherein 3 is said ratio, n is an exponent whose magnitude depends upon the characteristics of the valve, 2: is K t mes the ratio of the resistance to reactance, where K is the line voltage or voltagedrop across the impedance external to the valve structure divided by the number of valves in series, and Z is a constant.

35. The combination with a source of alternating current, of copper-cuprous oxide valve structure, an inductive reactance and resistance in series herewith, said reactance having such great magnitude with respect to said resistance that the ratio of direct to inverse current is at least four, and said ratio, resistance, reactance and number of valves in series hav ing the relation mg a ma wherein y is, said ratio, a is an exponent of the order of2, a: is K times the ratio of the resistance to reactance, where K is the line voltage or voltage drop across the im ance external to the'valve structure divided by the number of valves in series, and Z is anitude, the ratio of inductive reactance to resistanee external to said valve structure being at least ten, the ratio of forward to inverse current being at least six,and the fall of potential for the load current across the im-' peda'nce external to the valve structure hav- 'tude at least four times the fall of potential across said valve 87. The combination with a source of alternating current of valve structure of the copper-cuprous oxide ty in circuit therewith, the number of valves 111 series being such that substantial inverse current tends to flow, inductance in said circuit for limiting the inverse current to a substantially lesser magnitude, the ratio of inductive reactanoe to resistance external to said valve structure being .at least ten, the ratio of forward to inverse current being at least six, and the fall of potential for the load current across the im pedanceexternal to the valve structure having a magnitude at least four times the fall of potential across said valve structure, and means actuatedby the magnetic field of at least a portion of the inductance of said circuit for performing mechanical work.

38. In the art of rectification by imperfect valve action, the method which comprises impressing a voltage of such magnitude upon' imperfect valve structure of such number of valves in series that said voltage divided by the number of valves in series is greater than the breakdown voltage per valve, and applying inductive reactance, effectively in series with said valve structure, of magnitude to prevent injury to said valve structure.

39. In a rectifying system, thecombination with a source of alternating voltage and imperfect valve structure comprising such number of imperfect valves in series that said voltage divided by the number of valves in series is greater than the breakdown voltage per valve, and inductance, ,efl'ectively in series with said valve structure, of magnitude to prevent injury to said valve structure.

40. The combination with a source of alternating current, of a load circuit, imperfect valve structure, the number of valves in series being such that there tends to flow in verse current of such magnitude as to cause substantial deterioration of the valve structure, and an inductive translating device, effectively in series with said valve structure in said load. circuit, for performing mechanical work and whose inductive reactance varies in performance of the work, the inductance of said circuit notwthstanding said variation of reactance of said device limiting the inverse current to a substantiall lesser magnitude.

In testimony whereo I have hereunto affixed my signature the 30th day of April,

CARL S. WEYANDT.

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