US1824529A - Electrical condenser - Google Patents

Description

Sept. 22, 1931. w. M. BAILEY ELECTRICAL CONDENSER Original Filed May 2 1924 Patented Sept. 22, 1931 UNITED STATESPATENT OFFICE WILLIAM H. BAILEY, OI LYNN, MASSACHUSETTS, ASSIIGNOR TO WIRELESS SPECIALTY APPARATUS COIIPANY, OE BOSTON, MASSACHUSETTS, A CORPORATION OF NEW YORK ' ELECTRICAL CONDENSER Original application iiled Kay 27, 1924, Serial No. 716,107. Divided and this application iiled larch 80, 1926. Serial No. 88,412.

This application is a division of my application Serial No. 716,107, filed May 27, 1924. v

This invention relates to improvements in electrical condensers, particularly of the type wherein sheets of dielectric and conducting foils are built u 'in a stack, the dielectric sheets being pre erably at present of mica.

The invention relates more particularly to condensers designed to carry high currents of, say, ten amperes more or less and upwardly to hundreds of amperes; although certain structures embodying the invention are useful also for high potential service whether or not large currents be used. The invention is particularly useful with alternating currents of high amperage and high frequencies such as radio frequencies, as well-as for high potentials.

Heretofore in condensers of the foil-stack type, in designin the same for use 'with currents of more t an a few am eres, it has been necessary to increase great y the number of dielectric shee s, for the sole purpose of preventing serious over-heating of the condenser by such high currents. Inasmuch as good quality dielectric sheets for condenser work, such as good quality of the preferred mica sheets, is very expensive (i. e., many times more expensive than metal), and inasmuch as the amount of mica necessary to prevent over-heatin by the high currents increases ver rapidly with the am erage employed, t e cost in mica for suc high current mica-and-foil condensers has been very high heretofore. The reason wh the use of a much larger quantity of die ectric sheets resulted in reventing undue heating of the condenser y high currents was the consequent reduction ofcurrent per sheet and therefore the reduction of the watt loss per sheet, the total watt loss being dis ributed throu hout the increased number of sheets, there y providing a larger dissipating surface of the stack, 1. e., such surface comprising the margins of the mica sheets exposed from the foil-armature sheets in the stack. In order to maintain the originally desired capacity of the condenser when thus increasing the number of dielectric sheets, it was usually necessary to divide the stack into several serially-connected sections whereby the voltage per section was reduced and whereby also were reduced the losses due to brushing resulting "from high voltage. The greater part of the increase in dielectric shees to prevent over-heating by high currents was due to such series-sectional construction.

The principal and important object of the invention is to reduce the quantity of dielecw tric, such as mica, in condensers designed for high current duty. Other minor but valuable objects and results will be disclosed in connection with the drawings.

The invention consists, among other things, of a foil-stack condenser construction or the equivalent wherein the heat developed b the high alternating currents used is so e ciently conducted away from the stack as to make it unnecessary to increase the number of dielectric sheets (quantity of mica) for the purpose of causing, for each sheet, a lower heat generation and a higher heat-dissipation. In a certain sense, the invention involves to a certain extent the substitution of masses of metal constituting heat-absorbing, heat-conducting and heat-dissipating means, in lieu of the addition of much more expensive dielectric sheets.

Of the drawings,

Fig. 1 is a side elevation, partly in section, of the embodiment of the invention;

Fig. 2 is a sectional plan of Fig. 1 at lines 88 thereof, and

Fig. 3 is an exploded diagram showing the paths of the current thru the conducting foils of the two stack units connected in parallel.

There is shown an embodiment of the invention ina foil-armature and mica sheet condenser stack wherein the benefit of the thermal connection between the broad surfaces of the projecting foil-bunches and metal heat-conducting and heat-dissipating members, (such as and including the metal stack-clamps shown), is obtained by way of four projecting foil-bunches in a single clamped condenser unit, as" distinguished all ' ingseparator S between them. Metal members C1, C2 engage the end faces of the double stack and are held together by bolts B1 in their clamping positions. Insulating bushings I around bolts B1 insulate stack clamps C1 and C2 from one another. The parallel current paths through stack-units A and B are indicated most clearly in diagrammatic Fig. 3, with its arrows. Current enters t'rminal T1, say, and there divides. One path of the current extends from terminal T1 and through upper stack-clamp C1, to foil-bunch F1 of stack-unit A, to the interior of A itself, across the dielectric sheets to the oppositely poled foil-bunch F2, to and out of A via terminal T2. The other and parallel current path extends from terminal T1 through foilbunch F3 of stack-unit B, to the interior of B itself, across the dielectric sheets to the oppositely poled foil-bunch F4, to lower stack-clamp C2, and to and out terminal-T2. Thus both paths extend in parallel thru stack units A and B respectively en route from terminal T1 and stack-clampCl to terminal T2 and stack-clamp C2.

Referring to Figs. 1-2, (showing more of the structure yet in Fig. 1 somewhat exploded for clearness) right-hand projecting foilbunch F3 of lower stack unit B (Fig. 1) is clamped to upper stack-clamp C1 and to terminal T1, by means of auxiliary foil clamp memberKl and its bolts L1. Thus not only is terminal T1 electrically connected to foilbunch F3, but that foil-bunch is clamped in good thermal connection with upper stackclamp C1, so that the latter is a stack-terminal as well as a stack-clamp, the effect being that terminal T1 is provided, via heat-dissipator G1, with substantial heat-dissipating area exposed from the interior of the stack. The right-hand projecting foil-bunch F2 of upper stack unit A is clamped to lower stack clamp C2 and terminal T2 by auxiliary clamp member K4 and its bolts and compressing means L4. Thus not only is terminal T2 electrically connected to foil-bunch F2, but that foilbunch is clamped in good thermal connection with lower stack-clamp C2. so that the latter is a stack-terminal as well as a stackclamp, the-efiect being that terminal T2 is provided, via heat-dissipator G2, with sub- 1 stantial heat-dissipating area exposed from the interior of the stack; The above two foil clampings are permitted by cutting away part of (reducing) the width of the rightand projecting foil-bunches (see F2, F3, Fig. 2), so that these two foil-bunches may pass by one another without interference.

and its bolts L3. The individual armatures 1 of F 1 and F l need'not be reduced in width (see Fl, Fig. 2) because one bunch, F1, goes to C1 and the other, F4, to C2, i. e., away from one another without crossing.

In the form of Figs. 1-3, the total thermal and electrical path from the distributed dielectric sheets of the clamped stack is greatly increased (resistance is reduced) as compared with the condensers of the prior art, this result being due to the above-described constructionshown most clearly in Fig. 1; while the extended external area of heat-dissipators C1, C2 relative to the external area of the stack, affords ample means for dissipating at a desirable low stack-temperature such increased amount of heat conducted from the interior of the stack.

In general, condensers embodying this in-. vention are designed for moderate to high capacity of each clamped unit, .005 to .2 microfarad being obtained readily. With such rangeof capacity, almost any relation of capacity, voltage and current may be obtained by employin a plurality of units in various relations .0 series, parallel, or series-parallel.

The following has been a practical result of placing the distributed projecting .foilbunches in heat-conducting relation with one or more heat-dissipators of the below-specified order of exposed area. It has proven to be practicable to construct foil-stack condensers for high current duty with the same quantity of mica as for low current duty, and this whether the stack have only one or, a plurality of sections. That is, by positively removing from the stack, via-the foil-bunches and the heat-dissipators, the. heat developed in the stack by the use'of high currents, there is obviated all'need of increasing the quantity of mica for the purpose of ridding the stack of the heat so developed. And while, with the invention, some mica may be added to assist in removing heat from the stack, the need of the same is removed in proportion to the efficieney of application of this invention. Prior to the use of said invention, the use of high currents required each section of a series-sectional stack to contain additional sheets of mica (more than was needed to obtain a desired capacity, in order to avoid over-heating by such currents, and in order to maintain a given desired capacity -for the condenser'it was necessary to divide the stack into serially-connected sections (or to increase the number of sections in a stack already/comprising several series sections) when the number of s heets of mica in each original section was increased to prevent over l1eating. Hence the quantity of mica for a condenser of given capacity was great ly increased, due to the additional sheets in each section and to the additional sheets due to the addition of sections, so that a condenser for high current duty had very much more mica and a longer stack than a condenser for low current duty but of the same capacity. By this invention. the number of sheets. of mica in a condenser of given capacity can be kept substantially the same (for high or low current duty) whether the stack consist of a single section or of a plurality of sections connected in series. But the length of a stack provided with the invention (whether in a single section or a plurality of sections) is not necessarily less than that of a stack adapted by increase of mica to run without excessive heating under high current duty; because when the metal clamps for the condenser stack units are employed as in the invention. as the means removing heat via the projecting foil bunches. the metal of such clamps occupies more or less the same order of stack-length as when extra micas were employed for heat-distribution, being sometimes much greater due to the use of dissipating vaneson the clamps. In effect, therefore, the invention involves the substitution of metal for mica. the metal being very much cheaper. Various other advantages of the invention and of its various forms of embodiment have been specified above.

The efficiency oi the invention in removing heatfrom a'stack with which currents of very high amperage are employed may be dependent upon the etliciency of dissipation of heat from the metal masses which extract heat from the stack via the bunches of stackdistributed foils. That is, the maintenance of efiiciency in continuously maintaining the conduction of heat from the interior of the stack at a desirably low stack-temperature, is dependent upon the con inuous maintenance of heat-dissipation fromthe heat conducting metal masses.

The following general instructions are given for the guidance of the designer or constructor, relative to this important matter of exposed area of the heat-dissipating means of the invention. This is for condensers of various designs, and condensers for various services as to amperage frequencies and potential, in which the stack-generated heat may'vary within wide limits. This is on the premise that the heat-dissipators are the stack-clamps substantially enclosing the stack and thermally connected via the foils thermally to the dielectric sheets distributed through the stack; and that substantially sole reliance is placed on the exposed surfaces of the clamps for the removal of heat from the stack at the desirable low temperature thereareas of heat-dissipation should be increased at a more rapid rate than the increase in external stack area corresponding to the increased stack volume. The object of the designer of a given condenser for desired conditions of service is to ensure the removal of all stack-generated heat without permitting the temperature of the stack to rise above a given upper limit. I Therefore in designing a given condenser to embody the invention for given service, there will be calculated the amount of heatgenerated in the stack per unit of time, and the definite rate at which heat must be removed from the stack without blowing the stack or exceeding the upper limit of stack temperature. Since the invention provides adequate means of removing most rapidly from the interior of the stack,

the heat generated therein (provided thatafter being so removed it is dissipated from the removing means), therefore the designer is concerned onl in making sure to provide sufiicient exposed area of the heat-dissipator in good thermal connection with the distributed foils. provide such area sufiicient to dissipate the removed heat at the rate at which he has calculated that it will be generated in the stack. And while, in general, such area exposed to the cooling medium will be of a substantially greater general-order of magnitude than the exterior area of the electrostatically active portion of the stack itself, yet such area will vary within wide limits in various designs, on account of the several variables specified hereinbefore, including of course the kind of service and the amperage, frequency and potential to which the condenser is to be subjected. Within such wide limits there thus is provided a control by the designer of the stack temperature which he may desire to maintain. The area of the heat-dissipating means which is exposed to the cooling medium and thermally connected to the specified foils is, in any instance, that which causes dissipation of the heat generated inside the stack at the desired low stack-temperature. depending on the nature of the cooling medium, i. e., whether it is still air. a forced draft or a liquid circulation; and. of course, depending on the conditions of service, as to potential, amperage and frequency: this referring to the area of the heatdissipating projections or fins or vanes, if and when they are employed as they preferably will be, especially when still air is the cooling medium.

The designer therefore will Figs. 1 and 3, particularly Fig. 3 are diathe foils, butm'ay be any equivalent thermal connections between the armatures and the heat-dissipators. The preferred embodiment known'is as shown. I I particularly point out and distinctly claim the part, improvement, or combination which I. claim as my invention or discovery, as follows 1. The improvement in preventing undesirable temperature rise in the interior of an electrical condenser stack, which includes an electrically insulating separator dividing the stack electrically into two units; two metal clamping members in clamping engagement with the ends of the stack, and having substantial areas exposed from the stack for heat-dissipation; means holding said clamping members in their clamping positions;

' being connected thermally in parallel with heatdissi ators.

.means' insulating the clamping members from one another; wide armature-proj ections from armatures of each stack unit held in thermal connection'with one of said clamping and heat-dissipating members by lying fiat against it; and wide armature-projec-.

tions from other armatures of each stack unit held in thermal connection with the other clamping and heat-dissipating member by lying flat against it; the stack-units being connected thermally in parallel with one an- 4 other between the two clamping and heatdissipating members.

2. The improvement in 'preventing undesirable temperature rise in the interlor of an electrical condenser stack, which includes means dividing the stack electrically into two units; two metal stack-clamping members electricallyv insulated from one another, P

in clamping engagement with the ends of the stack, and having substantial areasexposed from the stack for heat-dissipation; armature-projections from armatures of each stack-unit, and two clamping devices holding said armature-projections respectively in thermal connection with the two stackclamping heat-dissipators; and armatureprojections from other armatures of each stack unitand two clamping devices holding said other armature-projections respectively in thermal connection .with the two stackclamping heat-dissipators; the stack-units one another between the two stack-clamping 3. The improvement in preventing undesirable temperature rise in-the interior of an electrical condenser stack, which includes means dividing the stack electrically into holding two units; two metal stack-clamping members electrically insulated from one another,

in clamping engagement with the ends of located alongside'the stack between the stacka I clamping members and respectively adjacent the respective stack-clamping members; armature-projections from armatures of the respective stack-units, and twoclamping devices holding said armature-projections respectively in thermal connection with the two stack-clamping heat-dissipators; and

the two separate terminals respectively in mechanical connection with the stack-clamping heat-dissipators and in electrical connection with said armature-projections; and armature-pro'ections from other armatures of the respective stack-units, and two clamping devices holding said other armature-projections respectivel in thermal connection with the two stack-clamping heatdissipators, and holding the two separate insulated terminals respectively in mechanical connection with the stack-clamping heatdissipators and in electrical connection with said last specified armature-projections.

4. The improvement in preventing undesirable temperature rise in the interior of an electrical condenser stack, which includes means dividing the stack electrically into two said thermal connections res ectively in therv mal connection with one 0 said heat-dissiating members; and two clam ing devices holding the other two of said t ermal connections respectively in thermal connection with the other heat-dissipating member; the stack units being connected thermally in parallel with one another between the two heatdiss'ipating members.

5. The improvement in preventing undesirable temperature rise in the interior of an electrical condenser stack, which includes means dividing the stack electricallyinto two units; two metal heat-dissipating members electrically insulated from one another; and fourk'wide armaturaprojections, two' from each stack unit; means holding each armature projection fiat-sided against aheat dissipating member so that each of the two heatdissipating members is thermally connected to two of the armature-projections leading respectively from the two stack-units, whereby the stack-units are connected thermally in parallel with one another to the two heatdissipating members.

6. The improvement in preventing undesirable temperature'rise in the interior of an electrical condenser stack, which includes means dividing the stack electrically into two units; two metal clamping members electrically insulated from one another, in clamping engagement with the ends of the stack, and having substantial areas exposed from the stack for heat-dissipation; and wide armature-projections extending between the respec'live stack-units and clamping members, and lying fiat-sided against the clamping members therebythermally connecting the stack-units in parallel with one another between the two clamping members.

7. The improvement in preventing undesirable temperature rise in the interior of an electrical condenser stack, which includes means dividing the stack electrically into two units; two terminals electrically insulated from one another and having substantial areas exposed from the stack for heat dissipation; and wide armature-projections extending be ween the respective stack-units and heat-dissipating terminals and lying flatsidedfagainstthe latter, and thermally and electrically connecting the stack-units in parallel withone mother between the two terminals.

v 8. The improvement in removing heat generated in the interior of an electrical condenser stack, which includes means separating the stack into two electrical units; and

two metal members having substantial areas exposed from the stack for heat dissipation, and arranged on the ends of the s ack as clamping means therefor; an armature-projection from the first stack-unit in thermal and electrical connection with the first stackclamping heat-dissipator adjacent said first unit; an armature-projection from the second stack-unit in thermal and electrical connection with the second stack-clamping heat-dis sipator adjacent said second unit; an armature-projection from the second stack-unit in thermaland electrical connection with the firststack-clamping heat-dissi ator; and an armature-projection from the rst stack-unit in thermal and electrical connection with the second stack-clampin heat-dissipator; said last two armature-pro ections having reduced widths for passing by one another without interference.

9. The improved condenser stack which includes two stack units stacked together end toend and constituting a double stack, each stack unit including at least two foil armatures separated from one another by a dielectric sheet', and each of such two foils in each of the two stack units projecting out beyond the dielectric sheet between them; metal clamping members engaging the outer ends of the double stack; two metal terminals; and

four clamping devices clamping said four foil-proj ections in thermal and electrical connection with said metal clamping members and metal terminals; two of said four clamping devices clamping to one clamping member and one terminal, one of the foil-projec tions of one stack-unit, and clamping to said clamping member, one of the foil-projections of the other stack-unit; and the other two of said four clamping devices clamping to the other clamping member and other terminal the other two of said four foil-projections of the two stack-units, whereby the two stackunits are connected in parallel thermally and electrically with one another between the two clamping members and two terminals. 10. The improved condenser stack which includes two condenser units stacked together end to end and constituting a double stack, each stack unit including at least two foil-armatures separated from one another by a dielectric sheet, and each of such two foils in each of the two stack-units rojecting out beyond the dielectric sheet etween them; metal clampin members engaging the outer ends of the ouble stack; and four clamping devices clamping said four foil-projections in thermal and electrical connection with said clamping members, and two of said clamping devices clamping to one clamping member. one of the foil-projections of one stack-unit and one of the foil-projections of the other stack-unit; and the other two of said four clamping devices clamping to the other clamping member, theother two of said four foil-projections of the two stackunits, whereby the two stack-units'are connected thermally in parallel with one another between the two clamping members.

11. The improved condenser stack which includes two condenser units stacked together end to end and constituting a double stack,

each stack unit including at least two foil armatures separated from one another by a dielectric sheet, and each of such two foils in each of the two stack units projectin out beyond the dielectric sheet between t em; two metal terminals insulated from one another and having substantial areas exposed from the stack for heat-dissipation; and means clamping said four foil-projections in thermal and electrical connection with said terminals, one terminal bein so connected with one of the foil-projections from one stack-unit and with one of the foil-projections from the other stack-unit, and the other terminal being so connected with the other two foil-projections of the two stackunits, whereby the two stack-units are connected in parallel with one another thermally and electrically between the two terminals.

12. The improved condenser stack which includes two stack units stacked together end to end and constituting a. double stack, each stack-unit including at least two foilarmatures separated from one another by a dielectric sheet, and each of such two foils in each of the two stack-units projecting out substantially half its width or more beyond the dielectric sheet between them; and two heat-conducting and heat-dissipating members of metal insulated from one another and having extended heat-dissipating area exposed from the double stack; said four foilprojections being thermally and electrically connected with said heat-dissipating members and lying flat-sided against them, one foil-projection from one stack-unit and one foil-projection from the other stack-unit being connected to one of said heat-dissipators, and the other two foil-projections ,from the two stack-units being connected to the other heat-dissipators, whereby the two stack-units are connected in parallel with one another, between the two metal heat-*dissipators.

13. The improvement in removing heat generated in the interior of an electrical con-v denser stack,'which includes means separate ing the stack into two electrical units; and two terminals insulated from one another and having substantial areas exposed from the stack for heat-dissipation; the arma tures of one of the stack-units being connected in parallel with the armatures of the other stack-unit; and wide extensions of said armatures respectively lying flat-sided against each of said heat-dissipating terminals so that each is thermally and electrically connected with armatures in the two stackun1ts whlcharmatures are connected in parv allel with one another.

14.-The improvement in removing heat generated in the interior of an electrical condenser stack, which includesmeans electrically separating the stack into two units; and two terminals insulated from one another and having substantial areas exposed from the interior of the stack; a thermal and electrical connection between the first of said heat-dissipating terminals and an armature of the first stack-unit; a thermal and electrical connection between the second of said heat-dissipating terminals and an armature of the second stack-unit; a thermal and electrical connection between said first terminal and an armature'of said second stack-unit;

and a thermal and electrical connection between said second clamping terminal and an armature of said first stack-unit. In testimony whereof I hereunto afiix my signature.

WILLIAM M. BAILEY;

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