US1824530A - Electrical condenser - Google Patents

Description

Sept. 22, 1931. w. M. BAILEY ELECTRICAL CONDENSER Original Filed May 27, 1924 .2 F 32 B 5 01A I J C max 1.

I417 BI T v Patented Sept. 22, 1931 UNITED STATES PATENT OFFICE- WILLIAM M. BAILEY, OF LYNN, MASSACHUSETTS, ASSIGNOR TO WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION 01' NEW YORK ELECTRICAL CONDENSER Original application filed May 27, 1924, Serial No. 716,107. Divided and this application filed larch 80,

1926. Serial No. 98,413.

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

This invention relates to improvements in electrical condensers, particularly of the type wherein sheets of dielectric and conducting foils are built up in a stack, the dielectric sheets being preferably 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 en'ibodying the invention are useful also for high potential service whether or not large currentsbe 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 designing the same for use with currents of more than a few amperes, it has been necessary to increase greatly the number of dielectric sheets, for the sole purpose of preventing serious overheating 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-heating by the high currents increases very rapidly with the amperage employed, the cost in mica for such high current micaand-foil condensers has been very high lurretofore. The reason why t e use of a much larger quantity of dielectr. c sheets resulted in preventing undue heating of the condenser by high currents was the consequent reduction of current per sheet and therefore the reduction of the watt loss per sheet, the total watt loss being distributed throughout the increased number of sheets, thereby providing a larger dissipating surface of the stack, i e.. such surfaces comprising the edges of the mica sheets in the stack. In order .0 maintain the originally desired capacity of the condenser when thusincreasing the number of dielectric sheets, it was usually necessary to divide the stack into several seriallyconnected sections whereby the voltage per Renewed April 6, 1931.

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 sheets to prevent overheating by high currents was due to such series-sectional construction.

The principal and important object of the invention is to reduce the quantity of dielectric, 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 its equivalent, wherein the heat developed by the high alternating currents used is so efliciently conducted away from the stack by means to be described as to make it unnecessary to increase the number of dielectric sheets (quantity of mica) for thefpurpose of causing a lower heat generation per sheet. 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 of an embodiment of the invention, and

Fig. 2 is a side elevation of a modification.

In Fig. 1 is shown a clamped unit of the invention wherein is a stack comprising two electrical sections or units A, B connected in series 1) the clamping and compressing means, t e adjacent faces of these two stacksections being separated from one another by insulating sheet S. The main body of alternating foils and micas is clamped between metal compression members C1 and C2 by four tension members as corner bolts B1; also projecting foil-bunch F1 (Fig. 1) of the stack-distributed foils is clamped to lower member C2 by auxiliary compression member K1 and two bolts or tension members L2; and projecting foil-bunch F2 is clamped to upper member C1 by auxiliary compression cated at the same side (left) of the unit, there are no insulating bushings between upper clamp member C1 and bolts B1, saidbolts B1 acting as electrical connections between C1 and 02 so that the clamping means as a whole seems to electrically connect stack sections'A and-B together (saidsections being separated from one another by insulating sheet S) The two terminals T1, T2 of this two-section clamped unit (soldered to the foil-bunches at the right instead of being connected to the clamping members) both extend from the same side thereof, this clamped unit, if desired, being supported on a rack P, or terminal-board or panel. This provides a strong construction of the terminal connections. The clamped two-section unit of Fig 1 may. be pluralized in any desired manner in a stack, if desired. All the clamping members of this unit of Fig. 1, however, are at the same potential, which is that of the midpoint between oppositely-poled terminals T1, T2.

The drawings are diagrammatic in the sense that the stack-sheets are shown as separated for clearness, so that the thickness and external area of each stack are greatly exaggerated.

In F ig- 2, two unit embodiments of the invention, unit 1 and unit 2, are combined end to end in a condenser in amanner as distinguished from assembly face to face in a stack.

11 Fig. 2, each of the two units 1 and 2 is similar (including insulating separator S) to the two-section stack-clamped unit of Fig. 1.

In the assembly (Fig. 2) of such double section stack in the clamping members, there are three features whereby the two sections A, A of the respective units are connected in series with one another, and the two sections B, B in series with one another, but sections A, A. are connected in parallel with sections B, B. First, at the left, circuit terminal T4 is clam ed as shown to ether with foil-bunch F1 an upper stack-c amp C1; and circuit terminal T3 is clamped as shown together with, foil-bunch F8 and lower stack-clamp C2. Second, at the right, foil-bunches F4, F5 are clamped together and to a heat-absorbing mass of metal K4, which may be provided with heat-dissipating vanes, fins or the like, not shown. And, third, where the two clamped units are electrically connected to-- gether, they are thermally connected by clamping to stack-clamps C1, C2 of unit 2, by the arrangement shown wherein foil-bunches F2 and F3 are clamped together and to stackclamp C1, and foil-bunches F6, F7 are clamped together and to stack-clamp C2. By this construction, the foil-bunch terminal of one clamped unit is clam ed directly to the foil-bunch terminal 0 an adjacent clamped unit.

In the above-described electricai arrangement of Fig. 2, T1 (at the extreme left) and T2 (at the extreme right) are the circuit terminals of the entire condenser comprising sections A, A, B, B, i. e., clampin units 1 and 2; but, all four stack-sections o the two independently-clamped double-section units- 1 and 2 (located alongside one another as in Fig. 2) may be connected successively in series by using terminals T3, T4 at the left of unit 1 as the two circuit terminals (not using T1 or T2 as circuit terminals or the connections shown between'terminals T3 and T4) and inserting insulating bushings between clamp C1 and bolts B1, in both unitsl and 2 of Fig. 2. y

In general, condensers embodying this invention are designed for moderate to high capacity of each clam ed unit, .005 to .2 microfarad being obtained readily. With such range of capacity, almost any relation of capacity, volta e and current may be obtained by employing a plurality of units in various relations of series, parallel, or seriesparallel.

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 pluralit of sections. That is, by positiveing heat-from the stack, the need of the same is removed in proportion to the eificiency 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 mice (more than was needed to obtain a desired capacity), in order to avoid over-heating by such currents, and in order to maintam a 'ven desired capacit for the condenser 1t was necessar to divide the stack into serially-connects sections (or to increase the number of sections in a stack already comprising several series sections) when the number of sheets of mica in eaeh original section was increased to prevent overheating. Hence the quantity of mice for a condenser of given capacity was greatl increased, due to the additional sheets in eac section and tn the additional sheets due to the addition of sections, so that a condenser for high current duty had very much more mica and 2. ion er stack than a condenser for a low current uty but of the same capacity. By this invention, the number of sheets of mica in a condenserof given ca acity can be kept substantially the same or high or low current duty) whether the stack consists 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 lurality of sections) is not necessarily less t an 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 heat removing means 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 reater due to the dissipating vanes. In e ect, 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 of the invention in removing heat from a stack with which currents of very high amperage are emplo ed may be dependent upon the efficiency 0 dissipation of heat from the metal masses which extract heat from the stack via the bunches of stackdistributed foils. That is, the maintenance of efficiency in continuousl maintainin the conduction of heat from t e interior 0 the stack at a desirably low stack-temperature, is dependent upon the continuous maintenance of heat-dissipation from the heat-extracting 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 andpotential, in which the stack-generated heat may vary within wide limits. This is on the remise that the heat-dissipators are the stac -clamps substantially enclosing the stackand thermally connected via the foils 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 thereof, it being kept in mind that a higher stacktemperature may be permitted by this invention on account of the permissive and preferred elimination of the previously customary paraffin embedment of the stack for high potential service. It should be noted that as the volume of the stack is increased (mica added for any reason), the exposed areas of heat-dissipation should be increased at a more rapid rate than the increase in external stack area correpsonding to the increased stack volume. v 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. Therefore in designing a given condenser to embody the invention for given service, there will be calculated the amount of heat generated 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 that after being so removed it is dissipated from the removing means, therefore the designer is concerned only in making sure to provide sufficient exposed area of the heatdissipator in good thermal connection with the distributed foils. The designer therefore will provide such area sufficient 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 substantially ,a greater general order of magnitude than the exterior area of the stack itself, yet it 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 is provided a control b the designer of the stack temperature which it may be desired 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 whichcauses 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 heat-dissipating projections or-fins or vanes, if and when they are employed as they preferably will be, especially when still air is the cooling medium.

7 I particularly point out and distinctly claim thepart, improvement, or combination which claim as my invention or discovery, as follows V 1. The improvement in preventing undesirable temperature rise in the interior of a foil-stack electrical condenser, which includes means dividing the stack electrically into two units, each comprising foil-armatures in inductive relation to one another;

two terminals insulated from one another;

electrically connected with said insulated terminals; metal stack-clamping means constituting a unitary electrical conductor and having a substantial area exposed from the stack for heat-dissipation, said clamping means ineluding metal compression members engaging and covering substantially the entire areas of the end faces of the stack, and including metal tension members mechanically and electrically connecting said compression members together; andfoil-projections from foils in both stack-units ih'direct thermal connection withsaid heat-dissipating clamping means, whereby the metal of said clamping means constitutes the electrical connection of the foil-armatures on ofie side of said dividing means with the foil-armatures lying on the other side of said dividing means.

2. The improvement in preventing undesirable temperature rise in the interior of a sheet-stack condenser, which includes a plurality of stacks each as follows, i. e., means dividing the stack electrically into two stackunits, none of the armature sheets inone of such units being directly connected with any of the armature sheets of the other unit;

stack-clamping means extending over substantially the entire area of the two end faces of the stack and having substantial area exposed from the stack' for heat-dissipation;

armature-sheet-projections from both sides of each stack-unit, two of such projections being indirect metallic thermal engagement with the heat-dissipating clamping means; such duplicate stacks being located alongside one another; and the two armature-sheetprojections in one of said duplicate stacks not connected to the stack clamping members.

thereof, being in direct thermal engagement with the two armature-sheet-pro]ections in the next of the duplicate stacks which are in thermal engagement with the clampingmeans thereof.

3. The improvement in preventing undesirable temperature rise in the interior of a sheet-stack of an electrical condenser, which includes means dividing the stack into two units whose armature sheets are mechanically separate and electrically connected; two termmals insulated from one another, but electrically connected with armature sheets respectively in the two stack-units; integral armature-sheet-projections from armaturesheets in the two stack-units which are in inductive relation with the armature sheets connected to said terminal; metal stack-compressing members respectively in clamping engagement with substantially the entire end-faces of the stack, said compressing members having substantial areas exposed from the stack for heat-dissipation; and metal tension means mechanically and electrically connecting said compression members together and constituting the entire clamping means as an electrically conducting unit; said integral armature-sheet-projections from one of the two stack-units being in direct metallic thermal engagement with one of said heat-dissipating compression members, and said integral armature-sheet projections from the other stack-unit being in direct metallic thermal engagement with the other heat-dissipating compression member; said clamping means, as an electrically conducting unit, constituting the series connection of the armature-sheet on one side ofsaid dividing means, with the armature sheets on the other side of said dividing means.

' 4. The improvement in preventing unde\ sirable temperature rise in the interior of a sheet-stack of an electrical condenser, which includes means dividing the stack into two units not electrically directly connected with one another by way of their armature sheets; two terminals insulated from one another but electrically connected with armature-sheets respectively in the two stack-units and projeoting from the same side of the stack; two bunches of integral armature-sheet-projections extending respectively from armaturesheets in the two stack-units and all extending from thesame side of the stack but from a side other than the side at which said terminals are located; metal stack-compressing members respectively in clamping engagement with substantially the entire end-faces of the stack, said compressing members having substantial areas exposed from the stack for heat-dissipation; and metal tension means mechanically and electrically con necting said compression members together and constituting the entire clamping means as an electrically conducting unit; said bunch of integral armature-sheet-projections tron" one of the two stack-units being in direct metallic thermal engagement with one of said heat-dissipating compression members, and said bunch of integral armature sheetprojections from the other stack-unit being in direct metallic thermal engagement with the other heat-dissipating-compression member;-said clamping means, as an electrically conducting unit, constituting a connection between said two stack-units.

5. The improvement in preventing undesirable temperature rise in the interior of a sheet-stack condenser, which includes means dividing the stack electrically into two units, the armature sheets in one unit being mechanically separate from the armatures in the other unit; stack-clamping means including two electrically connected compression members respectively extending over substantially the entire area of the end faces of the stack, and having substantial areas exposed from the stack for heat-dissipation; and armature-sheet-projections from armature sheets in the two stack-units and in direct metallic thermal engagement with said compression members, whereby heat is conducted via. the armature sheet-projections directly to the heat-dissipating clamping means from sirable temperature rise in the interior of an electrical condenser stack, which includes means dividing the stack electrically into two units; metal heat-dissipatin means having a substantial area exposed rom the stack;

and armature-projections from both of said stack-units and in direct thermal engagement with said metal heat-dissipating means, said heat-dissipating means connecting the stack-units to one another.

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; metal stack-clamping means including compression members in clamping engagement with the end faces of the stack, and including metal tension members electrically connecting together the two compression-members, said compression members having substantial heat-dissipating areas exposed from the stack; an armaturerojection from one stack-unit and thermal y connected with the compression members adjacent the unit; and an armature-proi'ection from the other stack-unit and thermal y connected with the compression member adjacent that unit; the stack-clamping means connecting the two stack-units electrically to one another.

8. 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; metal stack clamping means including compression 'members in clampin engagement with the end faces of the stac and including metal tension members thermally connecting the two compression members together, said com ression members havi substantial heatissipating areas exposiid from the stack; and armature-projections from both the stack-units and thermally directly engagin a portion of the exposed area of the stack-c ampingmeans whereby the metal thereof connects the two stack-units electrically together.

9. 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; metal stack-clamping means including compression members in clamping engagement with the end faces of the stack, and including metal tension members-then mally connecting the two compression members together, said compression members having substantial heat-dissipating areas exposed from the stack; armature-projections from both the stack-units; and means clamping said armature-projections directly in thermal engagement with a portion of the exposed area of said compression members, whereby said members cooperate with one another in dissipating heat from both stackunits, said stack-units being thermally connected in series with one another by way of said compression members.

10. 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; metal means clamping the stack, constituting a unitary electrically conducting structure, and having substantial heatdissipating area exposed from the stack; and armature-projections from both stack-units in direct thermal engagement with a portion of said heat-dissipating area; and terminals insulated from one another and connected to the other armatures of the two stackunits; all whereby the heat-dissipating clamping means constitutes the only electrical connection between armatures on one side of said dividing means and the armatures on the other side of said dividing means.

11. 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 having no direct electrical connection with one another, armature-projections from the respective units being connected respectively to terminals insulated from one another; and metal heatdissipating means having a substantial area exposed from the stack; the armature-projections from the stack which are in inductive relation to said terminal-connected armatures, having direct thermal engagement with a portion of the exposed surface of said metal heat-dissipating means, whereby the metal of said means constitutes the electrical connection between the armatures on one side of said dividing means with the armatures on the other side of said dividing means.

12. The improvement in preventing undesirable temperature rise in the interior of a foil-armature condenser-stack, which includes means dividing the stack electrically. into two units; metal heat-dissipating means having a substantial area exposed from the stack; two terminals insulated from one another; foil-projections from the two stackunits and electrically connected to said insulated terminals; and means clam ing in thermal engagement with a portion of the exposed surface of said heat-dissipating means, foil-projections from the'foil-armatures of the two stacks which are in inductive relation with said terminal-connected armatures of the two stack-units; whereby the metal. of the heat-dissipating means constitutes the electrical connection of the armatures on one side of said dividing means, with the armatures on the other side of said dividing means.

13. The improvement in preventing undesirable temperature rise in the interior of a condenser-stack, which includes means dividing the stack electrically into two units; metal stack-clamping means havin a substantial area exposed from the stack or heatdissipation; two terminals insulated from one another; armature projections from the stack-units and electrically connected with said insulated terminals; and means clamping in thermal engagement with a portion of the exposed area of said stack-clamping means, the armatures of the two stack-units which are in inductive relation with said' terminal-connected armatures of the two stack-units; whereby the metal of the stackclamping means constitutes the electrical connection of the armatures on one side of said dividing means,' with the armatures on the other side of said dividingmeans.

In testimony whereof I hereunto aflix my signature.

WILLIAM M. BAILEY.

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