DD151383A5 - BIPOLAR ELECTROLYTE CONDENSER - Google Patents

Abstract

The intention is to overcome the technical difficulties known in bipolar electrolytic capacitors, especially in alternating voltage operation, which are attributed to cathodic reaction processes on the respective negative-shaped electrode foil. According to the invention, an electrically floating unformed electrode foil is arranged between the formed electrode foils. In operation, this automatically adjusts itself to a small positive potential with respect to the respectively negative formed electrode foil, whereby at most a very small potential difference dU can occur between the negative electrode foil formed and the adjacent electrolyte boundary layers and disadvantageous cathodic reaction processes are avoided. The quality improvement achieved thereby makes it possible, for example in the case of motor-on-site electrolytic capacitors, to use cost-saving, highly roughened non-stabilized electrode films with a power-saving reinforced oxide layer instead of weakly roughened stabilized electrode films.

Description

2 12 1 4 ^^ Berlin, 5.11,1980

57 581/17

Bipolar electrolytic capacitor Applicable to the invention

The invention relates to bipolar electrolytic capacitors having at least two formed electrode foils of roughened or non-roughened valve metal provided with electrical power connections.

Characteristic of the known technical solutions

As is known, in the case of electrolytic capacitors, the dielectric consists of an oxide layer produced by anodic oxidation in suitable electrolytes on the electrode metal, a so-called valve metal, which is also called a valve layer because it blocks the current below the forming voltage but conducts it when the polarity is reversed "Valve metals are mainly aluminum, tantalum and niobium known. In anodic oxidation, the so-called formation or preforming, the valve layer grows as long as the electric field strength acting on it is sufficiently high to maintain the further ion transport therethrough. For aluminum as a valve metal, this minimum field strength is about 10 MV / cm. As soon as the valve layer has grown so far that the minimum field strength is no longer exceeded, the growth in thickness stagnates and the initially high forming current drops to a low residual current.

This residual current is due to the fact that even in the purest valve metal impurities in the

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Area of the valve layer cause conductive defects, and that the oxide layer is not completely insoluble in the forming electrolyte. By dissolution of oxide, the so-called deformation, the field strength increases again above the minimum field strength, and new oxide can be reformed «

A deformation also occurs in the finished electrolytic capacitor, with voltage-free storage, especially at elevated temperatures ,, But even when operating with an operating voltage Il occurs a deformation, because the valve layer is then only up to this operating voltage U. nachformiert, which a deformation of the Formierspannung Ur on the operating voltage U, can not prevent _e Since the deformation sets a deterioration of the electrical characteristics of an electrolytic capacitor, it is an important task for the developer to counteract deformation processes as possible _e

From dome initially described forming process, the skilled person readily the opportunity to determine what voltage the valve layer has been formed. For this purpose, it is only necessary to mount the electrode in question or a piece of it in a suitable Formier electrolyte together with a power supply electrode to apply a test DC voltage and this slowly hochzuregeln «, at a voltage below the forming voltage U ^ results in a low residual current, which passes into a high stream of forming when they are exceeded «

s.ii.1980

It is known to specify a rated voltage and a peak voltage in the case of electrolytic capacitors. These voltages are defined as the value of a DC voltage or the resulting peak value U of an alternating voltage superimposed thereon, whereby the capacitor is operated continuously (rated voltage) or only for a short time and peak voltage is never exceeded (peak voltage). The peak voltage is determined by the caption of the capacitor or by references to the condenser hor- ker on its own or by other applicable technical regulations and is often 1.1 to i, 3 times the rated voltage *

It is known to use for a given rated and peak voltage valve layers as a dielectric, which are formed at a forming voltage U, which is at least 1.05 times the peak voltage. For example, an electrolytic capacitor is preformed for at least 63 V for 50/60 V, for at least 420 V for 350/400 V, and for 600 V at 500/550 V *. This avoids further preforming and oxide formation when the peak voltage occurs the loss of capacity and / or destruction of the electrolytic capacitor would result. "The 5 percent or more safety margin takes into account the tolerances that occur in the manufacturing process,

This correlation between the rated / peak voltage and the forming voltage U _f results in the known advantage of being able to optimize electrolytic capacitors for arbitrary rated voltages up to approximately 600 V. Because the thickness of the dielectric valve layer is proportional to the forming voltage U _f

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is high capacitances at low forming voltages and lower capacitances at higher Forrniors voltage series

It is known to prepare ^ electrolytic capacitors as wound capacitors "When electrode foils roughened or nichtaufgerauhte films can be used," is well known, can be achieved by roughening the specific capacity, the capacity per unit area SSSR foil, increase to a multiple (and shrink the capacitor volume corresponding ), because the dielectric valve layers conform to any surface geometry.

Their structure distinguishes between polar and bipolar electrolytic capacitors. "In polar electrolytic capacitors, at least one formed and one unformed electrode foil, both provided with an electrical power connection, are wound together with interposable, removable spacers impregnated with suitable electrolyte and enclosed in a housing airtight. "The housing is provided with two mutually insulated power connections to which the electrical power connections of the electrode films are connected.

Usually, the unformed electrode foil of valve metal and with a thin by oxidation in the air resulting oxide layer, an air oxide layer covered, which acts as a valve layer and their blocking voltage is less than 5 volts and often at 1 to 4 volts polar electrolytic capacitor only with pure DC voltage or with a DC voltage

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superimposed AC voltage can only be operated so that the peak value of the resulting voltage does not exceed the rated or peak voltage, and that no false polarity by more than ca, 4 volts occurs.

A polar electrolytic capacitor having a plurality of parallel partial capacitances is obtained by winding together a plurality of formed electrode films with a common or with a plurality of separate unformed electrode films. Dede of these electrode films is then provided with at least one electrical power connection v /.

If polar electrolytic capacitors are to be suitable for frequent fast charging and discharging (for example as photoflash capacitors), then the unformed electrode foil must be chosen so that its specific capacitance C, with the peak value U of the capacitor peak voltage and the specific capacitance C of the formed electrode

UC ^ foil by the condition s * s ^. 5 volts is linked,

ΤΓοΓ

ΤΓ + οΓ sk

Only then is it ensured that the amount of charge flowing from the anode to the cathode during discharge of the electrolytic capacitor charges the unformed electrode foil at most to the blocking voltage corresponding to its air oxide layer. Otherwise, the unformed electrode foil would gradually formed to a higher voltage and a drop in capacity resulting from the series connection of the anode and cathode capacity Total capacity of the electrolytic capacitor, the result soin _e Oo on whether this condition is satisfied or · not, it is called switch-resistant or non-switching-resistant electrolytic capacitors,

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For use in changing polarization, it is known to make bipolar electrolytes capacitors characterized ^ that is used a second-formed electrode foil instead of the unformed electrode foil in polar electrolytic capacitors "There are then two provided with electrical Strotnanschlüssen-formed electrode foils with intermediate absorbent spacers wound together" After impregnation, each of the two formed electrode foils can serve either as anode or cathode. In anodic polarization the valve layer blocks and in cathodic it conducts _e

Oe after "if in a bipolar electrolytic capacitor, the forming voltages of both formed electrode foils are the same or different high, one speaks of reversible or semi-polar electrolytic capacitors." Reversible electrolytic capacitors are for alternating DC and / or AC and semipolar for asymmetric DC and / or AC voltages usable,

Electrolytic capacitors for AC operation enjoy a widespread application, for example as capacitors for audio crossovers (in loudspeaker systems) and as motor operating capacitors for continuous operation up to about 100 Vrms. For higher alternating voltages, electrolytic capacitors are used as motor starting capacitors, especially in intermittent operation »

In the case of electrolytic capacitors for AC operation, the specification of rated and peak voltage refers to "RMS values".

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known, the valve layers box a forming voltage Ur; which is at least the ifOSfache of the peak value U of the capacitor peak voltage «

Compared with ^J static capacitors, electrolytic capacitors are characterized by orders of magnitude higher volume capacity and corresponding cost advantages. However, they suffer from the disadvantage of relatively high loss factors, which greatly hampers and hampers their application, especially in AC operation *

A lossy capacitor can be considered as a series connection of a lossless capacitor of the capacitance C and an ohmic resistance R. "For the loss factor tancf then applies

tan / a RatC,

In the case of electrolytic capacitors, the resistance R is composed of several partial resistances and can be approximated by the notation ©

^R = ^r d ^{+ r} a ⁺ v

The partial resistors then correspond to the partial losses, namely r. the actual dielectric losses in the valve layer, r the losses from the ohmic resistances oer with electrolyte impregnated spacers and r_ with roughened electrode foil the losses from the

P with electrolyte-filled etch pore resistances «.

The developer is therefore endeavored, in particular in bipolar electrolytic capacitors for AC operation.

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good absorbent spacers with high pore volume and highly conductive electrolytes as well as weakly roughened electrode foils with wide etching pores to improve r and r use and valve layers with the lowest possible losses to improve r. to develop.

It should be noted that the roughening of the electrode films by chemical or electrochemical etching in acids or salt solutions, and that in the washing following the drying on the electrode film forms the mentioned air oxide layer «Reinforced this air oxide layer before preforming by boiling in pure »Stern water results in an increased specific capacity and a considerably reduced electrical energy consumption by as much as 50 percent during preforming, but also increased dielectric losses of the valve layer. Because of this cost reduction, electrode foils with reinforced oxide layers as anodes in high-voltage electrolyte Capacitors (with voltages over 100 volts) used for DC operation and as smoothing capacitors, whereas electrode foils with thin air oxide layers are used for low-voltage electrolytic capacitors (with voltages below 100 volts) _e

In the use of such electrode films in bipolar electrolytic capacitors arise in AC operation, especially at higher AC voltages, such as occur in Motoranlaß electrolytic capacitors, extraordinary difficulties in the form of unstable capacity, in use rapidly increasing loss factors * overheating, deformation, breakdowns and explosions. These difficulties are particularly evident when using electrode films with a reinforced oxide layer.

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Attempts have therefore been made to reduce the dielectric losses in the valve layer by using electrode films with extremely thin air oxide layers which are obtained by treating the electrode film with phosphate-containing solutions immediately after etching and washing and before drying. Electrode foils treated in this way are called stabilized.

Despite this cost-increasing overhead by stabilizing, by dispensing with reinforced oxide layers and by the restriction to low roughening, in bipolar electrolytic capacitors, especially in AC operation, such as higher voltage motor starting electrolytic capacitors, only one is not only economical , but also develop technically unsatisfactory quality standards.

Object of the invention

The aim of the invention is to avoid the disadvantages of the cited known solutions «

Explanation of the essence of the invention

The object of the invention is to provide by the realization of a new technical conception a so highly improved bipolar electrolytic capacitor that even with bipolar electrolytic capacitors for VVechselspannungsbetrieb, such as in motor starting electrolytic capacitors, and even at higher AC voltages the cost-saving use of highly roughened non-stabilized electrode films with reinforced oxide layer without technical disadvantages is made possible _e

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This is achieved in that a bipolar electrolyte condenser with at least two formed electrode foils provided with electrical current leads according to the invention at least one further integrally arranged between the formed electrode foils and this covering the entire surface and shielding each other and electrolytically to a series circuit "formed-unfonnierte-shaped electrode film" and in the potential gradient between the formed electrode foils electrically floating and unf shaped electrode foil

The transverse arrangement of the formed electrode foils is substantially superimposed and separated from each other by two unformed electrode foils and absorbent spacers and shielded from each other. With longitudinal arrangement of the formed electrode foils they are successive with an unformed electrode foil extending over the entire winding length and absorbent spacer sheaths wound together «These two embodiments will be explained in more detail later with reference to the drawing»

The starting point of the invention are on the one hand dio assumption that the known efforts to highly soluble electrolytes and stabilized electrode films and the cost-increasing waiver of high roughening and on reinforced oxide layers are only suitable to mitigate the symptoms of technical difficulties, and on the other hand, the concern that cathodic reaction processes at each negative formed electrode foil in the case of bipolar electrolyte condensation

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satorerv play an important role and gradually impair the functionality of the valve layer »especially at high operating voltages and above all when operating with alternating voltage and the resulting heating,

For example, play a role

the reduction of the valve layer by hydrogen developed in the statu nascendi at the cathode or the reducing action of the ammonia contained in the impregnating electrolyte,

- * deterioration of the valve through the layer due to hydrogen in the withdrawal of the electrode foil benachharten Elektrdyt boundary layers adversely increased pH of the electrolyte,

- The deposition of the smallest in the electrolyte always present heavy metal impurities that cancel the blocking effect of the valve layer, because they, as an electron «conductor applied to the valve layer, they are known to short circuit, and

- other cathodic reduction and decomposition processes of the electrolyte components at high operating voltages

and warming,

In Gleichspannungsbetrieb an electrolytic capacitor, the potential difference between the electrode films is almost exclusively on the valve layer of the positive electrode foil formed, the anode, according to the voltage division between the very high insulation resistance of the valve layer and many orders of magnitude Ele'ktrolyt-Vorwiederstand »The potential difference between the negative electrode foil, the cathode and the adjacent electrolyte boundary layers

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Therefore, virtually zero, and cathodic reaction processes do not play RpIIe ₈ During charging and discharging and equally in polarity reversal and ACBotrieb cause the associated charge shifts at sufficiently high operating voltages a sufficiently high potential gradient across the electrolyte resistor and thus between the negative electrode film and the electrolyte boundary layers adjacent to it, so that cathodic reaction processes on the negative electrode foil become effective and can gradually impair the functional efficiency of their valve layer.

Accordingly, the basic idea of the invention is to reduce in bipolar electrolytic capacitors the potential difference between the respective negatively formed electrode foil and its adjacent electrolyte boundary layers even at high operating voltages to such an extent that cathodic reaction processes and impairment of the functional efficiency of the valve layer form the respectively negative ones Electrode foil to be avoided *

This is effected in the electrolytic capacitor according to the invention by the electrically floating unformed electrode film * If this consists of a Ni-chtventilmetall, then it has no valve layer and therefore can assume with respect to the respective negative-formed electrode film only one of the electrolytic polarization corresponding low positive potential »If it consists of a valve metal, then it always has a thin layer of air acting as a valve layer, which corresponds to a forming voltage of 1 to 4 volts, for example, in aluminum, and can then with respect to the respectively negative electrode formed

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foil only assume a positive potential of a maximum of 1 to 4 volts, provided that it is free-floating, that is not electrically connected. Therefore, the electrically floating in potential gradient between the brief break in the electrode foils unformed electrode foil adjusts during operation to a low positive potential relative to the potential of each negative-formed electrode foil itself on _e The resultant small potential difference UU _t example ΔΌ = 1 to 4 Voit ₁ between the inventive electrically floating electrode film and the respective negative electrode film formed in the alternating voltage operation leads to a very small potential difference du < AU between the negative electrode foil formed and the adjacent electrolyte boundary layers, causing harmful cathodic reaction processes and the associated impairment of the functioning of their valve layer be avoided"

The cathodic reaction processes take place in the electrolytic capacitor according to the invention instead of the unformed electrode-foil as in polar electrolytic capacitors with an unformed electrode foil. An impairment of the functionality of a valve layer present on this is not only not detrimental, but even advantageous, because thereby the switching resistance of the series circuit "formed-undformierteformierte electrode film" improves and increases their total capacity and in the inventive electrolytic capacitor also the potential differences 4U and you even further reduce, resulting in the emanating from the electrically floating unformed electrode film protective effect

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even further increased to the valve layer of the negative-shaped electrode foil «

Regardless of the relevance of these considerations, the experimental test confirms the carrying capacity of the concept according to the invention to a surprisingly high degree, as the embodiments will still show »

In order to prevent the formation of the unformed electrode film in AC operation in the electrolytic capacitor according to the invention, if it consists of a valve metal, their specific capacity C. must be ^x with the peak value U of the capacitor peak voltage and the specific capacitances C _{o of} the formed electrode foils

U C be linked by the condition s * j ^ <, 10 volts »

In one embodiment of the invention, the unformed electrode film 'consists of difficult to formulate material with a content of less than 99.9 %, preferably less than 99.5 %, valve metal * In this case, it may, as in AC operation to a voltage up to about Adjust 10 volts, · without an undesirable formation occurs.

In order to ensure complete shielding of the formed electrode foils by the unformed electrode foil, even when the foil webs are not always completely avoidable during the winding, it is advantageous if the unformed electrode foil is wider than the formed electrode foils. Besides the complete shielding, this also results an improved one

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Capacity recovery and a lower loss factor as well as improved dissipation of the heat loss after the end surfaces of the capacitor coil »

Since the electrically floating unformed electrode film may not be connected, it is advantageous if it is not provided with an electrical power connection.

The bipolar electrolytic capacitor according to the invention is not to be confused with a polar electrolytic capacitor having a plurality of parallel partial capacitances and a common unformed electrode foil, which serves the power supply and therefore has an electrical power connection and must be connected. In contrast, in the case of the electrolytic capacitor according to the invention, there is an electrolytic series connection with an unformed electrode foil which is floating freely in the potential gradient between the formed electrode foils and which may not be connected.

In a further embodiment of the invention, the electrolytic capacitor consists of three formed electrode foils provided with electrical power connections and an unformed electrode foil without electrical power connection. This embodiment allows several partial bipolar capacitances in the same capacitor, for example in a motor starting electrolytic capacitor for intermittent operation Partial capacity as motor operating electrolytic capacitor for continuous operation,

In a particularly advantageous embodiment of inventive electrolytic capacitors for AC operation

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the electrolytic capacitor contains at least one shaped electrode foil, the forming voltage Up of which is based on the

Vertex Vert U is the peak capacitor voltage, a value s

U _f 4L 1.05 U, preferably a value in the range 0.5 U 4. U, 4. U, has »

Surprisingly, the experimental test has shown that electrolytic capacitors according to the invention according to this embodiment of the invention with at least one electrode film, which was formed on a forming voltage U ^ below the peak value U of the capacitor peak voltage, in AC operation with peak voltage not, as the skilled in the could expect state of the art, were gradually weiterformiert to degrade its electrical 'characteristics on the Schoitelwert U of the capacitor-peak voltage "to explain this surprising observation, one can assume that the space required for the anodic oxidation of ion transport through the valve layer with field strength dependent finite speed Then, it will be understood that for an additional thickness increase of the valve layer, a sparking time-dependent minimum period of time is required, and that short-term, limited voltage spikes are required frequent repetition can not cause any gradual further formation. If, for example, one chooses a multiplying tension Uo = 0.85 U, then aresin results in 0.85 = 58.2 °,

TS

and at a frequency of 50 Hz with a poriodendauer of 20 ms, the forming voltage U-. then exceeded in each case only for a period of 3.53 ms, which is not sufficient for further development according to the present test results. "An excessively high DC voltage remains when the alternating voltage is switched off arbitrarily

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by appropriate measures to avoid or by rapid lowering, for example with a discharge resistor to neutralize ₆

Surprisingly, the experimental test has also shown that electrolytic capacitors according to this embodiment of the invention show a still improved stability in the endurance, This can be explained by the assumption that by lowering the forming voltage U, on or below the vertex value U of AC operating voltage of the explained in the introduction deformation of the valve layer is optimally counteracted »

Electrolytic capacitors according to this embodiment of the invention are therefore characterized by the double advantage that both a deterioration of the functioning of the valve layer of the respective negative electrode foil and the inevitable deformation of the respective positive electrode foil are avoided in addition to the technical Significant economic benefits arise from this development, for example, results in a lowering of Formierspannung

U ^ of 1.05 U to 0.85 U at 19% in the use of τ * ss

roughened electrode foil as a result of the pore structure a capacity gain of about 19 %, for example, from about 25 to 30 %, and thus a saving of 25 to 30 % both electrode foil and spacer and impregnating electrolyte "Since the energy required during preforming with increasing Forming voltage increases strongly progressively, resulting in the example mentioned also a saving of electrical energy of 35 to 50 % and corresponding savings in chemicals,

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Excipients and time spent in the formation. The increased capacity yield leads not only to further time savings in the various manufacturing steps, but also to smaller dimensions of the electrolytic capacitors according to this embodiment of the invention.

In a semipolar embodiment of this embodiment of the invention with the peak values U. and U ~ of the peak voltages of a bipolar electrolytic capacitor for AC operation contains this formed Eloktrodenfolien with the forming voltages U ^ ₁ <C 1.05 U and U _f2 <l ₍ 05 U _s2 «

In a final embodiment of the invention, the electrolytic capacitor comprises at least one formed electrolytic foil on which a reinforced oxide layer is applied in any desired manner, for example by boiling in ultrapure water, before preforming.

As the experimental test has shown, the protective effect exerted by the (informed electrode foil on the valve layers of the respectively negatively formed electrode foils is so extensive that the cost-increasing use of slightly roughened and specially stabilized electrode foils is dispensed with, even in the case of motor starting electrolytic capacitors for higher voltages can favor cost-reducing high-roughened electrode films with reinforced oxide layers «

Upon exhaustion of the possibilities offered by the invention and explained above results in bipolar

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Electrolytic capacitors for AC operation, such as motor starting electrolytic capacitors, by using highly roughened electrode films with reinforced oxide layer and by lowering the forming voltage U _f despite the additional unformed electrode film, a cost reduction of 50 to 70 %,

For bipolar electrolytic capacitors for AC operation, such as motor starter electrolytic capacitors * can occur when switching on and off transients occurring high current and voltage peaks and lead to a disadvantageous overload. In the unformed electrode film according to the invention eich resulting series connection "formed-undeformed EO electrode sheet" results in addition to the advantages already described a significant increase in impedance at higher frequencies ,, at 5 kHz measured known motor starter electrolytic capacitors had a loss factor of 20 to 30 % _However, according to the invention, 70 % _t results in an advantageously high damping of transient effects *

Execution in spi e1

The invention will be explained in more detail below with reference to the drawings.

Fig. Xt 2 and 7: the winding structure;

Figs. 3 and 4: the voltage relationships;

Fig _e 5 and 6: the electrolyte boundary layers;

FIG. 8: a condenser winding of an electrolytic capacitor according to the invention

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Fig. 1 shows a schematic representation of a particularly suitable for explanation embodiment of the winding structure of an inventive electrolytic capacitor «with the electrical power terminals 3; 4, provided formed electrode sheets 1; 2 are arranged transversely to each other and through several layers of absorbent spacer 5; 6; 5) 6 ' of two unformed electrode films 7; 7 'separated »After winding in the direction of the arrow and impregnating the coil are the formed electrode foils 1; 2 of the unformed electrode films 7 arranged between them; 7 * over the entire surface covered and shielded against each other and electrolytically to a series connection "f ormierte-f o form-f ormierte Elektrodenf olie ',' integrated The unformierten electrode foils 7, 7 'are not electrically connected and therefore in the potential difference between the formed electrode foils 1, 2 electrically freischwebend and regulate in AC operation to a low positive potential less than 10 volts, with respect to the potential of each negative-formed electrode film, on automatically, for example, 1 to 4 volts.

Fig. 2 shows a schematic representation of a preferred simpler embodiment of the winding structure of an electrolytic capacitor according to the invention * The with the electrical power terminals 3; 4 provided formed electrode films 1 {2 are arranged longitudinally to each other and after winding in the direction of arrow with one or more layers of absorbent spacer 5; 6 and the unformed Elektrodenfolie.7 through the then arranged between them electrode film 7 over the entire surface and shielded from each other after impregnation of the capacitor coil with

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electrolytically integrated into a series circuit "formed-unformed-shaped electrode portfolio". The potential difference between the formed electrode foils 1; 2 electrically froischwebende (because not connected) undeformed electrode film 7 is controlled in operation to a low positive potential less than 10 volts, with respect to the potential of each negative-formed electrode film, automatically.

FIGS. 3 and 4 illustrate the potential difference between the electrode films resulting in the operation of the inventive electrolytic capacitors. The potential of the uniformed electrode film 7 is set equal to zero in the illustrations.

In Fig. 3, the power terminal 3 is positive, the power terminal 4 is negatively assumed. The unformed electrode sheet 7 can assume only a low positive potential less than 10 volts with respect to the negative electrode film 2 formed. The negative-formed electrode foil 2 therefore assumes only a correspondingly low negative potential with respect to the unshielded electrode foil 7 shielding it, and the small potential difference ΔΌ between the electrode foils 2; 7 causes with ά U <10 volts that no functionalities of the valve layer of the negative-shaped electrode foil 2 impairing cathodic reaction processes can occur at this.

Fig. 4 illustrates the Potentialgefällo in reverse polarization, in which the small potential difference Δ U <10 volts automatically between the electrode films 1; 7 has regulated, so that no the functionality

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the valve layer of the negative-shaped electrode foil impairing cathodic reaction processes occur at this *

FIGS. 5 and 6 illustrate the electrolytic capacitors according to the invention in the anions and cations occurring in the electrolyte boundary layers adjacent to the electrode foils, "

In FIG. 5, the electrode foil 1 is positive, the electrode foil 2 is assumed to be negative. In the range 1 to 7, the (corresponding to FIG. 3) high potential gradient causes the desired reforming of the positive electrode foil 1 (anode) by the anions entering the valve layer, where necessary, at which negative electrode foil 7 (cathode) can be used cathodic reaction processes affect only the functionality of their Vontilschicht, which is not only not detrimental, but the switching resistance of the series circuit 1 to 7 improved. In FIGS. 2 to 7, the (corresponding to FIG. 3) low potential difference .sub.U.sub.10 causes 10 volts between the electrode films 2; 7 a very small difference in potential between the negative electrode foil 2 formed and the electrolyte boundary layers adjacent to it, whereby disadvantageous cathodic reaction processes and the concomitant impairment of the functional efficiency of the valve layer of the negative electrode foil 2 are avoided. At the positive in the range 2 to 7 positive unformed electrode film 7 occurs at most one of the electrolytic polarization or the reverse voltage of its valve layer corresponding low positive potential through which the valve layer at most nach-

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formed, but can not be formed higher.

Fig. 6 illustrates the corresponding conditions with reverse polarization, which require no further explanation according to the embodiments of FIG. 5.

Fig. 7 shows a schematic representation of an embodiment of the IVickelauf construction of an electrolytic capacitor according to the invention with two partial capacities, the formed electrode films 1; 2; 8 are connected to the power terminals 3; 4; 9 and are provided with the spacers 5; 6 and the unformed electrode film 7 wound together in the arrow direction and after impregnation of the then arranged between them unscrewed electrode film over the entire surface and shielded from each other and electrolytically integrated into series circuits "Formed-unformed ~ formed electrode film". The films 1; 2, for example, have the same capacitance value, and their terminals provide the first sub-capacitance, the foil 8 has a different capacitance value, and the second sub-capacitance then stands between the terminals 3; 9 or 4; In a bipolar electrolytic capacitor for AC operation according to the present invention, the first sub-capacitance may serve as the intermittent operation motor starting capacitor and the second sub-capacity as the motor operating capacitor, for example. The heat loss generated in the latter distributed in this arrangement evenly throughout the capacitor winding and can be derived without overheating on this and the common capacitor housing to the outside.

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FIG. 8 shows an embodiment of the coil 10 of an electrolytic capacitor according to the invention. The electrical current connections 3; 4 lead to formed electrode foil 1; 2 (of which only the latter is visible at the winding end), with spacers 5; 6 and the unformed electrode film 7 as described in Fig _e 2 are wound together and integrated into a series circuit. The impregnated coil is hermetically sealed in a suitable housing, not shown, and the power connections 3; 4 are electrically connected to corresponding external terminals »

The invention will be illustrated below with reference to two exemplary embodiments. For the examples, bipolar electrolytic capacitors for high voltage operation are selected, namely reversible motor starting electrolytic capacitors, since technical difficulties according to the prior art mainly exist in these and are the result of the invention great technical and economic advantages can be demonstrated convincingly

example 1

For a motor starting electrolytic capacitor 360 / jF 110/140 V _Qff (U _s = -Γ2,140 = 198 V ₅ ) two electrode foils were formed on the voltage IL · = 150 V = 0.76 U

IPS

6 * 93 cm of the film type 2035 provided with power connections and according to FIG. 2 wound together with spacers and an unformed electrode foil of the film type Kappa 204.

An electrolyte was used to impregnate

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100 ml of ethylene glycol 70 g of boric acid

20 ml of 25 percent ammonia water and 4 g of diammonium hydrogen phosphate

mixed and heated until its resistivity Ohm.cm 80 at 80 ⁰ C was.

After impregnation OCE Kondensatonvickel was sealed in a casing of 36 mrn diameter and 80 mm length, fitted "

The film type .2035 is a highly roughened aluminum «electrode foil from the manufacturer ALUMINIUM-WALZWERKE SINGEN, D-7700 Singen am Hohentwiel (FRG), which is provided with a reinforced oxide layer by boiling in pure water before it is preformed Film type has hitherto been unsuitable for the production of high-quality motor starting electrolytic capacitors.

The film type Kappa 204 is a roughened aluminum electrode foil manufactured by BECROMÄL, 1-20100 Milano (Italia), which is produced as an unformed electrode foil for supplying current to polar electrolytic capacitors _β

The undeformed electrode foil according to the invention, which is electrically floating freely in the potential gradient between the formed electrode foils, avoids disadvantageous cathodic reaction processes and the concomitant impairment of the functional efficiency of the valve layer of the respectively negatively formed electrode foil.

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This allows the use of inappropriate high roughened electrode films and the lowering of the forming voltage U- to 76 percent of the peak value U of

T S

Condenser peak voltage and the associated extremely high economic benefits without technical disadvantages, as the following favorable results dee switching experiment at peak voltage show:

Average of 10 capacitors C yyF tan / % initial measurement 363 2.8 After 30 000 switching cycles with 1.2 see 140 V _ff and 1.2 min 0 V ₁ corresponding to i _f / % duty cycle, at 55 C ambient temperature 359 3.2

Example 2

For an engine starting electrolytic capacitor 80 220/275 V _rms (U _s = -f2,275 = 389 V _Q), two to the voltage U = 330 V = 0.85 U-formed electrode foils

1 rt S '

the dimensions 6.49 cm of the film type 2035 provided with power connections and as in Example 1 with spacers and an unformed electrode film Käppa 204 coiled, impregnated and installed *

As a result of the electrically floating unformed electrode foil according to the invention, the cost-reducing application of unsuitable, highly roughened electrode foil with reinforced oxide layer was also made in this example

5.11.1980 57 581/17

(With an energy savings in the preforming of ca, 50 %) and a lowering of the forming voltage (which in this example is at least 19 % compared to the prior art) and allows the state of the art previously unavoidable deformation on the one hand and the cathodic impairment of Functioning of the valve layers on the other hand avoided, as the following favorable results of the switching experiment at 85 % of the peak voltage impressively in mind:

Average of 25 capacitors C / jF tan / " % initial measurement 80.7 2.8 After 30 000 switching times with i, 2 see 234 V _ff and 1 _f 2 min OV, corresponding to l _t /% duty cycle, at 55 C ambient temperature 78.8 3.0

The fabrication of a capacitor winding of this example resulted in a cost reduction of 63 / o by using high roughened electrode film with reinforced oxide layer and lowering the forming voltage despite the overhead of the additional unformed electrode film over a prior art capacitor winding.

Claims (9)

22 1 21 & .5.11.1980 £. «& % & Ι ·» - 28 - 57 531/17 I n d a n d sa η sprue h _r l _e Bipolar electrolytic capacitor with at least two provided with electrical power connections formed electrode films, characterized by at least one arranged between the formed electrode foils and this over the entire area covering and against each other shielding and electrolytically formed into a series circuit ¹¹ un-formed «formed electrodes foil 'integrating and im Potential gap between the formed electrode foils electrically floating unformed electrode foil _# 2 _# electrolytic capacitor according to item 1, characterized in that the specific capacitance C _{1 of} the non-forming electrode foil with the peak value U of the capacitor peak voltage and the specific capacitances C d
U, C C of the formed electrode films by the condition 10 volts is linked. 3, electrolytic capacitor according to item 1, characterized in that the unformed electrode foil consists of difficult-to-formulate material with a content of less than 99.9 percent, preferably less than 99.5 percent, valve metal. « 4 »electrolytic capacitor according to item 1, characterized in that the unformed electrode film is wider than the formed electrode films. 5 »electrolytic capacitor according to item 1, characterized in that the unformed electrode foil has no electrical power connection, ' 5.11.1980 - 29 - 57 581/17 6 »Electrolytic capacitor according to item 1, characterized by three formed electrode foils provided with electrical power connections and an unformed electrode foil without electrical power connection. 7 «electrolytic capacitor according to item 1, characterized in that in at least one Poladßationsrichtung the forming voltage Urder formed electrode film, based on the peak value U of the capacitor peak voltage, a value U, / L 1.05 U, preferably a r s Value in the range 0.5 U ^ U, <£ U, has » 8, electrolytic capacitor according to item 7 and in semipolar design with the peak ^values U ₁ and U ₂ ° " ^ΘΓ capacitor peak ^voltages , characterized by the forming voltages Ur ₁ < 1.05 U * and U _f2 ^ 1.05 U _{2 of} the formed electrode foils " 8 fs "9 * electrolytic capacitor according to one of the items 1 to 8, characterized in that on at least one of the formed electrode films prior to the preforming in a conventional manner by boiling in ultrapure water or otherwise a reinforced oxide layer is applied. Hierms 1 page drawings