Electrical capacitor with temperature sensor

Abstract

The present invention relates to an electrical capacitor (100), such as an aluminum electrolytic capacitor (100), and a temperature sensor (12) or sensor system and a mounting method. The temperature sensor (12), housed in a capacitor housing, is adapted to exchange electrical signals non-contactly with a reading device (5) in the environment of the electrical capacitor (100), the electrical signals reflecting information about the temperature inside the capacitor housing (8, 10).

Description

Technical Field

[0001] This invention relates to an electrical capacitor, such as an aluminum electrolytic capacitor, and a temperature sensor or a sensor system and a mounting method. Background Technology

[0002] Several parameters affect the lifespan of electrical capacitors. These parameters include, for example, core temperature, ambient temperature, operating voltage, current in the capacitor, frequency of the AC voltage, and many other factors.

[0003] A crucial parameter is the core temperature of the capacitor. Using conventional solutions, this temperature cannot be measured in the field of electrical capacitors, but only in prototype capacitors whose casings are either open or not sealed at all, and which are subsequently no longer usable in the field. For this purpose, conventional thermometers and thermocouples can be used, for example, which require a power supply and an electrical connection to the outside of the capacitor. Summary of the Invention

[0004] In view of the shortcomings of existing solutions, the object of the present invention is to provide a novel sensor for measuring temperature in an electrical capacitor.

[0005] This invention relates to a capacitor, which in the context of this specification refers to an electrical capacitor throughout.

[0006] The basic construction of a capacitor corresponds to the technically conventional structure and parameters.

[0007] The capacitor includes a sealed capacitor casing and a temperature sensor housed within the capacitor casing. This means that the temperature sensor is placed inside the hollow cavity of the capacitor casing.

[0008] A temperature sensor is a sensor adapted to exchange electrical signals in a non-contact manner with a reading device in an electrical capacitor environment while the temperature sensor is in operation, the electrical signals reflecting information about the temperature inside the capacitor housing.

[0009] In other words, the temperature sensor detects the temperature inside the capacitor housing during its operation and transmits that temperature to a reading device outside the capacitor housing in a non-contact manner.

[0010] In one implementation, the temperature sensor is a surface acoustic wave (SAW) device. For such sensors that operate by means of SAW waves, the name SAW sensor or, for example, SAW temperature sensor is common, where SAW stands for "Surface Acoustic Wave".

[0011] SAW sensors, for example, include substrates containing LiNbO3 or LiTaO3. With such substrates, the surface acoustic wave velocity exhibits a favorable high temperature dependence, enabling very accurate measurement of the temperature within the capacitor. For example, with LiNbO3, the relative change in SAW velocity with temperature is approximately 100 ppm / °C.

[0012] Because the wavelength of a surface wave is defined by a suitable and specific finger structure of the SAW sensor, the resonant frequency of the SAW sensor changes accordingly. The resonant frequency is then the measurement variable to be determined.

[0013] In the first-order approximation, the change in relative sound speed and the change in relative resonant frequency are directly proportional to each other. Therefore, for example at a typical resonant frequency of 2.4 GHz, a frequency change of approximately 240 kHz / ℃ is obtained.

[0014] At higher or lower resonant frequencies, corresponding frequency variations are thus derived. An exemplary range of resonant frequencies is between 2 GHz and 3 GHz.

[0015] The sensor of this embodiment is suitable for: when the temperature sensor is in operation, the reading device queries the echo response sequence of the temperature sensor non-contactly by means of surface acoustic wave (SAW) technology.

[0016] In other words, with the help of SAW technology, electrical signals can be exchanged between the reading device and the temperature sensor using electrical surface acoustic waves (SAW).

[0017] An electrical signal emitted by a reading device and returned as an echo by a temperature sensor changes its characteristics according to the temperature within the capacitor casing; this signal is received and evaluated by the reading device. In particular, temperature affects the frequency of the surface acoustic wave. The temperature can be determined directly from the measured frequency change.

[0018] Therefore, the temperature sensor is configured as a passive device, which does not require an external current source.

[0019] In other words, the temperature sensor can be placed inside the capacitor housing in a connectionless and non-contact manner. Information about the temperature at the location where the temperature sensor is placed is measured and transmitted by exchanging surface acoustic wave and high-frequency signals with a reading device.

[0020] According to one embodiment, the capacitor is an aluminum electrolytic capacitor. Furthermore, the capacitor and sensor can be constructed as described above.

[0021] An aluminum electrolytic capacitor comprises a wound element and an electrolyte within a closed capacitor housing, the wound element being impregnated with the electrolyte.

[0022] The winding element typically consists of an anode foil and a cathode foil, which are wound around a mandrel that forms the central axis of the winding element during the manufacturing process.

[0023] After the winding element is wound, the mandrel is removed, and a cavity is formed along the central axis (central axis).

[0024] The temperature sensor is preferably positioned in the cavity along the central axis of the wound element.

[0025] The dimensions of the temperature sensor and the cavity are preferably selected such that the temperature sensor can be installed into the cavity of the capacitor during the manufacturing process of the capacitor without changing or modifying the sensor or winding element.

[0026] Preferably, the temperature sensor is clamped and fixed in the cavity. That is, the size of the temperature sensor is determined so that it fits, precisely fits or interferes with the inner wall of the cavity, and is fixed in the cavity by friction with the inner wall.

[0027] According to one embodiment, the enclosed capacitor housing of the aluminum electrolytic capacitor includes at least one cup, preferably made of metal, and a cover fixed thereon, preferably made of plastic.

[0028] The cup body, made of metal, conducts heat better than the lid, which is made of plastic.

[0029] According to one embodiment, the temperature sensor is positioned in the cavity along the central axis at the hottest point of the aluminum electrolytic capacitor during its operation, i.e., at the point with the highest temperature.

[0030] This temperature of an aluminum electrolytic capacitor is called the core temperature. The core temperature is the most important parameter used to calculate the lifespan of an aluminum electrolytic capacitor.

[0031] In other words, the core temperature is the highest temperature along the central axis, and preferably can also be the highest temperature in an aluminum electrolytic capacitor.

[0032] According to one embodiment, depending on the length and type of the electrolytic capacitor or central axis, the distance of the temperature sensor along the central axis in the cavity from the bottom of the capacitor housing opposite the cover is set to twice the distance from the cover.

[0033] According to one embodiment, depending on the length and type of the electrolytic capacitor or central axis, the temperature sensor is positioned at the same distance from the bottom along the central axis in the cavity as it is from the cover.

[0034] The selection of a temperature sensor location is particularly related to the type of capacitor, the type of capacitor connection, and the length of the capacitor.

[0035] In particular, for capacitors up to 100 mm in length, it is generally applicable that the temperature sensor should be at the same distance from the bottom and the cover.

[0036] For capacitors that are typically used where the temperature sensor should be positioned closer to the cover, the capacitor being longer than 100 mm and not having a cover with a snap-fit ​​interface, but rather having, for example, a threaded interface or other interface.

[0037] The inventors have discovered that the temperature measured at this location is preferably used to calculate the lifespan of aluminum electrolytic capacitors.

[0038] By designing the sensor, especially by using a passivating enclosure, such as the length and radius of a glass tube, and by placing the sensor within the enclosure, it is possible to ensure that the temperature sensor is installed at the location with the highest temperature and remains there during capacitor operation.

[0039] According to one embodiment, the aluminum electrolytic capacitor further includes an antenna adapted for non-contact signal exchange between the temperature sensor and the reading device, and the antenna is connected to or preferably part of the SAW sensor.

[0040] The antenna is preferably disposed in the cavity in the axial direction along the central axis of the winding element.

[0041] The axial direction is such that the central axis of the winding element extends along this direction.

[0042] The preferred resonant frequency of the SAW sensor is approximately 2.4 GHz, which corresponds to the ISM band of Bluetooth or WLAN. This corresponds to an electrical wavelength of approximately 12.5 cm in a vacuum.

[0043] Preferably, the antenna has a length of approximately one-quarter of the wavelength, i.e., approximately 3 cm, or in the range of 2 cm to 4 cm. Such an antenna ensures good reception at the desired frequency.

[0044] To achieve the required length, the antenna can be configured to extend from the cavity of the winding element into the capacitor housing.

[0045] The antenna can extend axially to the inside of the capacitor housing cover. The antenna is positioned as close as possible to the capacitor housing cover, which is made of plastic at least on its outer side. The antenna can be adjacent to the capacitor housing cover.

[0046] The cover can also be thinned to reduce the distance between the antenna and the environment, or to allow for a greater antenna length. A thinner cover also provides lower shielding.

[0047] Therefore, it is possible to realize or improve the reception or transmission of signals using SAW sensors.

[0048] Therefore, the cover should be configured such that it does not significantly obstruct the antenna signal.

[0049] Preferably, in order to simplify antenna installation, the antenna is made of a mechanically flexible material.

[0050] An antenna can be part of a unified sensor assembly, or at least a separate component that is electrically connected to the sensor.

[0051] The present invention also relates to a sensor suitable for insertion into the capacitor core of an aluminum electrolytic capacitor. The sensor and the aluminum electrolytic capacitor can be configured similarly to the previously described embodiment of an aluminum electrolytic capacitor with a sensor.

[0052] In the case of aluminum electrolytic capacitors, the winding element impregnated with electrolyte is called the capacitor core. Preferably, the sensor is disposed in a cavity inside the aluminum electrolytic capacitor along the central axis of the winding element.

[0053] The sensor includes a sensor component adapted for measuring the temperature of a capacitor core or wound element, preferably the hottest temperature of the capacitor core, and the sensor includes a cover adapted for passivation, the cover completely surrounding the sensor component and sealing the sensor component relative to the environment.

[0054] The covering part can also surround the antenna.

[0055] Preferably, the covering seals the sensor component in a way that prevents the exchange of substances between the sensor component and the environment.

[0056] Sensor components without a cover should already possess a certain degree of sealing, be waterproof, and insensitive to temperature. Preferably, the sensor component meets at least the IP67 industrial standard.

[0057] In particular, the encapsulation is impermeable to gases and liquids and has a lifespan of, for example, five years, which is sufficient to exceed the lifespan of aluminum electrolytic capacitors.

[0058] According to a preferred embodiment, the covering portion comprises or is made of glass.

[0059] To achieve this, the sensor components can be introduced into an inert glass tube, and then the two open ends of the glass tube can be fused together.

[0060] According to an alternative preferred embodiment, the covering portion comprises or is made of a suitable plastic.

[0061] Then the sensor components can be encapsulated in plastic.

[0062] The encapsulation portion of the sensor component includes or is composed of atactic polyalphaolefin (PAO).

[0063] The covering portion of the sensor component may contain atactic polypropylene (PP) or be composed of atactic polypropylene.

[0064] The materials mentioned ensure that the encapsulation adequately protects the sensor components throughout the capacitor's lifespan when used in the capacitor core. The typical lifespan is greater than 20 years.

[0065] In particular, the aforementioned covering prevents contact between the sensor components and the electrolyte, thereby also preventing contamination of the electrolyte or the inner cavity of the capacitor housing by the installed sensor.

[0066] In addition, sensors with a covering must withstand increased pressure exceeding atmospheric pressure and temperatures exceeding 100°C.

[0067] Preferably, the aluminum electrolytic capacitor described herein includes a sensor as a temperature sensor, the sensor comprising a covered sensor element.

[0068] The present invention also relates to a sensor system comprising the aforementioned aluminum electrolytic capacitor according to any embodiment, together with a temperature sensor, the temperature sensor being configured according to an embodiment of the aforementioned sensor.

[0069] The sensor system also includes a reading device adapted to non-contactly query the echo response sequence of the temperature sensor using surface acoustic wave (SAW) technology, as described above.

[0070] Preferably, the reading device is coupled to an evaluation electronics device adapted to calculate the lifespan of the aluminum electrolytic capacitor based on the received temperature information, and optionally also to display and / or store and / or calibrate it.

[0071] Service life is understood as the remaining operating time of a capacitor during which it meets the requirements for normal operation.

[0072] According to one embodiment, the sensor system includes: a plurality of aluminum electrolytic capacitors; a reading device having evaluation electronics; and a control unit. The evaluation electronics and the control unit can be configured separately, allowing them to be spatially separated, or connected to each other in a common device, such as a computer.

[0073] The control unit can also directly perform the function of evaluating electronic devices. Therefore, the control unit is also an evaluation electronic device.

[0074] According to one embodiment, the sensor system includes multiple aluminum electrolytic capacitors, a reading device, and a control unit. That is, the reading device is capable of reading multiple capacitors equipped with SAW sensors in parallel. This is achieved by using SAW sensors with different resonant frequencies within the permitted ISM band.

[0075] The control unit is suitable for using artificial intelligence to compare temperature information with calculated lifespan and analyze the differences based on predetermined task settings.

[0076] Core temperature can be read and evaluated continuously or event-dependently. This is particularly feasible at capacitors in operation in the field, not just at prototypes.

[0077] Core temperature can be read automatically via a fixed reading device, or manually, for example, during maintenance, using a mobile reading device.

[0078] Weak points and potential improvements in capacitors can be identified through data assessment. By regularly reading the core temperature, the lifespan of capacitors can also be determined and monitored during field operation. This allows for more precise setting of capacitor maintenance and replacement intervals, maximizing uptime and minimizing maintenance costs.

[0079] The operating parameters of the capacitor can therefore be improved. Furthermore, conclusions can be drawn regarding the potential for improvement when designing other capacitors. These potential improvements include both functional enhancements and improvements aimed at minimizing costs and expenses by avoiding unnecessary design overruns.

[0080] Capacitors with significantly high core temperatures can also be replaced before their standardized service life expires. Capacitors without significantly disruptive operating parameters can also continue operating beyond their standardized service life.

[0081] The present invention also relates to a method for mounting a SAW temperature sensor as described above in a closed capacitor housing as described above, the method comprising at least the following steps:

[0082] - Insert the winding element into the cup of the capacitor case.

[0083] - The winding element is impregnated with electrolyte.

[0084] - A SAW temperature sensor is provided by passivating the sensor element through the formation of an encapsulation portion, which encapsulates the sensor element.

[0085] - Insert the SAW temperature sensor and its connected antenna into the cavity along the central axis of the winding element.

[0086] - The capacitor housing is sealed by placing the cover onto the cup.

[0087] In an alternative method according to the invention, the SAW temperature sensor is not inserted into an existing cavity along the central axis of the winding element; instead, the cavity is first formed by winding the winding element around the SAW sensor. All other method steps remain unchanged.

[0088] The method may also include other working steps described in the context of this invention, such as encapsulating the sensor component with plastic for passivation, or introducing the sensor component into a glass tube and subsequently sealing the glass tube. Attached Figure Description

[0089] The embodiments are described in more detail below with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

[0090] The attached diagram shows:

[0091] Figure 1 A perspective exterior view of an embodiment of the winding element of an aluminum electrolytic capacitor is shown.

[0092] Figure 2 A cross-sectional view of an embodiment of an aluminum electrolytic capacitor with a cup body and a winding element is shown. Viewed from the cover body, the sensor is mounted at one-third of the height of the capacitor.

[0093] Figure 3 A cross-sectional view of one embodiment of an aluminum electrolytic capacitor having a cup body and a winding element is shown. The sensor is mounted at half the height of the capacitor.

[0094] Figure 4 An embodiment of a SAW sensor with a covering portion is shown.

[0095] Figure 5 The method is illustrated.

[0096] The accompanying drawings are not necessarily to scale. Similar elements may have the same reference numerals. Detailed Implementation

[0097] Figure 1 A first embodiment is shown. In particular, Figure 1 The winding element 1 of the aluminum electrolytic capacitor 100 is shown.

[0098] The winding element 1 includes an anode foil 2, a release paper 3, a cathode foil 4, and an aluminum tab 14 or an aluminum contact plate 14 for contacting the anode foil 2 and the cathode foil 4.

[0099] In the illustrated embodiment, the anode foil 2 and the cathode foil 4 are wound into a winding element 1, wherein the release paper 3 is disposed between the anode foil 2 and the cathode foil 4 for spatial isolation and is wound.

[0100] Both foils 2 and 4 comprise metal, preferably aluminum, and particularly preferably include a coating comprising aluminum oxide.

[0101] The entire winding element 1, and especially the release paper 3, is impregnated with a liquid electrolyte or electrolyte solution.

[0102] At the center of the winding element 1, a cavity 6 is preferably formed along the central axis over the entire axial height of the winding element 1. The cavity 6 can be determined, for example, by the production of the winding element 1. For example, during production, a mandrel is provided in the cavity 6, and foils 2, 4 and release paper 3 are wound onto the mandrel.

[0103] The cavity can also be used to fix the winding element 1 in the cup or other container, for example as a fitting part for the mandrel or the outward-facing part.

[0104] In this embodiment, the SAW temperature sensor is disposed in cavity 6 (not shown in the accompanying drawings).

[0105] The SAW sensor also contacts antenna 7, which extends from cavity 6. Antenna 7 serves as contact between the passive SAW sensor and the corresponding control and readout device 5.

[0106] Antenna 7 is adaptable to the transmission frequency used. The preferred antenna length is one-quarter of the wavelength used for transmission between the control and readout device 5 and the SAW sensor.

[0107] The preferred length of antenna 7 is between 2 cm and 4 cm, including boundary values, and particularly preferably between 2.5 cm and 3 cm, including boundary values.

[0108] The typical diameter of cavity 6 along the central axis of winding element 1 is between 1 mm and 15 mm, including boundary values. The typical measurement of sensor diameter (here, representing the length of the sensor in the same direction in the mounted state) is between 2 mm and 10 mm, including boundary values.

[0109] Preferably, the dimensions of the SAW sensor, together with the cover, are determined such that it can be clamped and fixed in the cavity 6 without the need for other auxiliary mechanisms. Alternatively or additionally, the SAW sensor can be adhesively bonded in the cavity 6. The SAW sensor can also be fixed in other ways.

[0110] Antenna 7 can be made of a flexible and bendable material and is positioned between the installed SAW sensor and the cover of the capacitor housing. The antenna can, but does not necessarily, need to touch the cover of the capacitor housing.

[0111] Figure 2 Another embodiment of the invention is shown, which can also be consistent with the first embodiment.

[0112] and Figure 1 The difference is that the entire construction of the aluminum electrolytic capacitor 100 is now shown.

[0113] A winding element 1 is disposed in the cup body 8. The cup body 8 has a bottom 9. Furthermore, the cup body 8 is closed at its upper side opposite to the bottom 9 by means of a lid 10. The lid 10 is not part of the cup body 8 and can be made of a different material than the cup body 8.

[0114] The winding element 1 is secured in the container, which consists of the cup body 8 and the lid body 10, for example, by clamping between the bottom 9 and the lid body 10. The winding element 1 can also be secured to the bottom 9 by an adhesive. Exemplary adhesives include polyalphaolefins, particularly polypropylene.

[0115] The winding element 1 can also be mechanically (e.g., by threaded connection) fixed in the housing.

[0116] The bottom 9 may also have a mandrel 11 that extends into the cavity 6 along the central axis of the winding element 1 in order to fix the position of the winding element.

[0117] A SAW sensor 12 is also disposed in the cavity 6, and the SAW sensor is connected to the antenna 7. Preferably, the antenna 7 is fixed at the SAW sensor 12. The SAW sensor 12 is a passive electrical device that functions as a temperature sensor 12, i.e., it provides a measurement value from which the temperature can be determined.

[0118] In this embodiment, the antenna exemplarily touches the cover 10. This contact occurs due to the maximum length configuration of the antenna 7; however, the contact is neither limiting nor necessary for the function of the antenna 7. Here, the cover 10 is non-conductive.

[0119] In this example, sensor 12 is positioned at one-third of the height of capacitor 100. Height is the distance between the outer surface of lid 10 and the outer surface of bottom 9. Here, the height is measured from the outer surface of lid 10. That is, sensor 12 is positioned closer to lid 10. In this example, the highest point along the central axis of cavity 6 is exactly one-third of the height h because lid 10 is made of plastic, while cup 8 is made of, for example, aluminum, which conducts heat better.

[0120] The control and reading device 5 is also electronically connected to the evaluation electronics 15, such as a computer, which is capable of calculating the temperature in the capacitor by means of the frequency of the transmitted and received electrical signals.

[0121] For example, the control unit 16, which is configured in the same computer as the evaluation electronics 15 and is electronically connected to it, can compare and analyze data from multiple reading devices 5 in order to subsequently improve the technical process parameters.

[0122] For example, if multiple capacitors that are spatially close to each other have excessively high temperatures, this may be due to excessively high ambient temperatures, which can then be reduced.

[0123] exist Figure 3 Another embodiment is shown, which is essentially the same as that from [source missing]. Figure 2 The embodiments are the same.

[0124] However with Figure 2 The difference is that the sensor 12 is positioned at half a height h between the lid 10 and the bottom 9. In this example, the lid 10 and the cup body 8 are made of similar materials and / or have similar thermal conductivity.

[0125] Because sensor 12 is positioned more centrally here, antenna 7 does not touch cover 10 in this example.

[0126] Figure 4 Sensor 12 is shown as an example. Sensor 12 is a SAW sensor, i.e., a passive component.

[0127] Sensor 12 itself does not require a power supply. Sensor 12 is addressed by an external control and reading device 5 that emits surface acoustic waves and then returns an acoustic echo signal. The temperature at the location of sensor 12 can be determined by the reading device 5 based on the acoustic echo signal, since the wavelength of surface acoustic waves depends on temperature.

[0128] To avoid interaction between the electrolyte and the sensor 12, such as contamination by the electrolyte or (chemical) damage to the sensor 12, the sensor 12 includes a sensor component 12A and a cover portion 13.

[0129] The sensor component 12A of the sensor 12 is a functional component required for temperature determination by the sensor 12. The sensor component 12A is surrounded by the cover portion 13.

[0130] The covering portion 13 is made of a chemically resistant and inert material that does not react with the electrolyte and does not contain any substances that may dissolve upon contact with the electrolyte.

[0131] Preferred materials (which have also been used in catalysts in some other respects) are: glass, preferably halogen-free glass; and non-conductive plastics.

[0132] The most important examples of plastics used herein are polyalphaolefins (PAO), especially atactic or amorphous polyalphaolefins, and especially polypropylene (PP), preferably atactic or amorphous polypropylene. The plastics used are preferably halogen-free. The sensor component 12A is encapsulated in plastic for passivation after its production and before installation in the capacitor housing.

[0133] The wall thickness of the covering portion 13 between the sensor component 12A and the environment of the SAW sensor 12 is preferably between 0.3 mm and 2 mm, including the boundary value.

[0134] Figure 5 The method according to the invention is illustrated schematically, having steps A to E, which are preferably performed in the given order.

[0135] A: Insert the winding element 1, which serves as the capacitor core, into the cup 8 of the capacitor housing.

[0136] B: The winding element 1 is impregnated with electrolyte, for example by submerging the winding element 1, or by allowing the electrolyte to flow through it, for example under increased pressure, through an overpressure pulse, etc. Step B can also be performed before step A.

[0137] C: The SAW temperature sensor 12 is provided by passivating the sensor element 12A by means of forming a covering portion 13, which surrounds the sensor element 12A. Passivation includes, for example, encapsulating the sensor element 12A with plastic, or introducing the sensor element 12A into a glass tube and then sealing the open end of the glass tube.

[0138] D: Insert the SAW temperature sensor 12 and the antenna connected to it into the cavity along the central axis of the winding element 1.

[0139] E: The capacitor housing is sealed by placing the cover 10 onto the cup 8. Optionally, the capacitor housing is then sealed and externally insulated.

[0140] List of reference numerals

[0141] 1 Winding element

[0142] 2 Anode foil

[0143] 3. Release paper

[0144] 4 cathode foil

[0145] 5. Control and Reading Devices

[0146] 6-cavity

[0147] 7 antennas

[0148] 8 cups

[0149] 9 bottom

[0150] 10 caps

[0151] 11 spindles

[0152] 12SAW sensor, temperature sensor

[0153] 12A sensor components

[0154] 13 Covering sections

[0155] 14 aluminum tabs or aluminum contacts

[0156] 15. Evaluation of electronic devices

[0157] 16 control units

[0158] 100 electrical capacitor

[0159] Steps from A to E

Claims

1. An electrical capacitor (100) comprising a closed capacitor housing (8, 10) and a temperature sensor (12) housed within the capacitor housing (8, 10), the temperature sensor being adapted to exchange electrical signals non-contactly with a reading device (5) in the environment of the electrical capacitor (100) during operation of the temperature sensor (12), the electrical signals reflecting information about the temperature inside the capacitor housing (8, 10).

2. The electrical capacitor (100) according to claim 1, wherein the temperature sensor (12) is a surface acoustic wave sensor (12) adapted to enable the reading device (5) to non-contactly query the echo response sequence of the temperature sensor (12) by means of surface acoustic wave technology while the temperature sensor (12) is in operation.

3. The aluminum electrolytic capacitor (100) according to claim 1 or 2, comprising a winding element (1) and an electrolyte in a closed capacitor housing (8, 10), wherein the winding element (1) is impregnated by the electrolyte, and wherein the temperature sensor (12) is disposed in a cavity (6) along the central axis of the winding element (1).

4. The aluminum electrolytic capacitor (100) according to claim 3, wherein the enclosed capacitor housing (8, 10) comprises at least one cup (8), preferably made of metal, and a cover (10) fixed to the cup, preferably made of plastic.

5. The aluminum electrolytic capacitor (100) according to claim 3 or 4, wherein the temperature sensor (12) is fixed in the cavity (6) by clamping.

6. The aluminum electrolytic capacitor (100) according to any one of claims 3 to 5, wherein the temperature sensor (12) is disposed in the cavity (6) along the central axis at the hottest point of the aluminum electrolytic capacitor (100) in operation.

7. The aluminum electrolytic capacitor (100) according to any one of claims 3 to 6, wherein, depending on the length and type of the electrolytic capacitor (100), the temperature sensor (12) is positioned at a distance from the bottom (9) of the capacitor housing (8, 10) opposite the cover (10) along the central axis in the cavity (6) at twice the distance from the cover (10), or The temperature sensor (12) is positioned at the same distance from the bottom (9) as it is from the cover (10).

8. The aluminum electrolytic capacitor (100) according to any one of claims 3 to 7 further includes an antenna (7) adapted for non-contact signal exchange between the temperature sensor (12) and the reading device (5), wherein the antenna is disposed in the cavity (6) along the central axis of the winding element (1) in the axial direction.

9. The aluminum electrolytic capacitor (100) according to claim 8, wherein the antenna (7) extends in the axial direction to the inside of the cover (10) of the capacitor housing (8, 10).

10. A sensor (12) adapted to be incorporated into a winding element (1) of an aluminum electrolytic capacitor (100), the sensor comprising: - Sensor component (12A), the sensor component being adapted to measure the temperature of the winding element (1), and - Covering portion (13), which completely surrounds the sensor component (12A) and seals the sensor component (12A) relative to the environment.

11. The sensor (12) according to claim 10, wherein the covering (13) seals the sensor component (12A) in such a way that the covering prevents the exchange of substances between the sensor component (13) and the environment.

12. The sensor (12) according to claim 10 or 11, wherein the covering (13) comprises or is made of glass.

13. The sensor (12) according to claim 10 or 11, wherein the covering (13) comprises or is made of a suitable plastic.

14. The sensor (12) according to claim 13, wherein the covering portion (13) comprises or is composed of atactic polyalphaolefin.

15. The sensor (12) according to claim 14, wherein the covering portion comprises or is composed of atactic polypropylene.

16. The aluminum electrolytic capacitor (100) according to any one of claims 3 to 9, wherein the temperature sensor (12) is the sensor (12) according to any one of claims 10 to 15.

17. A sensor system comprising an aluminum electrolytic capacitor (100) according to any one of claims 3 to 9 or 16 together with a temperature sensor (12) therein, and further comprising a reading device (5) adapted for non-contactly querying the echo response sequence of the temperature sensor (12) by means of surface acoustic wave technology.

18. The sensor system of claim 17, wherein the reading device (5) is coupled to an evaluation electronics (15) adapted to calculate and display the lifespan of the aluminum electrolytic capacitor (100) based on the received temperature information.

19. The sensor system according to claim 18, comprising: Multiple aluminum electrolytic capacitors (100); and one or more reading devices (5) having evaluation electronics (15); and a control unit (16) adapted to compare the temperature information with the calculated lifespan using artificial intelligence and to analyze the differences according to preset task settings.

20. A method for mounting a SAW temperature sensor (12) in a closed capacitor housing (8, 10), comprising the steps of: - Insert the winding element (1) into the cup (8) of the capacitor housing. - Impregnate the wound element (1) with an electrolyte. - The SAW temperature sensor (12) is provided by means of a cover portion (13) that passivates the sensor element (12A), the cover portion surrounding the sensor element (12A). - Insert the SAW temperature sensor (12) and the antenna (7) connected to it into the cavity (6) along the central axis of the winding element (1). - The capacitor housing (8, 10) is closed by placing the cover (10) on the cup (8).

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