Electrolytic Capacitor Lifetime Estimation via Case Temperature
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Solution Overview
Problem
Existing methods for estimating the lifetime of electrolytic capacitors are plagued by high uncertainties due to challenges in accurately measuring the core temperature, which is exponentially related to lifetime consumption. This uncertainty renders residual lifetime estimates of limited practical value, often exceeding +/â25% relative uncertainty.
Innovation Solution
A device comprising a temperature sensor thermally insulated from the ambient, either by arranging it between two equal electrolytic capacitors connected in parallel or by mounting it on the capacitor case with a thermally insulating layer. This setup allows for precise measurement of the case temperature, independent of the apparatus's arrangement and cooling efficiency, thereby reducing uncertainty in lifetime estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is arranged inside the capacitor to measure core temperature directly, then measurement precision is improved, but the sealing is compromised causing electrolyte evaporation and reduced reliability
Solution Approach 1:
The patent uses the capacitor case as an intermediary thermal element. Instead of measuring core temperature directly, a temperature sensor mounted on the case measures the case temperature, which serves as a reliable proxy for core temperature due to the predictable thermal relationship between case and core. This avoids penetrating the sealing while obtaining sufficient temperature data for lifetime estimation.
Solution Approach 2:
The patent replaces direct mechanical intrusion (inserting sensor through sealing) with a non-intrusive thermal measurement approach. By measuring case temperature externally and using thermal models to infer core temperature, the method substitutes a mechanical solution with a thermal-field-based solution that preserves sealing integrity.
2Device complexity
If thermal models are used to link ambient temperature to core temperature, then device complexity is reduced, but measurement precision deteriorates due to unknown cooling efficiency and apparatus arrangement
Solution Approach 1:
The patent makes the electrolytic capacitor itself serve as the thermal reference. By mounting the temperature sensor directly on the capacitor case, the measurement system uses the capacitor's own thermal characteristics rather than relying on ambient temperature readings from elsewhere in the apparatus. This self-referential approach eliminates dependencies on unknown cooling efficiency and apparatus arrangement.
Solution Approach 2:
The patent changes the measurement parameter from ambient temperature to case temperature. This parameter change fundamentally improves precision because case temperature is directly coupled to the capacitor's internal thermal state and is independent of external cooling conditions or apparatus configuration.
3Ease of operation
If ambient temperature sensors are used in different places of apparatuses, then ease of operation is improved, but measurement precision deteriorates due to uncertainty in representing core temperature
Solution Approach 1:
The patent creates a universal solution that works regardless of apparatus type, cooling method, or installation location. By measuring case temperature directly on the capacitor, the same measurement approach can be applied universally across different applications without needing to know or model the specific thermal characteristics of the surrounding apparatus.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution achieves a relative uncertainty in preliminary predicted lifetime between -10% and 10%, preferably between -5% and 5%, for regularly repeating usage cycles, significantly improving the accuracy of electrolytic capacitor lifetime estimation.
Implementation Method 1
a temperature sensor and a controller suitable to estimate the lifetime consumption of an electrolytic capacitor based on the measurement data of the temperature sensor, wherein the temperature sensor is thermally insulated from the ambient
Implementation Method 2
the temperature sensor is thermally insulated from the ambient, either by arranging it between two equal electrolytic capacitors connected in parallel or by mounting it on the capacitor case with a thermally insulating layer
Data Source
Figure 1~3
Figure 4~5b
Figure 6~7
AI summary
The device (3) to estimate the lifetime consumption (44) of one or more electrolytic capacitors (1,1a,1b) comprises a temperature sensor (32) which is thermally insulated from the ambient (15) by being arranged either between two equal electrolytic capacitors (1a,1b) connected in parallel with each other or on the case (11) of an electrolytic capacitors (1,1a,1b) and where it is covered with a layer of thermally insulating material (320). The device comprises further a controller (31) which is suitable to estimate the lifetime consumption (44) based on the measurement data of the temperature sensor (32).