[Explanation of the Cause of Capacitor Failure] Electrolytic capacitors connected in series are shorted.
Essential Reading for Circuit Designers: 15 Case Studies on Causes and Countermeasures for Capacitor Failures
Increase the rated voltage of the capacitor to reduce the difference in leakage current, and also review the voltage divider resistance value!
We would like to introduce a case where a series-connected aluminum electrolytic capacitor short-circuited. When a capacitor with a high leakage current is included in a capacitor series, the voltage balance can be disrupted, causing the voltage to drift above the rated voltage, which may lead to the capacitor short-circuiting. For this reason, it is recommended to connect resistors (voltage divider resistors) in parallel with each individual capacitor when connecting capacitors in series. However, in this case, the leakage resistances of the individual capacitors varied significantly, causing the voltage divider resistors to not function properly. 【Countermeasures】 - To achieve a uniform voltage distribution across the series-connected individual capacitors, increase the rated voltage of the capacitors to reduce the disparity in leakage currents, and review the values of the voltage divider resistors. - Use capacitors from the same manufacturing lot to align the behavior of leakage currents against temperature changes and voltage fluctuations. - This can help stabilize the voltage division. *For more details, please refer to the PDF document or feel free to contact us.
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Please pay attention to the following: ■ Selection of pressure resistors - Check the rated power and arrange the capacitors to avoid heating them. ■ The tolerance of the resistors should be within 1%. *For more details, please refer to the PDF document or feel free to contact us.*
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If you see the following symptoms in a capacitor, it is faulty: - The case is swollen (bulging) - There are cracks in the case - There is a gap between the case and the sealing part - The pressure valve has activated (the pressure valve has opened) - The case has burst - It is hot or generating heat - Smoke is coming out - There is liquid leakage - There are unusual sounds - There is an unusual smell *For more details, please refer to the PDF document or feel free to contact us.
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AIC tech handles Aluminum electrolytic capacitors and Film capacitors for industrial market. Our capacitors have a history of more than 70 years and have their origins in technological development in Japan. AIC tech delivers high-value, precision capacitors tailored for power electronics—from renewable energy and industrial systems to transportation, ICT/IoT, healthcare, and infrastructure. Please feel free to contact us if you have any requests.
