[Explanation of the cause of capacitor failure] The pressure valve does not operate, and steam is ejected from the grounding surface.
A Must-Read Guide for Circuit Designers: 15 Cases of Causes and Countermeasures for Capacitor Failures
Review the requirements for the pressure valve to operate and the regulations for ensuring safety, and secure the necessary space!
In this case, snap-in aluminum electrolytic capacitors were used in the power supply equipment, and to make the equipment thinner, the heat sink was closely positioned against the top of the capacitor. During a test for abnormal conditions in the equipment, an intentional overvoltage was applied to the capacitor, which caused the pressure valve located on the top of the capacitor to fail to operate and resulted in overheating. Subsequently, vapor from the electrolyte burst out from the grounding surface of the capacitor. The cause was that the capacitor shorted due to the overvoltage, leading to current flow and overheating. The heat vaporized the electrolyte, causing pressure inside the capacitor to rise, and since the pressure valve did not operate, gas from the electrolyte burst out from the sealing part of the capacitor on the grounding surface, shorting the wiring pattern on the substrate and causing a spark that resulted in smoke. [Countermeasures] - Review the requirements for the pressure valve to operate and the regulations for ensuring safety, and secure the necessary space. - If sufficient space cannot be secured, a type with a pressure valve on the side of the capacitor is recommended. *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: - Please ensure there is enough space near the capacitor's pressure valve for it to operate. - Since the electrolyte is conductive, if it adheres to the wiring or circuit patterns, it may cause a short circuit. - If the activated pressure valve comes into contact with the device's casing, it may create a ground fault by connecting the input voltage to the casing. *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 a liquid leak ■ 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.