[Explanation of the Causes of Capacitor Failure] A Case Where Sound Came from a Film Capacitor
A Must-Read Guide for Circuit Designers: 15 Examples of Causes and Countermeasures for Capacitor Failures
If the sound level exceeds the acceptable range, please use the "soundproofing product" with a short body type!
Here is a case where a sound like "zi" or "pi" was heard from a film capacitor when the power was turned on. Film capacitors have a structure that consists of extremely thin plastic film rolled up. While the electrodes at both ends of the element are fixed, the body part is not fixed, making it prone to vibration. When voltage is applied to the capacitor, the Coulomb force acting between the electrodes can cause the dielectric plastic film to vibrate mechanically, resulting in a humming sound. In particular, if there is distortion in the power supply voltage or if the waveform contains harmonic components, the sound level can be high. [Countermeasures] ■ Continuous vibration sound - It is not a malfunction; it does not affect electrical characteristics or reliability. - Capacitors with long cylindrical or flat-shaped elements tend to produce louder sounds. ■ If the sound level exceeds the acceptable range or if there are sporadic popping sounds - Please use a "sound-dampening product" with a short cylindrical shape. *For more details, please refer to the PDF document or feel free to contact us.
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Please be aware of the following: - When an AC voltage is applied to a multilayer ceramic capacitor, the capacitor itself may expand and contract, which can cause the circuit board to vibrate in the plane direction like a speaker. - When the vibration frequency matches the audible frequency range for humans (20 Hz to 20 kHz), it can be heard as sound. - The expansion and contraction of the capacitor is caused by the "electrostrictive effect" of the dielectric ceramics, but it is said that addressing this issue is difficult. *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 noises ■ 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.