Aluminum Electrolytic Capacitor

Aluminum electrolytic capacitors are polarized capacitors that use an aluminum oxide layer as the dielectric. They are widely used in power supplies, inverters, and electronic circuits for smoothing, filtering, and energy storage. These components are specified by capacitance, voltage rating, ripple current, and equivalent series resistance (ESR). Grades differ by temperature rating, lifetime, and ESR, with higher-grade versions intended for industrial or automotive applications.

Typical parameters, as referenced in IEC 60384-4, include capacitance from 0.1 to 100,000 µF with a tolerance of ±20% (standard) or ±10% (available), rated voltage from 6.3 to 450 V DC, and operating temperature range from -40 to +105 °C (extended up to 125 °C for high-temperature grades). Lifetime at rated temperature ranges from 2,000 to 10,000 hours, ESR at 100 kHz from 0.01 to 10 Ω, and ripple current at 100 kHz from 0.1 to 10 A. Leakage current is specified as 0.01 CV or 3 µA maximum after 2 minutes at rated voltage. Dissipation factor at 120 Hz and 20 °C is 0.1 to 0.5. Case dimensions vary: diameter 5–35 mm, height 11–50 mm, and lead spacing 2.5–10 mm for radial types. Surge voltage is 1.1× rated voltage for 30 seconds at 85 °C. Low-temperature impedance at -40 °C is ≤10× the value at 20 °C.

Materials include high-purity etched aluminum foil, aluminum oxide dielectric, electrolyte (borax or organic acid solution), paper separator, rubber seal, and aluminum case. Relevant standards include IEC 60384-4, GB/T 5993, and JIS C 5141. Always verify model-specific values and standards with the legal manufacturer or supplier before procurement.

The capacitor consists of two aluminum foils separated by paper soaked in electrolyte. Anodization forms a thin aluminum oxide layer on the anode foil, which acts as the dielectric. The high surface area of the etched foil and the thin oxide layer provide high capacitance per volume. When a voltage is applied, the oxide layer prevents DC current flow, while AC current can pass due to the capacitor's charging and discharging behavior.