Film Capacitor

Film capacitors are passive electronic components that store electrical energy in an electrostatic field. They use a thin plastic film as the dielectric, with electrodes typically formed by metallized film or aluminum foil. These capacitors are widely used in power electronics, audio circuits, motor drives, and power supplies for filtering, decoupling, and energy storage. Key specifications include capacitance value, voltage rating, tolerance, and temperature coefficient. Grades are distinguished by dielectric material (e.g., polypropylene, polyester, polyphenylene sulfide), film thickness, metallization quality, and construction (wound or stacked). High-grade film capacitors offer low loss, high stability, and long life. Typical capacitance ranges from 0.001 µF to 1000 µF, with rated voltages from 50 V to 2000 V (DC or AC). Common tolerances are ±1% to ±10%. Dissipation factor for polypropylene film is ≤0.001 at 1 kHz. Insulation resistance is ≥100,000 MΩ at 25°C and 100 VDC. Operating temperature range is -40 to +105°C. Dielectric strength is at least 1.4 times rated voltage for 1 minute. Capacitance drift is ≤0.5% after 1000 hours at rated voltage and 85°C. Low-inductance types have self-inductance ≤10 nH, and high-frequency types have ESR ≤5 mΩ at 100 kHz. Ripple current capability depends on size and cooling, typically 1–50 A. Lead spacing for radial types is 5–37.5 mm, and case dimensions range from 5×10×12 mm to 40×60×80 mm. Humidity resistance is tested at 85°C/85% RH for 500 hours. Relevant standards include IEC 60384-16, IEC 60384-17, GB/T 14579, and GB/T 10190. Always verify model-specific values and standards with the legal manufacturer or supplier.

A film capacitor consists of two conductive electrodes (usually metallized film) separated by a thin plastic film dielectric. When a voltage is applied, an electric field polarizes the dielectric, storing energy. The capacitance is determined by the electrode area, dielectric thickness, and dielectric constant. The film's low dielectric absorption and high insulation resistance make it ideal for high-frequency and high-voltage applications.