Capacitors Blog

Capacitor type

Dielectric used

Features/applications

Disadvantages

Polypropylene Plastic Film Capacitors

Polypropylene

Has become the most popular capacitor dielectric[citation needed]. Extremely low dissipation factor, higher dielectric strength than polycarbonate and polyester films, low moisture absorption, and high insulation resistance. May use plates of foil, metalized film, or a combination. Film is compatible with self-healing technology to improve reliability. Usable in high frequency applications due to very low dielectric losses. Larger value and higher voltage types from 1 to 100μF at up to 440V AC are used as run capacitors in some types of single phase electric motors.

More susceptible to damage from transient over-voltages or voltage reversals than oil-impregnated Kraft paper for pulsed power energy discharge applications.

Polysulphone Plastic Film Capacitors

Polysulfone

Similar to polycarbonate. Can withstand full voltage at comparatively higher temperatures. Moisture pick-up is typically 0.2%, limiting its stability.

Very limited availability and higher cost

PTFE Fluorocarbon (TEFLON) Film Capacitors

Polytetra- fluoroethylene

Lowest loss solid dielectric. Operating temperatures up to250°C, extremely high insulation resistance, and good stability. Used in stringent,

Large size (due to low dielectric constant), and higher cost than other film capacitors.

Polyamide Plastic Film Capacitors

Polyamide

Operating temperatures of up to 200°C. High insulation resistance, good stability and low dissipation factor.

Large size and high cost.

Metalized Plastic Film Capacitors

Polyester or Polycarbonate

Reliable and significantly smaller in size. Thin metalization can be used to advantage by making capacitors "self healing".

Thin plates limit maximum current carrying capability.