FIXED FILM CAPACITOR DIELECTRICS
Polyester (Mylar) Film:
A good general purpose plastic dielectric with relativity low cost and high volumetric efficiency. Still the most popular of the capacitor dielectrics. Available in both Metallized Polyester Film and Polyester Film & Foil designs.
Combination Polyester (Mylar) and Polypropylene. Extremely low temperature coefficient in the 0° C to 85° C temperature range. Volumetric efficiency similar to Polycarbonate. Available in both Metallized and Foil designs.
KF (Polymer) Film:
Extremely high volumetric efficiency with about 4 times the "K Factor" of mylar, making it about 1/4 the size. Higher DF and lower IR are its disadvantages along with cost.
Lower DF, higher IR, better temperature coefficient and better stability than mylar with a slightly lower volumetric efficiency. Second most popular Dielectric. Available in both Metallized Polycarbonate Film and Polycarbonate Film & Foil designs. Polycarbonate capacitors have a 100% voltage rating from -55° C to +125° C.
Electrical properties similar to Mylar with a much higher operating temperature going up to 250° C. A higher cost than mylar limits its use.
Very good temperature coefficient high IR, and low DF make it good for AC operation. Usable to 105° C without derating. Has become increasingly popular for AC applications. Available in both Metallized Polypropylene Film and Polypropylene film & Foil constructions.
Electrical properties similar to polycarbonate with a very good temperature coefficient and higher operating temperature. Very limited availability in the last few years has limited its use. Available in both Metallized Polysulfone Film and Polysulfone Film & Foil designs.
Very good electrical properties and excellent stability are its advantages. Its big disadvantage is its operation is limited to below 85° C and it is available in Polystyrene Film & Foil construction only.
SuperMetallized Polypropylene Film:
A very high current design for very high frequencies up to 1 Megahertz. The ultimate in high current capacitors. They are used for input filtering, high frequency transformer DC blocking and output filtering. They are dry-section non-polar metallized film dielectric with special high current end terminations resulting in very low ESR values and very high DV/DT ratings. Larger than SuperMetallized Polypulse. Also popular in snubber applications.
SuperMetallized Polypulse Film:
Developed by American Capacitor specifically for switching power supply type applications. They are used for input filtering, high frequency transformer DC blocking and output filtering. They are dry-section non-polar metallized film dielectric with special high current end terminations resulting in very low ESR values and very high DV/DT ratings. They are significantly smaller than metallized polypropylene capacitors and have a 100% voltage rating from -55° C to +125° C. Capacitance change over temperature is 4 times better than with polypropylene.
The best electrical properties of all the Dielectrics. Extremely high IR, low DF and operation to 250° C. Available in both Metallized Teflon Film and Teflon Film & Foil constructions.
Paper or Kraft Paper is the oldest of the film capacitor dielectrics. It is available in both Metallized Paper and Paper & Foil constructions. The paper must be impregnated with Epoxy, Wax, Oil, or other suitable impregnate. It is still popular for high voltage and AC rated capacitors operating at lower frequencies. Paper is also wound with plastic dielectrics in combination dielectric capacitors.
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Updated: August 21, 1997Publisher: American Capacitor Corporation
Copyright © 1997 American Capacitor Corporation. All rights reserved.