Polypropylene AC Capacitors Parametric Search

Polypropylene film capacitors have a dielectric made of the thermoplastic, non-polar, organic and partially crystalline polymer material Polypropylene (PP) from the family of polyolefins. Typically manufactured both as metallized wound and stacked versions, as well as film/foil types. Polypropylene film is the most-used dielectric film in industrial capacitors and also in power capacitor types. The polypropylene film material absorbs less moisture than polyester film and is therefore also suitable for "naked" designs without any coating or further packaging. But the maximum temperature of 105 °C hinders use of PP films in SMD packaging.

The temperature and frequency dependencies of electrical parameters for polypropylene film capacitors are very low. Polypropylene film capacitors have a linear, negative temperature coefficient of capacitance of ±2,5 % within their temperature range. Therefore, polypropylene film capacitors are suitable for applications in Class 1 frequency-determining circuits, filters, oscillator circuits, audio circuits, and timers. They are also useful for compensation of inductive coils in precision filter applications, and for high-frequency applications.

In addition to the application class qualification for the film/foil version of PP film capacitors, the standard IEC/EN 60384-13 specifies three "stability classes". These stability classes specify the tolerance on temperature coefficients together with the permissible change of capacitance after defined tests. They are divided into different temperature coefficient grades (α) with associated tolerances and preferred values of permissible change of capacitance after mechanical, ambient (moisture) and life time tests.

The table is not valid for capacitance values smaller than 50 pF.

In addition, PP film capacitors have the lowest dielectric absorption, which makes them suitable for applications such as VCO timing capacitors, sample-and-hold applications, and audio circuits. They are available for these precision applications in very narrow capacitance tolerances.

The dissipation factor of PP film capacitors is smaller than that of other film capacitors. Due to the low and very stable dissipation factor over a wide temperature and frequency range, even at very high frequencies, and their high dielectric strength of 650 V/μm, PP film capacitors can be used in metallized and in film/foil versions as capacitors for pulse applications, such as CRT-scan deflection circuits, or as so-called "snubber" capacitors, or in IGBT applications. In addition, polypropylene film capacitors are used in AC power applications, such as motor run capacitors or power-factor correction (PFC) capacitors.

Polypropylene film capacitors are widely used for EMI suppression, including direct connection to the power supply mains. In this latter application, they must meet special testing and certification requirements concerning safety and non-flammability.

Most power capacitors, the largest capacitors made, generally use polypropylene film as the dielectric. PP film capacitors are used for high-frequency high-power applications such as induction heating, for pulsed power energy discharge applications, and as AC capacitors for electrical distribution. The AC voltage ratings of these capacitors can range up to 400 kV.

The relatively low permittivity of 2.2 is a slight disadvantage, and PP film capacitors tend to be somewhat physically larger than other film caps.

The capacitor grade films are produced up to 20 μm in thickness with width of roll up to 140 mm. Rolls are carefully vacuum packed in pairs according to the specifications required for the capacitor.