INTRODUCTION

There are less than a dozen plastic films currently used as capacitor dielectrics, and polypropylene is by far the most widely used of these. Significant quantities are employed in commercial applications such as entertainment, motor run, power factor correction ballast, microwave, and other appliance uses. Capacitors manufactured for these applications use a film that is of comparatively low cost, however, this film has excellent dielectric strength, extremely low dielectric loss, and worldwide availability.

To put film usage into perspective, we refer to information published by Kalle. Worldwide use of plastic film for capacitors for 1983 by weight, was esitmated as follows:

Table 1
Film		Total Weight (%)
Polypropylene (PP) Polyester (PETP) Polycarbonate (PC)   All Others		70.0 27.0 2.3 0.7

Polyester and polycarbonate film capacitors presently dominate in applications serving military and industrial requirements. Utilization of these two films includes product types specified in MIL-C 19978, MIL-C-55514, MIL-C-39022, and MIL-C-83421.

The use of films listed as "All Others" is comparatively small, and generally directed toward

We will examine performance characteristics of polypropylene capacitors to provide a frame of reference from which this type of film capacitor can be selected for specific applications for military, industrial and instrumentation market segments. These capacitors should be excellent candidates for a variety of a-c devices including switched-mode power supplies, high frequency inverters, and snubber applications.

Polypropylene capacitors are now included in MIL-C-55514, and will shortly be added to MIL-C-39022. The performance data and related information obtained from these programs constitute a major portion of this paper. Sprague Technical Paper TP83-4, "A-C Applications of Plastic-Film Capacitors" is also used as a basic reference. The data used to generate tables, curves and graphs was obtained from actual measurements, and should not be interpreted as maximum/minimum values or limits for use in specifications.

Discussions are presented on the following subjects:

1. Performance Characteristics
2. Reliability
3. ESR
4. A-C Heating
5. Polypropylene-Foil Characteristics

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