DIELECTRIC MATERIALS
The electrical characteristics of plastic film capacitors are to a great extent dictated by the properties of their dielectric materials. WINDAY film capacitors uses the following film materials in their production:
POLYESTER FILM (PET)
Polyester film offers a high dielectric constant, and a high dielectric strength. It has further excellent self-healing properties and good temperature stability. The temperature coefficient of the material is positive. Polyester capacitors are regarded as “general purpose capacitors”. They provide the best volume efficiency of all film capacitors at moderate cost and are preferably used for DC applications such as decoupling, blocking, bypassing and noise suppressions.
POLYPROPYLENE FILM (PP)
Polypropylene film has superior electrical characteristics. The film features very low dielectric losses, a high insulation resistance, a low dielectric absorption, and a very high dielectric strength. The film provides furthermore an excellent moisture resistance and a very good long-term stability. The temperature coefficient of the material is negative. Polypropylene capacitors are typically used in AC and pulse applications at high frequencies and in DC-Link capacitors. They are further used in switched mode power supplies, electronic ballasts and snubber applications, in frequency discrimination and filter circuits as well as in energy storage, and sample and hold applications.
COMMON FILM DIELECTRICS USED IN FILM CAPACITORS PRODUCTS
|
| PARAMETER | DIELECTRIC (1) | UNIT |
| KT | KN | KI | KP |
| Dielectric constant 1 kHz | 3.3 | 3 | 3 | 2.2 | - |
| Dissipation factor 1 kHz | 50 | 40 | 3 | 1 | 10-4 |
| Dissipation factor 10 kHz | 110 | 70 | 6 | 2 | 10-4 |
| Dissipation factor 100 kHz | 170 | 100 | 12 | 2 | 10-4 |
| Dissipation factor 1 MHz | 200 | 150 | 18 | 4 | 10-4 |
| Volume resistivity | 10+17 | 10+17 | 10+17 | 10+18 | Ωcm |
| Dielectric stength | 400 | 300 | 250 | 600 | V/μm |
| Maximum application temperature | 125 | 150 | 160 | 110 | ℃ |
| Power density at 10 kHz | 50 | 40 | 2.5 | 0.6 | W/cm3 |
| Dielectric absorption | 0.2 | 1.2 | 0.05 | 0.01 | % |
（1）Dielectrics according to IEC 60062 has below four types:
| KT (PET) | KP (PP) | KI (PPS) | KN (PEN) |
| Polyester | Polypropylene | Polyphenylene sulfide | Polyethylene naphtalate |
• PET and PEN films are generally used in general purpose capacitors for applications typically with small bias DC voltages and/or small AC voltages at low frequencies.
• PET has as its most important property, high capacitance per volume due to its high dielectric constant and availability in thin gauges.
• PEN is used when a higher temperature resistance is required compared to PET.
• PPS film can be used in applications where high temperature is needed eventually in combination with low dissipation factor.
• PP films are used in high frequency or high voltage applications due to their very low dissipation factor and high dielectric strength. These films are used in AC and pulse capacitors and interference suppression capacitors for mains applications.
