The electrical characteristics of plastic film capacitors are largely determined by their dielectric properties. WDC film capacitors are mainly produced using the following film materials:
POLYESTERFILM(PET)
Mylar has high dielectric constant and high dielectric strength, good self-healing properties and good temperature stability, and the temperature coefficient of the material is positive. Polyester capacitors are known as "universal capacitors". They provide the best capacity efficiency of all film capacitors at a moderate cost and are suitable for DC applications such as decoupling, blocking, side and noise suppression.
POLYPROPYLENEFILM(PP)
Polypropylene film has superior electrical properties. The film has very low dielectric loss, high insulation resistance, low dielectric absorption and high dielectric strength. The film also provides excellent moisture resistance and very good long-term stability, with a negative temperature coefficient of the material. Polypropylene capacitors are commonly used in AC circuits, as well as pulse applications in high frequency and DC support (DC-link), and they are further used in switching power supplies, electronic ballast and buffer applications, frequency resolution and filtering circuits, and energy storage.
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It is a common film dielectric used in film capacitor products |
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| parameter | The 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 strength |
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) According to IEC60062, there are four types of dielectric
| KT (PET) | KP (PP) | KI (PPS) | KN (PEN) |
| Polyester | Polypropylene | Polyphenylene sulfide | Polyethylene naphtalate |
*PET and PEN films are commonly used in general-purpose capacitors, suitable for low DC voltages or small AC voltages at low frequencies.
* The most important feature of PET is its high capacity at the same volume due to its high permittivity, which makes it more usable in boards in confined Spaces.
*PET compared to PEN, PEN is used when higher temperature resistance is required.
PPS film can be used in applications where high temperature and low loss factor are ultimately required.
*PP films are used in high frequency or high voltage applications due to their very low loss factor and high dielectric strength. The film is suitable for AC and pulse capacitors as well as power supply interference suppression capacitors.
