Advantage of All Polypropylene Capacitors
The All PP (APP) capacitors have been developed recently to overcome the limitations of metallized PP (MPP) capacitors. APP capacitors are already working very well in high voltage systems. These capacitors could not be introduced in medium and low voltage ranges because thin PP films were not available. Then government gave concessional custom duty for PP films and power industry took advantage of this and asked overseas suppliers to develop thin films. Now it is possible to make economical APP capacitors in lower voltage ratings. APP capacitors have following advantages:
- PP film is stressed at half the level of this real strength and therefore APP capacitors give very reliable service.
- Absence of paper reduces the change of gas formation and therefore there is no fire hazard in APP capacitors.
- APP capacitors have very low losses (0.5 W/kvar) because of the absence of paper and consequently they have very low temperature rise (5 to 70 °C).
- APP capacitors have separate aluminum foil throughout length of the winding. The foils are extended out. The connection taken out from these foils are firm and results in very low resistance & inductance. This makes capacitor very strong for withstanding high in-rush current and hence best suited for automatic PF correction schemes.
- APP capacitors are impregnated with hydrocarbon base oil viz. PXE which is electrically much superior than easter base oil and is same as that used in high voltage capacitors.