Low ESR Aluminium Electrolytic Capacitors for Medium to High Voltage Applications

摘要

Low ESR (Equivalent-Series-Resistance) aluminium electrolytic capacitors for medium to high voltage applications have been developed, with a typical ESR reduction of up to 30%, in comparison with our current aluminium electrolytic capacitor products. The effects on ESR have been considered by a combination of modelling and experimentation, evaluating the electrolyte, paper separators, cathode foils, anode foils and the number of tab connections. This evaluation indicated that the electrolyte and paper combination make a significant contribution to the ESR under the application conditions. In order to achieve the target ESR reduction, a new electrolyte of increased conductivity had to be developed. The new electrolyte, namely NE-400, with a working temperature range of -40 to 105 °C, is suitable for voltage applications up to 400 V at 85 °C and 350 V at 105 °C. Capacitor endurance tests at 400 V and 85 °C, showed that the NE-400 electrolyte improves the capacitor performance significantly, when compared with the current CE-450 electrolyte. NE-400 results in low and stable ESR values over a testing period of 6000 hours. NE-400 was also compared to our current CE-350 electrolyte at 350 V and 105 °C, showing significant improvement in the capacitor ESR and stability by using the new electrolyte. Suitable surge voltage capability and excellent characteristics at both low and high temperatures were also achieved.