Ecap life计算(阿氏模型).doc

? PRECAUTIONS AND GUIDELINES CAT.No.E1001E ?Contents ??? Next? The life of aluminum electrolytic capacitors is largely dependent on environmental and electrical factors. Environmental factors include temperature, humidity, atmospheric pressure and vibration. Electrical factors include operating voltage, ripple current and charge-discharge duty cycles. The factor of temperature (ambient temperature and internal heating due to ripple current) is the most critical to the life of aluminum electrolytic capacitors. General formula to estimate lifetime : The lifetime of non-solid aluminum electrolytic capacitors is generally expressed by using three elements representing the effects of ambient temperature, applying voltage and ripple current, which is shown by the following equation: KTemp(Effects of ambient temperature on life) : Because an aluminum electrolytic capacitor is essentially an electrochemical component, increased temperatures accelerate the chemical reaction producing gas within the capacitor which is diffused through the end seal, and consequently accelerates a gradual decrease in capacitance and a gradual increase in and ESR. The following equation has been experimentally found to express the relationship between the temperature acceleration factor and the deterioration of the capacitor. This equation is similar to Arrhenius equation that expresses a relationship between chemical reaction rates and temperature, and called Arrhenius rule of aluminum electrolytic capacitors. The temperature acceleration factor (B) is approximately 2 over an ambient temperature range (Tx) from 40oC to the maximum rated category temperature of each capacitor. It means that the lifetime is approximately halved with every 10oC rise in ambient temperature and can be extended by using the capacitors at low temperatures. For an ambient temperature range (Tx) of 20oC to 40oC, the factor B will be close to 2, and the lifetime will actually be extended. However, operating and surroun