1. Life Expectancy of a Power Supplies
Aluminum electrolytic capacitor is the shortest life expectancy parts in a power supply. Other parts, like resin, have also their life expectancies , but they are 20 - 30 or over years. So the life expectancies on electric devices generally are not problems.
Aluminum electrolytic capacitor is the most important parts in terms of reliabiliety, and life expectancy of a power supply can be estimated by calculating the estimation of life expectancy of aluminum electrolytic capacitor.
Life expectancy of aluminum electrolytic capacitor is determined by the amount of too much electorlyte, speed that electrolyte passes through a stopper rubber and evaporates, and temperature to determine the speed.
The relationship between ambient temperature and capacitor life has been confirmed to follow ARRHENIUS' equation:
Life Expectancy of Electrolytic Capacitor : L = Lo x 2 (T1-T2) / 10
Lo : Lifetime Under Maximum Rated Operating Temperature
T1 : Permissible Maximum Temperature
T2 : Capacitor Temperature on operation
Life expectancy is determined by a coefficient depending on temperature, based on Lo.
2. Influence to a Power Supplies
Life expectancy of aluminum electrolytic capacitor is a condition that capacitance is below tolerance, tan gets large, or leakage current gets large.
Aluminum electrolytic capacitor is used in a power supply. When it comes to life expectancy, each circuit is affected differently.
Table 1 shows situation of each circuit and influence to a power supply.
|No.||Used Place||Situation||Influence to PWS|
|1||Input Filtering Circuit||Higher Ripple Voltage||Power Supplies Stopped|
|2||Output Filtering Circuit||Higher Ripple Voltage||Square Wave Output Voltage|
|3||Auxiliary Power Supplies Circuit||Control Operation Stopped||Power Supplies Stopped|
|4||Phase Adjustment of Control Circuit||No Control||Unstable Output Voltage|
Since life expectancy of alunimum electrolytic capacitor is determined by ambient temperature, a power supply should be used a well-ventilated place.
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