Electrolytic capacitors feature one: the capacitance per unit volume is very large, dozens to hundreds of times larger than other kinds of capacitors.
Electrolytic capacitor characteristics two: the rated capacity can be very large, can easily do tens of thousands of μf or even a few f (but not and double layer capacitance ratio).
Electrolytic capacitors feature three: the price has an overwhelming advantage over other kinds, because the electrolytic capacitors are composed of ordinary industrial materials, such as aluminum and so on. Aluminum electrolytic capacitor manufacturing equipment is also common industrial equipment, can be mass production, relatively low cost.
The aluminum electrolytic capacitor is bound to fail, it's just a matter of time. There are many reasons affecting the capacitor life, such as overvoltage, reverse voltage, high temperature, rapid charge and discharge, and so on. Under normal use, the biggest influence is temperature, because the higher the temperature, the faster the evaporation loss of electrolyte. It should be noted that the temperature here does not refer to the ambient or surface temperature, but to the working temperature of the aluminum foil. Manufacturers usually label the capacitor life and test temperature on the capacitor body.
Because the working temperature of the capacitor increases by 10℃, the life of the capacitor is halved, so do not think that the aluminum electrolytic capacitor with a life of 2000 hours is better than that of 1000 hours, and pay attention to the test temperature to confirm the life. Every manufacturer has a formula for calculating temperature and life, which should be calculated with reference to actual data when designing capacitors. It should be understood that to improve the life of aluminum electrolytic capacitors, firstly, the working temperature should be reduced, and the heat source should be kept away from the PCB. Secondly, the capacitor with the highest working temperature should be used. Of course, the price will be higher.
Electrolytic capacitor in the circuit to withstand the actual voltage can not exceed its voltage value. In the filter circuit, the voltage value of the capacitor should not be less than 1.42 times the effective value of the AC. When using electrolytic capacitors, but also pay attention to the positive and negative terminals do not connect. Different types of capacitors should be used for different circuits. Mica and high-frequency ceramic capacitors can be used in the wiper vibration loop; paper, polyester, mica, electrolytic and ceramic capacitors can be used for DC isolation; electrolytic capacitors can be used for filtering; and polyester, paper, ceramic and electrolytic capacitors can be used for bypass. Before loading the capacitor into the circuit, check whether it has short circuit, open circuit and leakage phenomenon, and check its capacitance value. When installing the capacitor, make it easy to see the type, capacity, voltage resistance and other symbols for verification.
life expectancy: the time of sustainable action of the electrolytic capacitor at the highest working temperature.
lx=lo*2(to-ta)/10
lx= actual service life
lo= guaranteed life
to= maximum operating temperature (85℃105℃)
ta= actual working ambient temperature of the capacitor
example: Standard value 105℃/1000hrs
Life estimation at 65℃ : lx=1000*2(105-65)/10
Actual service life: 8000hrs
The rated working voltage of the electrolytic capacitor at the highest operating temperature shall conform to the following changes after a continuous specified completion time: δcap: within 20% of the value before the test.