General Descriptions of Aluminum Electrolytic Capacitors
1. General Description of Aluminum Electrolytic Capacitors
1-1 Principles of Aluminum Electrolytic 1-2 Capacitance of Aluminum Electrolytic Capacitors Capacitors An aluminum electrolytic capacitor consists of cathode The capacitance of an aluminum electrolytic capacitor aluminum foil, capacitor paper (electrolytic paper), may be calculated from the following formula same as for electrolyte, and an aluminum oxide film, which acts as the a parallel-plate capacitor. -- 8 εS dielectric, formed on the anode foil surface. C = 8.855 10 (µF) (1 - 1) A very thin oxide film formed by electrolytic oxidation d (formation) offers superior dielectric constant and has ε : Dielectric constant of dielectric rectifying properties. When in contact with an electrolyte, S : Surface area (cm2) of dielectric the oxide film possesses an excellent forward direction d : Thickness (cm) of dielectric insulation property. Together with magnified effective surface area attained by etching the foil, a high To attain higher capacitance "C", the dielectric constant capacitance yet small sized capacitor is available. "ε" and the surface area "S" must increase while the As previously mentioned, an aluminum electrolytic thickness "d" must decrease. Table 1-1 shows the capacitor is constructed by using two strips of aluminum dielectric constants and minimum thickness of dielectrics foil (anode and cathode) with paper interleaved. This foil used in various types of capacitors. and paper are then wound into an element and With aluminum electrolytic capacitors, since aluminum impregnated with electrolyte. The construction of an oxide has excellent withstand voltage, per thickness. And aluminum electrolytic capacitor is illustrated in Fig. 1-1. the thickness of dielectric can be freely controlled according to the rated voltage of the aluminum electrolytic Electrolyte capacitor. (Real Cathode) Therefore, in compare to other dielectric, similar voltage endurance is provided by dielectric even if thickness ("d" in the above formula) is thin.