1.电容器其本原理.doc

电容器简介 Revision: A Writer: Jerry lin PAGE  页数:PAGE 12 Date: DATE \@ yy/MM/dd 17/04/28 电容器其本原理: 电容器之结构图: Q = CV(coulomb) C = (ε0*ε*A) / t 电容器之定义: 容量之单位: 电容器所储存电荷之能力,称为此电容器之容量,其单位为法拉(Farad).由于法拉之单位太大,一般均用microfarads 1uF=10-6F,1pF= 10-12F, 电容器之标示: 电容器是一种用来储存电荷(electrical charge)的组件,其构造包含有两片金属片,当作电极,如铝箔等.储存正电荷之电极称为阳极(Anode),反之称为阴极(Cathode) 容量与两极板之面积关系: 当两电极板之面积增大时,其容量亦随之增大,即容量与面积成正比. 容量与两极板之厚度关系 电容器所储存之电荷储存于两极板之表面,因此其容量与两极板之厚度无关,依此原理,可使用很薄之电极板制作电容器. 容量与两极板之距离关系 两面积之极板,当??极板间之距离愈小其容量愈大,故容量与两极间之距离成反比. 容量与介质之关系 电容器之两电极不可接触,否则正负电荷将彼此中和,此现象称为电容崩溃(Capacitor breakdown).因此为了避免此现象之发生,一般于两极间有一绝缘层,任何绝缘层均含有原子和分子,此分子即产生极化,以产生极化,以增加容量;电容器放电时,分子之极化性即随之消失.此种之含有极化性原子的绝缘物质,称为介质(Dielectric),介电质之极化能力系受介电常数(Dielectric constant)之影响,一个含有”高介电常数”的电容器,其较”低介电常数”的容量为大. 结论 C =( ε* A) / d ε= εm * ε0 ε0 (真空介电常数) = 8.85 * 10 –12 F/M = 8.85 * 10 –8 uF/cm εm = the permittivity of dielectric material A = 面积. d = 距离. 各种类之介电材质,介电系数,耐压: Type of CapacitorDielectricDielectric Constant “ε”Dielectric thickness “d”(um)Aluminum Electrolytic CapacitorAluminum Oxide 铝氧化皮膜 (Al2O3)7-10(0.0013 – 0.0015 / V)Tantalum Electrolytic CapacitorTantalum Oxide 钽氧化皮膜 (Ta2O5)10-24(0.001 – 0.0015 / V)Paper Capacitor (Metal Foil)Oil Impregnated Paper 矿物油纸3.5 – 5.08Paper Capacitor (Evaporated Metal)Oil Impregnated Paper 矿物油纸3.5 – 5.08Film Capacitor (Metal Foil)Polyester Film 塑料薄膜3.22Film Capacitor (Evaporated Metal)Polyester Film 塑料薄膜3.22Ceramic Capacitor (High Dielectric Constant Type)Barium Titanate 钡汰酸盐500 – 20000100Ceramic Capacitor (Temp. Compensation Type)Titanium Oxide 汰氧化物15 – 250100Air 空气1  电容器之等效电路及相关公式: 电容器之等效电路及相关公式 C = Capacitance Ls : Series Inductance(LL+LW) LL = Inductance of Leads LW = Inductance of Winding Rs : Series Resistance [ESR(Equivalent Series Resistance) = RL + RC + RW] RL : Resistance of Leads RC : Resistance of Contacts RW : Resistance of Winding Z : Total Impedance Rs : Series Reisistance Xc: 容抗(Capacitive Reactance) =