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## SR215C104DAT Datasheet(HTML) 4 Page - AVX Corporation

 4 / 72 page2GENERAL INFORMATIONAcapacitorisacomponentwhichiscapableof storing electrical energy. It consists of two conductiveplates (electrodes) separated by insulating material which iscalled the dielectric. A typical formula for determiningcapacitance is:C =.224 KAtC = capacitance (picofarads)K = dielectric constant (Vacuum = 1)A = area in square inchest = separation between the plates in inches(thickness of dielectric).224 = conversion constant(.0884 for metric system in cm)Capacitance – The standard unit of capacitanceis the farad. A capacitor has a capacitance of 1 faradwhen 1 coulomb charges it to 1 volt. One farad is a verylarge unit and most capacitors have values in the micro(10-6), nano (10-9) or pico (10-12) farad level.Dielectric Constant – In the formula for capacitancegiven above the dielectric constant of a vacuum isarbitrarily chosen as the number 1. Dielectric constantsof other materials are then compared to the dielectricconstant of a vacuum.Dielectric Thickness – Capacitance is indirectly propor-tional to the separation between electrodes. Lower volt-age requirements mean thinner dielectrics and greatercapacitance per volume.Area – Capacitance is directly proportional to the area ofthe electrodes. Since the other variables in the equationare usually set by the performance desired, area is theeasiest parameter to modify to obtain a specific capaci-tance within a material group.Energy Stored – The energy which can be stored in acapacitor is given by the formula:E = 1⁄2CV2E = energy in joules (watts-sec)V = applied voltageC = capacitance in faradsPotential Change – A capacitor is a reactivecomponent which reacts against a change in potentialacross it. This is shown by the equation for the linearcharge of a capacitor:Iideal =CdVdtwhereI = CurrentC = CapacitancedV/dt = Slope of voltage transition across capacitorThus an infinite current would be required to instantlychange the potential across a capacitor. The amount ofcurrent a capacitor can “sink” is determined by theabove equation.Equivalent Circuit – A capacitor, as a practical device,exhibits not only capacitance but also resistance andinductance. A simplified schematic for the equivalentcircuit is:C = CapacitanceL = InductanceRs = Series ResistanceRp = Parallel ResistanceReactance – Since the insulation resistance (Rp)is normally very high, the total impedance of a capacitoris:Z =R2S + (XC - XL )2whereZ = Total ImpedanceRs = Series ResistanceXC = Capacitive Reactance =12π fCXL = Inductive Reactance= 2π fLThe variation of a capacitor’s impedance with frequencydetermines its effectiveness in many applications.Phase Angle – Power Factor and Dissipation Factor areoften confused since they are both measures of the lossin a capacitor under AC application and are often almostidentical in value. In a “perfect” capacitor the current inthe capacitor will lead the voltage by 90°.The CapacitorRLRCPS