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SR217C104GAT Datasheet(PDF) 5 Page  AVX Corporation 

SR217C104GAT Datasheet(HTML) 5 Page  AVX Corporation 
5 / 72 page 3 In practice the current leads the voltage by some other phase angle due to the series resistance R S. The comple ment of this angle is called the loss angle and: Power Factor (P.F.) = Cos f or Sine Dissipation Factor (D.F.) = tan for small values of the tan and sine are essentially equal which has led to the common interchangeability of the two terms in the industry. Equivalent Series Resistance – The term E.S.R. or Equivalent Series Resistance combines all losses both series and parallel in a capacitor at a given frequency so that the equivalent circuit is reduced to a simple RC series connection. Dissipation Factor The DF/PF of a capacitor tells what percent of the apparent power input will turn to heat in the capacitor. Dissipation Factor = E.S.R. = (2 π fC) (E.S.R.) X C The watts loss are: Watts loss = (2 π fCV2) (D.F.) Very low values of dissipation factor are expressed as their reciprocal for convenience. These are called the “Q” or Quality factor of capacitors. Insulation Resistance – Insulation Resistance is the resis tance measured across the terminals of a capacitor and consists principally of the parallel resistance R P shown in the equivalent circuit. As capacitance values and hence the area of dielectric increases, the I.R. decreases and hence the product (C x IR or RC) is often specified in ohm farads or more commonly megohm microfarads. Leakage current is determined by dividing the rated voltage by IR (Ohm’s Law). Dielectric Strength – Dielectric Strength is an expression of the ability of a material to withstand an electrical stress. Although dielectric strength is ordinarily expressed in volts, it is actually dependent on the thickness of the dielectric and thus is also more generically a function of volts/mil. Dielectric Absorption – A capacitor does not discharge instantaneously upon application of a short circuit, but drains gradually after the capacitance proper has been dis charged. It is common practice to measure the dielectric absorption by determining the “reappearing voltage” which appears across a capacitor at some point in time after it has been fully discharged under short circuit conditions. Corona – Corona is the ionization of air or other vapors which causes them to conduct current. It is especially prevalent in high voltage units but can occur with low voltages as well where high voltage gradients occur. The energy discharged degrades the performance of the capacitor and can in time cause catastrophic failures. CERAMIC CAPACITORS Multilayer ceramic capacitors are manufactured by mixing the ceramic powder in an organic binder (slurry) and cast ing it by one technique or another into thin layers typically ranging from about 3 mils in thickness down to 1 mil or thinner. Metal electrodes are deposited onto the green ceramic layers which are then stacked to form a laminated structure. The metal electrodes are arranged so that their terminations alternate from one edge of the capacitor to another. Upon sintering at high temperature the part becomes a monolithic block which can provide extremely high capacitance values in small mechanical volumes. Figure 1 shows a pictorial view of a multilayer ceramic capacitor. Multilayer ceramic capacitors are available in a wide range of characteristics, Electronic Industries Association (EIA) and the military have established categories to help divide the The Capacitor E.S.R. C I (Ideal) I (Actual) Phase Angle Loss Angle V IR s f 
