Metallized Polypropylene Film Capacitors (Mkp) Dependent Values With Equivalent Circuit.

Abstract

The dominant capacitor type used in a wide range of power and electronic circuit applications capacitors are Metallised polypropylene (MKP) capacitors . MKP capacitors offer high volumetric capacitor density, low cost, excellent frequency characteristics and a unique ability to recover from point failures in the dielectric film. These properties and especially the self healing capability make the MKP capacitor the capacitor of choice around the world for low power applications. Equivalent series resistance and capacitance of the traditional capacitor equivalent circuit, to frequency and the physical parameters of a capacitor are demonstrated. Spiral-wound cylindrical capacitors without schooping end spray connections were used to model metalized film disconnected from direct connection to the schooping in corroded capacitors are formulated relatedly.The simple formulae for equivalent series resistance and capacitance, derived empirically from the diffusion equation modelling, were found to accurately reproduce experimental results for model experimental capacitors. Source or connection impedance was found to accurately model a rise in dissipation factor at higher frequencies. The paper presents a best fit values for external inductance and source resistance were used in this modeling. Inclusion in the discrete model of a series resistance inversely proportional to frequency effectively modeled the flat low frequency dissipation factor of the commercial polypropylene capacitor.