Title

High current and field characteristics of metalized film capacitors

Date of Completion

January 2006

Keywords

Engineering, Electronics and Electrical|Engineering, Materials Science

Degree

Ph.D.

Abstract

Self-clearing metalized film capacitors provide outstanding energy density by facilitating operation of the polymer dielectric with a relatively small margin to its breakdown strength. As a result, metalized film capacitor technology offers the highest energy density among high voltage capacitor technologies. The primary limitation of this technology under pulse discharge conditions is failure of the plasma sprayed metal end connections. This failure mechanism is investigated through transient nonlinear finite element analysis with coupled thermal and electric fields as well as analytic approximations. The analysis indicates that end connection degradation is an electro-thermal-mechanical phenomenon related to the inhomogeneous temperature distribution in the dielectric under transient conditions. Magnetic forces can also play a role. The analysis indicates that dielectric loss measurements cannot reveal the "quality" of the capacitor end connection. Two experimental approaches to assessing winding "quality" have been developed, one based on desorption current measurement and the other based on a novel SCR capacitor discharge circuit.^