FILAMENTARY ELECTROMECHANICAL BREAKDOWN

A new breakdown mechanism is proposed in which a filamentary-shaped crack propagates through a dielectric, releasing both electrostatic energy and electromechanical strain energy stored in the material due to the applied electric field. The mechanism predicts a breakdown strength which is proportional to the fourth root of Young's modulus and a time to breakdown comparable with that taken for a sound wave to cross the dielectric (almost-equal-to 0.1-mu-s in 25-mu-m thick polyethylene films). Analysis of previously unexplained results of Hikita et al. on thin films of polyethylene yields good agreement with the proposed mechanism and a filament radius which is comparable to the gross morphological features of the dielectric.