The Theory of Thermal Breakdown of Solid Dielectrics

The purpose of the paper is to correlate the work which has been done on thermal breakdown and to put it in a form in which it can be used by the electrical engineer in the calculation of breakdown voltage. Besides a treatment of the Fock theory, the paper includes the derivation of new formulas for breakdown of very thin and very thick samples and for internal temperature rise and current. A startling fact brought out by this analysis is that before breakdown the internal temperature never rises more than about 10 deg. cent. above ambient temperature. The Fock tables of breakdown voltage are extended to cover a wider range of temperature and thickness, and the results are put in several convenient forms for numerical calculation. Experimental data are also presented to verify the theory.