Distribution regularity of breakdown field strength of high voltage ceramic capacitor

Electrical breakdown tests on high voltage ceramic capacitors, whose ceramic disks were in two kind of geometry, were carried out under various rates of voltage rise. It was shown that the breakdown field strength of samples in the same form displayed a Weibull distribution for the same rate of voltage rise. With increasing rate, the slope and character strength of the Weibull line improved in the flat samples, but was unchanged in concave samples. In the mean time, the mechanical strength of the ceramic material used in the capacitor was examined and obeyed the Weibull distribution. The Weibull line slope of mechanical strength was nearly same as that of the breakdown strength of concave samples. We concluded that the alternative breakdown of high permittivity ceramic happens when the degree of discharge at weak points exceeds some certain amount. The weak points are the voids and cracks contained in the ceramic, and the discharge at those weak points and electric-mechanical stress seem to be the main sources of electrical breakdown