A Precision Measurement of Puncture Voltage

A description is given of an apparatus for the automatic determination of the dielectric strength of thin sheet insulation. The machine makes about 1000 breakdown tests in a day. Almost no attention is required, thus reducing the human element to a minimum. The results of over 100,000 punctures are given. An investigation of the effect of temperature indicates that none of these punctures occurred according to the thermal theories of breakdown. Tests to determine the effect of electrode area are also described. It is shown that statistical theory can be applied to the results with some success. The standard deviation of the breakdown values is a measure of the inherent variability of the material, and thus gives promise of value in the specification of insulation.