METHOD FOR SORTING ZNO VARISTOR

摘要

PURPOSE:To sort out a ZnO varistor having an inferior service life characteristic in an early stage by easily and inexpensively ascertaining the characteristics of the varistor regarding the service life characteristic in an early stage, because some of ZnO varistor elements used for protecting various kinds of electric apparatuses from external surges are finally broken down due to gradually increasing leakage currents when voltage loads and surge loads are applied across the elements for a long period. CONSTITUTION:A ZnO varistor element which is abnormally low in (CXV1mA).(Rs) is sorted out by measuring the capacitances (C), series resistance components (Rs), and varistor voltage (V1mA) of ZnO varistor elements. The ZnO varistor element which exceeds the triple of a standard deviation in the (CXV1mA).(Rs) value largely varies in varistor voltage (V1mA) and is finally broken down when a voltage load and surge load are applied across the element. When the ZnO varistors are sorted based on the (CXV1mA).(Rs) value in such a way, highly reliable ZnO varistor elements can be obtained.