Failure of Arcing Contacts in Low Voltage Switching Devices --Examples, Root Causes, Counter Measures

The paper deals with unexpected test results and field failures of arcing contacts in low voltage power engineering switching devices. Different possibilities of failure modes and their consequences on device performance are presented starting with the contact material, the joining technology and process parameters in contact part production and handling as well as set up and design of the switching device. Examples presented show contact problems as high contact resistance and thus elevated overtemperature results, reduced electrical service life and welding of contacts. After indications how to fix the problems and to find the root causes the paper provides recommendations to avoid such failures.