Investigation of Switching Characteristics of Contact Materials for Inductive Load

Electrical performance and failure mechanisms of electromechanical relay for switching inductive load (such as motor or electromagnetic valve) are urgently demanded to know. In this work, the silver tin oxide contact material has been tested with a series of inductive load (1mH, 2mH, 3mH and 3.5mH) by using our designed novel model switch. The observed longer arcing duration and overload voltage results in the obvious material transfer features between contacts. The shrinkage of effective contact gap is the root reason for failing to break arc, which would lead to the final contact welding failure. Also, the observed sharp increment of arcing duration and contact force could be treated as the precursor of welding failure.