A novel test rig for in situ and real time measurement of welding force and impact force of contacts within electromagnetic relay

Bounce and welding phenomena during contact make and break causes contact resistance degradation and contact material transfer. The correlative failure modes affect electromagnetic relay life greatly. An experimental rig is developed in order to measure the welding force and the impact force of contacts within electromagnetic relay. Furthermore, time parameters (pick-up time, arcing time and bounce time etc.) are also measured synchronously. This is achieved by using a piezoelectric force sensor connected with the stationary contact in addition to synchronization with data acquisition and processing circuit to obtain in situ and real time measurement. And this novel apparatus is designed with five Liner Translation Stages (LTS) to modify the tested-relay's structure parameters, including magnetic gap, contact gap, contact position and spring force. The various features and capabilities of the test rig are presented along with some preliminary experimental results of welding force and impact force behavior to assess relay's failure mechanism.