Investigations on the make-welding behavior of high power contactors for AC and DC applications up to 3kV

Abstract

Contrary to other test setups, a virtually unmodified contactor actuator has been integrated into a model switch to reproduce contact bouncing of make operations. This allows for a less complex machine than an electro mechanical or pneumatic replica of the original actuator. Furthermore optical and mechanical access to the contacts is significantly improved compared to a standard contactor. Scattered failure of the contact system has been traced down to contact welding during make operations instead of welding by over-currents in the on-state. Investigations of the welded contact have been rather limited without completely destroying the contactor housing for extraction. The model setup facilitates series switching with recording of electrical parameters as well as contact closing and separation forces and contact bridge displacement. Welded contacts can be teared open by an additional actuator to detect welding forces in place or can be simply disassembled for further analysis without damaging the weld spot. The authors present first results from their test sequences and reveal the significance of pre-impact arcing for the total energy dissipation in make operations.