Research on mechanical reliability of a permanent magnetic actuator for a 126kV vacuum circuit breaker

The objective of this paper is to investigate mechanical reliability of a permanent magnetic actuator (PMA) for a 126kV vacuum circuit breaker. Impact characteristics and fatigue life of the collision components in actuator were analyzed by experiment and simulation. 3D finite element model of impact components were built up. Dynamic impact force between armature and static magnetic conductive yoke were calculated by explicit method. It was also verified by PVDF piezoelectric sensors in the experiments in opening operation. Based on the impact simulation and operating test results, failure mode and fatigue life of the static magnetic conductive yoke and armature were calculated. Experiment results showed that maximum impact force in opening and closing operations of PMA were 892kN and 198kN. Simulation results indicated that the maximum stress in impact process is 871kN, which is verified by experiments. In addition, fatigue mode of impact component was low-cycle crack fatigue. The outside part and inside part of opening static magnetic conductive yoke had appeared failure after 3990 and 3027 operations respectively by using oil damper. Their mechanical lives met the requirement of IEC standard. When the impact velocity was lower than 1.3m/s, the fatigue lives of impact components for opening could meet the IEC standard requirement of class M1.