Method for Matching the Suction Characteristics and Enhancing the Action Reliability of the Electromagnetic Operating Mechanism of Low-Voltage Circuit Breakers

This study proposes a suction characteristic matching strategy and reliability enhancement method for the electromagnetic operating mechanism (EOM) in low-voltage circuit breaker (LVCB) and the obvious influence of environmental stress on its operation reliability. First of all, the specific structure of EOM in the circuit breaker is examined, and the adaptation criteria for its suction-reaction force characteristics are explored. A fully coupled simulation model of electro-magnetic-mechanical is constructed. Based on finite element software, the electromagnetic system’s structural parameters are optimized. Combined with multi-body dynamics analysis via Automatic Dynamic Analysis of Mechanical Systems (ADAMS), a dynamic matching model of suction-reaction force characteristics is established. By adjusting the stiffness of the reaction spring and the initial contact pressure, the characteristics are accurately adapted. In addition, fault tree analysis is introduced to quantitatively analyze the failure probability of key components such as the electromagnetic system and contact system. The operating mechanism before and after optimization is tested under multiple working conditions. Experimental results under various overload conditions (105%I, 135%I, 150%I) show that the relative error between simulation and measurement decreases from 1.60%–2.06% to 0.62%–1.07% after optimization. Accelerated life tests based on the Arrhenius model indicate that the mean time between failures (MTBF) increases from $1.0\times {10}^{5}$ h to $1.05\times {10}^{5}$ h, and the electrical life of main contacts reaches $1.1\times {10}^{5}$ operations. The maximum breaking speed of the moving contact increases from 5660 mm/s to 6000 mm/s. The results show that the proposed multi-physics coupling simulation method can accurately predict the variation law of suction characteristics. Dynamic adaptation of suction and reaction force characteristics is realized through the structural optimization strategy; this method provides theoretical support for the digital design and reliability improvement of EOM in LVCB.