Development of a Molded Case Circuit Breaker with a Spring-Actuated Linkage Based on Multi-Body Dynamics Analysis

摘要

In this research we present multi-body dynamics analysis can be applied in product development using a case study of a Molded Case Circuit Breaker (MCCB) with a spring-actuated linkage, which can save time and cost considerably. In particular, we demonstrate how to evaluate and improve durability of the MCCB based on multi-body dynamics and finite element simulation given SM45C steel used for the MCCB links. Toward this goal, a 3D MCCB dynamic model is first developed and dynamic forces are analyzed by using the multi-body dynamics software, ADAMS. Finite element simulation is then performed to examine maximum principal stresses considering deflections and dynamic loads. Further, mechanical properties of SM45C steel are measured experimentally from tensile and fatigue tests. As a result, we verify that stress loads acting on the latch pin of the spring-actuated linkage are critically higher, which ultimately leads to a low-cycle fatigue fracture of the pin. Based on our analytically estimated maximum principal stresses in the MCCB and experimentally measured mechanical properties of SM45C steel, we evaluate design durability and improve our design. As a result, using a 4 mm diameter pin and modifying SM45C with heat treating that includes quenching and tempering, we successfully achieve a MCCB product development, which provides sufficient strengths to prevent yielding and fatigue failures from repeated dynamic loads.