Dynamic Analysis of a Drive Unit for Molded Case Circuit Breakers with Electromagnetic Repulsion Forces

Abstract:
To design the interrupter part of Molded Case Circuit Breakers (MCCB) and analyze the interruption characteristics, it is necessary to carry out the dynamic analysis considering not only driving force of a drive part, but also electromagnetic repulsion forces between contacts. In this study, a dynamic analysis model for the operation mechanism of MCCB is built and the fault current is assumed to flow on contacts in a closed state. The electromagnetic repulsion forces are defined as the contact reaction force from Holm's equations, the arc reaction force from energy equilibrium equations of arc and the conduct reaction force from electromagnetic analysis considering time, voltage, current and distance of the contacts. These forces are applied to moving electrodes of the dynamic analysis model. And then dynamic analysis results are verified by experiments. The kinematic quantities for a drive unit of MCCB can be predicted and evaluated by this simulation method.