Extended FEM Simulation and Experimental Validation of Magnetic Fields in AMF Contacts for Vacuum Circuit Breakers

Abstract

This work presents an expanded experimental and numerical investigation of the magnetic field distribution in axial-magnetic-field (AMF) contact systems under static conditions for large gaps. AMF contacts are used in vacuum circuit breakers (VCBs). Building on an earlier study, a finite-element-method (FEM) model and a physical test method using copper rods as a metal-vapor replacement are employed to characterize the axial magnetic flux density within the contact gap. A calibrated Hall sensor enables magnetic-field measurements, which are compared directly with FEM results. Additional measurements, conducted under revised rod configurations and sensor positions, further validate the repeatability of the method. Beyond validating the simulation against measurements at gap distances of 20, 30, and 40 mm, the present work extends the analysis by examining the spatial distribution of the axial magnetic flux density $B_{\mathrm {z}}$ for a 40-mm contact gap in greater detail. Instead of restricting the evaluation to the mid-gap plane or the centerline, the magnetic-field profiles are extracted radially on the lower contact surface and at axial positions 5–20 mm above it. This approach captures the characteristic field distribution across the whole gap. The resulting field distributions are compared with published plasma-simulation data, demonstrating that the simplified static model reproduces key trends of more complex metal-vapor arc simulations. This agreement indicates that the method can provide meaningful insight into AMF behavior and enables qualitative conclusions regarding expected erosion patterns and contact-design implications.