Study on Magnetic Field Characteristics of Variable-Opening Flux-Concentrating Ring Structure Based on Finite Element Analysis

To enhance the sensitivity and stability of Tunnel Magnetoresistance (TMR) current sensors under complex electromagnetic environments, this paper systematically investigates the influence of key structural parameters of the magnetic flux concentrator. A three-dimensional magnetic field model is established using the finite element simulation software COMSOL Multiphysics, based on a 500 A current excitation. The effects of three critical parameters-the air gap width (L), ring width (W), and inner diameter (R)-on the magnetic flux density at the sensor measurement point are thoroughly analyzed. Simulation results reveal that the air gap width L has the most significant impact: as L increases, the magnetic flux density decreases sharply. Increasing the ring width W effectively enhances the magnetic field intensity until saturation is approached. In contrast, variations in the inner diameter $\mathbf{R}$ lead to non-monotonic fluctuations in the magnetic field distribution. These findings provide both theoretical guidance and engineering references for the structural optimization of magnetic rings and the integration of TMR current sensing systems.