Linear stability analysis of magnetic track brakes considering different electrical wiring configurations

Magnetic track brakes (MTBs) are additional braking systems in railway vehicles used under low-adhesion and emergency conditions. However, their operation at low velocities can induce self-excited vibrations, resulting in high mechanical loads on the structure. Previous studies have identified coupled electromagnetic-mechanical interactions and velocity-dependent friction characteristics as key contributors to these vibrations. Based on energy considerations in a basic MTB model, the phase shift between the varying normal force and mechanical oscillation, which depends on the dynamics of the electromagnetic system, was identified as a key factor for the corresponding excitation mechanism in the literature. Published strategies to prevent self-excited vibrations at MTBs indicate that a modified electrical connection can notably enhance the system's stability behaviour. However, a detailed understanding of the electrical topology influencing the underlying excitation mechanism, i.e. the vibrational behaviour, is still pending. This work introduces a novel nonlinear system model of the MTB that fully integrates the mechanical interaction of the brake frame, the electromagnetic subsystems, and the electrical wiring network. With the proposed framework, parametrised by a numerical eigenmode analysis, the impact of different wiring topologies on the onset of self-excited vibrations is examined. The results demonstrate that the electrical coupling between the corner electromagnets significantly alters the effective energy input, explaining how the coupling can either intensify or suppress self-excited vibrations. Certain configurations are shown to enlarge the stable operational domain without additional mechanical damping or active control. The findings extend previous work on fundamental self-excitation mechanisms and provide new insight into the coupled electromagnetic-mechanical dynamics of MTBs.