Keywords: energy harvesting, railway monitoring, magnetic field, traction return current, finite element modelling, field measurement, accumulated energy.

An H-shaped magnetic field energy harvester was investigated for converting the alternating field generated by railway traction return current into electrical energy. A finite element model coupled to an external circuit was used to determine the equivalent impedance, tuning capacitance, matched load, and output response. At 50 Hz, the equivalent inductance and resistance were 18.4 H and 430 ?, corresponding to a tuning capacitance of 550.66 nF and a matched load of 430 ?. With a rail current amplitude of 300 A, the maximum average power and voltage amplitude across the load reached 763 mW and 25.6 V. Field measurements over 14 h 29 min 31 s recorded 140 train passages. The current in one rail was reconstructed from the measured magnetic flux density and used to estimate the temporal power profile. A representative interval of 3317 s containing 12 passages yielded 5.81 J at the load, whereas the complete campaign yielded 48.95 J. Sustained responses at moderate power contributed more energy than brief high power peaks, demonstrating that both output magnitude and duration are required to assess railway energy harvesters.

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