This work reports a modeling methodology for the prediction of conducted emissions (CE) in a wide frequency range (up to 100 MHz), which are generated by dc/dc converters and propagate along the power buses of satellites. In particular, the dc/dc converter seen as a source of CE is represented by a behavioral model, whose parameters can be identified by two unit-level experimental procedures performed in controlled test setups. A simplified multiconductor transmission-line (MTL) model is developed to account for the propagation of CE in shielded bundles of twisted-wire pairs used as power cables. The whole power system is represented by the interconnection of the circuit models of dc/dc converters, cables, and Power Conditioning and Distribution Unit (PCDU). By solving the obtained network, frequency spectra of CE can be predicted. Experimental results are reported to substantiate the accuracy of the proposed unit-level dc/dc converter model and the MTL model of cables. Finally, a system-level test setup composed of three dc/dc converters connected to a PCDU is considered, and predicted CE are compared versus experimental measurements.

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This paper deals with the assessment of low-frequency magnetic-field emissions (MFE) in the engine-driver cab and the passengers' compartments of rolling stock. For emissions' measurement, an experimental setup is designed, involving a three-axial magnetic-field sensor mounted on an antenna positioner, and optically linked to the data-handling system. Measurement is accomplished in the time domain and allows one to retrieve digitized time series of the spatial components of the magnetic-flux density (MFD) vector, at specific points in the measurement volume. Worst case emissions are related to the train operating modes by referring to an experiment that includes acceleration from an initial stop, inertial motion, and braking up to a new stop. The nonstationary behavior of the most relevant MFD sinusoidal components is evidenced, and it is accounted in the spectral analysis by resorting to short-time Fourier transform based on a fixed-length time windows of proper duration. For safety assessment, a compliance check of MFE levels with exposure limits is proposed, based on the computation of an instantaneous safety parameter, obtained by extending requirements developed in the International Commission on Non-Ionizing Radiation Protection guidelines for the simpler case of multiple-frequency steady-state fields.