Disclosed are designs for inductor cores for electromagnetic interference (EMI) filters. In some embodiments, an inductor core comprises a plurality of enclosed structures, where each enclosed structure of the plurality of enclosed structures includes a plurality of elongated bars and at least one connection device. In some embodiments, an enclosed structure is configured to encompass a signal bus. In some embodiments, an enclosed structure has a longitudinal axis and a triangular cross-sectional shape taken perpendicular to the longitudinal axis.