A number of toroidal ferromagnetic cores for an inductor may be arranged to form a ferromagnetic multi-core array, through which a calculated sequence of wire turns is wound. The array may be structured within certain permitting geometries, to a preferred geometrical shape for use within a downhole tool. The array of cores can take any practical form, include square, rectangular, hexagonal, circular, or the like, as long as the magnetic fluxes of all coils wound about a given core create a magnetic flux within the core that flows in the same direction within the core.