Using the source-field approach, the formulation is adapted to magnetodynamic cases. This chapter presents the case of the scalar potential since it is, in terms of convergence, very robust compared with vector potential formulations. The time stepping technique is a very useful procedure since it allows solving non-linear cases and it can also consider different feeding source types with not necessarily sinusoidal shapes. In many practical applications, the exciting coil is fed by voltage sources. In such cases, the current established in the coils is also unknown and depends on the magnetic flux created in the structure as well as on the coil resistance. The progressive complexity of cases is detailed in the text and the final formulation takes into account, at the time, hysteresis, magnetic anisotropy, and electrical circuit coupling.