A small electrical generator based on vibrations and using the efficient electromagnetic transduction mechanism is presented. The system is using a magnetic core made of FINEMET nanocrystalline ribbons with specific magnetic properties to harvest and convert the energy of vibrations into the active energy, at a maximum efficiency of about 50%. The system consists of a pair of movable magnets attached to an elastic lamella working as cantilever and fixed coil. When subjected to vibrations, the oscillation of the permanent magnets induces an electromotive force in the coil surrounding the magnetic core. A model that simulates the behavior of the small electrical generator is proposed. The model provides information about the influence of different parameters on the transduction mechanism, the optimal conversion efficiency, and the reliability of the system, being extremely useful to properly design the energy harvester.