The PIV series of industrial inverters allow the conversion of a wide range of DC voltages into a stabilized single- or three-phase alternating voltage for the power supply of critical installation loads. Using IGBT technology, the system provides a clean sine wave output minimizing the harmonic content of the wave even with non-linear loads. The presence of the manual by-pass (make-before-brake) and its mechanical conformation, allow maintenance operations to be carried out in total safety for both the load and the operator.