Power Electronic Variable Frequency Drives (VFD) are a well proven, reliable and cost efficient solution to ensure precise control of torque and speed of electrically driven rotating machines (such as pumps, compressors, fans, extruders etc.) in a wide range of industrial process. For the purpose of pumps applications, if compared to conventional mechanical flow regulation systems (vanes, gearbox, hydraulic coupling etc.) VFD provides the advantages of more efficient energy management as well as better accuracy and flexibility in process control. Latest technologies in silicon power devices, microprocessors and software development allowed remarkable improvements in performances, reliability and cost reduction; as a consequence energy savings due to VFD use are ensuring investment pay back in a very short time. After a quick summary about basic concepts on VFD for fluid flow control and a short description of different VFD's topologies presently available, special attention is focused on a recent application for pump in a MSF desalination, as well as in other applications in pumping stations for water transmission systems associated to desalination plants.