HMI, VFD, DCS Training Institute in Srivilliputhur. We are leading HMI, VFD, DCS Training Centre in Srivilliputhur. The Human Machine Interface, commonly known as HMI, is the means by which humans engage with machines to monitor, control and/or carry out processes. Simple examples of Human Machine Interfaces are keyboards and touchscreens. A variable frequency drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply. The VFD also has the capacity to control ramp-up and ramp-down of the motor during start or stop, respectively. Distributed control systems (DCS) are dedicated systems used in manufacturing processes that are continuous or batch-oriented. Processes where a DCS might be used include: Chemical plants. Petrochemical (oil) and refineries.