Power Efficient Motor Driver - VFD

VFD is known as the variable frequency deriver. It is used to derive a motor at different speed. In the power plant commonly induction motors are used to run fans and pumps. In which fluid coupling, blade pitch control, damper, inlet guide vane control or any other type of mechanical method is used to reduce the speed of the motor to get desired output. In this way speed of the motor is controlled to maintain the output of motor according to load on the plant. But as the motor is giving the desired output but still it is running at full load i.e. it is giving the reduced output at same power consumption. So at this situation we can consider a part of power as loss. To improve this situation VFD is used. It is an electronic circuit that accurately control the speed of standard AC induction or synchronous motors. With VFDs, speed control with full torque is achieved from "0" rpm through the maximum rated speed and, if required, above the rated speed at reduced torque. VFDs manipulate the frequency of their output by rectifying an incoming AC current into DC, and then using voltage pulse-width modulation to recreate an AC current and voltage output waveform. In this way we get the desired output at reduced power but the torque remains constant. This method is very efficient for fans used in plants. In this paper working of VFD, its principal, circuit and how it saves power, the difficulties faced during implementation and their possible solution is discussed.