VFD Fundamental's
A Variable Frequency Drive (VFD) is an electronic device that vary the frequency and voltage of the power supplied to an electric motor to alter the speed and torque of the electric motor. The primary purpose of a most VFDs is to adjust the speed of the motor to match process requirements. For example, in a gas processing plant there are various aftercooler fans driven by VFD-fed motors, the VFD increases or decreases the speed on the cooler fan in response to the process variable setpoint. In this case, the temperature of the gas to be cooled is the process variable. HOW A VFD WORKS A VFD works in three stages namely, Rectifier Stage, DC bus and Inverter stage. In the rectifier stage , AC supplied to the VFD is converted to DC using diodes. The output from the rectifier is a pulsating DC. The Pulsating DC is smoothened out in the DC bus stage using capacitors and/or inductors. The Filtered DC from the DC Bus supplies electrical energy to the inverter stage of the VFD. The inverte