Drive and Inverter

A VFD (Variable Frequency Drive), or rather a VVFD (Variable Voltage and Frequency Drive) is a precision electronic device specifically designed and used to control the speed of AC induction motors (single as well as three phase) without affecting the electric consumption, torque, impedance, magnetic flux, etc. of the motor. It is integrated to an operator interface for receiving the required speed control commands (using keypads). Why can’t VFDs be replaced by other straightforward means? The following discussion will provide the exact purpose of using VFDs to control AC motor speed. The purpose of a VFD is specifically intended to control the speed of an AC motor by strictly observing the above parameters. Here, the speed of the motor is varied by changing the magnitude of the input voltage as well the frequency at a constant ratio and thus the motor is able to maintain a constant torque even at lower speeds.