A Variable Frequency Drive (VFD) is an electrical device that controls the speed of an electric motor by varying its input voltage. It is a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply. VFDs are used to control pumps, fans, conveyor belts, and other types of machinery in industrial plants. They are used in many types of industries, mostly the mechanical and electrical industry where they are found in servo systems, VFD-based control systems, VFD-fed inverters for traction applications (like trains), VFDs that regulate frequency for power plants, VFDs that run compressors or pumps at their best efficiency, VFDs that run the spindle on CNC machine tools for improved precision, VFD-fed inverters for welding power supplies, and VFD-fed control systems.
The VFD works by converting direct current (DC) into variable-frequency alternating current (AC) . It varies the field on the stator and rotates its angle to control the speed of the motor. The VFD can vary the power supplied to match the energy requirement of the driven equipment, and this is how it saves energy or optimizes energy consumption. The drive can dramatically reduce energy consumption when compared to direct-on-line (DOL) operation, where the motor runs at full speed regardless of the demand. Using a drive, power or fuel savings of 40% are common.
The main advantage of using a VFD is that it can vary the power supplied to match the energy requirement of the driven equipment, which saves energy or optimizes energy consumption. VFDs allow users to choose the speed that they want their motors to run at, and VFDs also allow process manufacturers to improve energy efficiency because VFDs can match the motor speed with an optimum electrical frequency. VFDs can provide substantial savings on power bills, improved performance, and protection of valuable motor and equipment.
