Knowledge Base
Variable Frequency Drive (VFD)
An electronic device that controls the speed and torque of an AC motor by varying the frequency and voltage of the power supplied to it.
A variable frequency drive (VFD) is a power electronics device that controls the speed of an AC electric motor by adjusting the frequency and voltage of the electrical supply. VFDs are among the most important energy-saving devices in modern industry.
How VFDs Work
- Rectifier — converts AC input to DC
- DC link — smooths and stores energy
- Inverter — converts DC back to variable-frequency AC using PWM
Why VFDs Need Reactors
VFDs are significant sources of harmonic distortion. Line reactors on the input side reduce harmonic current distortion, protect from voltage spikes, and improve power factor.
Energy Savings
In pumps, fans, and compressors, VFDs can reduce energy consumption by 20–50%. Power varies with the cube of speed — reducing speed by 20% cuts energy use by nearly 50%.