How Variable Frequency Drives Work in HVAC Systems - MEP Academy

What Is a VFD? A Variable Frequency Drive is used to regulate the rotational speed of an AC motor. It does this by varying the frequency and voltage of the electrical power supplied to the motor. Since the speed of an AC motor is directly proportional to the frequency of the power supply, controlling frequency allows precise speed control. How Does a VFD Work? The operation of a VFD involves three main stages: 1. Rectification (AC to DC) - Incoming AC power is converted to DC using a rectifier.