A Variable Frequency Drive (VFD) (also known as AC Drive, Inverter, Adjustable Frequency Drive, Adjustable Speed Drive, Variable Speed Drive Or Variable Frequency Variable Voltage Drive) is a type of equipment used in electro-mechanical drive systems to control & manage motor speed and torque by altering motor input voltage and frequency. First, the Converter (a diode rectifier) converts three-phase AC power to DC power. Next, the DC Bus stores and filters the DC power in a large bank of capacitors. Last, the Inverter (a set of IGBTs) switches or inverts the DC power in a Pulse Width Modulated (PWM) AC waveform to the motor.