Name and describe the four stages of the VFD.

Rectifier (sometimes called a converter)
This is the stage of the VFD that rectifies the AC input power to DC power.Some VFDs include additional filtering circuitry to negate any harmonic conditions that could cause power supply problems.DC Bus (sometimes called the DC link)
The DC bus stage of the VFD prepares the DC power from the rectifier stage, for use by the inverter stage.Inverter
The input to the inverter is the DC power on the DC bus.The inverter, under control of the control and regulation stage of the VFD, changes the DC bus power to a controlled frequency AC on the output.Control and regulation
In this section, complex mathematical algorithms are used to separate the torque producing current from the magnetizing current.The control and regulation section of the VFD senses the CEMF of the motor to make adjustments and regulate the inverter section output.