Allen Bradley VFD PowerFlex 400 AC Drives:PowerFlex400 VFD is optimized for control of commercial and industrial fans and pumps. Built-in features such as purge and damper input provide a cost-effective solution for speed control in a broad range of variable torque fan and pump applications. An available packaged PowerFlex 400 Fan and Pump drive provides additional control, power, and enclosure options in standardized designs for a cost-effective solution for speed control in variable torque fan and pump applications.