The application of adjustable-frequency controllers to forced-draft fans for improved reliability and energy savings

A method of utilizing an adjustable-frequency controller (AFC) with a line bypass, to provide the energy saving potential of an AFC coupled with the inherent reliability of a simple magnetic starter, is presented. The proposed system allows the transfer of the motor between the AFC and the power line, even after a controller fault or power interruption, without causing a significant loss of air. A specific operating application is reviewed. The operating experience for the first year for this AFC on a forced draft (FD) fan has met the expectations of the user and manufacturer. When operating this FD fan from the main control panel, the operating procedure remains the same in either the AFC or bypass mode