Energy-Saving Project of 5500-HP 13-kV Wound Rotor Induction Motor on a Kiln ID Fan Using a Low-Voltage Slip Power Recovery Drive—A Case Study

Once upon a time, there was a cement kiln with a 5500-HP induced draft (ID) fan powered by a wound rotor induction motor. The process controlled the airflow with an inlet damper operating in 35% open range. The plant wished for a more energy efficient means of controlling airflow and power demand for this fan. This paper reviews the options and decision processes that made this wish come true. A novel method was used to reduce the power consumed and control the fan's speed based on a lower airflow demand. The solution was implemented with participation from the utility, the energy saving consultants, and the equipment suppliers. This paper also covers the challenges presented by the ID Fan wound rotor motor design, the plant operational situation, and the technology selected to solve the problem. Details of the wound rotor motor speed control will be discussed and its application reviewed. The significant energy savings and process improvements are covered as well.