Development of mill drives for the cement industry

The cement industry depends on large electric motors to drive cement mills. As energy cost continues to rise, it becomes increasingly important to explore the drive options available in order to make an objective selection of a drive train. The author attempts to provide the industry with an overview of these drives and discusses their relative merits and disadvantages. Particular attention is given to the ring gear and pinion drive, larger drives, and adjustable-speed drives. It is noted in particular that adjustable-speed drives carry a significant premium cost in both first cost and in energy cost, and this requires critical evaluation of the benefits of adjustable speed. The existence of natural and forcing frequencies in the drive train can be responsible for unstable or destructive performance. It is pointed out that the need for a torsional analysis of the drive train cannot be emphasized too strongly, particularly with a slip energy recovery type of adjustable-speed drive. Existing North American technology enables analysis of the drive train to ensure that stable operation will be achieved in service