Adjustable speed AC drive for fan vibration control

Vibration was once a damaging problem to the fans for the coke emission control system at the Ashland, Kentucky plant of Armco Inc. After evaluation of several ways to correct the problem, Armco elected to install an adjustable speed AC drive system which used the existing motor to control the air flow and to remove the damper, which was the cause of the flow instability and the resultant vibration. The adjustable speed drive system not only corrected the vibration problem, but also increased the operating efficiency of the system and reduced the annual power costs by several thousand dollars in the first year. The authors present the problem, the alternate corrective actions which were evaluated, the system performance after the retrofit, and the design considerations for the adjustable speed drive system. They also address current fan application considerations at Armco and the state-of-the-art technology and hardware for adjustable speed AC drive systems.<>