Engineering considerations when replacing an old DC drive system

Utilizing new drive technology has enabled more applications for AC machines where DC machines have typically been used. In the past, DC machines have been implemented for their good torque characteristics throughout a variable speed range. However, some of these older DC drive systems are becoming obsolete and availability of replacement parts is becoming a concern. This sort of scenario will often be accompanied by a consideration for a drive retrofit project. This paper presents a tutorial style review of DC and vector control AC drive systems. Furthermore, some of the design considerations needed when choosing a drive for a replacement or retrofit application will be discussed.