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 article covers some key points and comparisons between the two different technologies that may help make that decision a bit easier.