INTRODUCTION In the application of industrial servo drives to machines it is important that the drive be large enough to meet all the load torque requirements and be stable. It is necessary to make sure that the servo drive torque rating is large enough to meet the load thrust and acceleration requirements plus the machine friction losses; an organized method to accomplish this is referred to as ‘‘sizing the drive.’’ There are many drive-sizing software programs available from commercial servo drive suppliers. It is of critical importance that machine designers size the servo drive in an organized engineering manner. Either manual.