Computer Analysis of the Static Stiffness of SCR DC Feed Drives Used on NC Machine Tools

It is shown that the SCR dc feed drive stiffness depends upon the torque and speed of the motor. In particular, changing from continuous to discontinuous conduction in the armature circuit has a significant effect upon the drive stiffness. Analytic expressions for both static and dynamic stiffnesses are derived, and computer-calculated diagrams of the static stiffness are presented. The digital computer programs calculating the drive stiffness are described.