Stepping Motor Failure Model

The phase portrait for a stepping motor with fast current buildup drive is developed. The shape of the trajectories depends on dimensionless load torque and damping ratio but reflects changes in load torque, inertia, damping and stator current. Motor stepping failures occur when the response crosses separatrices in the phase plane during the stepping sequence. Many modes of stepper failure during start-stop or slewing sequences or underload are explained by the phase portrait for the motor and drive. In addition, the global picture of response obtained from the aalysis is useful in developing slewing strategies and evaluating unusual step command sequences.