Dynamic performance of permanent-magnet stepping motors

The paper deals with the dynamic performance of permanent-magnet stepping motors as affected by various kinds of practical load torques. The constant component of load torque, including coulomb friction, results in stable and unstable equilibrium regions, while the viscous torque component is analogous to the damping-factor increase. The technique of generating phase trajectories for a 2-phase permanent-magnet motor, using a digital-computer program, can take into account the actual static torque/angle characteristic of the motor. Pull-in and pull-out stepping rates, obtained from the phase planes, change significantly on account of the variation in motor damping. The technique can also be applied to other types of stepping motors.