Speed–Torque Characteristic Behavior of Stepping Motors
In the previous section, the dynamic behavior of stepping motors was studied. In many applications the stepping motor is required to move several steps. In this case the motor is moved one step at a time. It is interesting to study that how fast the motor can be moved one step at a time. It obvious that when the motor is moved one step the next step must be applied when the rotor has reached at least 80 or 90 % of the previous step. This is shown for a typical stepping motor in Fig. 5.7. It shows the speed-torque characteristic of a typical stepping motor. The stepping rate depends on the applied torque and implicitly depends on the rotor inertia. At zero torque, maximum stepping rate defined by manufacturer can be used which means the motor can be moved by maximum speed and then decelerate so the rotor has moved to the required position.
There are two curves on the diagram; one for pull-in torque and one for pull-out torque. It means that once the rotor has accelerated to the near maximum speed the switching rate can be increased further. This diagram must be provided by manufacturers.