4.27
EDH0162En1040 – 06/99
MM4005
Motion Control Tutorial
Fig. 4.39
— Single Phase Energization.
Once the closest rotor tooth has been pulled in, assuming that we don’t
have any external load, the motor does not develop any torque. This is a
stable point.
If external forces try to move the rotor (Fig. 4.40), the magnetic flux will
fight back. The more teeth misalignment exists, the larger the generated
torque.
Fig. 4.40
— External Force Applied.
If the misalignment keeps increasing, at some point, the torque peaks and
then starts diminishing again such that, when the stator is exactly between
the rotor teeth, the torque becomes zero again (Fig. 4.41).
Fig. 4.41
— Point Unstable Point.
This is an unstable point and any misalignment or external force will cause
the motor to move one way or another. Jumping from one stable point to
another is called missing steps, one of the most critiqued characteristics of
stepper motors.
The torque diagram versus teeth misalignment is shown in Fig. 4.42. The
maximum torque is obtained at one quarter of the tooth spacing, which is
equivalent to one full step.
Fig. 4.42
— Torque and Tooth Alignment.
Torque
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