Siemens SIMATIC S5 Manual page 22

job
Fig. 2/4 Open-loop position control
Stepper motors are drives which rotate by going through a sequence of individual step angles. If
the stepper motor receives a pulse, it revolves through a fixed angle; if the number of pulses and
their frequency is increased, a continuous rotation is gradually achieved.
A pulse train is applied to the stepper motor power circuitry; the number of pulses determines
the distance travel led, the frequency of the pulses determines the speed.
Example
Stepper motor with 500 steps/revolution, per step the motor travels through an angle of
If 10,000 pulses are output, the stepper motor rotates through 20 complete revolutions.
If the pulses are output at a frequency of 1 kHz, the motor requires 10 seconds for the 20
revolutions.
A direction signal is required to control the direction.
Based on the technical data of the plant (machine data) and the required traversing job (target
position, speed), the IP247 positioning module supplies a corresponding pulse train and the re-
quired direction of travel.
The stepper motor drive (stepper motor and power circuitry) converts these pulse trains into a
traversing movement.
The advantage of positioning with stepper motors is that the motor remains at a fixed position
when it is at a standstill, In contrast to this, the drive in closed-loop systems always oscillates
slightly.
Positioning Axes
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