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Starting Direction of AC Synchronous Stepper Motor | 18 Mar 2014 | |

Starting Direction of AC Synchronous Stepper Motor

The AC Synchronous stepping motor may initially start in the opposite direction from the one desired.

The two conditions which determine the instantaneous starting direction of an AC Synchronous Stepping motor are the position of the rotor prior to start and what portion of the AC sine wave is apparent when it is first applied to the motor windings.

Curve A in the attached diagram shows the motor starting in the correct direction.

The motor may momentarily start in the opposite direction, then quickly reverse and rotate in the correct direction.  See Curve B in the diagram.

In most instances, this action is negligible and is of no consequence. The motor will still start within 25 milliseconds.

In applications where no motion in the opposite direction can be tolerate most people will use a digitally controlled stepper motor.

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Paul Coughlin