A motor rotating at a speed corresponding correctly to the applied step pulse frequency is said to be in synchronism. Load torques in excess of the motor's capacity (rated torque) will cause a loss of synchronism. This condition is not damaging to a step motor.
A motor is in synchronism if its rotational behavior corresponds directly to the input step pulse rate. Loss of synchronism occurs if the motor fails to rotate at the commanded speed, this is frequently the result of excessive load or very high commanded speed.
The condition is which a rotor's rotation matches the rotation of the magnetic field created by the stator's windings. In synchronism, the motor's step rate equals the controller's input pulse rate. When synchronism is lost, the motor will stall or misstep.