The phase currents decrease with rising step frequency caused by the motor's regenerative action. The amplitude of the current curve becomes lower and the motor loses torque.
The Overdrive function counteracts this by automatically raising the effective phase current by a factor of √2 from a defined limit frequency (generating a step curve). This countervails the torque reduction. When the speed decreases, the Overdrive function is automatically switched off with a certain hysteresis.
The input control frequency for switching on or off the Overdrive function depends on the step resolution:
Input Control Frequency
Overdrive on at>
Overdrive off at <