A new torque calculator for axial winders with AC motor drives

The authors present a new torque calculator for winders with a AC motor. A precise torque with a defect lower than 1% is often required for an axial winder in the paper or iron and steel industries. These demands are hard to meet and at the moment are realised only with DC-drives. The reasons for using AC motors in winders are their higher qualities with respect to robustness and maintenance. The implementation of an exact torque computation for an AC motor is more difficult than for a DC motor because there exist more variable machine parameters (inductances and resistances). The authors show a torque calculator with a robust flux observer, which permits computation of the torque with a precise static and good dynamic behaviour