Selecting the flux reference for induction machine drives in the field weakening region

In a conventional rotor flux oriented induction motor drive, the flux reference is usually made proportional to the inverse of the rotor speed for field weakening operation. The authors indicate, however, that such a variation cannot maintain optimal (maximum) torque capability maintain optimal (maximum) torque capability of the machine over the entire speed range. It is further shown that nearly optimal torque capability can be achieved in a stator flux oriented system when the stator flux reference is varied as the inverse of the rotor speed.<>