Stator flux orientation control of induction machines in the field weakening region

The behavior of a director stator-flux-oriented (SFO) system in the field weakening region is studied and compared with that of a direct rotor-flux-oriented (RFO) system. The steady-state analysis shows that the SFO system always retains maximum torque capability, not matter how large the error in the parameters. In contrast, RFO is sensitive to variations in leakage and magnetizing inductances. When detuned, RFO yields reduced torque capability and poorer torque/ampere ratio, or even static instability. Digital simulation also shows that SFO can have dynamic response comparable to tuned RFO.>