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This paper describes improved torque control of an induction motor. The control is based on direct field orientation with a rotor flux simulator, and motor parameters in the simulator are estimated by a robust identifier with no sensitivity to the stator resistance. Owing to model mismatch in the controller caused by the equivalent core loss resistance, however, both the field orientation and the parameter identification cannot be carried out perfectly, which results in degradation of torque control performance.In order to improve accuracy of the output torque, the proposed system employs a modified machine model taking the core loss into consideration. Consequently, it has been verified through computer simulations that the technique achieves high precision in torque control within a few percent errors.

The extended cantilever model is modified to enable broadband representation of multiple magnetic windings using -domain transfer functions. A linear formulation for extracting the parameters is proposed in which the current-sense impedances do not have to be assumed negligible. The model has been implemented in a circuit simulator that supports transfer function blocks. It has been verified experimentally using a five-winding power transformer. The experimental transformer is simulated embedded in a two-transistor forward converter to examine simulation speed and convergence issues.Index Terms-Broadband winding model, inductor model, magnetic winding model, transformer model.