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This paper proposes a novel sliding mode (SM) disturbance observer-based technique to diagnose demagnetization fault of interior permanent magnet (IPM) motors with stator parameter mismatch impacts eliminated. First, the IPM motor model incorporating the disturbances caused by the PM demagnetization and stator parameter mismatch is established. Then, an SM disturbance observer is constructed to identify the overall disturbance caused by all parameters, with its stability discussed by using the Lyapunov function. Third, a current-analysis-based method is developed to extract the disturbance only caused by flux linkage mismatch from the overall disturbance. Third, the extracted disturbance is adopted to calculate the real flux linkage, achieving demagnetization fault judgment and demagnetization degree calculation. Finally, experiment is conducted on two IPM motors to validate the proposed flux linkage estimation and fault diagnosis methods.

Identifying the air-gap flux is a prerequisite for realizing the decoupling control between air-gap flux and torque in an electrically excited synchronous motor (EESM) vector control system. For the nonlinear problem of EESM, the frequency response function method is introduced to analyze the air-gap flux voltage and current models' sensitivity to the motor parameters in this paper. A dynamic air-gap current model for EESM based on the equivalent reaction inductance is proposed to solve the parameter dynamic-variant problem caused by the nonlinear magnetic distribution of the EESM. Meanwhile, the comparative analysis of effectiveness caused by linear and nonlinear flux identification errors in the hybrid air-gap flux model of vector control system is carried out. The effectiveness of the nonlinear dynamic model has been verified by simulation and experiment results, which shows its excellent control performance.

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120° phase belt toroidal winding solid rotor induction motor (120°PBTWSRIM) has advantages of simple structure, short end winding, and high overload capacity, thus it has good development prospects. To study the influence of different structural parameters on 120°PBTWSRIM performance, the 2D finite element model is established, and the electromagnetic characteristics are analyzed. The influence of six structure parameters on the average output torque, power factor, and torque ripple are analyzed, which are slot opening width, slot opening height, slot width, slot height, slot radius, and copper layer thickness. It is found that copper layer thickness has a significant effect on the performance of 120°PBTWSRIM. When the copper layer thickness is 0.5 mm, locked average output torque is increased to 2.784 Nm, locked power factor is increased by 64.6%, and locked torque ripple is reduced by 79.7%. Finally, a prototype of 120°PBTWSRIM is built and experimented, the correctness of performance influence analysis is verified by the comparison of results of the simulation and the experiment.