Improvements to the Permanent Magnet Synchronous Motor Torque Model Using Incremental Inductance

This study proposes a method to improve the permanent magnet synchronous motor (PMSM) dq 0 model for torque using incremental inductance. The torque model is essentially a partial differential equation considering flux linkage and magnetic energy. In practice, non-ideal factors, such as saturation non-linearity, the cogging structure, and the distortion current, increase the difficulty of solving this equation. In this study, two parameters related to flux linkage and magnetic energy are derived using incremental inductance. In the differential range, they are independent of the currents. Therefore, the partial derivatives of flux linkage and magnetic energy can be expressed in the form of derivatives under the saturation non-linearity conditions. Thereby a dq 0 model that describes the torque ripple of a PMSM is established. This model can be used to calculate and analyse the transient characteristics of torque regardless of steady or unsteady current excitation. The main parameters of the model are obtained from finite-element analysis (FEA). To reduce the dependency on FEA in the application, a derived version of this model is obtained by extending the range of the linearisation assumption. Finally, the rationality and effectiveness of the models are proven by comparison with the FEA and experiments, respectively.