Study On Inductance Of PMSM Considering Cross-coupling Effect

Permanent magnet synchronous motor(PMSM) has outstanding advantages in energy consumption, structure and reliability. With the development of motor control theory and material science, PMSM has been widely used in industrial and domestic appliance drive systems. Inductance is a key parameter in the designing and controlling process of PMSM. Due to the complex rotor structure, it is difficult to calculate and test the inductance precisely. Moreover, both the cross-coupling effect and material nonlinearity have significant influence on the analysis of motor operating characteristics. Given all the questions above, this paper studied the inductance parameter of PMSM.Firstly, the basic structures and related theories of PMSM are introduced. With the help of Ansys Maxwell, the finite element analysis models of SPMSM and IPMSM are established. Besides, the basic principle of finite element method(FEM) and the cross-coupling effect are simply discussed.Secondly, the principles of three inductance calculation methods based on FEM are deduced, and inductance calculations of two types of PMSM are completed. The cross-coupling effect is not taken into consideration in the flux current method and the flux perturbation method, but this effect is considered in the differential flux method. The differences of three calculation methods are analyzed, and the results show that magnetic saturation and cross-coupling effect should be considered to obtain high accuracy results. The differences of inductance variation between IPMSM and SPMSM are analyzed as well. The flux-weakening control system for IPMSM is established, and the influence of inductance on the system performance is studied.Finally, the principle of AC standstill method is analyzed, which is simple to get inductance of IPMSM. Because the excitation source of conventional AC standstill method applied to IPMSM is different from the actual situation, the test result contains some errors. To solve this problem, an improved AC standstill method is proposed, so that the test process is closer to the actual condition of the motor, and the cross-coupling effect is considered. Simulation and experimental verifications of the two methods are carried out, the results show the improved method is effective.