抄録
It has become more important to estimate harmonic electromagnetic fields in induction motors due to the design trends of smaller size, higher output and spread of inverter drives. Owing to this tendency, the 2D nonlinear time stepping finite element method is widely applied to the analyses of the motors. This method often needs more than thousands of iterative calculations. Furthermore, 3D analyses are required to estimate the effects of the end-rings of the motors accurately. In this case, vast calculation time is required if a full 3D method is carried out.
From the points of view, we introduce the 2D analysis with the approximated modeling of end-rings obtained by the limited 3D analysis. In the method, the 3D analysis is used only to calculate the secondary current distributions, not to estimate magnetic saturation and harmonics. As a result, the 3D analysis can be a linear one using phasor that needs only small computer resources. The results of the 3D analysis modify the 2D nonlinear time-stepping analysis to calculate the characteristics of the induction motors accurately and efficiently.
In this paper, two types of the proposed methods are investigated to clarify the advantages and the break points of the approximations. One is the 2D analysis coupled with the secondary conductor circuit obtained by the 3D analysis. The other is the 2D analysis with the bar conductivity modified by the 3D analysis. From numerical experiments and applications of the motor, it is clarified that the various types of induction motors can be analyzed accurately and efficiently by using the proposed methods properly.
