An Efficient Modeling of Air Gap and Nonlinear Analysis of Magnetic Equivalent Circuit for Large Turbogenerators Under No-Load Condition

Fast and accurate modeling of large turbogenerators is of great importance for optimal design and commercial value. Therefore, a 2-D nonlinear magnetic equivalent circuit (MEC) model considering saturation and rotor motion is proposed in this article. When the node-based MEC adopts relaxation iteration for nonlinear calculation, it is not easy to converge by using traditional interpolation function and piecewise fitting of the core B-H or u(r) (B) curve. The main contribution of this article is to find that using continuous fitting function is of great significance for the convergence of nonlinear iteration. At the same time, a simple and effective MEC of air gap is also provided. The flux density of air gap and stator tooth obtained by the proposed method is in good agreement with results of the finite element. No-load characteristics were also verified by the finite element and experiment. The calculation time of a cycle takes about 700 s by the finite element, and however, MEC only takes about 2 s.

Automated summary

In this article, a fast and accurate modeling method for large turbogenerators is proposed using a 2-D nonlinear magnetic equivalent circuit (MEC) model that considers saturation and rotor motion. The use of continuous fitting function is found to be crucial for the convergence of nonlinear iteration, and a simple and effective MEC for the air gap is provided.