Modeling of magnetic non-linear characteristics in electric machines.

摘要

Modeling magnetic non-linear characteristics of electromechanical systems usually represents a challenge for designers and engineers and often requires the use of rough approximations. Finite Element Analysis (FEA) coupled with Electromagnetic Transient Simulation Programs (ETSP) using time stepped field solutions can yield accurate results [2], however such approaches require long simulation times.; This paper explores the applicability of FEA and ETSP in a decoupled manner. For such purpose a model of the magnetic non-linear characteristics of a contactor is derived by means of multiple magneto-static FEA. This model is fed into the ETSP in the form of lookup tables where different time dependent scenarios are simulated. The same scenarios are simulated using the coupled transient electromagnetic-FEA engine. It is found that the decoupled approach yields closely comparable results to the transient FEA as long as the eddy currents do not play a key role in the application.; A three-phase power transformer is modeled using a non-linear lumped magnetic circuit. The performance of this model is compared against a 2D transient electromagnetic-FEA model for different levels of core magnetization in the steady state. The finding of this simulation is that the lumped method can yield accurate results for nominal levels of core magnetization.; Finally, a single-phase transformer model is created using two different kinds of non-linear lumped magnetic and electric circuits. These models are compared against a 2D FE axisymmetric model for transitory events, namely energization events. It is found that the calculated inrush current and core flux density do not differ by more than 10% when the leakage flux is incorporated into the magnetic circuit as leakage reluctances.