High-frequency numerical modelling for impedance frequency response in electrical machine stator coils – a comparative study

The broadband frequency behavior of rotating electrical machine windings has been extensively investigated due to the impact of terminal over-voltages, electromagnetic emissions and related phenomena, which directly affect the electrical insulation in terms of stresses and lifespan. Therefore, modeling approaches for purposes relating to winding diagnosis represents an asset to increase the reliability and comprehension of several techniques such as impedance sweep frequency response analysis (SFRA). In this context, numerical methods and multiconductor transmission line theory represent the most comprehensive approaches for high-frequency modelling of windings. The frequency dependence of per-unit-length parameters, along with the large number of circuit elements, makes the selection of an appropriate circuit simulation strategy a critical consideration. This work presents a comparative and critical comparison of circuit simulation methods in the context of high-frequency modelling of electrical machine windings. To this aim, an air-core winding is built and simulated via Finite Element Analysis (FEA). Then, three methods of modelling implementation are introduced and compared, thus being two hybrid Matlab-SPICE co-simulation approaches utilising transient analysis and frequency sweep respectively in tandem with purely analytical Modified Nodal Analysis (MNA).