Measurement of frequency- and field-dependent permeability of stator laminated core for high-frequency modeling of traction motors

Abstract One of the most important aspects that scientists working on electric drive systems are concerned with is the impacts of using inverters to feed electric machines. These include bearing currents and high-frequency electric oscillations in the windings. The pre-calculation of such effects has become increasingly important in recent years and is based on geometric and material data, including the permeability of the stator laminated core. The permeability depends on both the frequency and the amplitude of the magnetic field. Data sheets for electrical steel laminations specify the permeability for frequencies up to $$f =1\,\mathrm{kHz}$$ and magnetic field amplitudes above $$H = 20\,\mathrm{Am^{-1}}$$ . To predict high-frequency machine behavior, it is necessary to know the permeability at higher frequencies and lower field amplitudes. This work presents a measurement method for measuring permeability up to a field frequency of $$f =40\,\mathrm{MHz}$$ and a field amplitude of $$H = 5\,\mathrm{Am^{-1}}$$ . In addition, the permeability was measured as a function of pre-magnetization. The results show that the permeability decreases by up to 85% when the material is saturated due to pre-magnetization.