Core loss estimation of high speed electric machines: An assessment

High speed electric machines have been gaining significant interest over the last several years. This is mainly due to several advantages including increased power density and lower cost. High speed machines can allow for the elimination of gear box to achieve higher reliability and reduced maintenance of the full drive system. One of the challenges with designing high speed machine is accurate estimation of core loss. This paper will introduce both opportunities and challenges of estimating core loss for high speed electric machines. First, this paper will summarize core loss characterization and modeling based on physical and mathematical formulation. The limitation of classical Steinmetz equation is explained and a modified Steinmetz equation with variable coefficients is presented to improve accuracy of the core loss estimation for wide frequency and flux density range. Several contributing factors are also reviewed for estimation of core loss with consideration of arbitrary excitation waveform, flux density distribution, and the skin effect. This paper explains a core loss model for permanent magnet electric machines and discusses the dependency of core loss on machine dimensions as well. Finally, future opportunities are suggested for core loss estimation of high speed machines.