In this paper, more than ten different iron loss models are experimentally evaluated, which cover alternating and rotating fields, influence of temperature, DC bias flux density and distorted flux density due to PWM inverter. Iron loss models considering alternating fields are evaluated by the measured results of a lamination ring specimen. The iron loss model considering rotating field and non-sinusoidal field are evaluated by the measured results of an electrical machine under different conditions. The iron loss models considering temperature influence are also evaluated by thermal analyses and experimental tests. Based on these comprehensive investigations, the iron loss models having the best prediction accuracy for each case are identified.Index terms --Electrical machine, Iron loss, Thermal analysis.Z.Q. Zhu (M'90-SM'00-F'09) received the B.Eng. and M.Sc. degrees in electrical engineering from Zhejiang University, . His major research interests include design and application of electric machine and drive system.Jun Peng received the B.Eng. degree in mechanical design