Study of the Copper Losses in a High-Speed Permanent-Magnet Machine With Form-Wound Windings

This paper investigates the profile of the copper losses in a 5.0-MW high-speed permanent-magnet machine with form-wound winding. The machine was tested, and the test data were used in conjunction with the results obtained from finite-element simulations to calculate the copper losses over the complete speed range. A retardation test in open-circuit conditions was performed to calculate the eddy current loss induced inside the stator coils by the rotor magnetic flux. The results demonstrate that this component of the copper losses is significantly high in form-wound machines at high-speed operation. The impact of the slot configuration on the proximity effect was also investigated. Open and semiclosed slots were compared, and the study results show that the high flux concentration in the slot opening region associated with semiclosed slots increases the proximity copper loss compared with the open-slot topology. At the end, this paper proposes the stator-alone test as a valid method to calculate resistance per phase at high frequency and estimates its increment over the direct current resistance.