Approximate methods for calculating rotor losses in permanent-magnet brushless machines

This paper describes approximate methods for calculating the rotor losses due to induced currents in rotors of permanent-magnet brushless machines, that is, in the magnets, the shaft, and in any retaining can. Different methods are developed for surface-magnet and interior-magnet machines. The methods include segmentation of the magnets and the rotor can in both the axial and circumferential directions. They can be extended via the frequency-response method to calculate the subtransient reactance and time-constant needed for fault calculations.