Relationship between rotor losses and size of permanent magnet machines

The computation of rotor losses is a crucial aspect in Permanent Magnet (PM) machine design. In particular, with the adoption of fractional-slot windings (which causes an increase of the space harmonics content of magneto motive force), the rotor losses assume a dominant role in the machine performance, since it is extremely difficult to measure them, their prediction is becoming more and more important. The aim of this paper is to study the rotor losses phenomenon going through different machine sizes rotational speeds and electrical loadings. The analysis is developed in order to provide the PM machine designers a guideline in rotor losses behavior.