Proper selection of number of slots and poles in fractional slot permanent magnet machines: Loss reduction approach

Spatial harmonics of magneto motive force induces electrical current in conductive parts of rotor which causes losses in rotor. These losses in fractional slot machines due to high content of spatial harmonic are high. This article aims at introducing a method for rotor losses comparison in different combination of slot per pole in fractional slot andintegral slot machines. In order to do that, first a method for winding design and then a method for analyticalcalculation of losses will be provided. Next a rotor loss index will be introduced by which comparison of different combination of slot per pole is achieved. This index enables one to choose the slot per pole combin ation that the minimum losses. Finally using the obtained information, two motor with different slot per poles combination were designed and built. The two motor losses were also comparing

Keywords:

Rotor loss , Permanent magnet motor , Fractional slot winding , Magneto motive force harmonic , Star of slot theory , Rotor losses , winding design