Design criteria of high efficiency SPM synchronous motors

This paper deals with the design criteria of high efficiency PM synchronous motors. The goal is not pursued by a reduction of the electric and magnetic loadings (which obviously decrease motor losses) but operating on a set of motor design variables, without increasing the overall dimensions, whose limits are typically imposed as design constraints. The main losses of the motor, i.e. copper losses and iron losses, are considered. An analytical approach is adopted to make the results readily transferable to machines of any size. The effect of the number of slots and of the ratio between the inner and the outer diameter on the motor lows has been studied. The possibility to design a stator with a tooth length lower than the total core length, using soft magnetic composites, has been investigated. Finally, a criteria to evaluate the convenience to use a non-overlapping winding has been proposed.