Nonlinear scaling rules for brushless PM synchronous machines based on optimal design studies for a wide range of power ratings

A large-scale unitary study for a generic topology of surface-mounted permanent-magnet brushless motors operated from sine-wave current-regulated drives is described. A parametric motor model employing eight independent variables is introduced. A wide range of power ratings, from 1 kW to 1 MW, and a large spread of physical dimensions, with a stator inner (air-gap) diameter as low as 50 mm and as high as 500 mm, were considered. A sensitivity analysis based on the response surface method was performed, and a differential evolution algorithm was applied to find the optimal solutions for different power ratings. A computationally efficient finite-element analysis ultrafast technique was employed in order to calculate the performance of approximately 30 000 candidate machine designs within a reasonable time. The study provides rules for scaling the machine main design parameters with the power rating in order to achieve minimum active material cost per point of efficiency.