Computationally Efficient and Flexible Magnetic-Field-Analysis-Based Scaling Strategy for Permanent-Magnet Machines

Electric machine performance (peak torque versus speed) and efficiency characteristics are frequently estimated using magnetic finite element analysis (FEA). In this paper, it is shown that the governing mathematical relationships that are solved in such an analysis allow for the implementation of straightforward scaling laws. Instead of rerunning the FEA code for a variety of electric machine lengths, diameters, excitation frequencies, and number of winding turns, only one FEA simulation or experimental characterization is required. The results from that single FEA or experimental result can then be incorporated into the scaling laws derived here to determine the performance and efficiency of permanent-magnet machines with a variety of lengths, diameters, excitation frequencies, and number of winding turns. The utility is a significant speedup in the computation of a variety of design choices as a result of not having to re-execute the FEA for each design iteration or option. Following a mathematical development, scaling-law-based performance/efficiency estimates and those from FEA are directly compared and shown to be exactly the same.