Magnet selection for permanent magnet synchronous machines by decision science

Abstract

This work investigates magnet selection for permanent magnet synchronous machines (PMSMs) by decision science. 20 multiple-attribute decision-making (MADM) methods ranked a list of 45 industrial-grade permanent magnets based on eight property requirements―high energy density (BHMAX), high coercivity (HC), high magnetic remanence (BR), high electrical resistivity (ρ), high Curie temperature (TC), high maximum service temperature (TS), low linear thermal expansion coefficient (α), and low density (d)―targeted to selecting magnets for PMSMs. The Shannon's entropy method evaluated the objective attribute weights of ρ, BHMAX, and HC, as ∼46%, ∼24%, and ∼23%, respectively, and the rest—BR, TC, TS, d, and α―combined as ∼7%; equal weights (∼12.5% each) to all the attributes were the subjective weights. Principal component analysis (PCA) consolidated ranks from various MADM methods, and hierarchical clustering (HC) grouped magnets based on their similarities. For PMSMs in applications where ρ, BHMAX, and HC, are more critical compared to the rest of the properties, the eight top-ranked magnets are N35 (Neodymium® 35), N35H (Neodymium® 35H), N30 (Neodymium® 30), N30H (Neodymium® 30H), N27H (Neodymium® 27H), N27 (Neodymium® 27), F5–S (Ferrite 5, Sintered Iron Strontium Oxide), and F3–S (Ferrite 3, Sintered Iron Barium Oxide) in that order. On the other hand, for PMSMs in applications where all the attributes are equally important, the eight top-ranked magnets are N35 (Neodymium® 35), N35H (Neodymium® 35H), N30H (Neodymium® 30H), N30 (Neodymium® 30), N27H (Neodymium® 27H), N27 (Neodymium® 27), CS4 (Samarium Cobalt 4), and F5–S (Ferrite 5, Sintered Iron Strontium Oxide) in that order. The consolidated ranks of the magnets obtained by assigning objective and subjective attribute weights showed a strong correlation of ∼0.94. This investigation targeted magnet selection for PMSMs from a comprehensive dataset of industrial-grade permanent magnets, utilizing several property requirements, applying both objective and subjective attribute weights identified Neodymium® 35 as the top-ranked magnet.