Comparison of synchronous PM machine types for wide constant‐power speed range operation

Abstract

PurposeThe purpose of this paper is to provide a comparison of synchronous permanent magnet machine types for wide constant power speed range operation.Design/methodology/approachA combination of analytical models and finite element analysis is used to conduct this study.FindingsThe paper has presented a detailed comparison between various types of synchronous PM machines for applications requiring a wide speed range of constant‐power operation. Key observations include: surface permanent magnet (SPM) and interior permanent magnet (IPM) machines can both be designed to achieve wide speed ranges of constant‐power operation. SPM machines with fractional‐slot concentrated windings offer opportunities to minimize machine volume and mass because of their short winding end turns and techniques for achieving high‐slot fill factors via stator pole segmentation. High back‐emf voltage at elevated speeds is a particular issue for SPM machines, but also poses problems for IPM machine designs when tight maximum limits are applied. Magnet eddy‐current losses pose a bigger design issue for SPM machines, but design techniques can be applied to significantly reduce the magnitude of these losses. Additional calculations not included here suggest that the performance characteristics of the inverters accompanying each of the four PM machines are quite similar, despite the differences in machine pole number and electrical frequency.Research limitations/implicationsThe paper is targeting traction applications where a very wide speed range of constant‐power operation is required.Practical implicationsResults presented are intended to provide useful guidelines for engineers faced with choosing the most appropriate PM machine for high‐constant power speed ratio applications. As in most real‐world drive design exercises, the choice of PM machine type involves several trade‐offs that must be carefully evaluated for each specific application.Originality/valueThe paper provides a comprehensive comparison between different types of synchronous PM machines, which is very useful in determining the most suitable type for various applications.