Impact of Flux-Modulated Rotor Design on Special Flux Density Harmonics in PS-DSPM for Cogging Torque Minimization

Wilaiphorn  Nokklang; Pattasad  Saengwong; Apirat  Siritaratiwat; Warat  Sriwannarat

doi:10.6180/jase.202606_29(6).0018

Impact of Flux-Modulated Rotor Design on Special Flux Density Harmonics in PS-DSPM for Cogging Torque Minimization

Wilaiphorn Nokklang¹, Pattasad Saengwong², Apirat Siritaratiwat², and Warat Sriwannarat¹This email address is being protected from spambots. You need JavaScript enabled to view it.

¹the Department of Electrical and Computer Engineering, Faculty of Science and Engineering, Kasetsart University Chalermphakiet Sakon Nakhon Campus, Sakon Nakhon 47000, Thailand

²the Department of Electrical Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand

Received: August 5, 2025
Accepted: October 26, 2025
Publication Date: November 20, 2025

Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.6180/jase.202606_29(6).0018

High cogging torque caused by a fluctuating magnetic flux distribution in the partitioned stator doubly salient permanent magnet machines (PS-DSPM), due to their double air gap design, limits their application despite excellent torque density characteristics. This paper targets cogging-torque minimization through flux-modulated rotor design that shapes specific f lux-density harmonics in PS-DSPM. The designs of flux-modulated rotors are presented and analyzed, with a detailed explanation of the behavior of the air-gap flux density and its harmonic content driving cogging torque. The simulation result using the 2D finite element method shows that the cogging torque variation with designs of the flux-modulated rotors is identified by the specific air-gap flux-density harmonics. The flux-modulated rotors, classified into three designs, indicate that the designed III ( θ_o > θ_i ) produces better effective cogging torque, which is 85.35% and limits the ripple torque to 5.36% when compared to the conventional PS-DSPM structures. These improvements enhance starting performance and reduce acoustic noise while preserving torque density advantages. Therefore, the proposed flux modulation technique is broadly applicable to other double air gap machine topologies to minimize the cogging torque.

Keywords: Flux-modulated rotor, flux density harmonics, partitioned stator permanent, magnet machine, cogging torque minimization.

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