start-ver=1.4 cd-journal=joma no-vol=5 cd-vols= no-issue= article-no= start-page=1251 end-page=1273 dt-received= dt-revised= dt-accepted= dt-pub-year=2024 dt-pub=2024 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Skewing Technology for Permanent Magnet Synchronous Motors: A Comprehensive Review and Recent Trends en-subtitle= kn-subtitle= en-abstract= kn-abstract=This article gives a comprehensive overview of the current research trends in the skewing technique for permanent magnet synchronous motors (PMSMs). The skewing technique has been widely used in many applications to reduce the cogging torque and torque ripple in PMSMs. There are many ways to implement the skew, and new techniques are continually being developed. First, this article summarizes the types of skew structures and presents a survey of existing techniques. Specific emphasis is placed on what kind of skew structure is selected depending on the PMSM configuration. Second, the optimal value of the skew angle for each structure is comprehensively explained, and the discrepancy between theory and finite element analysis is discussed. The definition of skew angle varies across the literature, and one of the purposes of this article is to organize the definition in an easy-to-understand manner. In addition, this article offers three-dimensional finite element analysis (3D-FEA) results of various PMSMs employing the skew for quantitative comparison. Then, this article discusses the properties of PMSMs using the skew by structure and the latest trends, and finally describes future prospects. en-copyright= kn-copyright= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= en-keyword=Additive manufacturing (AM) kn-keyword=Additive manufacturing (AM) en-keyword=axial leakage flux kn-keyword=axial leakage flux en-keyword=cogging torque kn-keyword=cogging torque en-keyword=electrical machine kn-keyword=electrical machine en-keyword=finite element analysis (FEA) kn-keyword=finite element analysis (FEA) en-keyword=induction motor (IM) kn-keyword=induction motor (IM) en-keyword=interior permanent magnet synchronous motor (IPMSM) kn-keyword=interior permanent magnet synchronous motor (IPMSM) en-keyword=noise kn-keyword=noise en-keyword=patents kn-keyword=patents en-keyword=permanent magnet synchronous motor (PMSM) kn-keyword=permanent magnet synchronous motor (PMSM) en-keyword=skew kn-keyword=skew en-keyword=surface permanent magnet synchronous motor (SPMSM) kn-keyword=surface permanent magnet synchronous motor (SPMSM) en-keyword=torque ripple kn-keyword=torque ripple en-keyword=total harmonic distortion (THD) kn-keyword=total harmonic distortion (THD) en-keyword=traction motor kn-keyword=traction motor en-keyword=transportation kn-keyword=transportation en-keyword=vibration kn-keyword=vibration END start-ver=1.4 cd-journal=joma no-vol=60 cd-vols= no-issue=5 article-no= start-page=6736 end-page=6751 dt-received= dt-revised= dt-accepted= dt-pub-year=2024 dt-pub=202409 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Superior Efficiency Under PWM Harmonic Current in an Axial-Flux PM Machine for HEV/EV Traction: Comparison With a Radial-Flux PM Machine en-subtitle= kn-subtitle= en-abstract= kn-abstract=This paper evaluates the harmonic current caused by a pulse width modulation (PWM) inverter and how it affects the efficiency of a novel axial-flux permanent-magnet machine using a ferrite permanent magnet (AF-FePM) in traction applications. First, differences between the finite element analysis (FEA) and experimental results are discussed using a prototype of the proposed AF-FePM. Second, the AF-FePM is compared with a commercially available radial-flux permanent-magnet machine using a Nd-sintered magnet (RF-NdPM). For both machines, the efficiency and loss are calculated using FEA when applying the sinusoidal and harmonic currents. Additionally, we present the superior efficiency of the AF-FePM under the PWM harmonic current during a WLTC driving cycle because the designed model employs the ferrite magnet and a round copper wire, unlike the RF-NdPM. Finally, motor and inverter losses at different switching frequencies are also evaluated. This paper eventually shows that the proposed AF-FePM would be one of the suitable candidates to enhance high efficiency under PWM harmonic current condition based on comprehensive discussion. en-copyright= kn-copyright= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=ImaiJun en-aut-sei=Imai en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=SaitoTatsuya en-aut-sei=Saito en-aut-mei=Tatsuya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=UenoTomoyuki en-aut-sei=Ueno en-aut-mei=Tomoyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Sumitomo Electric Industries Ltd. kn-affil= affil-num=5 en-affil=Sumitomo Electric Industries Ltd. kn-affil= en-keyword=Axial gap motor kn-keyword=Axial gap motor en-keyword=axial-flux machine kn-keyword=axial-flux machine en-keyword=carbon-fiber-reinforced plastic kn-keyword=carbon-fiber-reinforced plastic en-keyword=ferrite magnet kn-keyword=ferrite magnet en-keyword=iron loss kn-keyword=iron loss en-keyword=PWM drive kn-keyword=PWM drive en-keyword=PWM harmonic current kn-keyword=PWM harmonic current en-keyword=radial-flux machine kn-keyword=radial-flux machine en-keyword=soft magnetic composite kn-keyword=soft magnetic composite en-keyword=switching frequency kn-keyword=switching frequency en-keyword=WLTC drive kn-keyword=WLTC drive END start-ver=1.4 cd-journal=joma no-vol=60 cd-vols= no-issue=3 article-no= start-page=3934 end-page=3949 dt-received= dt-revised= dt-accepted= dt-pub-year=2024 dt-pub=20240301 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Designing and Prototyping an Axial-Flux Machine Using Ferrite PM and Round Wire for Traction Applications: Comparison With a Radial-Flux Machine Using Nd-Fe-B PM and Rectangular Wire en-subtitle= kn-subtitle= en-abstract= kn-abstract=This paper proposes a novel axial-flux permanent magnet machine (AFPM) employing ferrite permanent magnets (PMs) and round copper wire. The proposed AFPM adopts a novel rotor structure and uses tooth-tips with a suitable trapezoidal shape. These structures compensate for the low magnetomotive force of the round copper wire and ferrite PMs, achieving high performance at low cost. Additionally, compared with an off-the-shelf radial-flux permanent magnet machine (RFPM) using Nd-sintered PMs and rectangular copper wire, the proposed AFPM achieves the same output power and higher efficiency, despite using ferrite PMs and the round copper wire. Finally, a prototype of the proposed AFPM was manufactured and evaluated experimentally. The prototype achieved a high efficiency of over 95% across a wide operating area while maintaining required maximum torque, suggesting its potential for traction applications. en-copyright= kn-copyright= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=IzumiyaKosuke en-aut-sei=Izumiya en-aut-mei=Kosuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=ImaiJun en-aut-sei=Imai en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=SaitoTatsuya en-aut-sei=Saito en-aut-mei=Tatsuya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=UenoTomoyuki en-aut-sei=Ueno en-aut-mei=Tomoyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=5 en-affil=Sumitomo Electric Industries Ltd. kn-affil= affil-num=6 en-affil=Sumitomo Electric Industries Ltd. kn-affil= en-keyword=Axial gap motor kn-keyword=Axial gap motor en-keyword=axial-flux machine kn-keyword=axial-flux machine en-keyword=carbon fiber rotor kn-keyword=carbon fiber rotor en-keyword=carbon fiber-reinforced plastic kn-keyword=carbon fiber-reinforced plastic en-keyword=city commuter kn-keyword=city commuter en-keyword=ferrite magnet kn-keyword=ferrite magnet en-keyword=flat copper wire kn-keyword=flat copper wire en-keyword=high circumferential speed kn-keyword=high circumferential speed en-keyword=radial-flux machine kn-keyword=radial-flux machine END start-ver=1.4 cd-journal=joma no-vol=11 cd-vols= no-issue= article-no= start-page=109435 end-page=109447 dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20231004 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=A Proposal of an Axial-Flux Permanent-Magnet Machine Employing SMC Core With Tooth-Tips Constructed by One-Pressing Process: Improving Torque and Manufacturability en-subtitle= kn-subtitle= en-abstract= kn-abstract=This study aims to improve the torque performance and manufacturability of axial-flux permanent magnet (AFPM) machines. Hence, we propose a novel AFPM machine that employs a soft magnetic composite (SMC) core with tooth-tips constructed by a one-pressing process and die. In this paper, the proposed AFPM machine is compared to two conventional AFPM machines using an SMC core. One of them has open-slot structure without tooth-tips. Another model employs an SMC core with tooth-tips pressed by a conventional pressing process that requires multiple operations and dies. As a result of the comparison, the proposed AFPM machine realizes a much higher torque than the two conventional machines. Additionally, the manufacturability of an SMC core with tooth-tips pressed by the proposed method is superior to the conventional one because the proposed structure can be realized by the one-pressing process and die. Furthermore, two prototypes of the proposed AFPM machine and the conventional one with an open-slot structure are fabricated, and then, they are compared by experiments. Consequently, the proposed AFPM machine achieves a 15.7% higher torque than that of the conventional machine using an open-slot structure. Finally, this paper presents an improved design of an AFPM machine with SMC cores using the proposed pressing process. As a result, the proposed AFPM realizes a 20% larger torque than that of a conventional model employing an open-slot structure. en-copyright= kn-copyright= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=ImaiJun en-aut-sei=Imai en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=SaitoTatsuya en-aut-sei=Saito en-aut-mei=Tatsuya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=UenoTomoyuki en-aut-sei=Ueno en-aut-mei=Tomoyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Sumitomo Electric Industries Ltd. kn-affil= affil-num=5 en-affil=Sumitomo Electric Industries Ltd. kn-affil= en-keyword=Pressing kn-keyword=Pressing en-keyword=Stator cores kn-keyword=Stator cores en-keyword=Magnetic cores kn-keyword=Magnetic cores en-keyword=Torque kn-keyword=Torque en-keyword=Atmospheric modeling kn-keyword=Atmospheric modeling en-keyword=Presses kn-keyword=Presses en-keyword=Manufacturing kn-keyword=Manufacturing en-keyword=Mass production kn-keyword=Mass production en-keyword=Axial-flux permanent magnet machine kn-keyword=Axial-flux permanent magnet machine en-keyword=soft magnetic composite (SMC) kn-keyword=soft magnetic composite (SMC) en-keyword=PMSM kn-keyword=PMSM en-keyword=tooth-tips kn-keyword=tooth-tips en-keyword=torque kn-keyword=torque en-keyword=press process kn-keyword=press process en-keyword=semi-closed slot structure kn-keyword=semi-closed slot structure en-keyword=axial gap motor kn-keyword=axial gap motor en-keyword=mass production kn-keyword=mass production en-keyword=YASA motor kn-keyword=YASA motor en-keyword=shoe kn-keyword=shoe END start-ver=1.4 cd-journal=joma no-vol=59 cd-vols= no-issue=3 article-no= start-page=3353 end-page=3367 dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230313 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Comparison of Thermal Characteristics in Various Aspect Ratios for Radial-Flux and Axial-Flux Permanent Magnet Machines en-subtitle= kn-subtitle= en-abstract= kn-abstract=This paper proposes an axial-flux permanent magnet machine (AFPM) that uses a neodymium-bonded permanent magnet (Nd-bonded PM) and a coreless rotor structure and assesses how it performs in industrial applications requiring high efficiency and low cost. The AFPM is able to achieve high efficiency in high-speed regions because its Nd-bonded PM can restrain eddy current loss. Additionally, the AFPM can continuously function at the rated operating point without a cooling system, so the expenses for one can be eliminated. Hence, the AFPM can simultaneously achieve high efficiency and low-cost mass production. In this paper, a comprehensive comparison including the thermal characteristics of the proposed AFPM and a conventional radial-flux permanent magnet machine (RFPM) is shown. Furthermore, this paper also focuses on how the aspect ratio influences the thermal characteristics of both machines. Finally, the effectiveness of the proposed AFPM in industrial applications is assessed using 3D-FEA and experimental results. en-copyright= kn-copyright= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=ImaiJun en-aut-sei=Imai en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=SaitoTatsuya en-aut-sei=Saito en-aut-mei=Tatsuya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=UenoTomoyuki en-aut-sei=Ueno en-aut-mei=Tomoyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Division of Industrial Innovation Sciences Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Sumitomo Electric Industries Ltd kn-affil= affil-num=5 en-affil=Sumitomo Electric Industries Ltd kn-affil= en-keyword=Aspect ratio kn-keyword=Aspect ratio en-keyword=axial-flux machine kn-keyword=axial-flux machine en-keyword=axial-gap motor kn-keyword=axial-gap motor en-keyword=cooling kn-keyword=cooling en-keyword=high efficiency kn-keyword=high efficiency en-keyword=mass production kn-keyword=mass production en-keyword=PMSM kn-keyword=PMSM en-keyword=radial-flux machine kn-keyword=radial-flux machine en-keyword=soft magnetic composite kn-keyword=soft magnetic composite en-keyword=thermal characteristic kn-keyword=thermal characteristic END start-ver=1.4 cd-journal=joma no-vol=11 cd-vols= no-issue= article-no= start-page=82024 end-page=82036 dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230803 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Design and Analysis of Hybrid-Excitation Variable Flux Memory Motor for Traction Applications: Improving Output Power in High-Speed Area During Six-Step Operation Mode en-subtitle= kn-subtitle= en-abstract= kn-abstract=Variable flux motors with adjustable magnetic flux have been gaining attention because of their capability to simultaneously achieve a high torque density and high efficiency. In addition, the output power characteristic, which is related to acceleration performance, in high-speed areas is important in traction applications. However, typical traction motors have lower output power in high-speed areas. In this paper, a Hybrid-Excitation Variable Flux Memory Motor (HE-VFMM) is therefore proposed to enhance output power characteristics under six-step operation mode in high-speed area. The proposed HE-VFMM can perform magnetic flux adjustment with two components: field winding and variable flux permanent magnet (VPM), thus dramatically increasing flux adjustment range. The simulation results show the proposed HE-VFMM achieves 23.7% higher output power at 17,000 rpm than that of an existing traction motor in Prius 4th generation that has the same size while maintaining high efficiency in the frequently used operating area. Additionally, it was found that variable magnetic flux is very effective in enhancing the output power, especially in the high-speed region because the magnetic saturation in the stator core is mitigated by field-weakening control. Consequently, as the rotational speed increases, an increase ratio of the output power caused by the adjustable magnetic flux becomes higher. This paper shows that the proposed HE-VFMM is an effective method for improving the problem of low output power in high-speed regions in traction motors. en-copyright= kn-copyright= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YokomichiKeito en-aut-sei=Yokomichi en-aut-mei=Keito kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=ImaiJun en-aut-sei=Imai en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Graduate School of Environmental, Life, Natural Science and Technology, Okayama University kn-affil= en-keyword=Variable flux memory motor kn-keyword=Variable flux memory motor en-keyword=hybrid excitation motor kn-keyword=hybrid excitation motor en-keyword=traction applications kn-keyword=traction applications en-keyword=EV kn-keyword=EV en-keyword=HEV kn-keyword=HEV en-keyword=six-step operation kn-keyword=six-step operation en-keyword=one-pulse drive kn-keyword=one-pulse drive en-keyword=output power density kn-keyword=output power density END start-ver=1.4 cd-journal=joma no-vol=11 cd-vols= no-issue= article-no= start-page=4740 end-page=4751 dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230111 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Reduction in Eddy Current Loss of Special Rectangular Windings in High-Torque IPMSM Used for Wind Generator en-subtitle= kn-subtitle= en-abstract= kn-abstract=A special rectangular winding structure, which has different cross-sectional shape but the same cross-sectional area for each turn, has been adopted in a high-torque IPMSM used for a wind generator to improve slot factor and heat dissipation. However, large eddy current loss occurs to the rectangular windings. According to this problem, this paper proposes three improvements to reduce the eddy current loss. Among them, removing a portion of windings and replacing a portion of windings with aluminum are discussed to realize a tradeoff between eddy current and copper losses. And adjusting the tooth-tip shape is discussed to suppress the magnetic flux passing through the windings by mitigating magnetic saturation around the tooth-tip. Additionally, manufacturing costs can also be reduced by adopting a portion of aluminum windings. Moreover, a 3-step-skewed rotor structure is discussed to reduce cogging torque and lower the start-up wind speed. And its influence on losses is also discussed. Furthermore, three models adopting round windings are made and discussed for comparison. The FEM (Finite Element Method) results show that compared with the three round windings models, the proposed model still has a better performance in the reduction of windings eddy current loss. Finally, a prototype machine is manufactured to verify the FEM results, and the experimental results show that the maximum efficiency of the prototype can exceed 97.5%. en-copyright= kn-copyright= en-aut-name=TaoXianji en-aut-sei=Tao en-aut-mei=Xianji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=OgasawaraSatoshi en-aut-sei=Ogasawara en-aut-mei=Satoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Graduate School of Information and Technology, Hokkaido University kn-affil= affil-num=2 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Graduate School of Information and Technology, Hokkaido University kn-affil= en-keyword=IPMSM kn-keyword=IPMSM en-keyword=IPMSG kn-keyword=IPMSG en-keyword=high-torque kn-keyword=high-torque en-keyword=concentrated windings kn-keyword=concentrated windings en-keyword=rectangular windings kn-keyword=rectangular windings en-keyword=eddy current loss kn-keyword=eddy current loss en-keyword=wind generator kn-keyword=wind generator END start-ver=1.4 cd-journal=joma no-vol=11 cd-vols= no-issue= article-no= start-page=2848 end-page=2862 dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20221228 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Novel Rotor Structure Employing Large Flux Barrier and Disproportional Airgap for Enhancing Efficiency of IPMSM Adopting Concentrated Winding Structure en-subtitle= kn-subtitle= en-abstract= kn-abstract=Interior permanent magnetic synchronous motors (IPMSMs) adopting concentrated windings have been widely used in industrial applications. To reduce operating costs, it is an important issue to enhance the efficiency of an IPMSM as much as possible while maintaining manufacturing costs. In general, an IPMSM used for an industrial application always operates in a specific operating area according to the required load. Therefore, this paper has two purposes. The first purpose is to propose a novel rotor structure which can enhance efficiency at the target wide-speed middle-torque operating area without additional manufacturing costs. The second purpose is to clarify the design method for a suitable rotor structure depending on its target operating area. Reducing losses is the key to enhancing efficiency. This paper first examines the effects of adopting large flux barriers and a disproportional airgap on copper and iron losses, and clarifies their merits and respective high-efficiency operating areas. Furthermore, to take advantage of the two rotor structures, a novel rotor structure which employs both large flux barriers and a disproportional airgap has been proposed. 2D-FEM (Finite-Element Method) is used for discussion first, and a prototype machine is manufactured to verify the 2D-FEM results. Both 2D-FEM and experimental results show that the proposed rotor structure can enhance the efficiency of an IPMSM most effectively at the target operating area. Moreover, for a low-speed high-torque operating area, adopting only large flux barriers is most suitable. And for a high-speed low-torque operating area, adopting only a disproportional airgap is most suitable. en-copyright= kn-copyright= en-aut-name=TaoXianji en-aut-sei=Tao en-aut-mei=Xianji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakemotoMasatsugu en-aut-sei=Takemoto en-aut-mei=Masatsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TsunataRen en-aut-sei=Tsunata en-aut-mei=Ren kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=OgasawaraSatoshi en-aut-sei=Ogasawara en-aut-mei=Satoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Graduate School of Information and Technology, Hokkaido University kn-affil= affil-num=2 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Graduate School of Information and Technology, Hokkaido University kn-affil= en-keyword=Rotors kn-keyword=Rotors en-keyword=Magnetic flux kn-keyword=Magnetic flux en-keyword=Atmospheric modeling kn-keyword=Atmospheric modeling en-keyword=Torque kn-keyword=Torque en-keyword=Iron kn-keyword=Iron en-keyword=Copper kn-keyword=Copper en-keyword=Costs kn-keyword=Costs en-keyword=IPMSM kn-keyword=IPMSM en-keyword=concentrated winding structure kn-keyword=concentrated winding structure en-keyword=high efficiency kn-keyword=high efficiency en-keyword=flux barrier kn-keyword=flux barrier en-keyword=disproportional airgap kn-keyword=disproportional airgap END