In field modulation machine (FMM), the high speed armature magnetic field is modulated to couple with a low speed magnetic field generated by rotor with multiple pole-pair number of permanent magnets (PMs) for high output torque [1]. In order to increase torque production furtherly, dual stator FMM (DSFMM) is proposed, which can fully utilize space and PMs [2]. Another approach to enhance torque production is to increase airgap flux density by using interior PM (IPM) or bilateral PM (BPM) arrangements in DSFMMs [3]. However, DSFMM excited by IPM or BPM alone can not achieve high sinusoidal airgap magnetic field. This paper proposes a new staggered DSFMM with O-shape PM arrangement (ODSFMM), which provides high sinusoidal airgap magnetic field for high quality torque production. Two radially magnetized PMs with opposite polarity are sandwiched between two tangentially magnetized PMs with opposite polarity, which forms the proposed O-shape PM arrangement for high sinusoidal airgap magnetic field with high flux density. The inner stator is rotated along shaft to form staggered DS structure for flux leakage reduction. The angle between the central axes of inner and outer stator teeth (α) is 15°. The open stator teeth play the role of modulation poles to modulate the magnetic field excited by O-shape PMs. The stator of the proposed machine employs three-phase 12-slot/2-pole single layer integral-slot distributed windings for high slot utilization and back electromotive force (EMF). To verify the merits of the proposed ODSFMM that is simply referred as Model I, the DSFMM with BPM excitation (simply referred as Model II) and with unrotated inner stator (simply referred as Model III) are designed, which share identical key design parameters, such as the volume of PM, outer radius, airgap length, and active stack length. The back-EMF, cogging torque, steady torque at rated state and steady torque at different current angles of the proposed designs are analyzed using finite element analysis (FEA). The FEA-predicted results show that the proposed ODSFMM can provide high sinusoidal back-EMF waveforms with high amplitude and high torque production with low torque ripple, which is desirable for accuracy operation applications.

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A New Staggered Dual Stator Field Modulation Machine with O-Shape Permanent Magnet Excitation

Field modulation machine (FMM) operates based on magnetic gear effect, which has the merit of high torque production at low operating speed [1]. Thus, FMM is suitable in direct-drive applications such as astronomical telescope and robot arms [2]. Hybrid magnet dual stator FMM (HMDSFMM) is developed for increasing output torque furtherly and obtaining high power factor [3]. Generally, the multiple-tooth stator is employed to increase split ratio for high torque density [4]. Nevertheless, the existing DSFMM with the same split ratio of inner and outer stators can not achieve the best electromagnetic performances. This paper proposes a new HMDSFMM with different split ratios of stators (DSR-HMDSFMM), which can achieve high quality torque production. The split tooth numbers of the outer and inner stators of the proposed DSR-HMDSFMM are designed as 2 and 3, respectively, which is expressed as K1=[2,3]. The inner and outer stators using different split ratios take the advantage of reducing flux leakage and increasing torque quality. The total tooth numbers of inner stator is equal to that of outer stator because the same armature windings and PM excitation are used. The consequent pole rotor with NdFeB magnets establishes the main magnetic circuit for high PM utilization. Ferrite magnets are embedded between split teeth, which aim to enhance the airgap flux density and suppress the harmonic distortion. In order to find out the optimal combination of split ratios of stators, the proposed DSR-HMDSFMMs with K2=[1,2], K3=[1,3] and K4=[2,2] are analyzed, which are simply referred as Model II, III, IV, respectively. Both of the inner and outer stators employ the three-phase 12-slot/2-pole integral-slot distributed double layer windings which can fully utilize slot space and high back electromagnetic force (EMF). The electromagnetic performances of proposed designs are analyzed by finite element analysis, including back-EMF, cogging torque, steady torque at rated condition and steady torque characteristics against current angle. The calculated results show that the proposed DSR-HMDSFMM with K1=[2,3] exhibits the highest back-EMF and high quality torque production, which is suitable for the accuracy operation applications.

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A New Hybrid Magnet Dual Stator Field Modulation Machine With Different Split Ratios of Stators

The flux switching machine (FSM) and flux reversal machine (FRM) attract great attention because of simple structure of rotor, excellent heat dissipation and high reliability [1]. But both of the permanent magnets (PMs) and the armature windings placed in stator may decrease the space utilization, which limits the further torque production improvement [2]. Thus, the partitioned stator machines (PSMs) are developed, in which the armature windings and PMs are allocated in outer and inner stators to achieve high electromagnetic performances, respectively [3]. However, the existing PSMs with conventional PM arrays evolved from FSM or FRM can not provide high quality torque production. This paper proposes a new PSM with H-shape PM array (HPMPSM), which operates based on flux modulation effect and can offer high quality torque output and space utilization. In addition, the evolution process from conventional FSM and FRM to existing partitioned stator machines that operate based on flux modulation effect are described. H-shape PM (HPM) can be regarded as the combination of the interior PM array (IPM) in FSM and the surface mounted PM array in FRM, which could reduce the flux leakage and improve the flux density in airgaps effectively. HPM is composed of two tangentially magnetized PMs with opposite polarity and one radially magnetized PM. The polarity of the adjacent PMs in radial magnetization are opposite to form one-pole-pair PM excitation. The concentrated windings are adopted on outer stators for high efficiency, and the iron-pieces rotor is sandwiched between stators and has the merit of simple structure and high robustness. FSM, PSM with IPM, FRM, and PSM with surface mounted PM are designed and analyzed, which are simply referred as Models I, II, III, IV and V, respectively. By using finite element analysis (FEA), the electromagnetic performances of proposed HPMPSM are analyzed, containing back electromotive force (EMF), cogging torque, steady torque at rated condition and steady torque characteristics against current angle. The FEA-calculated result shows that the proposed HPMPSM can provide high back-EMF and high torque production with lowest torque ripple, which is desirable for electric vehicle application.

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A New Partitioned Stator Machine Based on Flux Modulation Effect

**Session chair:** Shuangxia Niu, The Hong Kong Polytechnic University



JPF - Vernier Machines

poster

The 15th Joint MMM-INTERMAG Conference (2022 Joint) is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a plenary session, and an evening session, with about 1500 presentations overall. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

The 2022 Joint Conference will offer both in-person and prerecorded on-demand content.

For tickets to the event, please register at the following link: https://magnetism.org/register

Please register for the Joint MMM-Intermag conference to join the event.

2022 Joint MMM-INTERMAG

This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

**Session chairs:** Metin Aydin, Kocaeli University and Chunhua Liu, City University of Hong Kong and Kenji Nakamura, Tohoku University



Heng Zhu

3

SHORT BIO

Presentations

A New Staggered Dual Stator Field Modulation Machine with O-Shape Permanent Magnet Excitation

A New Hybrid Magnet Dual Stator Field Modulation Machine With Different Split Ratios of Stators

A New Partitioned Stator Machine Based on Flux Modulation Effect

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