The permanent magnet synchronous machine with integrated motoring and generating windings (PMSM-IMGW) has shown promising potential for application in microgrid power supply system due to its advantages of high torque density and real moment of inertia. The output voltage of the machine is affected by the armature magnetic fields of both motoring windings (MWs) and generating windings (GWs), as well as the permanent magnet (PM) field, resulting in complex electromagnetic coupling characteristics. This characteristic brings great difficulty to the performance analysis of the PMSM-IMGW. To explore the main factors affecting the quality of the output voltage, the relationship between output voltage and air-gap magnetic field is derived using the flux linkage method and magnetomotive force (MMF) analysis. Then, the spatial distribution characteristics of armature MMF with different winding configurations are analyzed, and the influences between harmonics of the MMF on output voltage are investigated. Next, the output voltage under different power and the loss and efficiency are analyzed. Finally, the validity of the theoretical analysis is verified through finite element analysis (FEA) and experimental results.

In direct-drive systems that require high torque density and low-speed control, some applications need permanent magnet synchronous motors (PMSMs) to operate under continuous stall conditions. This operational mode causes a significant local temperature rise due to the uneven distribution of winding losses. This paper investigates the effect of pole/slot combinations and winding configurations on the temperature rise of fractional slot concentrated winding (FSCW) PMSMs. Four PMSMs with single-layer and double-layer windings in 18-slot/20-pole (18s/20p) and 24-slot/20-pole (24s/20p) FSCWs are first designed. Then, the loss distribution is calculated at different rotor stall positions. The finite element method (FEM) is used to investigate temperature distribution and thermal properties for four PMSMs under stall conditions. Results demonstrate the superior thermal performance of the 24s/20p double-layer winding under stall conditions. Finally, the proposed analysis is validated by experiments.

The slot shape of a yokeless and segmented armature (YASA) motor differs significantly from that of traditional motors due to its dual-slot openings. An analytical method is proposed for determining the slot leakage inductance of a novel slot of the YASA axial flux permanent magnet (AFPM) motor. A general analytical formula for calculating the slot leakage inductance component within a single YASA slot is derived, and the phase-slot leakage inductance of a YASA-AFPM motor is further determined based on its unique winding distribution. This reveals that the coil-side width has a significant influence on the slot leakage inductance component, whereas the pole-slot combination has a notable influence on the number of slot leakage inductance components in the phase inductance. Additionally, the relationships between the coil-side width, pole-slot combination, and slot leakage inductance are analytically established. Finally, the slot leakage inductance of a 20-pole-24-slot AFPM-YASA motor is calculated using the proposed method, and the results are in agreement with those obtained using the finite element method (FEA), verifying the accuracy of the proposed method.

The dual-stator axial flux permanent magnet machines (AFPMMs) with sandwich rotor have attracted increasing attention owing to their advantages of low rotor eddy current loss and high operational efficiency. However, due to the three-dimensional (3D) structure of AFPMMs, the finite element method (FEM) imposes a substantial computational burden during the simulation process. To address this issue, a hybrid analytical model (HAM) that integrates subdomain method and magnetic equivalent circuit (MEC) approach is proposed in this paper to predict the magnetic field distribution in AFPMMs with sandwich rotor. By introducing virtual winding into the slot subdomain, the nonlinear behavior of the stator iron is effectively accounted for. The proposed HAM achieves higher accuracy in predicting the electromagnetic performance of AFPMMs with sandwich rotor under load conditions compared to the conventional subdomain model, while avoiding the complicated air-gap permeance modeling required by the MEC method. The accuracy and the effectiveness of the proposed HAM are validated through FEM and prototype experiments.

Dual-stator axial flux permanent magnet (DS-AFPM) machines with fractional-slot concentrated windings (FSCWs) have attracted considerable attention owing to their high-power density. Nevertheless, the abundant harmonic content of the stator magnetomotive force (MMF) leads to severe rotor eddy current losses. To address this issue, this study analyzes the stator MMF under various pole-slot combinations and employs an equivalent current-sheet model to identify the harmonics that dominate rotor losses. A selective space harmonics suppression method is then proposed by introducing mechanical angular offsets between the two stators. The optimal offset angle, determined by the pole-slot combinations, effectively suppresses the dominant loss-inducing harmonics while preserving the working harmonic. Furthermore, the overall performance of a 24-slot/20-pole DS-AFPM machine with and without stator offset is compared, including back electromotive force (EMF), torque, and rotor eddy current losses. Finally, temperature field analysis and prototype experiments confirm that the proposed method substantially reduces rotor eddy current losses without degrading electromagnetic performance.

To address the issue of rich armature magnetomotive force (MMF) harmonic content in dual-stator axial flux permanent magnet (DSAFPM) machines with fractional-slot concentrated windings (FSCWs), which leads to increased eddy current loss and excessive temperature rise in permanent magnets, this paper proposes a dual-stator shifted axial flux permanent magnet machine based on a star-delta hybrid winding configuration. Firstly, the winding function method is employed to theoretically analyze and compare the harmonic components of the armature MMF in the conventional, the stator-shifted, and the proposed machine models. Subsequently, three-dimensional finite element analysis (3D-FEM) is used to simulate and compare the performance of the three machines under both no-load and load conditions. The results show that the proposed machine effectively suppresses high-amplitude low-order harmonics in the armature MMF, significantly reduces rotor eddy current losses, and exhibits higher output power and efficiency. Finally, the temperature field analysis conducted using Fluent is used to compare the rotor temperature rise of the three machines, further verifying the effectiveness of the proposed design in suppressing temperature rise. This study provides a feasible solution for reducing rotor eddy current losses in axial flux permanent magnet machines.

The performance of dual-stator axial flux permanent magnet machines (AFPMMs) is constrained by significant eddy current loss in the permanent magnets (PMs). In this article, a method is proposed to reduce PM eddy current loss by employing sandwich rotor to divert the armature field harmonics. Based on the minimum reluctance principle, the feasibility of sandwich rotor preventing armature field harmonics from penetrating in PM is first investigated. Then, a general quasi-3D magnetic field analytical model based on the subdomain method is established, and the effectiveness of soft magnetic material in diverting high-order armature field harmonics is quantitatively analyzed. Moreover, a PM eddy current loss evaluation model using equivalent resistance network is developed. The overall performance, including no-load back electromotive force (EMF), output torque, and PM eddy current loss with different thicknesses of soft magnetic material, is analyzed, and guidelines are provided for the design of sandwich-rotor AFPMMs. Finally, a prototype is manufactured, and the feasibility and effectiveness of the proposed method are confirmed through finite element method (FEM) and prototype experiments.

This paper proposes an improved quasi-3D mesh-based equivalent magnetic network (EMN) for optimal design of the yokeless and segmented armature (YASA) axial flux permanent magnet (AFPM) machines. Besides the magnetic field in the air gap, the improved EMN can also predict the armature field in the slots accurately, which is realized by discretizing the armature magnetomotive force (MMF) sources into multiple sub-MMF sources with reference to the distribution of conductors in the slots. The improved EMN can be employed to predict the synchronous inductance, back electromotive force (EMF), electromagnetic torque, and efficiency. Combined with the proposed EMN, a genetic algorithm with elite strategy is applied for the multi-objective optimal design, aiming to improve the YASA-AFPM machine’s torque density and efficiency, with constraints of inverter’s terminal voltage and rated current. Finally, a prototype was manufactured based on the optimized design, and the 3D finite element analysis (FEA) simulation and experiment results verify the accuracy of the proposed EMN and multi-objective optimal design.

Plenty of grid-connected power electronic devices may significantly weaken the voltage/frequency stability of microgrid system. The system employing a motor/generator pair (MGP) can effectively improve stability. However, the MGP is composed of two machines, the integration is insufficient. In addition, when the generator is connected with load, the output voltage will drop due to the reason of voltage regulation rate. This paper proposes a novel permanent magnet synchronous machine with integrated motoring and generating windings (PMSM-IMGW) and applies it to microgrid system. The PMSM-IMGW has the advantages of lower voltage regulation rate and higher integration. The topology, operational principles, and control system are presented. The steady-state voltage equations are employed to investigate the d-and q-axis armature effects under strong magnetic coupling between the motoring windings (MWs) and generating windings (GWs), revealing the reason of achieving low voltage regulation rate. A 7.4kW prototype is designed and analyzed by finite element analysis (FEA). Simulation results show that compared to the voltage regulation rate of the generator (Delta u = 4.35%), the voltage regulation rate of the PMSM-IMGW (Delta u = 1.86%) decreases by 57.24%. Finally, a prototype is manufactured and tested to validate the effectiveness.

The calculation accuracy of unbalanced magnetic forces (UMF) is very important to the design of rotor length, because it will effect the shaft deflection. But in some permanent magnet synchronous motors (PMSMs) with fractional slot concentrated windings (FSCW), the UMF caused by asymmetrical stator topology structure is not considered in the existing deflection calculation, which is very fatal for the operational reliability, especially for the PMSMs with the large length-diameter ratio, such as submersible PMSMs. Therefore, the part of UMF in the asymmetrical stator topology structure PMSMs caused by the choice of pole-slot combinations is analysized in this paper, and a more accurate rotor deflection calculation method is also proposed.

In order to match the electromagnetic damping force generated by the generator with the simple harmonic motion (SHM) system such as thermoacoustic power generation and wave power generation, and to make the oscillating generator's mover in a resonant state. A tubular frequency multiplication permanent magnet linear oscillation generator (TFMPMLOG) is proposed in this paper, to solve the problem of low efficiency of the linear oscillation power generation system. The generator connects the permanent excitation magnetic flux generated by the excitation permanent magnet (PM) in parallel with the armature reaction flux generated by the stator winding, so that the frequency of the voltage and current output by the generator is twice of the SHM frequency of the mover. The Ansoft software was used to establish a two-dimensional model of the generator for electromagnetic field simulation analysis. And optimize the generator structure parameters. A balanced PM is installed at two longitudinal ends of the stator core. Calculate detent force fluctuations of generator no load when the height of different balanced PM. The optimum results show that the detent force fluctuation of generator is reduced by 76%.

According to the principle of magnetic energy virtual displacement and the characteristics of double Y shifted by 30° winding, the analytical expression of torque in six-phase permanent magnetic synchronous motor (PMSM) is derived, and the impact of harmonic magnetic field on torque is analyzed in this paper yet. On this basis, the torque performance of three-phase and six-phase PMSM with 96 slots 88 poles are simulated, and six-phase motor with the third harmonic current injection is simulated meanwhile. The simulation results show that the analytical expression is correct, and the six-phase double Y shifted by 30° winding PMSM with similar pole and slot number can eliminate the sixth ripple torque in the three-phase one, and the third harmonic current loaded in it can also produce average electromagnetic torque.