In this paper, a high-speed Halbach-array PM rotor for ironless stator axial-flux permanent magnet (AFPM) machine is proposed and researched with consideration of the multi-physics constraints, including the electromagnetic characteristics, mechanical strength and rotor dynamics. Considering the severity of attractive force between twin rotors, the complex repulsive force among permanent magnet (PM) segments of Halbach-array and centrifugal force, the new hybrid sleeve and PM fixation method are proposed to improve the rotor mechanical strength. Then, the rotor stress is analyzed by numerical analysis and 3D finite element analysis (FEA). Furtherly, the sleeve thickness and interference fit are optimized by 3D FEA. The rotor dynamics and bearing arrangement are analyzed to validate the effectiveness of the high speed Halbach-array PM rotor. A 50kW, 9000r/min ironless stator AFPM machine prototype with Halbach-array PM rotor is manufactured and tested. The measured results show that the output power is up to 53.8kW at 9000r/min. The feasibility of high speed Halbach-array PM rotor and accuracy of analysis method are validated by both simulated and measured results.

Due to the high-power density and compact structure, axial-flux permanent magnet (AFPM) machines have gradually received much attention with a view to researching breakthroughs in the next generation electric drive technology for electric vehicles in the recent decades. The AFPM machines with factional slot concentrated winding (FSCW) and yokeless stator, namely yokeless, and segmented armature (YASA) motors, have drawn much attention for its high-power density and potential manufacturability due to the concentrated winding and modular stator core configuration. However, the significant rotor loss resulting from the abundant armature reaction harmonics in FSCW machines imposes a great challenge to the rotor heat dissipation, especially when the pursuit of higher speed has become the trend for electric vehicle applications. On the other hand, distributed winding is widely used in high speed radial flux permanent magnet (PM) machines due to its low armature reaction harmonics. In order to figure out the advantages and disadvantages of various winding arrangement and rotor configuration of AFPM for electric vehicle applications, the comparative study of four AFPM machines with various winding configurations and rotor PM arrangements are comprehensively conducted in this article. First, the design and primary optimization of the four AFPM machines are conducted for the electric vehicle requirement specifications. Then, a comprehensive three-dimensional finite-element analysis (FEA) is employed to compare the electromagnetic performance including torque/power density, efficiency, and flux-weakening capacity. Furthermore, the guideline of winding selection of AFPM machines for electrical vehicle is given. Finally, a yokeless stator AFPM prototype with ISDW configuration is manufactured and tested to verify the validity of the FEA results, as well as confirm the comparison conclusion.

Ironless stator axial-flux permanent magnet (AFPM) machines provide many attractive electromagnetic performances such as high efficiency in high-frequency mode and strong short-term overload ability, which make them more competitive in flywheel energy storage applications. However, designing high-torque-density AFPM machines, particularly their ironless stators, is with significant challenges and needs great efforts. In this paper, a high-strength oil-immersed cooling stator with non-overlapping concentrated winding is proposed for high-power ironless stator AFPM machine applications. The paper explains in detail the design, analysis and manufacturing process of the proposed oil-immersed cooling stator. With the three-dimensional finite-element analysis (3-D FEA), a 9000rpm/50kW 12-slot/10-pole prototype for a flywheel energy storage system is successfully designed and developed using the proposed high-strength oil-immersed cooling ironless stator. The experimental test results demonstrate the effectiveness of the cooling design and mechanical strength.

This study introduces a doubly salient brushless dc (DSBLDC) generator with stator‐field winding, which incorporates the doubly salient electromagnetic (DSEM) machine and its associated rectifier. The configuration, operation principle, and armature reaction of different generating mode are overviewed. The sizing equation is derived for the initial dimension design of the DSEM machine. Then the non‐linear varying‐network magnetic circuit method for preliminary design is proposed to determine the fundamental geometric parameters, the corresponding field magnetomotive force, and winding configurations iteratively, in which the magnetic saturation is taken into account. Furthermore, optimal design of the geometric parameters is comprehensively investigated by finite‐element analysis, and the optimised coefficients obtained for different generating mode. The operating characteristics of the DSBLDC generator with compensation capacitors are investigated to improve the voltage regulation performance. A prototype of 12 kW DSEM machine has been designed and optimised by the proposed design methods. Experiments are performed and the results verify the predictions and the design methods. Due to the simple and robust structure without permanent magnet, as well as convenient and flexible control, the promising DSEM machine is a desirable candidate for dc power generation.

This paper presents integrated design and analysis of a new axial-flux permanent magnet (AFPM) machine, which consists of an ironless stator with double-layer concentrated non-overlapping windings and twin external rotors with Halbach-array PMs. A general sizing equation based on fundamental theory, easily adjustable for ironless stator AFPM machine with concentrated windings, is derived to obtain preliminary parameters. Then, by using three dimensional finite element analysis (3-D FEA), the optimization of a primary machine are implemented. A precise and fast calculation method based on 3-D FEA model is proposed to confirm the eddy-current loss for ironless stator winding. By making tradeoff between DC current loss and eddy-current loss of Litz wire for winding, the efficiency is further improved for high frequency operation. Despite using Halbach-array PMs, a certain thickness of rotor yoke is recommended to increase air-gap flux density. Finally, a prototype machine is developed, experimented and evaluated. The test results reveal the strong overload and heat dispersal capacity of proposed stator ironless AFPM machine with the maximum efficiency of 98.5%. Measured performances of the manufactured prototype verify the validity of the proposed analysis method and FEA results.

Phase-shift or pole-shift method can reduce the detent force of the double-sided permanent magnet linear synchronous motor (DS-PMLSM) dramatically. However, this method causes a decrease in thrust and an increase in normal force simultaneously. To overcome this drawback, a novel slot-shift structure whose slots on the two sides of the primary component are staggered by an optimal distance is proposed in this paper. The models of the detent force including the end force and cogging force is established theoretically, and then verified by finite element (FEM) analysis. The windings in the upper primary and the lower primary are arranged differently to improve the average thrust. The thrust characteristics of the DS-PMLSM under different shifted distances are analyzed and compared in detail. Furthermore, the primary component employing two kinds of core laminations is proposed to reduce both the dc component and ripple of the normal force. Finally, a DS-PMLSM prototype is tested, and the experimental results are compared with the analytical results to verify the effectiveness of the theoretical and simulation research.