ABSTRACT Conventionally, three‐phase dual electrical–mechanical port machines are employed in contra‐rotating wind energy conversion systems for power extraction. However, the power and torque densities of these machines are inherently constrained by their low phase number. Recent advancements in power electronics have significantly accelerated the development and adoption of multiphase electrical machine topologies, improved fault tolerance, enabling enhanced performance and greater flexibility in high‐performance electric drive applications. In this article, the five phase decoupled winding dual flux modulated machine is designed, analysed and optimised for a direct drive gearless contra rotating wind energy conversion system. The proposed machine integrates the Vernier and magnetically geared machine configuration, resulting in a dual flux modulation phenomenon that enhances the overall electromagnetic performance. Furthermore, two sets of decoupled windings are placed on the stator, providing better fault‐tolerant capability and enabling flexibility in the control mechanism; by regulating the current in the windings, dual maximum power point tracking is achieved. The detailed electromagnetic performance of the machine is first analysed using the finite element method, and a multi‐objective genetic optimisation technique is utilised to further enhance the electromagnetic performance. Moreover, to further evaluate the maximum overload capability of the proposed machine, the output power, torque, losses and efficiency are investigated under various current values. The fault‐tolerant capability of the proposed machine is subsequently assessed under both open‐circuit and short‐circuit fault conditions to substantiate winding decoupling. Finally, a comparative analysis is conducted with the conventional five‐phase dual‐rotor permanent magnet synchronous machine in terms of torque density and PM utilisation.
ABSTRACT High‐power‐density PMSMs with a wide operating speed range exhibit complex electromagnetic excitation characteristics. Performing vibration and noise optimisation over the full operating speed range using multi‐physics finite element (FE) methods incurs prohibitive computational costs. To address the limitations of conventional surrogate models in multi‐condition optimisation across wide speed ranges, which include excessive data volume requirements and limited iteration capability, this paper proposes a rapid electromagnetic vibration and noise optimisation framework for high‐power‐density PMSMs over the full speed range under representative no‐load and peak‐load conditions. This framework reduces the data sampling burden by leveraging operating condition characteristics, constructs an electromagnetic force prediction model based on deep neural networks (DNNs), and incorporates a hierarchical multi‐objective optimisation method to achieve noise reduction across the full speed range under these conditions. Following the proposed workflow, a parametric optimisation study is conducted on a high‐power‐density PMSM prototype, and its rapid iterative optimisation capability is verified by comparison with the conventional multi‐physics coupled iterative optimisation scheme. Finally, the absolute noise performance of the prototype is validated through no‐load speed ramp tests, and the optimisation effect is confirmed via comparative multi‐physics simulations under peak load conditions.
ABSTRACT This paper presents the analytical modelling and design of a high‐acceleration double‐sided linear motor with an arbitrary Halbach array for lithography machines used in semiconductor manufacturing. The Halbach array, combined with a slotless stator, improves performance in terms of vibration, acoustic noise, and precision compared with slotted motors. Amperian current and magnetic charge models of permanent magnets are integrated into a hybrid analytical framework. Unlike conventional methods that treat magnets as source terms in Poisson's equations, the proposed approach reduces the problem to Laplace's equations by representing the magnets through boundary conditions. The magnetic fields and potentials in the different regions, along with machine quantities such as shear stress, force‐angle characteristics, force profile, attraction force, misalignment force, back‐EMF, and demagnetisation index are derived, comprehensively analysed, and validated against FEM results. To provide a broader modelling framework, two additional analytical models based on the solution of Poisson's equations in terms of scalar and vector potentials are also derived, compared, and analysed. Finally, the design optimisation and sensitivity analysis of a linear stage for lithography applications are discussed.
Under long-term high-current and high-flux-density operating conditions, the cores of HVDC converter-valve saturable reactors are prone to severe local looseness, repeated gap opening-closing, and abnormal acoustic emissions. However, existing studies have not fully elucidated the underlying vibro-acoustic response mechanisms under such conditions. In this paper, micro-impact theory is introduced to construct an analytical vibro-acoustic model for severely loosened cores. First, an electro-magnetic-structural multiphysics finite-element model is established to determine the ranges of key structural and material parameters corresponding to severe looseness. Subsequently, for the dynamic gaps and discontinuous contact caused by significant looseness, the harmonic components of the converter-valve operating current are used as excitation and mapped to the spectral representations of the Maxwell attraction force and magnetostrictive stress, while a magnetic hysteresis model is incorporated to derive the electromagnetic negative stiffness and the linearized equilibrium equations. The core gap-opening process is then formulated as a coupling between a sequence of impact impulses driven by the re-contact velocity and the structural modes, yielding broadband impact-type acoustic signatures characteristic of severe looseness. Finally, field measurements are carried out on a saturable reactor exhibiting overheating and abnormal noise. The results show that the proposed model effectively identifies the dominant frequency bands and reasonably reproduces the energy distribution characteristics in the 0-5 kHz and 5-30 kHz ranges, and faithfully reproduces the broadband energy rise above 30 kHz, thereby validating the effectiveness of the model. This study reveals the physical mechanisms governing the frequency-band characteristics of looseness-related vibro-acoustic signals and offers important theoretical support for the early identification of severe core looseness in HVDC saturable reactors.
The permanent magnet vernier machine (PMVM) offers several advantages, including higher torque density, lower cogging torque, a simpler and more robust structure and improved efficiency compared to other permanent magnet-based topologies. This machine is a suitable candidate for use in small electric vehicles such as e-bikes, scooters and motorcycles. This paper evaluates various configurations of permanent magnet vernier motors designed for a 450 W electric scooter. The proposed configuration employs an outer-rotor spoke-type arrangement, in which the central magnets are angularly shifted relative to the side magnets. The shifted spoke configuration is modelled using a magnetic equivalent circuit (MEC) and subsequently optimised through sensitivity analysis of its parameters. Finally, a prototype of the proposed structure is developed, and its performance is compared with finite element method (FEM) and analytical modelling results. The proposed array demonstrates higher power factor, increased torque density and reduced cogging torque compared to the conventional design. Furthermore, the mechanical robustness of the rotor is enhanced owing to the inclusion of an iron bridge structure.
