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Rotor excited flux‐switching permanent magnet machines (REFSPMs) have been recently introduced exhibiting high power density and low permanent magnet consumption. Despite the advantages, 12/8 configuration of REFSPM has an intrinsic unbalanced voltage waveform due to the existence of even‐order harmonics. Aiming to improve the machine voltage THD, using notches on the rotor segments is proposed. To study the effects of the rotor notch on machine performance with low computational time, the non‐linear magnetic equivalent circuit is developed taking into account the effects of fringing fluxes, iron saturation, and rotor transition. An optimisation procedure based on Taguchi method is applied to minimise the voltage THD value taking the effects of uncontrollable factors into account. Finally, the REFSPM is prototyped and the measured results are compared with the analytical and numerical results. [ABSTRACT FROM AUTHOR]

Here, static and dynamic (rotating) misalignments between the low-speed rotor (LSR) and the stator of axial flux magnetically geared machines are studied with the aid of 3-D finite element analysis (FEA). The influence of rotor/stator axis misalignments on machine performance in terms of cogging torque, air-gap flux density, and back-EMF is investigated with reference to the fully healthy condition. The results show that the LSR and HSR cogging torques are significantly affected by such misalignments due to distorted air-gap flux density. However, the amplitude and the harmonics of the back-EMF are only slightly changed. Furthermore, the influence of the misalignments on the machine torque performance is investigated. It is shown that the machine torque is significantly reduced when the LSR axis is misaligned with the axis of the stator. Thus, it is concluded that the torque performance of axial flux magnetically geared machines significantly deteriorates under static and dynamic axis misalignments. In addition, the two types of misalignments have similar effects on machine performance. [ABSTRACT FROM AUTHOR]

V‐shape interior permanent‐magnet machines (IPMs) have been widely utilised in the industry due to their high‐power density, high efficiency, and low manufacturing cost. There has been growing interest in applying multi‐objective optimisation to the design of electric machines. In the context of V‐shape IPM designs, it is important to include stress analysis in the optimisation design analysis as the steel bridges in the IPM rotor are structural weak points, where high stresses develop. However, traditional finite element analysis (FEA) that is normally used to compute bridge stresses becomes cumbersome due to its high computational cost. In this study, a computationally efficient analytical method is proposed to compute the mechanical stresses developed within the steel bridges in a V‐shape IPM. The proposed method is shown to yield accurate predictions compared with FEA while reducing computational cost. A design study is conducted that demonstrates that the machine performance can be improved by incorporating the proposed structural analysis in a multi‐objective optimisation‐based‐design environment. [ABSTRACT FROM AUTHOR]

This study illustrates the design of a low‐torque ripple ferrite‐assisted synchronous reluctance machine. The design strategy initially adopts a simplified analytical model in order to select the optimal values for the flux barrier angles that mainly affects the torque ripple. Then, synchronous reluctance rotor geometries selected on the basis of analytical results are analysed by finite elements (FEs) simulations. The simulated geometries are provided by ferrite permanent magnets (PMs) to enhance machine performance. The optimisation steps are properly coordinated in order to realise the maximum reduction of the torque ripple, taking into account the PM quantity and the flux barrier shape as well as the demagnetisation risk. Two optimal rotor geometries are presented and compared in terms of torque ripple by FEs simulations. Then, the comparison have been extended to other machine characteristics (as high‐frequency saliency and demagnetisation tolerance) to the aim of selecting the more promising one. Available measurements on prototypes are reported to confirm the simulation results and the design approach. [ABSTRACT FROM AUTHOR]

A novel indirect vector control system for induction machines is proposed. To ensure accurate rotor flux orientation in face of severe thermal drift of the rotor resistance during practical operation, the system features a new rotor resistance adaptation method. The latter is based on the elimination of the q-axis rotor flux, which is calculated from steady-state relations of the induction machine. Compared with other rotor resistance adaptation methods found in the literature, for example, observer-based and model reference adaptive system-based methods, the proposed one poses much less computation burden and is quite convenient for online implementation. The basic principle and theoretical analysis are presented. The effects of other motor parameters on the adaptation method are also investigated. Based on the investigation results, a stator resistance compensation algorithm is incorporated to reduce the impact of incorrect stator resistance at low speeds. Some non-negligible issues in practical applications, such as dead-time effect and transport delay of digital pulse-width modulation process, are also investigated and taken care of. Simulation and experimental results show good dynamic and steady-state performance. [ABSTRACT FROM AUTHOR]