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This study is aimed at investigating the growth rate of azimuthal perturbation modes in an ideal annular linear induction pump model. The positive growth rate of azimuthal perturbation modes is associated with the unstable behaviour of the annular linear induction pump and is known in the literature as MHD instability characterized by strong low-frequency oscillations of magnetic field, flowrate, and pressure. A linear stability analysis of a height-averaged quasistationary main flow in the ideal annular linear induction pump has been conducted, where only temporally evolving azimuthal modes of the axial velocity and magnetic field perturbations were considered. The obtained results predict damped or damped oscillating perturbations in a stable regime as a function of Rm, Rms, N and κm. In the studied parameter range, an amplification of perturbations without oscillations was observed above the instability threshold. It can be concluded that the analysed model of the ideal annular linear induction pump cannot predict experimentally and numerically the observed low frequency oscillations. [ABSTRACT FROM AUTHOR]

In this work, a novel dual‐stator hybrid excited linear flux switching machine (DSHELFSM) is proposed. The proposed machine is suitable for long‐stroke applications as all the excitation sources are mounted on a short mover and the stator is completely passive. Second, the proposed machine uses ferrite magnets rather than the expensive rare earth permanent magnets (PMs) with the addition of field excitation to achieve flux‐regulation capability at various field currents. An iron bridge that provides an additional path for flux linkage to complete its circuit is used. Various design parameters such as split ratio, stator pole width, width and height of PM, the width of the iron bridge, width of mover's tooth, and stator slot depth are optimised using multivariable geometric optimisation (MGO) while keeping the slot area, electric and magnetic loading constant. The optimised design has improved the performance as compared to the initial design. Furthermore, the results obtained by 2D analysis are verified by 3D analysis. Thermal analysis is carried out to set the operating limit of the proposed machine. [ABSTRACT FROM AUTHOR]

Operation of Vernier machines is based on flux modulation. They have some advantages including maintaining the rated torque in motor applications and the rated output power in generator applications at low speeds, high torque density and relatively low torque ripple due to their magnetic gear property and fault‐tolerance. In recent years, the motor with various topologies has been developed for different applications. Therefore, analysing and monitoring different faults is essential in the design and implementation stages. This study has two main purposes. First, to introduce an accurate frequency index independent of load variations for detecting the turn‐to‐turn short circuit (TTSC) faults in the stator windings of a permanent magnet Vernier machine. Second, modelling the machine in a healthy condition and in the presence of TTSC faults to investigate its effect on machine performance and output characteristics. An analytical model is presented using the modified winding function theory under the TTSC fault by taking into account the effect of stator slots which enhances the accuracy of the air‐gap permeance function estimation. In the process of calculating the fault index, frequency components of the output characteristics of the machine are obtained from the mathematical equations of the magnetic field. It is shown that the proposed indicators are robust against load variations. [ABSTRACT FROM AUTHOR]