Iet Electric Power Applications最新文献

Machine acoustics is an important area of research impacting the quality and comfort of human life. With increased levels of electrification and the wider use of electric motors, the contribution of motor drives towards quieter acoustic systems becomes increasingly important. This paper presents a novel acoustic improvement method involving the use of acoustic waves generated from High Frequency Injection to perform Active Noise Control. Although High Frequency Injection has been used widely in the domain of sensorless motor control, its acoustic generation process has been so far perceived as a negative by-product. This paper presents the analysis and experimental results from the application of the proposed method to the Helicopter Electro-Mechanical Actuation System. Considering the extensive use of motor drives in a number of industries, the proposed practice of High Frequency Injection Active Noise Control can have a significant impact to future applications.

Magnet cracking is a common issue in external rotor motors. To investigate the causes of magnet cracking and propose solutions, the authors consider the effects of magnet shape, magnet and yoke material fit on the motor rotor magnets, perform a static analysis of the motor rotor. The simulation and test results show that the stress distribution of tile-shaped magnets is better than that of rectangular magnets. The highest safety margin of 56.41% is achieved for the magnet and yoke material fit of DT4/N35(EH). The maximum force of the permanent magnet (PM) exceeds 22.38% of the stress limit when the material fit is DT4/SmCo28, which can lead to cracks in the PM. The results of this paper have important reference significance for the structural design of the external rotor motor and their safe and reliable operation.

This paper introduces a novel application of the inverse modelling method, which is designed to estimate core losses in both the stator and rotor regions of an electrical machine. The technique focuses on the use of short-term transient temperature measurements obtained from the stator core of a slotless induction machine, with a focus on validating the measured temperature rise through a forward model. The measurement setup involves two primary approaches: (i) the use of thermal sensors embedded in a printed circuit board inside the stator core and (ii) surface sensors embedded on the stator yoke. Through the use of this innovative approach, the results indicate that the inverse modelling technique is highly effective in predicting core losses based on short-time transient temperature rise measurements.

Precisely interpreting frequency response analysis (FRA) curves is crucial when investigating mechanical malfunctions in power transformer windings (TWs). However, many conventional explanations of FRA features cannot be validated by an equivalent circuit (EC) that represents winding structures using resistance, inductance, and capacitance components in a ladder network. Incorrect interpretation can lead to misdiagnosis and confusion in asset management. Previous ECs are often proposed by analysing winding structures without rigorous verification compared to the corresponding FRA data. The specific EC is acquired using the transfer function (TF) derived from the measured FRA data. This allows for the establishment of the relationship between TW FRA curves, TF equations, and EC topologies. The precise interpretation of FRA curves can be achieved by closely observing the FRA curves created from TFs and ECs. The remarkable similarity between the measured and modelled FRA curves verifies the authenticity of the derived ECs. This significant achievement clarifies many misunderstandings regarding FRA and represents a substantial advancement in FRA technology.

During geomagnetic storms, geomagnetically induced currents (GICs) occur in the power grid. GIC is a quasi-direct current, which is represented by using a fixed DC current, the authors propose an approach that combines field-circuit-coupled and weakly coupled magneto-mechanical models to investigate the magnetostriction characteristics of single-phase, four-column autotransformer cores excited by GICs. A non-linear magnetostrictive constitutive model that considers the impact of stress and magnetisation intensity on ferromagnetic materials is introduced. The model reveals that the strain in the core initially increases as the magnetisation intensity increases; however, when the core begins to saturate, the magnetostrictive strain weakens as the magnetisation intensity increases. Moreover, the results of multiphysics finite-element modelling are experimentally verified using a direct current bias platform. The results show that when excited by GICs, there is an enhancement in the vibration of the iron core, and the harmonic content of the vibration acceleration increases considerably, with the odd harmonics most significantly increasing in amplitude. The conclusion drawn is that GICs can exacerbate transformer vibration and significantly increase the content of harmonics, especially odd harmonics.

Rare-earth permanent magnet synchronous machines face challenges in manipulating their magnetic fields, which hinders the ability to extend the operation speed range. Moreover, this inflexibility leads to reduced efficiency in high-speed scenarios when the machine is under flux-weakening control and increases the risk of the magnets becoming demagnetised. The authors propose an alterable-magnetic-circuit variable-flux memory machine (AMC-VFMM) and a multi-objective hierarchical optimisation method is conducted to optimise the machine. Firstly, the topology and alterable-magnetic-circuit principle of the proposed AMC-VFMM are introduced. Then, optimisation objectives including torque production capability, flux regulation capability, and resisting unintentional demagnetisation capability are defined, and the hierarchical optimisation approach is established by stratifying the optimisation objectives and variables through the sensitivity analysis. Finite element analysis indicates that electromagnetic performances of the optimised design scheme are significantly enhanced. The bench test of the prototype demonstrates the superiority of the proposed AMC-VFMM and validates the effectiveness of the optimisation design method.

There is not only thrust but also normal force between the primary and secondary components for the single-side flat plate permanent magnet linear synchronous motor (PMLSM). The normal force will fluctuate periodically, which will cause friction perturbation and finally affect the positioning accuracy of linear feed system. For the single-side flat plate PMLSM, the variation law of normal force ripple under the coupling effect of multiple effects is studied, and the method of primary component segmental design to suppress it is proposed. Firstly, the influence of the cogging effect, the end effect and the armature reaction on the normal force ripple is analysed. Meanwhile the mathematical model of normal force ripple is established. Secondly, the PMLSM with segmental primary component is introduced and its suppression mechanism to the normal force ripple is expounded. On this basis, a scheme combining the non-integer pole slot matching with the primary component segmental design is proposed to further suppress the normal force ripple. Finally, an 18-slot 96/5-pole prototype is taken as an example to carry out the finite element simulation and experimental test, of which the results verify the research theory in this paper.

The authors investigate a semi-flooded cooling technology for modular permanent magnet machines using flux gaps (FGs) in alternate stator teeth for extra cooling channels. The investigated machine is separated into stationary and rotational components by a polyether ether ketone sleeve. Liquid is directed into the stationary component to achieve a significant temperature reduction, at the same time, avoiding the liquid leakage into the rotating component that will cause an increase in friction losses. The FGs in the modular machine increase the contact area between coolant and machine components, resulting in better cooling efficiency. Furthermore, the FGs contribute to reduced pressure loss by minimising system flow resistance. The influence of the FG width on improving machine cooling efficiency, lowering machine temperature, and reducing pressure losses is delved. Additionally, the investigation considers the impact of inlet and outlet areas to reveal the influences stemming from fluid expansions and contractions in these regions. Computational fluid dynamics (CFD) modelling is employed to simulate the cooling performances of the investigated machines. In addition, the flow network analysis has also been employed to help understand the fluid behaviour within machines. A series of tests have been carried out to validate the CFD modelling.

Vector control of induction motors has provided us with both good performance and acceptable efficiency at rated loads. Using this method at light loads reduces the efficiency due to the adjustment of motor flux at the rated value. Electric motors are normally used even at lower loads than the rated ones and often selected oversized. Enhancing the efficiency of induction motors at light loads will significantly reduce electric energy consumption. A novel method called Flux Angle Control (FAC) of the induction motor is presented to improve efficiency in the steady state at light loads. To increase the accuracy of the induction motor model we consider iron losses. This method controls the angle between the stator flux (stator current) and the d-axis (rotor flux direction). The primary aim of the flux angle control method is to reduce the flux level and increase the flux angle at light loads. The optimal flux angle is sensitive to some induction motor parameters. The proposed method offers several advantages compared to similar methods, including high efficiency, minimal sensitivity of the optimal flux angle to changes in motor parameters, a reduced number of calculations, and easy implementation. The validity of this method is examined through experiments.