Abstracts:For a five-phase permanent magnet synchronous machine (PMSM), the third-order harmonic back EMF is increased by changing the shape of the permanent magnet for increasing average torque in healthy operation. Additionally, in the open-circuit (OC) and short-circuit (SC) faults, the effect of injected third-order harmonic back EMF also needs to be considered. Therefore, this paper proposes a fault-tolerant control method with original transformation matrixes and coefficients reconfiguration in fundamental and third-order harmonic subspaces for both single-phase OC and SC faults. Fault tolerance can be applied by reconfiguring the relative coefficients after an OC or SC fault occurs, depending on the type of fault. Besides, the proposed method aims to optimize the OC fault tolerance strategies and effectively solve the single-phase SC fault, considering the influence in the third-order harmonic back EMF. According to experimental results, the torque fluctuation after applying the proposed method is similar to that in the healthy stage and much lower than that using most fault-tolerant control methods without considering the third-order harmonic back EMF.

Abstracts:In order to further improve the torque density of the permanent magnet motor, a novel 650 kW circumferentially excited permanent magnet (CEPM) motor is proposed and designed. The response surface method and particle swarm optimization (PSO) algorithm are used to obtain the optimal design of the circumferentially excited permanent magnet motor. The electromagnetic performance is analyzed under the different operating conditions. The mathematical model of three-dimensional end transient electromagnetic filed is calculated to obtain the end leakage magnetic flux and end component losses, which provides the heat source for thermal analysis. Novel air-water cooling dual self-circulation ventilation system with the axial-flow fan is proposed. The complex fluid flow and the temperature distribution of each component are determined in the circumferentially excited permanent magnet motor based on three-dimensional fluid-solid thermal coupled model. The highest temperature of the components is determined. This novel ventilation cooling system can effectively take away the heat in the circumferentially excited permanent magnet motor. A prototype of circumferentially excited permanent magnet motor is manufactured. The designs and analyses are validated.

Abstracts:Accurate remaining useful life (RUL) prediction of lithium-ion (Li-ion) batteries contributes to the safe and reliable operation of batteries and reduces safety risks. The simple pipeline and outstanding performance of the deep learning technology have made it a widespread popular prediction method. However, most existing methods focus on the construction of the network and rarely consider incorporating task and data characteristics to impose preferences on the model, i.e., inductive biases. Therefore, a temporal and differential guided dual attention neural network (TDANet) is proposed in this article to overcome the above limitations. First, the raw and differential capacity degradation data are separately fed into the proposed temporal-guided module (TGM) and differential-guided module (DGM) to capture global time-space correlations and local fluctuations. Then, following these two modules, self-attention and convolutional layers are introduced to extract global features guided by TGM and local features guided by DGM in parallel. Finally, the output layer is applied to fuse the above features for capacity prediction. The average mean absolute error (MAE) on the NASA and CALCE databases can reach 0.0167 and 0.0153 when the prediction starting point is 40%, and the prediction results of TDANet outperform known state-of-the-art methods, indicating its superior performance.

Abstracts:Electrical rotating machines are often system-relevant in their application. To avoid unplanned failures, the machines are regularly checked for faults. A novel way to do this is the SFRA method. It is non-invasive and can be carried out with little effort and short measurement time. Furthermore, it is possible to detect different faults in the magnetic or electrical circuit simultaneously. The main objective of the present paper is to give the theoretical background for this new application. For this purpose, empirical measurements are carried out on fifteen different synchronous machines and induction machines. The power classes and designs are very different and thus provide important information on the transferability of the measurements. A generally valid trace, consisting of four frequency ranges, is developed. This is used for verification of the developed gray box model. Important influences such as the neighboring phases and the actual position of the rotor are taken into account. A periodically repeating behavior as a function of the number of pole pairs is shown, which can only be observed in certain frequency ranges. This periodicity must be taken into account in reference measurements. The influence of the neighboring phases overlaps the main resonance of the measured phase. A second resonance point is formed in a similar frequency range. Finally, three examples for fault detection are given. Short circuit faults are investigated using an induction machine stator. Even a single shorted turn is already changing the frequency response. Ground faults have a greater effect on SFRA measurements. Due to the additional conducting path to ground within the winding, the initial damping becomes larger. The remaining frequency ranges are also strongly influenced by this fault type. A fault that is usually difficult to detect is the rod rupture in the damper cage of synchronous machines. With the help of SFRA measurements, this fault can be detected via the periodicity even without a reference measurement. In summary, it is shown that short circuits, ground faults and rod ruptures in the damper cage can be detected with the method.

Abstracts:The need to reduce computational burden in the preliminary design stage of switched reluctance machines is fostering the interest in design-oriented analytical modelling. To this end, this work proposes a novel design-oriented analytical model that comprises two main parts, each of them containing an original scientific contribution: 1) a new interpolation technique for the flux loci based on 2${\text{nd}}$-order Fröhlich-Kennelly equations, and 2) an analytical model that calculates flux linkage in partial overlap and saturated conditions. The model is validated against finite element analyses of four switched reluctance machines and the experimental results of a physical prototype. Finally, an in-depth discussion on the use, accuracy and limitations of proposed analytical model is provided.

Abstracts:This article deals with the issue of manufacturing processes leading to rotor surface losses through analytical, finite element analysis (FEA) and experimental methods. Based on experiments, it is found that the rotor surface losses make the rotor temperature of radial magnetic bearings (MBs) higher than expected, and thermal ablation appeared on the rotor surface. First, we investigate the mechanism of rotor surface loss in radial MBs using an improved analytical method. The FEA is then used to validate the analytical results and explore the correlation between the degree of short-circuit faults on the rotor surface and the surface losses. This yields a more comprehensive understanding of the loss characteristics and provides ideas for improving manufacturing methods to reduce surface losses. Finally, a simple method of rotor outer circle machining, namely finish turning with fine feed, is proposed. Comparison prototypes were manufactured using the proposed method and the conventional method. The results demonstrate that the proposed method can effectively reduce the rotor surface losses of radial MBs.

Abstracts:This article presents a comprehensive analysis of a novel complementary dual-stator Vernier machine (DSVM) with improved performance. In contrast to conventional DSVMs, the proposed machine employs a unique configuration featured by a complementary stator design alongside phase-shifted dual stator winding. Therefore, the symmetry of flux distribution is improved, and the non-working even order harmonics produced by the armature winding are effectively reduced. Consequently, the power factor is notably improved to 0.91, and the unbalanced force is reduced by 60.14% compared to the conventional DSVM. The electromagnetic performance, mechanical structure and thermal analysis are well investigated by using finite element analysis (FEA). In addition, the temperature rise under the rated load condition with natural cooling is safe, and the mechanical strength is proved to be sufficient, which validates the feasibility of the proposed novel design. Finally, a prototype is fabricated, and the performance is tested to verify the feasibility of the proposed design.

Abstracts:Benefiting from the distinct capability enabling flexible flux regulation, variable flux memory machines (VFMMs) are considered as an excellent candidate for electric vehicles to achieve overall high efficiency. However, the structural connections and evolutionary laws between different VFMMs remain unrevealed, resulting in the lack of a comprehensive design method for VFMMs. This article investigates the VFMMs with various permanent magnet (PM) arrangements from the perspective of the elementary-unit-combined concept. Besides, a topology construction method and several novel topologies for VFMM are further proposed. First, the evolution of different magnetic circuits and their inherent characteristics are introduced to form a series of emerging single- and dual-layer PM configurations. Meanwhile, a topology construction method based on the elementary-unit-combined concept is proposed, as well as three novel hybrid magnetic circuit (HMC) topologies are deduced based on three elementary units. Then, the electromagnetic characteristics in the existing and newly proposed HMC-VFMMs are comprehensively investigated utilizing the simplified magnetic circuit model and the finite element (FE) method. Finally, an HMC-VFMM prototype is manufactured and tested to confirm the validity of the previous analyses.

Abstracts:This article presents the force ripple reduction method for iron-cored permanent-magnet linear synchronous motors (PMLSMs) in both the tangential and normal directions. Iron-cored PMLSMs yield significant geometry-driven and current-driven ripples in the moving and normal directions due to the magnetic saliency in the airgap, deteriorating the servo control performance and causing unwanted vibration and noise. In order to resolve such issues, a control method is proposed in this article to simultaneously reduce the motor force ripples in both directions, using position-dependent force constants. Considering the effects of the D- and Q-axis current on the motor force directions in PMLSMs, the identification methods are presented for the force constants and the geometry-driven ripples in the tangential and normal directions to be used in the force ripple reduction method. An experimental testbed of PMLSM-driven stage is constructed to validate the motor force parameter identification methods and ripple reduction method. Using the proposed methods, the significant force ripple reductions are experimentally achieved as 91.2 % and 94.5 % in peak-to-peak and RMS (root-mean-square) values in the tangential direction, and 82.4 % and 86.6 % in the normal direction, without sacrificing the motor thrust performance.

Abstracts:This article proposes a computationally efficient (CE) semi-analytical method for winding power loss calculation of high speed permanent magnet machines induced by circulating current. It combines a CE magnetostatic finite element method (FEM) for rapid slot leakage field extraction and an analytical circuit model for circulating current calculation. Time-space transformation based CE FEM is applied for efficient slot leakage field extraction considering the polyphase windings. Besides, a conductor model with an automatic and practical turn splitting strategy is proposed to consider the effect of conductor positions and bundle shapes on the circulating current loss. The results on circulating current waveforms and corresponding losses show that the proposed method has high accuracy and can significantly reduce the simulation time, with an error less than 2% and the simulation time only 1/400 for the studied machine compared with the commercial FEM. Using the proposed method, the influence of some factors, including the turn number, the transposition effect and the bundle shape on the circulating current loss are investigated. Finally, the proposed method is further verified by experimental measurements implemented on two stator specimens.