A simple and practical magnetic equivalent circuit (MEC) based analytical technique for calculating the performance parameters of the permanent magnet (PM) eddy current coupling is presented. In the ...proposed MEC model built with the lumped parameters, the eddy current effects are inherently taken into account by introducing a branch magnetic circuit allowing for the magnetomotive force and the reaction magnetic flux. A complete formulation for the reaction flux which is treated as a kind of leakage flux is derived. A verification process is conducted and it is shown that in a considerably wide range of slip speeds, the torques predicted by the presented method match well with those obtained by both the three-dimensional finite element analysis and experimental measurement. The new MEC-based method also proves to be effective in the performance simulation of the PM eddy current coupling with different design parameters. In addition, the limitation of the proposed approach is also discussed and the reasons are fully investigated.
Among the different types of multiferroic compounds, bismuth ferrite (BiFeO3; BFO) stands out because it is perhaps the only one being simultaneously magnetic and strongly ferroelectric at room ...temperature. Therefore, in the past decade or more, extensive research has been devoted to BFO-based materials in a variety of different forms, including ceramic bulks, thin films and nanostructures. Ceramic bulk BFO and their solid solutions with other oxide perovskite compounds show excellent ferroelectric and piezoelectric properties and are thus promising candidates for lead-free ferroelectric and piezoelectric devices. BFO thin films, on the other hand, exhibit versatile structures and many intriguing properties, particularly the robust ferroelectricity, the inherent magnetoelectric coupling, and the emerging photovoltaic effects. BFO-based nanostructures are of great interest owing to their size effect-induced structural modification and enhancement in various functional behaviors, such as magnetic and photocatalytic properties. Although to date several review papers on BFO and BFO-based materials have been published, they were each largely focused on one particular form of BFO. There have been very few papers addressing the different forms of BFO in a comprehensive manner and providing a comparison across the different forms. As BFO has been extensively studied over the past more than one decade especially in the past several years, there have been new phenomena arising more recently. Naturally they were not included in the early reviews. Here, we provide an updated comprehensive review on the progress of BFO-based materials made in the past fifteen years in the different forms of ceramic bulks, thin films and nanostructures, focusing on the pathways to modify different structures and to achieve enhanced physical properties and new functional behavior. We also prospect the future potential development for BFO-based materials in the cross disciplines and for multifunctional applications. We hope that this comprehensive review will serve as a timely updating and reference for researchers who are interested in further exploring bismuth ferrite-based materials.
For high-speed permanent magnet machines (HSPMMs), the permanent magnet (PM) is more likely to suffer irreversible demagnetization because the heat dissipation is serious in the HSPMMs, especially ...for the high-power machines. This paper focuses on the comprehensive research results on the power loss and thermal characteristic for a high-power HSPMM. First, the power loss at the rated load is investigated by finite-element analysis. Then, the temperature distribution of four cooling schemes is compared by the electromagnetic-thermal iteration calculation. The effect of different parameters on thermal behavior is obtained to reduce rotor temperature, which includes an examination of the axial flow duct, cooling medium, sleeve thickness, and sleeve thermal conductivity. Finally, an improved loss separation method is employed to obtain the loss distribution from the measured total loss, and the comprehensive experiments are implemented based on one HSPMM prototype (800 kW, 15 000 rpm) to verify the related theoretical analysis.
For accurate position tracking and robust control of permanent magnet linear synchronous motor (PMLSM) servo systems against various uncertainties, such as parameter change, load disturbance, ...friction force, and so on, this article proposes a novel super-twisting nonsingular terminal sliding mode control method based on a high-order sliding mode observer. First, a dynamic model of PMLSM with uncertainties is established. A novel nonsingular terminal sliding mode function combined with the super-twisting algorithm is then proposed to design a robust super-twisting nonsingular terminal sliding mode controller, which ensures the system convergence to the equilibrium state within a finite time, effectively eliminating the chattering phenomenon and improving the system robustness. To further improve the system tracking performance and anti-interference ability, a high-order sliding mode observer is used to estimate the system uncertainties. The effective tracking performance and robustness of the proposed control method are validated by the experimental results.
This work presents the analysis, design and optimization of a permanent magnet synchronous motor (PMSM) for an electric vehicle (EV) used for campus patrol with a specific drive cycle. Firstly, based ...on the collected data like the parameters and speed from a test EV on the campus road, the dynamic calculation of the EV is conducted to decide the rated power and speed range of the drive PMSM. Secondly, according to these requirements, an initial design and some basic design parameters are obtained. Thirdly, optimization process is implemented to improve the performance of the designed PMSM. The permanent magnet (PM) structure, airgap length and stator core geometry are optimized respectively in this step. Different optimization processes are proposed to meet multiple optimization objectives simultaneously. Based on the finite element analysis (FEA) method, it is found that the harmonic of the optimized PMSM is lower than that of the initial design, and the torque ripple is reduced by 24%. The effectiveness of optimization on the core loss and PM eddy loss is validated and the temperature rise is suppressed effectively. Finally, a prototype is fabricated for the optimized PMSM and an experimental platform is developed. The test results verify that the optimized PMSM meets the requirements of the specific campus patrol EV well.
The multilevel method has been presented for design optimization of electrical machines and drive systems for optimal system performances and efficiency in our previous work. For framework design of ...the multilevel optimization method, four techniques are presented in this paper, including the sizing equation, local sensitivity analysis, global sensitivity analysis, and design of experiments techniques. For each technique, a general and theoretical analysis procedure is presented before the application study. To demonstrate the effectiveness, a permanent magnet claw-pole motor with soft magnetic composite core and 3-D finite-element analysis model is investigated to minimize the material cost and maximize the output power while keeping the volume constant. The calculated motor performance based on this 3-D finite-element model has been verified by the experimental results. As shown, these techniques are simple to implement, and the resultant multilevel optimization framework can significantly improve the motor performance and reduce the required sample number of finite-element analysis.
In conventional direct torque controlled (DTC) permanent magnet synchronous motor drive, there is usually undesired torque and flux ripple. The existing literature have proposed some methods to ...reduce torque and flux ripple by optimizing the duty ratio of the active vector. However, these methods are usually complicated and parameter dependent. This paper first compares the performances of three duty determination methods in detail and then proposes a very simple but effective method to obtain the duty ratio. The novel method is superior to the existing methods in terms of simplicity and robustness. By appropriately arranging the sequence of the vectors, the commutation frequency is reduced effectively without performance degradation. To further improve the performance of system, a low-pass filter-based voltage model with compensations of amplitude and phase is employed to acquire accurate stator flux estimation. The proposed scheme is able to reduce the torque and flux ripple significantly while maintaining the simplicity and robustness of conventional DTC at the most. Simulations and presented experimental results validate the effectiveness of the proposed schemes in this paper.
A system-level design optimization method under the framework of a deterministic approach was presented for electrical drive systems in our previous work, in which not only motors but also the ...integrated control schemes were designed and optimized to achieve good steady and dynamic performances. However, there are many unavoidable uncertainties (noise factors) in the industrial manufacturing process, such as material characteristics and manufacturing precision. These will result in big fluctuations for the product's reliability and quality in mass production, which are not investigated in the deterministic approach. Therefore, a robust approach based on the technique of design for six sigma is presented for the system-level design optimization of drive systems to improve the reliability and quality of products in batch production in this work. Meanwhile, two system-level optimization frameworks are presented for the proposed method, namely, single-level (only at the system level) and multilevel frameworks. Finally, a drive system is investigated as an example, and detailed results are presented and discussed. It can be found that the reliability and quality levels of the investigated drive system have been greatly increased by using the proposed robust approach.
This paper presents a model predictive direct power control strategy for a grid-connected inverter used in a photovoltaic system as found in many distributed generating installations. The controller ...uses a system model to predict the system behavior at each sampling instant. The voltage vector that generates the least power ripple is selected using a cost function and applied during the next sampling period; thus, flexible power regulation can be achieved. In addition, the influence of a one-step delay in the digital implementation is investigated and compensated for using a model-based prediction scheme. Furthermore, a two-step horizon prediction algorithm is developed to reduce the switching frequency, which is a significant advantage in higher power applications. The effectiveness of the proposed model predictive control strategy was verified numerically by using MATLAB/Simulink and validated experimentally using a laboratory prototype.
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