Interest in permanent magnet synchronous machines (PMSMs) is continuously increasing worldwide, especially with the increased use of renewable energy and the electrification of transports. This book ...contains the successful submissions of fifteen papers to a Special Issue of Energies on the subject area of “Permanent Magnet Synchronous Machines”. The focus is on permanent magnet synchronous machines and the electrical systems they are connected to. The presented work represents a wide range of areas. Studies of control systems, both for permanent magnet synchronous machines and for brushless DC motors, are presented and experimentally verified. Design studies of generators for wind power, wave power and hydro power are presented. Finite element method simulations and analytical design methods are used. The presented studies represent several of the different research fields on permanent magnet machines and electric drives.
It was recently demonstrated that the synchronous reluctance motor is well suited for electric as well as for hybrid electric vehicles. This paper deeply investigates the capabilities of a ...synchronous reluctance motor and compares them with those of a permanent-magnet-assisted synchronous reluctance motor, according to the typical requirement of a traction application. A proper rotor design is necessary. The average torque is due to the rotor anisotropy. The permeance difference between the direct- and the quadrature-axis is achieved by means of a high number of flux barriers. The position of the flux barrier ends and proper rotor asymmetries are chosen so as to reduce the torque ripple, mainly due to the slot harmonics. The impact of the rotor design on the motor performance is presented deeply, showing several simulation and experimental results, carried out on synchronous reluctance motors with different rotor geometries. Permanent magnets can be inset in the flux barriers to assist the synchronous reluctance motor improving its capabilities, but avoiding to use rare-earth permanent magnets. The main advantages of the permanent magnet assistance is an increase of the main torque density and of the power factor. They are evaluated experimentally. However, the drawback of adopting permanent magnets is the possible demagnetization of the magnets themselves. This can greatly limit the maximum overload capability of the motor, which is a salient requirement of a traction motor.
Background: Resurveying historical vegetation plots has become more and more popular in recent years as it provides a unique opportunity to estimate vegetation and environmental changes over the past ...decades. Most historical plots, however, are not permanently marked and uncertainty in plot location, in addition to observer bias and seasonal bias, may add significant errors to temporal change. These errors may have major implications for the reliability of studies on long-term environmental change and deserve closer attention of vegetation ecologists. Methods: Vegetation data obtained from the resurveying of non-permanently marked plots are assessed for their potential to study environmental change effects on plant communities and the challenges the use of such data have to meet. We describe the properties of vegetation resurveys, distinguishing basic types of plots according to relocation error, and we highlight the potential of such data types for studying vegetation dynamics and their drivers. Finally, we summarize the challenges and limitations of resurveying non-permanently marked vegetation plots for different purposes in environmental change research. Results and conclusions: Re-sampling error is caused by three main independent sources of error: error caused by plot relocation, observer bias and seasonality bias. For relocation error, vegetation plots can be divided into permanent and non-permanent plots, while the latter are further divided into quasi-permanent (with approximate relocation) and non-traceable (with random relocation within a sampled area) plots. To reduce the inherent sources of error in resurvey data, the following precautions should be followed: (i) resurvey historical vegetation plots whose approximate plot location within a study area is known; (ii) consider all information available from historical studies in order to keep plot relocation errors low; (iii) resurvey at times of the year when vegetation development is comparable to the historical survey to control for seasonal variability in vegetation; (iv) retain a high level of experience of the observers to keep observer bias low; and (v) edit and standardize data sets before analyses.
This reprint is comprised of eleven articles that are screened by our hard-working peer reviewers. It mainly focuses on the recent advances in electric motors and drives, to adapt to the ongoing ...trends of electrification in both transportation and industry. New structural motors, such as the axial flux machine and the multi-phase machine, are introduced because of their enhanced reliability for use in next-generation electrified transportation. Special attention is also given to the micro PM motor, which has a broad use in many areas. In addition, advanced control techniques, such as position sensorless control and fault-tolerant control, are also incorporated to fulfill the demand for safe crucial applications, and the modeling of the bearing voltage and a line-start permanent magnet motor can be of particular interest to the industrial sectors. Through this reprint, we hope to provide a new perspective for the readers to manage their encountered problems, as well as stimulate innovative ideas for the electrified transportation of the next generation.
Nowadays, in-wheel drive mode is considered as one of the most promising modes for electric vehicles (EVs). The motor type plays a significant role to the vehicle performances. This paper focuses on ...performance between permanent magnet synchronous motor (PMSM) and vernier motor (PMVM) for in-wheel direct drive. Firstly, the required performances are determined by the vehicle requirements. The prototypes of PMVM and PMSM are manufactured after the comparison. Then, the expressions of air-gap magnetic field harmonic, electromagnetic torque, and power factor are theoretically derived, where the parameter torque ratio is introduced to evaluate the torque ratio between PMVM and PMSM. Based on experiment, the back-EMF harmonics, cogging torque, maximum torque per ampere capability, flux-weakening capability, torque, efficiency, power factor, are compared and analyzed. Subsequently, the discussions are carried out, where the strength and weakness of two-type motors for in-wheel drive are concluded and the future prospects are suggested. Finally, the conclusions of two-type in-wheel motors are then extracted. This paper aims at providing a reference for the exploration of alternating in-wheel motor types, which can promote the development of high-performance in-wheel drive system for EVs.
In this paper, a linear active disturbance rejection controller is applied for sensorless control of internal permanent-magnet synchronous motors. A hybrid position estimation strategy combining the ...high-frequency (HF) current injection for low-speed region with the electromotive force (EMF) estimation for high-speed region is presented. In contrast to conventional hybrid methods, the two schemes were integrated into the same control structure, and the position observer is embedded into the current controller. The high performance of position estimation was achieved using line extended state observers (ESOs). Compared with conventional sliding-model observer, the phase delay and speed chattering was obviously reduced. The robustness of the hybrid sensorless control system was well performed in the full-speed range. Experimental results were presented to verify the application of proposed method.
In this article, based on flux modulation theory, torque characteristics improvement method is proposed for double-stator vernier permanent magnet (DS-VPM) motor. Also, the detailed torque production ...mechanism of DS-VPM motor is derived. Based on theoretical analysis results, key design parameters which possess significant influence on motor torque characteristics are selected to be further optimized purposefully. Non-dominated sorting genetic algorithm is then adopted to obtain increased output torque and reduced torque ripple of inner, outer, and total DS-VPM motor. Besides, based on finite-element analysis, motor performances before and after optimization are compared in detail. Finally, a prototype motor is built and corresponding experiments are carried out. Both theoretical analysis and experimental results verify the effectiveness of the proposed torque characteristics improvement method, which provides a potential research path for the design optimization of high-performance VPM motors.
Owing to the competitive advantages of cost reduction, system downsizing, and reliability enhancement, position sensorless control methods for permanent magnet synchronous machine drives have drawn ...increasing attention from academia to industrial applications. In this article, a survey of the major sensorless control techniques for a wide speed range from low to high speeds is presented. The different high frequency signal injection schemes, fundamental pulsewidth modulation excitation methods, and model-based sensorless control are displayed and compared, which is able to facilitate the sensorless control implementation.
In this study, a robust fault-tolerant predictive current control (RFT-PCC) algorithm based on a composite observer is proposed for permanent magnet synchronous motors (PMSMs), which can eliminate ...the influence of motor parameter perturbation and permanent magnet demagnetization. First, the effects of the parameter perturbation and permanent magnet demagnetization on the current vector are analyzed based on the conventional predictive current control. The composite observer based on the sliding mode observer and the Luenberger observer is then designed to observe the compensation voltage and current prediction value of the next time simultaneously. Finally, an RFT-PCC method is developed. The proposed RFT-PCC is able to effectively enhance robustness against parameter perturbation and permanent magnet demagnetization by adding compensation voltage. The current prediction value of the next time is used to replace the sampled current in RFT-PCC to compensate for the influence of the one-step delay. Comparative simulations and experimentations verify that the proposed RFT-PCC can improve the robustness while maintaining quick dynamic response of the current control loops.
Low speed, high torque machines are used in wind turbines where the turbine rotor is directly connected to the generator. A permanent magnet synchronous generator using high-energy rare-earth ...permanent magnets (PMs) is one common choice for this application, but rare-earth PMs have supply insecurities and cost risks. A rare-earth free 32-pole PM generator, using ferrite PMs in a spoke-type rotor, for use in a 12 kW experimental wind turbine is built and tested. Voltages and currents at load and no load are measured, as well as the magnetic field in the end regions of the machine. The generator can deliver the required power at nominal speed and has low harmonic content in the output. The electrical measurements are compared to two-dimensional finite element design calculations and the experimental results are lower than expected from simulations. The measured voltage is lower than expected, requiring a higher current than calculated for the rated power. Three-dimensional magnetic field simulations show that there are leakage flux paths in the end-regions that the two-dimensional design calculations overlook, explaining the discrepancy between simulations and measurements.
PDF
