Analysis on the Cogging Torque of Permanent Magnet Machine for Wind Power Applications

This paper discusses the new feature implemented in most social media messaging applications: the unsent feature, where the sender can delete the message he sent both in the sender and the recipient devices. This new feature poses a new challenge in mobile forensic, as it could potentially delete sent messages that can be used as evidence without the means to retrieve it. This paper aims to analyze how well Autopsy open-source mobile forensics tools in extracting and identifying the deleted messages, both that are sent or received. The device used in this paper is a Redmi Xiaomi Note 4, which has its userdata block extracted using linux command, and the application we’re using is WhatsApp. Autopsy will analyze the extracted image and see what information can be extracted from the unsent messages. From the result of our experiment, Autopsy is capable of obtaining substantial information, but due to how each vendor and mobile OS store files and databases differently, only WhatsApp data can be extracted from the device. And based on the WhatsApp data analysis, Autopsy is not capable of retrieving the deleted messages. However it can detect the traces of deleted data that is sent from the device. And using sqlite3 database browser, the author can find remnants of received deleted messages from the extracted files by Autopsy

Design Methods for Surface-Mounted Permanent Magnet Synchronous Machines

Permanent magnet synchronous machines (PMSMs) provide several advantages compared with induction machine, such as higher power and torque density, and better dynamic response. Among PMSMs, Surface-mounted permanent magnet (SPM) machine has simple rotor configuration and easy control strategy due to its isotropic characteristics. Plenty of publications have illustrated the fundamentals and the design methods of SPM machines. Based on these, this dissertation presents new design methods for SPM machines. Both design methods are comprehensively illustrated. The presented design methods are embedded into a machine design platform available online. One of the new methods is an automatic design procedure using multi objective optimization method, whose principle is to combine multi objective differential evolution (MODE) optimization with finite element analysis (FEA) to obtain the machine with the best trade-off among the targeted objectives, like maximum torque, minimum torque ripple, good flux weakening capability, etc. Two cases are reported by using such automatic design method, one for a SPM machine with concentrated winding (CW-SPM) and the other with distributed windings (DW-SPM), respectively. The CW-SPM machine is designed for traction application. In this case, design equations, magnetic FEA, multi objective optimization, simplified structural and thermal co-design are presented. Torque and power profiles of the designed machine are reported. The losses and efficiency map are also presented. The DW-SPM machine is capable of low cogging torque thanks to the automatic design procedure. Dependent on demagnetization limit and optimal magnet span calculation, the magnet bounds in optimization process are obtained. The cogging torque and maximum torque waveforms of three different machines on Pareto front are shown, which are obtained by MODE optimization and FEA simulations. One optimum machine is selected as the best trade-off machine among PM volume, torque and cogging torque behaviors. Besides the automatic design process, the other design method called parametric design for SPM machines is reported. The parametric design provides a very effective and concise solution for SPM machine design without losing precision on the machine performance calculation. Three steps of parametric design development are reported. For each step, design flowcharts and examples are presented. Firstly, a parametric design plane was established based on rotor split ratio x and per unit magnetic loading b. All the sizing equations, torque and power factor calculation are functions of x and b. An example for designing a CW-SPM for traction application is reported. Later the parametric design plane was modified into the x and l_m⁄g plane, the latter parameter being the magnet-airgap length ratio. The design process of DW-SPM machines using the parametric plane is described. A prototype 一s built and verified the validity of the design process. Then, a general design approach based on accurate steel loading for both DW and CW SPM machines is proposed. By using subdomain model during the design process, the stator sizing equations are improved by considering the only one most loaded slot pitch rather than the entire pole pitch. Five different cases of SPM machines are analyzed to get the precise flux quantities passing through the most loaded teeth in one slot. A comprehensive parametric design flowchart for SPM machines is addressed. By using the parametric method, machine models are built according to each sizing situation. The steel loadings on both each tooth and yoke are measured by FEA and compared with target steel loading B_fe at open load condition, which shows good agreements with analytical cases. Finally, the designs are also tested at the respective rated currents. The presented methods give insightful and effective means in SPM machine desig

Performance evaluation of a stator modular ring generator for a shrouded wind turbine

This paper presents the performance evaluation of a stator modular ring permanentmagnet generator to be embedded in a shrouded wind turbine. That is done to increase the power conversion for the same turbine area when compared to more conventional ones. An adapted structure allows the assembling of the prototype, aiming to verify its performance under controlled conditions. Aiming to verify the accuracy of an analytical subdomain model for a large diameter machine, the evaluation compares the results obtained by the electromagnetic finite element method and experimental measurements. The results of the components of the air-gap flux density, back EMF and electromagnetic torque obtained by the proposed analytical model and finite-element method are in good agreement with the experimental measurements. The experimental measurements of the iron loss and copper loss show that the prototype efficiency can reach 90% approximately

STUDY AND DEVELOPMENT OF ANALYTICAL AND ANALYTICAL-NUMERICAL METHODS FOR THE STUDY OF ELECTRICAL MACHINES

L\u2019attivit\ue0 di ricerca si \ue8 focalizzata sulla determinazione di metodi analitici e analitico-numerici per la soluzione di alcuni problemi \u201caperti\u201d di interesse nella progettazione e l'analisi di macchine elettriche. La tesi include una gamma piuttosto ampia di argomenti, ma \ue8 stata sviluppata seguendo una singola linea di indagine unitaria, che consiste nel tentativo di cercare e, dove possibile, definire e implementare, metodi matematici sufficientemente veloci ma accurati per eseguire calcoli su macchine elettriche in modo da evitare l'uso massiccio di tecniche basate su analisi agli elementi finiti. Queste infatti sono note per essere precise ed affidabili, ma allo stesso tempo richiedono ingenti risorse computazionali e sono quindi poco adatte quando \ue8 necessario esplorare un gran numero di varianti di progetto, come nel caso di programmi di ottimizzazione progettuale basati su algoritmi genetici. I metodi agli elementi finiti non sono stati esclusi, naturalmente, ma piuttosto utilizzati come \u201cbenchmark\u201d per valutare la validit\ue0 delle tecniche di calcolo alternative proposte, ove non fosse possibile effettuare un confronto diretto con dati sperimentali. I tipi di macchine elettriche a cui si sono applicati i metodi di calcolo sviluppati in questa tesi sono diversi e vanno dai motori a magneti permanenti superficiali con cave statoriche a motori a magneti permanenti superficiali con statore slotless ,dalle macchine sincrone a riluttanza alle macchine sincrone a rotore avvolto, per finire con motori a induzione a gabbia di scoiattolo. Tutti questi tipi di macchine sono sempre pi\uf9 importanti nelle applicazioni odierne, sia nel settore industriale che per i sistemi di trazione. Per affrontare lo studio di queste macchine si sono di volta in volta sviluppati approcci di calcolo analitico diversi, anche in funzione degli obiettivi da raggiungere. Esempi di questi approcci analitici impiegati sono i seguenti: la teoria della \u201cwinding function\u201d applicata al calcolo della coppia di macchine a magneti superficiali; la teoria della \u201cpermeance function\u201d applicata al calcolo delle macchine con eccentricit\ue0 di rotore ; l'approccio mediante circuito equivalente magnetico o reti di riluttanze in combinazione a tecniche basate sulle mappe conformi per lo studio dei motori sincroni a riluttanza; la soluzione delle equazioni di Laplace e di Poisson per determinare il campo magnetico nelle macchine a magneti permanenti superficiali slotless e a gabbia di scoiattolo. Inoltre, l'applicazione degli algoritmi di calcolo proposti \ue8 illustrata mediante opportuni casi di studio ed i risultati ottenuti sono sempre convalidati mediante confronto con tecniche di calcolo alternative (in particolare l\u2019analisi agli elementi finiti

Diagnostics and analytical modelling for permanent-magnet synchronous machines

This dissertation proposes a novel diagnostic technique that utilises two air-gap search-coils which couple magnetically only under faulty conditions and can detect all the faults occurring in permanent-magnet machines. Furthermore, an existing search-coil-based method was expanded for detecting partial demagnetisation. A formula was developed which detects the frequency spectrum signatures under dynamic eccentricity, again in permanent-magnet machines. In the second stage, a magnetic field calculation algorithm was developed for the two basic rotor geometries of permanent-magnet synchronous machines, i.e. surface-mounted and surface-inset. The dissertation was divided into four parts and seven chapters. The first part is devoted on talking about the motivation that lead to work on this research subject and the objectives that this dissertation aims to satisfy. The fundamentals of permanent-magnet machines are also presented along the machine topologies that are used in this thesis to prove various methodologies and validate algorithms. In the second part, the diagnostic aspect of permanent-magnet machines is examined initially by doing a detailed literature review. The purpose of this comprehensive literature review is to become acquainted with the state-of-the-art fault diagnostic methods, identify what problems the existing methods cannot solve, and use the material for inspiration to develop a new diagnostic method. Afterwards, the review oriented the research towards the direction of air-gap flux monitoring, having single and double search-coil configurations validated using a Finite-Element Analysis software and experimental measurements taken by machines operating in a laboratory environment. The faults studied are partial demagnetisation, inter-turn fault and static-, dynamic- eccentricity. Lastly, based on the gaps found in the literature review, a method is presented to calculate the harmonics excited by the dynamic eccentricity fault. The third part of this thesis dealt with calculating the magnetic field distribution in radial-flux permanent-magnet machines with the surface, -mounted and -inset magnets. What triggered this research are the possibilities that come from having the components of the magnetic field distribution for every angle of the stator and rotor magnetic fields. This technique makes it possible to calculate all operational parameters that project the machines' performance. These are the Back-EMF and the types of torque, cogging, electromagnetic and reluctance. Finite-Element Analysis was used to validate the analytical subdomain model with great success. The fourth and last part of this dissertation summarises the conclusions and contributions of this work along with leads for future work

High-speed single-phase permanent magnet brushless DC motor.

Due to high efficiency, high power density and low cost, single-phase permanent magnet brushless DC motor has increasingly been used in industrial and domestic applications. This thesis focuses on the design and analysis of high-speed, single-phase, conventional and flux-switching permanent magnet brush less DC motors. This thesis presents a comparative study of conventional three-phase and single-phase permanent magnet brush less DC motors, which operate at 45,OOOrpm with I.lkW output power for the pump application, in terms of their machine design, drive system and electromagnetic performance. It is found that the single-phase permanent magnet brush less DC motor has a relatively lower drive system cost without significantly compromising the electromagnetic performance. Further, significant rotor eddy current loss exists in both motors. Hence, the analytical models are developed to predict the rotor eddy current loss which is resulted from the armature reaction field. By comparing with the 2D finite element method (FEM) predicted results, good agreement is obtained over the full speed range if the eddy current reaction field is taken into account. FEM is further employed to investigate open-circuit, armature and on-load rotor eddy current losses of the permanent magnet brushless DC motors. Particular emphasis is placed on the single-phase motor having an eccentric airgap with consideration for degree of airgap eccentricity, excitation current waveform, magnet segmentation, thickness and electrical conductivity of the retaining sleeve. The single-phase flux switching permanent magnet motor, which operates at 100,000rpm with 1.2kW output power for the automotive electrical turbo-charger application, is also investigated. Its operational principle is introduced and winding topologies are investigated. In addition, the chamfered rotor pole is optimised to improve the starting capability. In order to investigate the influence of significant end leakage-flux, a 3D lumped circuit magnetic model is developed to predict the back-EMF and the inductance and validated through experiment. This model is also employed to optimise the rotor pole width for increasing the motor power density and to investigate the relationship between the magnet dimensions and the motor end effect. Finally, the dynamic simulation models are developed to predict the dynamic electromagnetic performance and experimentally validated for a three-phase and a single-phase permanent magnet brush less DC motor, and a single-phase flux switching permanent magnet motor

Mathematical Models for the Design of Electrical Machines

This book is a comprehensive set of articles reflecting the latest advances and developments in mathematical modeling and the design of electrical machines for different applications. The main models discussed are based on the: i) Maxwell–Fourier method (i.e., the formal resolution of Maxwell’s equations by using the separation of variables method and the Fourier’s series in 2-D or 3-D with a quasi-Cartesian or polar coordinate system); ii) electrical, thermal and magnetic equivalent circuit; iii) hybrid model. In these different papers, the numerical method and the experimental tests have been used as comparisons or validations

Two-Steps Slotting Method in Magnet Edge of PMG for Wind Energy Harvesting

This paper focuses on the study of how to decrease the value of the cogging torque in an Inset Permanen Magnet Generator. The permanent-magnet generator of an integral slot number with 24 slots and 8 poles was selected and investigated for the purposes of this study. The cogging torque of the permanent-magnet generator can be minimized by combining two slottings in the magnet edge with a gradually inclined surface end. The electromagnetic simulations and analysis of the permanent-magnet generator studied were performed using numerical analysis by means of FEMM 4.2. To obtain a faster computation, FEMM 4.2 was combined with LUA 4.0 programming. Using FEMM 4.2, it was found that by applying two-step slotting in the magnet edge combined with a gradually inclined surface end, the cogging torque of the permanent-magnet generator selected can effectively reduce the cogging torque of the machine by approximately 98.14% compared against the initial magnet model. It can be concluded that the integration of the two-step slotting in the magnet edge and the gradually inclined surface end can effectively reduce the cogging torque of the permanent-magnet generator machine. Furthermore, decreases in the density of the magnetic flux in the core of the permanent-magnet generator can also be found

Design of High Efficiency Brushless Permanent Magnet Machines and Driver System

The dissertation is concerned with the design of high-efficiency permanent magnet synchronous machinery and the control system. The dissertation first talks about the basic concept of the permanent magnet synchronous motor (PMSM) design and the mathematics design model of the advanced design method. The advantage of the design method is that it can increase the high load capacity at no cost of increasing the total machine size. After that, the control method of the PMSM and Permanent magnet synchronous generator (PMSG) is introduced. The design, simulation, and test of a permanent magnet brushless DC (BLDC) motor for electric impact wrench and new mechanical structure are first presented based on the design method. Finite element analysis based on the Maxwell 2D is built to optimize the design and the control board is designed using Altium Designer. Both the motor and control board have been fabricated and tested to verify the design. The electrical and mechanical design are combined, and it provides an analytical IPMBLDC design method and an innovative and reasonable mechanical dynamical calculation method for the impact wrench system, which can be used in whole system design of other functional electric tools. A 2kw high-efficiency alternator system and its control board system are also designed, analyzed and fabricated applying to the truck auxiliary power unit (APU). The alternator system has two stages. The first stage is that the alternator three-phase outputs are connected to the three-phase active rectifier to get 48V DC. An advanced Sliding Mode Observer (SMO) is used to get an alternator position. The buck is used for the second stage to get 14V DC output. The whole system efficiency is much higher than the traditional system using induction motor

Magnetic Field and Force Calculation in Linear Permanent-Magnet Synchronous Machines Accounting for Longitudinal End Effect

© 1982-2012 IEEE. This paper presents an improved analytical method for predicting the magnetic field and forces in linear permanent-magnet synchronous machines (LPMSMs) accounting for both the primary end effect and secondary end effect. So far, the magnetic field calculation of LPMSM in most studies is conducted in Cartesian coordinate, whereas the end effect is neglected by applying periodic boundary. In this paper, to implement the analytical model, a polar presentation of the machine geometry is proposed and the subdomain method is applied to calculate the magnetic field. Then, according to the developed model, the tangential thrust and normal forces are calculated based on the Maxwell stress theory. Numerical results are subsequently obtained by finite-element method and employed to validate the analytical model. Finally, an LPMSM prototype is manufactured and experiments are conducted. The results show that the developed analytical model has high accuracy for predicting the magnetic field and forces