Sharif Digital Repository

Direct-drive permanent magnet synchronous generators enjoy numerous advantages including improved reliability, low maintenance, long life, and developed performance characteristics. In recent years, many researchers have worked on these generators to enhance their performance, especially for the wind turbine application. The focus of this paper is on the development of a step-by-step method for the design of a permanent magnet synchronous generator. Then, the winding function method is used to model the generator and calculate its output characteristics analytically. The analytical results of the designed generator are validated using Finite Element Analysis (FEA) and it is demonstrated that... 

Direct drive motors have the excellent ability for precision position control due to their direct connection to load and elimination of the gearbox and pulley backlash. Among the direct drive motors, permanent NdFeB magnet synchronous motors (PMSMs) are the best choice for control systems due to their high efficiency, high power density, good dynamic behaviour, and excellent controllability. This study deals with the design, analysis, and fabrication of a direct drive PMSM for precision position control. To reach this aim, the designed motor should have very low cogging torque and torque ripple to avoid the motor deviation at the target point. To achieve these purposes, at first, a suitable... 

In recent years axial flux permanent magnet (AFPM) machines have found industrial applications because of such characteristics as high power density, compact structure and disc-like shape. Like other electrical machines, prediction of flux density distribution in the air gap of AFPM is essential. In this paper, an analytical method for calculation of air gap flux density caused by armature reaction is presented. The solution is based on Maxwell's equations. Separation of variables method is applied to field equations and 2D distribution of magnetic flux density in the air gap calculated in term of Fourier series. The 2-D distribution of three-phase armature winding is modeled exactly.... 

High frequency (HF) carrier injection schemes can estimate rotor position in a wide speed range. In these methods, first a HF voltage is injected to stator windings and then the corresponding HF current is exploited to estimate the position of rotor using a closed loop tracking observer. The tracking observer is capable to track rotor saliency with no steady state error. However when the motor starts to move or whenever the rotor speed changes a transient error appears. In this paper a new solution is proposed to compensate the transient error in estimation of rotor position  

Modular linear doubly salient permanent magnet motors are well adapted to linear propulsion systems because of their distinct characteristics, such as high efficiency and power density, reduced maintenance and initial cost, low noise and permanent magnet (PM) leakage flux, and fault tolerance capability. However, such motors suffer from high cogging thrust. In this study, various techniques based on previously proposed methods for PM machines are applied on the studied motor and evaluated by using non-linear three-dimensional time-stepping finite element analysis; three novel, optimised techniques are then presented. The techniques presented are based on the minimisation of the variation in... 

Reo is a connector language for the exogenous composition and orchestration of components in a software system. An operational semantics of Reo connectors can be given in terms of Büchi automata over a suitable alphabet of records, capturing both synchronization and context dependency requirements. In this paper, we define an action based linear time temporal logic for expressing properties of Reo connectors. Formulas can be synthesized into Büchi automata representing Reo connectors, thus leading to an automata based model checking algorithm. By generalizing standard automata based model checking algorithms for linear time temporal logic, we give an efficient on-the-fly algorithm for the... 

The binary powder blending technique (BPBT) was employed in production of anisotropic (Nd, MM)2(Fe, Co, Ni)14B-type sintered magnets (MM: denotes a Misch-metal). The composition of the master alloy was close to the stoichiometric Nd2Fe14B compound, while the sintering aid (SA) had a composition of MM38.1Co46.4Ni15.4. The magnets were made by blending different ratios of the master alloy and the sintering aid. The corrosion behavior of these magnets was compared with that of the Nd17Fe75B8 base alloy by potentiodynamic polarization measurements in H2SO4 solution. By decreasing the amount of Nd-rich grain boundary phases and substitution of some Fe atoms by Co and Ni, an improvement in the... 

The study reported in this paper deals with the problem of developing a controller with tolerance to current sensor faults. To achieve this goal, two control strategies are considered. In the first method, field oriented control and a developed observer are used in case of no fault. The second approach is concerned with fault tolerant strategy based on an observer for faulty conditions. Current sensors failures are detected and the current will be estimated successfully in order to allow continuous operation of the vector control. Based on the motor model, currents can be estimated using a nonlinear observer. A decoupling current vector control strategy is developed to ensure high... 

Although permanent magnet synchronous motors (PMSMs) are inherently of high efficiency, their efficiency is enormously dependent on their control strategy. The purpose of this paper is to improve the efficiency of PMSMs under a direct torque control (DTC) method. The main idea behind the proposed method is to predict a required small change of the statorflux amplitude at each sampling period to reduce the machine electrical loss before the change is applied. Accordingly, at every sampling time, a voltage vector is predicted and applied to the machine to change the flux amplitude in a xvay that the electrical loss decreases. The results of simulation show significant improvement in the... 

In the presented paper, an analytical model is developed for calculation of the air gap magnetic flux density in the axial-flux surface-mounted PM machines. The slotting effect is taken into account in the air gap magnetic flux distribution, accurately. The main novelty of this study is replacing the stator teeth by some surface currents at the border of the removed stator teeth. The uniqueness theorem is applied to find the surface currents. The two-dimensional (2D) field solution in the slotless machine is solved easily by separation of variables method. The multi-slice quasi-3D method is applied for taking 3D nature of field distribution into account. In addition, the back-EMF, armature... 

In this study, a novel prototype high-efficiency miniature pump that uses magnetic properties of a ferrofluid in both pumping and valving mechanisms is presented. The minichannel consisting of a cylindrical pumping chamber, a check valve, an inlet and an outlet, comprises six bonded layers of PMMA. A cylindrical permanent magnet that is placed inside the chamber and is externally actuated by a motorized off-center permanent magnet, functions as a revolving piston which sweeps the perimeter of the cylinder. Ferrofluid is used to cover the gaps between the magnetic piston and the channel walls, also serves as a separating plug between the inlet and the outlet of the chamber preventing... 

In this paper an analytical approach is proposed to formulate the proper set of phase currents reference to ride the permanent magnet synchronous generator (PMSG)-based wind turbine (WT) through faults properly, regardless of fault type. Hence, the WT is forced to inject required reactive current by grid codes together with active power injection, to help support grid frequency during faults and reduce the energy storage system (ESS) power rating. Moreover, it prevents pulsating active power injection to the grid. During grid faults, the DC-link voltage is controlled by the ESS instead of the grid-side converter (GSC) and the GSC controller applies calculated reference currents. The ESS... 

Control of Synchronous Motors at low speed has been the topic of several studies for the last years. Due to the lower amplitude of Back-EMF voltage in lower speed, it is inappropriate to merely rely on induced voltages for position estimation. In this paper, a new double carrier PWM modulation is presented in which two carrier frequencies are utilized for two legs of the inverter. This proposed method rectify the need of powerful processors which decreases the cost of the electric drive system. Employing a non-linear control system and an automatic gain control, ensures the sensorless control of the motor for a wide range of speed. © 2019 IEEE  

Resolvers as position sensors need a high frequency AC excitation voltage, and the induced voltage in their 2-phase perpendicular windings are amplitude modulated (AM) signals. For calculating the position, it is required to demodulated the output signals and calculate their envelopes. Then, inverse tangent can be used for calculating the position. Despite the advantages of resolvers, there are some drawbacks in their application. Calculating the envelopes is always one of the deep concerns in using resolvers. Furthermore, due to low-amplitude of the excitation flux, the performance of the resolvers is strongly affected by electromagnetic interference by the stray fields of motor and brake.... 

In this paper, a new scheme for position control of a mechanical load driven by a permanent magnet DC motor and a gearbox is presented. The gearbox is assumed to have some amount of backlash. The paper derives a model for the backlash nonlinear behavior. It then proposes a new control structure composed of feedback and feed forward control systems. The feedback control system is designed based on zero backlash. The feed forward part is employed to minimize the backlash effects. The new method is evaluated via simulations in MATLAB/SEVIULINK environment. Simulations results are provided to show the response of the proposed technique to various input references. © 2006 IEEE  

The main purpose of this paper is to minimize the loss while reducing the flux and torque ripples in permanent magnet synchronous motors (PMSMs) under direct torque control (DTC). Offline method is used to minimize the loss and obtain the optimal flux. To reduce the amount of computation, the optimal flux table is produced according to the conditions in which the machine works. To reduce the flux and torque ripples and to control the switching frequency, SVM-DTC method is applied. Simulation results depict a noticeable increase in efficiency of the motor and a reduction in flux and torque ripples  

This paper proposes a novel design of the variable reluctance permanent magnet (VRPM) resolvers. It utilizes a slotless stator to reduce the resolver volume. The proposed design overcomes the complex structure of windings by replacing them with magnetic flux measurement units (MFMU). The new design eliminates the computationally-expensive demodulation process of output signals by relying on none-modulated signals. An analytical model based on the nonlinear magnetic equivalent circuit (MEC) method is used to extract the output signals of the proposed resolver design. The accuracy of applied analytical model is verified against the time-stepping finite-element method (TSFEM). An optimization... 

An analytical solution for obtaining steady-state eddy-current-based force on a levitated permanent magnet above a plate with linear conductivity in the field of an electromagnet having cylindrical symmetry is presented in this paper. In literature, the force due to eddy current in this levitation system have been used for high precision positioning of a levitated permanent magnet without providing an explicit analytical model. In this system, a change in the coil's current and also the motion of the levitated permanent magnet in 3-D space generate eddy current in the plate. A novel explicit solution for obtaining damping forces due to these eddy currents is obtained as a function of... 

Since any error in the rotor angle caused by the resolver affects the entire permanent magnet synchronous motor (PMSM) control drive system, it is necessary to investigate its effect on mechanical vibrations. Torsional vibration is accordingly considered in the following study. Thereby, first, the effect of resolver errors on the harmonic content of motor current and, subsequently, torque ripple (TR) was investigated. Then, dynamical modeling is done for the generator-motor-resolver set to get the mechanical frequency response (FR) resulting from the resolver errors. Based on the above modeling, the dynamic equations (DEQs) of the system were derived, and the mechanical characteristics of... 

High-efficiency Permanent Magnet Synchronous Motors (PMSMs) are widely used in industry. Subsequently, resolvers' employment is increasing in the drive of PMSMs. Measuring the rotor angle using a resolver needs a costly Resolver to Digital Converter (RDC). Therefore, a low-cost analog RDC is designed against the conventional Angle Tracking Observers (ATOs) in the following study. The designed RDC has satisfactory accuracy, simplicity, and enduring against excitation frequency. Firstly, an overview of the resolver is shown, and subsequently, the circuit of the designed RC is described thoroughly. Ultimately, the simulations' outcomes are displayed, and comparing our design with others...