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The multiobjective design optimization of brushless permanent magnet motor (BLPMM) solved by genetic algorithm (GA) and 3D equivalent magnetic circuit network method is described. The airgap length, teeth width and magnetization angle of permanent magnet (PM) are selected for the design variables respectively.

A permanent magnet of two layer magic rings driven by a motor is designed to produce a rotating magnetic field with tunable frequency a tunable magnetic flux density. In the design of a simple 3D computing method is adopted to do the optimization.

A superconducting permanent magnet system capable of generating the highest magnetic field of 3.15 T in the open space between the face-to-face magnetic poles containing the melt-processed RE-Ba-Cu-O bulk superconductors is described. The highest magnetic field obtained by the field cooling method operated at 5 T has reached 1.4 T on the right-hand side magnetic pole surface and 0.9 T at the center of the open space of 34 mm between the magnetic poles.

This paper derives the relative air-gap-specific permeance distribution function by Schwarz-Christoffel Transformation, considering the effect of slotting. Neglecting the iron saturation, and employing the analytical algorithm for partial differential equations, efficient and effective analytical calculations of no-load air-gap magnetic field distribution, armature field distribution, and phase electromotive force (EMF), are demonstrated, considering the stator slots. Subsequently, based on the main circuit topology of a brushless dc motor (BLDCM), the field-circuit coupling model is constructed for the motor, and then the phase current waveforms and load air-gap magnetic field distribution at any time are determined. Consequently, the instantaneous electromagnetic torque is computed, which underpins the quantitative analysis of torque ripple and the pulsation induced by commutation. Hence, the present work paves the way to precise prediction of the motor's performance and acoustic noise. It is a powerful tool for the design of surface permanent magnet brushless dc motors. Index Terms--Air gaps, brushless machines, electromagnetic fields, partial differential equation, permanent magnet motors, simulation.

This paper presents an analytical method of modeling permanent magnet (PM) motors. The model is dependent only on geometrical and materials data which makes it suitable for insertion into design programs, avoiding long finite element analysis (FEA) calculations. The modeling procedure is based on the calculation of the air gap field density waveform at every time instant. The waveform is the solution of the Laplacian/quasi -Poissonian field equations in polar coordinates in the air gap and takes into account slotting. The model allows the rated performance calculation but also such effects as cogging torque, ripple torque, back-emf form prediction, some of which are neglected in commonly used analytical models. Index Terms--Analytical models, finite element analysis, permanent magnet synchronous motor design.

A development feasibility study has been conducted for magnetizing the rotor of a 1.7-MVA, 20-r/min, permanent magnets (PMs) excited synchronous wind turbine generator. Various technical problem areas and their likely influence on the overall design concept, are reviewed. Thus, some particularly important problems are identified: KERI's conventional facilities ensure sufficient energy for magnetizing, pair by pair, of all the PMs of the rotor. A rotor and inductor optimal arrangement for a magnetizing system's configuration is required in order to avoid a wrong, strong magnetization of the neighboring poles. It is also needed to take into account the mechanical strength of the magnetizing inductor winding to withstand electromagnetic forces. This paper presents the result of the analytical calculation of such a specialized inductor and a PC Spice-based software simulation of the magnetizer circuit; finally, a transient finite element method (FEM) simulation of the inductors connected by the external electric circuit had been done. All three methods confirm the possibility for a successful magnetization, pair by pair, of all rotor poles. Design proposals are detailed and conclusions are relevant for magnetizing large rotors with surface-mounted PMs in general. Index Terms--Magnetizing inductors, rare-earth PMs, surface mounted PM's rotors.

This paper proposes and implements a novel rotor position sensorless technique for PM ac motor drives, which allows acceleration from standstill and can operate under various practical operating conditions including transient speed changes. The technique developed here relies on the measurement of the phase voltages and currents of the motor. It uses the incremental values of flux linkage, and the back-EMF functions to estimate incremental rotor position. Using a phase-locked loop (PLL) algorithm, an internal closed-loop correction algorithm can correct rotor position estimation drift, which may be due to the motor parameter variations or measurement inaccuracies. The method is implemented in closed-loop using a digital signal processor (DSP), and details of the implementation are provided in the paper. To demonstrate accuracy, robustness and reliability of the position estimation scheme, the paper presents a number of real-time experimental results, including dynamic operating conditions. Index Terms--DSP based motor control, permanent magnet motors, position estimation, sensorless operation.

This paper deals with the optimization of the performances of permanent magnet synchronous couplings. A nonlinear optimization process is used in association with a seminumerical method based on magnetic pole theory. This approach allows to find efficient and original structures of coupling. These unconventional structures are advantageous in terms of pull-out torque, inertia, and magnet volume. Index Terms--Magnetic coupling, optimization, permanent magnet.

Among several niching methods, the restricted competition selection (RCS) method searches almost all the location of multiple solutions in the search space. This paper proposes a neo-niching method using the RCS method combined with pattern search method to reduce the calculation time. Through application to the numerical examples and optimal design of interior permanent magnet synchronous motor, it is verified that the proposed method searches the peaks fast and is appropriate for the design of electric machines. Index Terms--Genetic algorithm, interior permanent magnet synchronous motor, niching method, pattern search method, restricted competition selection.

A general analytical technique predicts the magnetic field distribution in brushless permanent magnet machines equipped with surface-mounted magnets. It accounts for the effects of both the magnets and the stator windings. The technique is based on two-dimensional models in polar coordinates and solves the governing Laplacian/quasi-Poissonian field equations in the airgap/magnet regions without any assumption regarding the relative recoil permeability of the magnets. The analysis works for both internal and external rotor motor topologies, and either radial or parallel magnetized magnets, as well as for overlapping and nonoverlapping stator windings. The paper validates results of the analytical models by finite-element analyses, for both slotless and slotted motors. Index Terms--Electrical machines, magnetic field, permanent magnet.

This paper deals with the study of the cogging torque of a small two phases axial flux permanent magnet synchronous machine (AFPMSM). Analytical models of airgap permeance and of magneto-motive force (MMF) are proposed. In order to validate the developed analytical model, the obtained results are compared with that of a three dimensional (3D) finite element method (FEM) simulation of the motor in a special case. The cogging torque due to the permanent magnets (PM) is then estimated based upon the virtual works method. The influence of both magnetization distribution and shape of stator auxiliary poles on the cogging torque is evaluated by means of the developed analytical model. Index Terms--Airgap permeance, axial flux permanent magnet synchronous motor, cogging torque, magnetization distribution.

The affects of mixing samarium and gadolinium on the crystallographic and magnetic properties of [Sm.sub.y][Gd.sub.2-y][Fe.sub.17-x][Si.sub.x] (x = 0, 0.33, 0.67, 1, 2, 3 and y = 0.33, 0.67, 1, 1.33, 1.67) intermetallics have been investigated using x-ray diffraction techniques and SQUID and Vibrating Sample Magnetometer measurements. The [Sm.sub.y][Gd.sub.2-y][Fe.sub.17-x][Si.sub.x] samples, except for the sample with x = 3 and y = 1, crystallized in the rhombohedral [Th.sub.2][Zn.sub.17]-structure with little or no impurities. For a given silicon content (fixed x), the unit cell volume and saturation magnetization increases at the approximate average rates of 4 [[Angstrom].sup.3] and 24 emu/g per substituted samarium atom, respectively. The Curie temperature ([T.sub.c]) for a given silicon content, on the other hand, decreases with increasing samarium content at an average rate of 30-40 [degrees] C per substitution. The affect of substituting silicon for iron on [T.sub.c] is more marked, with [T.sub.c] increasing at a rate of almost 70 [degrees] C per silicon substitution at low silicon concentrations. For a given samarium content (fixed y), the unit cell volume and saturation magnetization decreases at approximate rates of 5 [[Angstrom].sup.3] and 9 emu/g per substituted silicon atom, respectively. X-ray diffraction studies of magnetically aligned powders indicate that the easy direction of magnetization is in the basal plane of the rhomhohedral unit cell. All of the samples were found to have very little magnetic anisotropy with no apparent dependence of the anisotropy on the samarium or silicon content. The 340 [degrees] C [T.sub.c] measured for the SmGd[Fe.sub.14][Si.sub.3] sample is unusually high for these intermetallics and its XRD pattern is indicative of a phase other than the rhombohedral [Th.sub.2][Zn.sub.17]-type. Index Terms--Permanent magnets, rare earth magnets, transition metals.

Magnetic measurement and cross-sectional Magnetic Force Microscopy images were obtained from [Nd.sub.2][Fe.sub.14]B ribbons melt-quenched at a circumferential wheel speed of 10 m/sec in three different atmospheres: 1 atm Ar, 1 atm He and 1/3 atm He. The striking effects of the quenching gas type upon the microstructure is correlated with room-temperature demagnetization curves that confirm the presence of multiple, yet discontinuous, grain size zones. A model for the rapid solidification of [Nd.sub.2][Fe.sub.14]B based on consideration of recalescence relative to the peritectic temperature is invoked to explain the experimental results. The recalescence causes breakup of the [Nd.sub.2] [Fe.sub.14] B dendrites formed during the first phase of solidification and results in a layered structure within the ribbon possessing distinct transition regions where the solidification front temperature crosses the peritectic temperature. Index Terms--Magnetic force microscopy, microstructure, permanent magnet, rapid solidification.

In the paper the exact tracking of permanent magnet AC servodrives with dynamic field-weakening is presented. The analytical solution given in the form of a reference dynamic model of the direct axis current and corresponding transition conditions is derived from the inverse motor dynamics. The presented solution guarantees the control voltage to remain within the constraint during steady states and transients, and also preserves exact tracking of the prescribed mechanical trajectories in the field weakening mode. The suggested method is independent of the implemented control structure. Analytical results have been confirmed by the experiments.

In this paper, magnetic field analysis of a new doubly salient permanent magnet (DSPM) motor is carried out based on finite element method (FEM). Hence, the corresponding static characteristics, including PM flux linkage, self-inductance, mutual inductance, and static torque are deduced (the interaction between the PM field and armature field are taken into account). New methods for measuring the motor inductance are also proposed. The theoretical analysis is verified by experimental results. Index Terms--Doubly salient motors, finite element methods, inductance, inductance measurement, permanent magnet machines, static characteristics, torque.

This paper presents a new speed and position sensorless control method of permanent magnet synchronous motors based on the sliding mode observer. The sliding mode observer structure and its design method are described. Also, Lyapunov functions are chosen for determining the adaptive law for the speed and the stator resistance estimator. The effectiveness of the proposed observer is confirmed by the experimental results. Index Terms--PMSM (Permanent magnet synchronous motor), sensorless control, sliding mode control, stator resistance estimation.

A pulsed magnetometer is useful for testing high-performance magnets because it can produce high magnetic fields that are sufficient to magnetically saturate them. We installed a cryostat in a pulsed magnetometer and tested several prevailing permanent magnets at low temperatures. The measurements were successfully performed down to 4.2K, and it was shown that a pulsed magnetometer is useful for low-temperature measurement on permanent magnets as well as room-temperature measurements. Index Terms--High-performance magnets, magnetic properties, magnetization curve, NdFeB, pulsed magnetometer, SmCo.

A finite element approach is used to calculate the influence of different grain boundary phases on the reversal process of sintered Nd-Fe-B magnets. To calculate equilibrium states of the magnetic polarization the total Gibbs' free energy is minimized with a quasi-Newton conjugate gradient method. It was found that the grain boundary phases influence the coercive field significantly. For a perfect microstructure the numerical results agree well with the Stoner-Wohlfarth theory. A reduction of the magnetocrystalline anisotropy near grain boundaries leads to a linear decrease of the coercive field. In contrast to the Stoner-Wohlfarth theory the coercive field will decrease with increasing alignment of the easy axies if the anisotropy is reduced near grain boundaries. The finite element simulations confirm the experimental results that nonmagnetic Nd-rich phases at grain boundary junctions significantly increase the coercive field. Index Terms--Finite element method, grain boundary phases, NdFeB-magnets, numerical micromagnetics.

This paper presents the analysis, design and performance of an axial flux permanent magnet (AFPM) machine with an ironless stator. The topology has a large airgap length and zero core losses. A machine model that uses both lumped magnetic circuit and finite element method results is used with a multi-variable optimization algorithm to obtain the optimum machine dimensions. Special attention is given to the magnet interpolar gap to ensure a certain minimum plateau width for brushless DC operation. The large airgap length allows several approximations to be made that simplifies the machine model. A prototype machine is constructed and evaluated. Measured results of the armature reaction effect in the large airgap are given and discussed. Keywords--Axial flux, permanent magnet, ironless stator.