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In order to increase the torque performance of the conventional surface-inset Halbach machines, a surface-inset Halbach machine with trapezoidal mixed grade magnets is proposed and investigated. Based on a layered and linear superposition method, the air-gap magnetic fields are analytically obtained from solution of matrix equations. In addition, the dimensions of mid-magnet and the remanences of Halbach magnets are analytically optimized. In order to show its advantages, the optimized performances of the proposed machine model are compared with those of the conventional Halbach and trapezoidal equal grade Halbach machines. The prediction shows that the proposed optimized machine model has the largest electromagnetic torque and the lowest torque ripple. The demagnetization performance is also investigated. Finally, the finite element analysis (FEA) results verify the analytical predictions. [ABSTRACT FROM AUTHOR]

A surface-inset machine model having harmonics injected into Halbach magnet shape with salient iron and an analytical modeling method have been proposed. For the proposed model, considering the magnet outer surface shape with sinusoidal and third harmonic injection, after the analytically derived magnetic fields by solving the constructed matrix equations, the optimal third harmonic amplitude to fundamental amplitude ratio and the optimal magnetization angle have been determined from the field functions. The electromagnetic performances have been predicted and compared with other two surface-inset models. The comparison results show that the proposed optimized model has the largest electromagnetic torque with the same magnet consumption. Finally, the finite element analysis predictions have been provided for verification the analytical performances. [ABSTRACT FROM AUTHOR]

General analytical optimization model has been proposed for brushless surface-inset permanent magnet (PM) machines having even-/odd-segment Halbach array. The air-gap magnetic fields have been analytically obtained by solving the matrix equations of subdomain model. For the maximum air-gap magnetic field, electromotive force (EMF), and electromagnetic torque of the even-/odd-segment Halbach, the optimal pole-arc ratio of each magnet segment, and/or the optimal magnetization angle of each side-magnet have been analytically determined. Taking 16-pole/21-slot surface-inset machines with three-/four-segment Halbach magnet array as examples, the predicted results show that the globally optimized electromagnetic torques of Halbach surface-inset machine are significantly enhanced. Analytically predicted results have been validated by a finite-element (FE) technique. [ABSTRACT FROM AUTHOR]

In this article, a linear analytical model has been proposed for solving and optimizing the magnetic fields in brushless permanent magnet (PM) electrical machines having eccentric surface-inset magnets. Using a subdomain model with an equivalently split method, on the basis of a linear superposition, the magnetic fields have been analytically obtained and optimized in the PM machines having the assumed linear materials with proposed eccentric surface-inset Halbach magnets. Moreover, the induced phase electromotive force and instantaneous electromagnetic torque have been also derived. Compared with the conventional and concentric Halbach surface-inset models, the optimized eccentric Halbach model exhibits good performances with the equal magnet volume. The prediction results of the linear analytical model are coincided with finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

The split ratio, defined as the outer radius ratio of the magnet to stator, has been investigated and optimized in surface-mounted permanent magnet (PM) machines having conventional/novel pieced Halbach magnet array. The air-gap magnetic field in PM machine with novel pieced Halbach magnet has been analytically obtained. The influences of split ratio and magnet arc length ratio on the torque density have been separately and analytically investigated for the machines with conventional pieced Halbach magnet array. In order to achieve the maximal torque density in the conventional pieced Halbach magnetized machines, the optimum split ratio and/or pole arc ratio have been obtained. In addition, the influences of one or both of the split ratio and magnetization angle on the torque density have been analytically investigated for the machines with novel pieced Halbach magnet array. In order to achieve the maximal torque density in the novel pieced Halbach magnetized machines, the optimum split ratio and/or magnetization angle have been determined. Finally, the linear analytical predictions have been compared with linear and nonlinear finite element analyses. [ABSTRACT FROM AUTHOR]

In this article, two kinds of dual-layer segmented Halbach arrays have been proposed for permanent-magnet (PM) brushless machines. The analytical expressions of magnetic fields due to the inner-/outer-layer Halbach magnets have been separately obtained. For the maximal flux density in the air gap, the optimal magnet segment radian ratios or magnetization angles for each dual-layer Halbach array have been analytically determined separately. The induced back electromotive force and electromagnetic torque have been analytically obtained. The prediction results show that the optimized electromagnetic performances for each double-layer segmented Halbach array with different slot and pole combinations are better than those for the corresponding single-layer one. The proposed analytical model can also be applied for optimizing the multi-layer segmented Halbach array. The analytical prediction results of a PM machine with the double-layer segmented Halbach array have been compared with those obtained by a finite-element method. [ABSTRACT FROM AUTHOR]

Although star-delta winding can improve the efficiency of motors because of a higher fundamental winding coefficient and lower harmonic winding coefficient. The requirement of turns ratio is very strict. If the turns ratio is not ideal, the core loss of the motor cannot be reduced, thus the efficiency will not be improved. In this paper, a design method for converting a star-delta winding of stator in small- and medium-sized motor into the concentric single-double layer star-delta (CSDLSD) winding is introduced and compared with a traditional delta winding and a star-delta winding. Besides, a method is provided to calculate the winding coefficients of the motors with CSDLSD winding according to the turns number per slot. Harmonic component of magnetic flux density in stator tooth and yoke is consequently reduced, combined with partial core loss calculation method, the core loss is decreased. In addition, the core loss in three-phase induction machines equipped with front three winding types is also been estimated and analyzed. To check the analysis validity, two-dimension (2-D) Finite element method (FEM) is applied on three cage induction motors equipped with different winding types but the same prototypes. [ABSTRACT FROM AUTHOR]

Nowadays, studies of the control of brushless dc motor (BLDCM) are mainly focused on motor state. However, it may also work in generator state. Current hysteresis control (CHC) is very suitable for the motor control, because it can directly control current. In this paper, a multimode CHC for BLDCM in motor and generator state is presented. It can not only complete commutation successfully but also reduce commutation torque ripple. Moreover, a novel transition control method based on the background of CHC with fast response is proposed to carry out commutation and the transition processes simultaneously. Finally, the effectiveness and insensitivity to the parameters of the proposed control algorithm are verified by experiments. [ABSTRACT FROM AUTHOR]

An active power filter (APF) plays an important role in compensating the harmonic component of a nonlinear load current. In this paper, deadbeat control (DBC), which has high control performance and fast dynamic response, is used as a current controller for an APF. An improved DBC (Imp_DBC) is introduced to suppress the adverse effect of the current sampling error and to enhance the interference rejection capability of the control system. The characteristics of the conventional DBC and Imp_DBC are analyzed using transfer functions in the discrete-time domain. The robustness of the system is improved with the inductance variation. Specifically, aiming at the dramatic change of the harmonic component of the nonlinear load current, a current-tracking error compensation method is proposed. The phenomena of the upper co-nvex and lower concave in grid current are eliminated. Finally, the experimental setup of three-phase three-line APF is built, and the effectiveness of this method is verified by experiments. [ABSTRACT FROM PUBLISHER]