Rotor Permanent Magnet Brushless Research Articles

Torque optimization strategy for outer rotor permanent magnet brushless DC motor based on metamodel and CRITIC–TOPSIS method

Torque optimization strategy for outer rotor permanent magnet brushless DC motor based on metamodel and CRITIC–TOPSIS method

Radial basis function‐based Pareto optimization of an outer rotor brushless DC motor

AbstractThis paper presents the development of an optimization and modeling method for the objective functions of output power, efficiency and weight of an outer rotor permanent magnet brushless DC (BLDC) motor based on radial basis function (RBF) approximation technique. The proposed RBF‐based Pareto optimization method requires less knowledge about electric/magnetic formulas and can replace conventional optimizations based on these equations with higher accuracy. To apply the proposed optimization method, the initial design should be developed using such equations. Therefore, RBFs are used to model and predict engine behavior. To optimize the objective functions, we used a genetic algorithm optimization technique with nonlinear electric and magnetic constraints to find the Pareto front set. The design obtained by the proposed radial basis function Pareto optimization (RBFPO) method was finally verified by Ansoft Maxwell. The results of optimal design using the RBFPO method have higher output power and efficiency. Also, in addition to the advantage of a favorable accuracy, RBF‐based models are significantly faster than models available in simulation tools.

Efficiency Improvement of Permanent Magnet BLDC With Halbach Magnet Array for Drone

In this paper, the outer rotor permanent magnet brushless DC motor (BLDC) with halbach magnet array was studied to improve the power characteristics of BLDC for drones. First, the BLDC motor applied to the currently commercial drone was selected as the target model and improved design was carried out. Spec generation was carried out for target BLDC model and the base model was designed and manufactured. Based on the base model, am improved design was applied using the halbach mag-net array using Response Surface Method (RSM). Applying the halbach magnet array can reduce the leakage flux and improve the efficiency by reducing the iron loss of the motor. In addition, the design for reducing the weight of the motor was carried out using RSM. It was confirmed by Finite Element Analysis (FEA) that the power characteristics of the designed improved model improved compared to the target BLDC model.

Selected Rolling Bearing Fault Diagnostic Methods in Wheel Embedded Permanent Magnet Brushless Direct Current Motors

In recent years, the number of outer rotor permanent magnet brushless direct current (PM BLDC) motor drives has been intensively growing. Due to the specifics of drive operation, bearing faults are especially common, which results in motor stoppage. In a number of these types of motor applications, the monitoring and diagnostics of bearing conditions is relatively rare. This article presents the results of research aimed at searching for simple and simultaneously effective methods for assessing the condition of bearings that can be built into the drive control system. In the experimental research, four vibration signal processing methods were analysed with regards to the identification accuracy of fault symptoms in the geometric elements of bearings (characteristic frequencies). The results are presented for three cases of bearing faults and compared with a new bearing, they were obtained based on a vibration signal analysis using the classical fast Fourier transform (FFT), Fourier transform of signal absolute values, Fourier transform of an envelope signal obtained using the Hilbert transform, and the Fourier transform of a signal filtered with the Teager–Kaiser energy operator (TKEO).

Influence of static eccentricity on unbalanced magnetic force of external rotor permanent magnet brushless direct current motor used as In‐wheel motor

Here, analytical expressions of the unbalanced magnetic force (UMF)of the stator and the rotor under static eccentricity (SE) are deduced by using complex relative magnetic conductivity method and Maxwell stress tensor method. The frequency characteristics of the UMF are obtained. Further the influence of different eccentricity ratio on the UMF is researched. Then, an external rotor permanent magnet brushless direct current motor (PMBLDCM) with 46 poles and 51 slots used as an in-wheel motor is taken as an example to verify the frequency characteristics by finite element analysis (FEA). The research shows that the frequency characteristics of the UMF of the stator s related to electric frequency. The frequency characteristics of the UMF of the rotor are related to the power source frequency and the rotation frequency of the wheel. It does not introduce new frequency components when the motor SE occurs. As the SE ratio increases, the amplitude of the UMF increases. The UMF without eccentricity exists in all directions with the change of the time. However, as the eccentricity ratio increases, the direction of the UMF is closer to the eccentric direction.

Effects of static eccentricity on the no‐load back electromotive force of external rotor permanent magnet brushless DC motor used as in‐wheel motor

The no-load radial magnetic field and no-load back electromotive force (EMF) of external rotor permanent magnet brushless DC motor (PMBLDCM) are calculated by applying the correction coefficient of magnetic conductance here, taking into account the stator slotting and static eccentricity effects. An external rotor PMBLDCM with 51-slot/46-pole, used as in-wheel motor, is taken as an example, the analytical calculation results of the no-load back EMF are validated by the finite-element method and experiment. The influences of static eccentricity ratio on the no-load radial magnetic field and no-load back EMF are investigated based on the analytical model. The investigation shows that static eccentricity does not change the harmonic contents of no-load radial magnetic field, so it does not change the harmonic contents of three-phase no-load back EMFs. However, static eccentricity changes the space order of no-load radial magnetic field, resulting in the different total harmonic distortions of three-phase no-load back EMFs; in other words, the asymmetric distortions of three-phase no-load back EMFs are generated. The asymmetric distortions of three-phase no-load back EMFs are intensified with the increase in static eccentricity ratio.

Comparison of Two Magnetizing Fixture Designs to Achieve Radial Magnetization Profile for Isotropic-Bonded Neo Magnets

The requirement of stringent environment and fuel efficiency target on automotive demand the use of lighter, smaller and efficient motors. The advantages like higher magnetic properties than ferrite, near net shape magnet production, and no use of heavy rare earth elements makes the use of bonded neo magnet in an automotive accessory motors very attractive. The isotropic nature of bonded neo magnets offers a feasibility to obtain wide range of magnetization profiles. The magnetization of the magnet influences the air-gap flux distribution and hence the motor performance 1. The performance of permanent magnet motors using isotropic bonded neo magnet can be improved by optimizing the air-gap flux profile using magnetization. Based on the magnet circumference touching the motor air-gap and the desired magnetization profile, an appropriate magnetization fixture needs to be designed. In an external rotor permanent magnet brushless (PMBL) DC motor and brushed DC motors, the inner circumference of the magnet touches the airgap and hence the magnet is magnetized using an inner-only fixture which has magnetization coils next to the inner circumference of the magnet. When the radial magnetization is desired, a double sided magnetization can also be used to magnetize bonded neo ring magnets 2. The use of double sided magnetization helps in enhancing the motor performance 3. To ensure that the bonded neo magnet is fully saturated a minimum magnetizing field of around 3T is to be generated throughout the magnet thickness 4. Considering this required magnetizing field, a fixture each offering inneronly and inner-outer magnetization (double sided magnetization) is designed using Finite element analysis (FEA) to achieve the radial magnetization. The simulation based results on the performance comparison of two fixtures is summarized. Figure 1 shows the simulated mid airgap flux density when magnet is magnetized with inner-only and inner-outer magnetizing fixtures. From this figure it is observed that, compared to inner-only fixture, the inner-outer fixture results in flat topped radial wave shape of flux density. Both designed fixtures are fabricated and the measured performance is used to validate the simulation results. It is observed that the peak magnetizing current and the energy required to achieve the magnet saturation in an innerouter fixture is 19.8% and 26.5% less respectively compared to inner only fixture. The reduction in peak magnetizing current and magnetization energy requirement will lead to reduced thermal stress and improved fixture reliability. It will also help in reducing the magnetization cycle time due to better heat dissipation in inner-outer fixture. During magnetization of the magnet, the effectiveness of the inner-outer fixture depends highly on the alignment of the inner and outer magnetization coils. The alignment and hence the performance of the fixture is influenced by the fabrication tolerances 5. Even a small misalignment between the coils on either side of the magnet will result in flux waveform distortion and reduction in magnetic flux. Considering the manufacturing tolerances, the effect of the various misalignment angles between the inner and outer magnetization coils on the magnet flux is arrived at using the FEA based simulation. The magnetization result is also measured by creating various misalignments between the inner and outer magnetization coils in the fabricated inner-outer magnetization fixture. Table I gives the measured magnet flux integral for various misalignment angles. It is observed from Table I that the $\pm 2 ^{circ}$ mechanical misalignment between the coils will not result in significant change in magnet flux and higher misalignment angles will result in considerable reduction of flux per pole. It is also observed that the misalignment effect is symmetric about the aligned position and higher degree of misalignment causes drooping wave shape on one side and a hump on the other side in any given pole depending on the direction of misalignment.

Analytical Calculation of No-Load Magnetic Field of External Rotor Permanent Magnet Brushless Direct Current Motor Used as In-Wheel Motor of Electric Vehicle

An analytical method for calculating the no-load magnetic field of external rotor permanent magnet brushless direct current motor (PMBLDCM) used as in-wheel motor of electric vehicle in the stator static coordinate and the rotor motion coordinate is presented in this paper. First, the analytic formulas of slotless permanent magnetic field in both coordinate systems are derived, respectively. Then, the complex relative permeance of external rotor PMBLDCM in both coordinate systems is calculated. Finally, the analytical solution of the no-load magnetic field in both coordinate systems is derived by applying the magnetic potential multiplied by the complex relative permeance. In this paper, a 46-pole-51-slot external rotor PMBLDCM is taken as an example, and the accuracy of the proposed analytical model is verified by the finite-element results. Based on the analytical model, the influences of the stator slotting effect on the no-load magnetic field of the external rotor and the inner stator are analyzed. The spatial order characteristics and frequency characteristics of the no-load magnetic field of the external rotor PMBLDCM in both coordinate systems are revealed, respectively.

Analytical model for armature reaction of outer rotor brushless permanent magnet DC motor

This study presents an analytical model for calculating the armature reaction magnetic field of outer rotor permanent magnet brushless DC motor (PMBLDCM) in stator stationary coordinate system (SSCS) and rotor rotation coordinate system (RRCS). Firstly, an expression of armature reaction magnetic field of single-phase winding is deduced, without considering slotting effect. Afterwards, analytical expressions of armature reaction magnetic field in both SSCS and RRCS regardless of slotting effect are obtained using vector addition method. Then complex relative permeances of outer rotor BLPMDCM in SSCS and RRCS are analysed, respectively. Finally, analytical solutions of the armature reaction magnetic field in both SSCS and RRCS are derived, respectively, by multiplying the slotless armature reaction magnetic field and the complex relative magnetic permeance, the self- and mutual inductance are calculated by the armature reaction magnetic field. A 46-ploes-51-slots outer rotor BLPMDCM is set as an example, the accuracy of proposed analytical model is verified by the Finite Element Method. Based on this analytical model, the pattern of slotting effect on armature reaction of both outer rotor and internal stator are analysed, respectively, as well as spatial order characteristics and frequency characteristics of armature reaction for outer rotor PMBLDCM in SSCS and in RRCS.

Exterior Rotor Permanent Magnet Brushless Dc Motor through Numerical Method of the Electromagnetic for Torque Improvement

In this paper, Numerical method based Exterior Rotor Permanent Magnet Brushless Direct Current (ERPMBLDC) is proposed aiming to integrate its torque. The ERPMBLDC Machine construction and principle of operation will be designed using Finite Element Method Magnetic 4.2(FEMM4.2) software. Then the flux pattern distribution based on the numerical method of ERPMBLDC motor estimation derived. The proposed motor parameters such as flux pattern, phase angles for maximum torque and torque were analyzed and compared by simulation and by experimental results.

Numerical and Experimental Investigation of Heat Flow in Permanent Magnet Brushless DC Hub Motor

This paper investigates the heat dissipation in the hub motor of an electric two-wheeler using lumped parameter (LP), finite element (FE) and computational fluid dynamic (CFD) models. The motor uses external rotor permanent magnet brushless DC topology and nearly all of its losses are generated in the stator. The hub motor construction restricts the available conductive paths for heat dissipation from the stator to the ambient only through the shaft. In contrast to an internal rotor structure, where the stator winding losses are diffused via conduction, here convection plays a major role in loss dissipation. Therefore, a LP thermal model with improved convection modelling has been proposed to calculate the temperature of the components inside the hub motor. The developed model is validated with the FE thermal model and the test data. In addition, CFD tools has been used to accurately model the internal and the external flow as well as the convective heat transfer of the hub motor. Finally, an optimization study of the hub motor has been carried out using the CFD model to improve heat transfer from the stator.

Optimization of the permanent magnet brushless DC motor employing finite element method

PurposeThe purpose of this paper is to elaborate the algorithm and computer code for the structure optimization of the outer rotor permanent magnet brushless DC motor and to execute optimization of selected motor structure using the non‐deterministic procedure.Design/methodology/approachThe mathematical model of the device includes the electromagnetic field equations with the nonlinearity of the magnetic core taken into account. The numerical implementation is based on the finite element method and stepping procedure. The genetic algorithm has been applied for the optimization. The computer code has been elaborated.FindingsThe elaborated computer software has been applied for the optimization and design of BLDC motors. The elaborated algorithm has been tested and a good convergence has been attained.Originality/valueThe presented approach and computer software can be successfully applied to the design and optimization of different structure of BLDC motors.

Simulation of Outer Rotor Permanent Magnet Brushless DC Motor Using Finite Element Method for Torque Improvement

A method of simulation and modeling outer rotor permanent magnet brushless DC (ORPMBLDC) motor under dynamic conditions using finite element method by FEMM 4.2 software package is presented. In the proposed simulation, the torque developed at various positions of the rotor, under a complete cycle of excitation of the stator, is analysed. A novel method of sinusoidal excitation is proposed to enhance the overall torque development of ORPMBLDC motor.

Analytical Prediction of Optimal Split Ratio for Fractional-Slot External Rotor PM Brushless Machines

The split ratio is one of the most important design parameters for permanent-magnet (PM) brushless machines. It has been optimized for maximum torque density with both internal rotor and tubular PM brushless machines in existing papers. This paper proposes an analytical model to determine the optimal split ratio for external rotor PM brushless machine having nonoverlapping winding. The influence of winding factor, tooth tip, and end winding on the split ratio is considered. The theoretical analyses are verified by finite element analysis and validated with experimental measurement.

Field‐circuit simulation of the dynamics of the outer rotor permanent magnet brushless DC motor

PurposeThe purpose of this paper is to elaborate a mathematical model of dynamic operation of the permanent magnet brushless DC (BLDC) motor with outer rotor and investigate the influence of magnets width on the dynamic parameters.Design/methodology/approachThe mathematical model of the devices includes: the equation of the electromagnetic field, the electric circuit equations and equation of mechanical motion. In elaborated algorithm, all these equations are coupled – therefore they are solved simultaneously. The numerical implementation is based on finite element method and step‐by‐step algorithm. The non‐linear‐coupled field‐circuit equations have been solved by using the Newton‐Raphson algorithm. The computer code for dynamics simulation of the machine has been developed.FindingsThe elaborated algorithm and the computer code have been applied for the 2D simulation of BLDC motor dynamics. The algorithm has a good convergence and its usefulness was proved. Various results of the analysis are presented and discussed.Originality/valueThe presented approach and computer code can be successfully applied to the design and optimization of different structure of the BLDC motors.