Review of Field Weakening Control Strategies of Permanent Magnet Synchronous Motors

Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the speed range under finite DC-bus voltage,extensive research on field weakening(FW)control strategies has been conducted.This paper summarizes the major FW control strategies of PMSMs,which are categorized into calculation-based methods,voltage closed-loop control methods,and model predictive control related methods.The existing strategies are analyzed and compared according to performance,robustness,and execution difficulty,which can facilitate the implementation of FW control.

Static characteristics of a novel flux-switching permanent magnet linear motor

A novel flux-switching permanent magnet linear motor（FSPMLM） is proposed for linear direct driving machine tools.First,the two-and three-dimensional topological configuration of the proposed motor is presented;the basic operational principle of the FSPMLM is introduced;and the magnetic fields at the two typical conditions of no-load are analyzed.Secondly,the FSPMLM is analyzed by the two-dimensional finite element method（FEM） to investigate the static electromagnetic characteristics such as flux-linkage,back EMF（electromotive force） and inductance performances.The cogging forces of two kinds of FSPMLMs with different shaped cores are analyzed and compared,and the results show that the cogging force is significantly reduced by using the E-shaped cores.Additionally,based on the co-energy method,the thrust equation is derived and verified by the simulation results obtained by the FEM.Finally,an experimental prototype is used to test the characteristics under open circuit and load conditions.The simulation and experimental results indicate that the proposed motor has advantages of a sinusoidal back-EMF waveform,a small cogging effect and a high thrust density,and it is suitable for the application of linear direct driving machine tools.

Optimization Design and Analysis of a Hybrid Permanent Magnet Flux-Switching Motor with Compound Rotor Configuration

This paper proposes a type of flux-switching permanent magnet(FSPM)motor,where the design concept of the hybrid permanent magnets(HPM)and the compound rotor are incorporated into the motor design.In such design,the proposed motor can not only realize the significant reduction of NdFeB volume,but also artfully convert external magnetic flux leakage into the air-gap field to achieve competitive torque density and desirable PM usage efficiency.For extensive investigation,two topologies of the HPM are designed and analyzed for the proposed motor,which consist of the parallel-magnetic-hybrid(PMH)mode and serial-magnetic-hybrid(SMH)mode.To fully exploit the potential advantages of the proposed motor,a multi-objective optimization design is conducted,where the response surface method(RSM)and sequential non-linear programming(SNP)method are purposely utilized.After optimization,the electromagnetic performances of the motor with PMH mode and SMH mode are evaluated and compared by using finite element method(FEM),which include the back-EMF,cogging torque,output torque,and so on.Furthermore,the partial demagnetization of the ferrite PM is also investigated in the paper.Finally,the theoretical analysis and simulation study verify the effectiveness of the proposed motor and corresponding optimization design.

A novel fuzzy logic direct torque controller for a permanent magnet synchronous motor with a field programmable gate array

A high-performance digital servo system built on the platform of a field programmable gate array (FPGA),a fully digitized hardware design scheme of a direct torque control (DTC) and a low speed permanent magnet synchronous motor (PMSM) is proposed. The DTC strategy of PMSM is described with Verilog hardware description language and is employed on-chip FPGA in accordance with the electronic design automation design methodology. Due to large torque ripples in low speed PMSM,the hysteresis controller in a conventional PMSM DTC was replaced by a fuzzy controller. This FPGA scheme integrates the direct torque controller strategy,the time speed measurement algorithm,the fuzzy regulating technique and the space vector pulse width modulation principle. Experimental results indicate the fuzzy controller can provide a controllable speed at 20 r min-1 and torque at 330 N m with satisfactory dynamic and static performance. Furthermore,the results show that this new control strategy decreases the torque ripple drastically and enhances control performance.

Magnetic Field and Operating Performance Analysisof Conical-rotor Permanent Magnet Synchronous Motor

In order to accurately analyze the magnetic field of conical-rotor permanent magnet synchronous motor(CR-PMSM),the effectiveness of two methods was studied on handling of problems concerned with non-uniform distribution of magnetic field along axial direction in CR-PMSM,which were sectional calculation(SC)method and three-dimensional finite element(3-D FE)method.On this basis,the influence of the axial displacement and dq-axis currents on the operating characteristics of axial magnetic force and torque is analyzed by using the 3-D FE model.Analysis results show that the axial magnetic force and torque decrease with the increase of axial displacement of the rotor,and the amplitude regularity of the axial magnetic force is affected by the d-axis current.A prototype machine is fabricated and tested,in order to validate the design theory.

Analysis of temperature field for a surface-mounted and interior permanent magnet synchronous motor adopting magnetic-thermal coupling method

Aiming at obtaining high power density of surface-mounted and interior permanent magnet synchronous motor(SIPMSM),it is important to accurately calculate the temperature field distribution of SIPMSM,and a magnetic-thermal coupling method is proposed.The magnetic-thermal coupling mechanism is analyzed.The thermal network model and finite element model are built by this method,respectively.The effects of power frequency on iron losses and temperature fields are analyzed by the magnetic-thermal coupling finite element model under the condition of rated load,and the relationship between the load and temperature field is researched under the condition of the synchronous speed.In addition,the equivalent thermal network model is used to verify the magnetic-thermal coupling method.Then the temperatures of various nodes are obtained.The results show that there are advantages in both computational efficiency and accuracy for the proposed coupling method,which can be applied to other permanent magnet motors with complex structures.

Analytical calculation of electromagnetic, torque for surface mounted permanent magnet brushless motors

With the air gap magnetic field distribution of surface mounted permanent magnet （PM） motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis （FEA）. In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.

Cogging Torque Reduction in Axial Flux PMSM with Different Permanent Magnet Combination

With the increasing requirement for the mechanical vibration and acoustic noise of the permanent magnet synchronous motor(PMSM)drive system,the demand for cogging torque reduction of PMSM has been considerably increased.To solve the problem of oversized cogging torque of axial flux PMSM,a rotor topology with hybrid permanent magnet is proposed to weaken the cogging torque.Firstly,the expression of the cogging torque of the axial flux motor is derived,and the influence of the pole-arc ratio of the permanent magnet on the cogging torque is analyzed.Secondly,the rotor structure with hybrid permanent magnet is adopted to reduce the cogging torque.According to the analytical analysis,the constraints of the size and pole-arc ratio between the hybrid permanent magnets are obtained,and the two permanent magnets related to the minimum cogging torque are determined.And the analysis results are verified by the finite element simulation.Furthermore,the motor performance with and without the hybrid permanent magnet is compared with each other.Finally,the cogging torque is significantly reduced by adopting a rotor structure with hybrid permanent magnets.

Study on three dimensional electromagnetic model for permanent magnet linear synchronous motor

In this paper, with the non-salient pole permanent magnet linear synchronous motor (PMLSM)being cited, by using Fourier transform method and "slot-by-slot", "pole -by-pole" current approach, a 3D electromagnetic field model of PMLSM is established. Special attention is paid to its structure and the influence of longitudinal and transverse end effect. The distribution of electromagnetic field of PMLSM can be obtained directly and promptly by using FFT algorithm. It can also be used for the analysis of other LSM.

Developing a 3D-FEM Model for Electromagnetic Analysis of an Axial Flux Permanent Magnet Machine

Recently, many optimal designs for axial flux permanent magnet (AFPM) motors were performed based on finite- element (FE) analysis. Most of the models are based on reduction of 3D problem to 2D problem which is not accurate for design aspects. This paper describes an accurate electromagnetic analysis of a surface mounted, 28 pole AFPM with concentrated stator winding. The AFPM is modeled with three-dimensional finite-element method. This model in-cludes all geometrical and physical characteristics of the machine components. Using this accurate modeling makes it possible to obtain demanded signals for a very high precision analysis. Magnetic flux density, back-EMF, magnetic axial force and cogging torque of the motor are simulated using FLUX-3D V10.3.2. Meanwhile, the model is paramet-ric and can be used for design process and sensitivity analysis.

Research on Thermal Calculation and End Winding Heat Conduction Optimization of Low Speed High Torque Permanent Magnet Synchronous Motor

Because of its simple structure,large torque and high efficiency,permanent magnet synchronous motor of low speed and high torque is widely adopted in many fields.In this paper,a 394.5k W mining low-speed high-torque permanent magnet synchronous motor(LSHTPMSM)is regarded as the study object.According to the physical model,a three-dimensional equivalent heat transfer temperature field calculation model of the motor is built to simulate the temperature distribution of the motor under rated conditions.In terms of the serious issue of stator winding temperature increase of permanent magnet synchronous motor of low speed and high torque,the heat conduction optimization of the end of the stator winding is studied,which enhances the heat dissipation effect of the stator end winding,effectively reduces its temperature increase and temperature gradient with the winding in the slot,and improves the practical efficiency and service life of the motor.Finally,the motor temperature rise test platform is constructed for the verification of the feasibility of the optimization scheme,which provides a reference direction for the heat dissipation optimization of permanent magnet synchronous motor of low speed and high torque.

Temperature Rise Calculation and Velocity Planning of Permanent Magnet Linear Synchronous Motor under Trapezoidal Speed

For permanent magnet linear synchronous motor(PMLSM) working at trapezoidal speed for long time, high thrust brings high temperature rise, while low thrust limits dynamic performance. Thus, it is crucial to find a balance between temperature rise and dynamic performance. In this paper, a velocity planning model of the PMLSM at trapezoidal speed based on electromagnetic-fluid-thermal(EFT) field is proposed to obtain the optimal dynamic performance under temperature limitation. In this model, the winding loss is calculated considering the acceleration and deceleration time. The loss model is indirectly verified by the temperature rise experiment of an annular winding sample. The actual working conditions of the PMLSM are simulated by dynamic grid technology to research the influence of acceleration and deceleration on fluid flow in the air gap, and the variation rule of the thermal boundary condition is analyzed. Combined with the above conditions, the temperature rise of a coreless PMLSM(CPMLSM) under the rated working condition is calculated and analyzed in detail. Through this method and several iterations, the optimal dynamic performance under the temperature limitation is achieved. The result is verified by a comparison between simulation and prototype tests, which can help improve the dynamic performance.

Optimal design of modular dual-field modulated permanent magnet linear motors with thrust characteristics

To reduce thrust ripple and cost and improve the average thrust of permanent magnet linear motors,a modular dual-field modulation permanent magnet linear motor was studied,and the parameters were optimized.First,sensitive parameters were selected using the Taguchi method,and then the optimal variables were sampled using the optimal Latin hypercube experimental design method and an ensemble of surrogates model of optimization objectives,and its accuracy was verified.Next,a multi-objective particle swarm optimization algorithm was used to optimize the purpose of“maximum average thrust and minimum thrust ripple”,and the Pareto front of average thrust and thrust ripple was obtained.Finite element analysis showed that the optimized modular dual flux-modulation permanent magnet linear motor(MDFMPMLM)had a 29.5%reduction in thrust ripple and a 5%increase in average thrust compared to the original motor.This study provided an effective method for improving the performance of permanent magnet linear motors.

AN ANALYSIS OF AXISYMMETRIC MAGNETIC FIELD OF LINEAR OSCILLATION MOTOR

In this paper, using axial field finite analysis method, the field of a movable core type linear oscillation motor is analyzed. The program of axial field finite analysis is worked out. Using this program, we analyze various fields, including the field excited by permanent magnet materials, the field by two coils respectively, and the fields with the core moving to various positions.

Design of Axial-Flux Motor for Traction Application

This paper deals with the design of high power – low dimensions axial-flux permanent-magnet motor intended for trac-tion application. First, two motor configurations are analytically designed and compared using finite element calcula-tion. Then, the configuration yielding the best performances is integrated and modelled with the whole traction chain under MATLAB/SIMULINK environment in order to demonstrate the motor operation on a large speed band.

Design of a PCB stator coreless axial flux permanent magnet synchronous motor based on a novel topology Halbach array

A novel topology Halbach permanent magnet array is proposed and applied to the design of a printed circuit board(PCB) axial flux permanent magnet(AFPM) motor. Compared with the traditional coreless AFPM motor, this novel topology for a Halbach permanent magnet array PCB stator AFPM motor has larger air-gap magnetic flux density and air-gap flux per pole. The magnetic flux leakage is effectively reduced, and the air-gap magnetic density is close to the sine wave. Results of the finite element analysis and prototype experiments verify the feasibility and effectiveness of the novel Halbach permanent magnet array PCB stator motor. A reference basis and practical value for the design of the PCB AFPM motor are provided.

Static magnetic field analysis of hollow-cup motor model and bow-shaped permanent magnet design

The hollow-cup Permanent Magnet(PM) motors have the characteristics of low power consumption, and are widely used in the aerospace field. At present, the tile-shaped PMs used by hollow-cup PM motors have poor sinusoidal characteristics of the air gap magnetic flux density waveform, which will cause torque ripple. The existing method for improving the air gap magnetic flux density waveform is not very effective when applied to hollow cup, a special motor with no stator core and large air gap. A bow-shaped PMs structure is designed for the hollow-cup motor in this paper. First, the equivalent surface current method is used to calculate the analytical formula of the static magnetic field of the model. Then, the Finite Element(FE) method is used to calculate the static air gap flux density waveform of conventional tile-shaped PMs and bow-shaped PMs with different bow heights, and the corresponding harmonics and sine distortion are obtained by Fourier decomposition. The simulation results show that the bow-shaped PMs can effectively improve the sinusoidal characteristics of the static air gap flux density waveform. And the suitable bow height is determined. Finally, a prototype is made based on the suitable bow height for experiments, and compared with the analytical result and the FE result, and the accuracy and effectiveness of the bow-shaped PMs with the suitable bow height are verified.

No-Load Iron Loss Model for a Fractional-Slot Surface-Mounted Permanent Magnet Motor Based on Magnetic Field Analytical Calculation

The common analytical models for the no-load iron loss of permanent magnet(PM)motors usually neglect the iron loss caused by the rotating magnetic field in the tooth tips and the harmonics of the magnetic fields in the teeth and yokes.This paper presents an analytical model for no-load iron loss of a fractional-slot surface-mounted permanent magnet motor.According to the existing analytical model of the magnetic field distribution in the slotted air gap,the magnetic flux densities considering the harmonics of the stator tooth and yoke are both derived based on the continuity of magnetic flux.Due to the complexity of the magnetic field in the tooth tip,the tangential flux density of the tooth tip is approximated by an equivalent sine wave and the radial component is regarded to be the same as that of the corresponding tooth.After obtaining the magnetic fields in stator different regions,the analytical iron loss is calculated by using the Bertotti model and the orthogonal decomposition model.A 20-pole/24-slot PM synchronous motor is taken as an example.The maximum error between the analytical model and finite element model(FEM)is 5.46%,which verifies the validity of the proposed method.

基于MAGNET的低速永磁直线同步电动机电磁场数值计算与分析

提出了一种新型直线电机,简要介绍了这种电机的基本结构及运行机理,应用Magnet软件对具有不同结构的两种电机的电磁场进行了数值计算。通过计算结果进一步分析和计算得到了低速永磁直线同步电机的二维磁场分布和气隙磁密的变化波形。所做研究为新型低速永磁直线同步电动机提供了一种行之有效的设计方法。

基于Magnet的永磁直流电动机漏磁仿真分析

在分析永磁直流电动机漏磁机理的基础上,利用有限元分析软件M agnet,建立实体有限元模型,确立边界条件并在不断变换的边界条件下进行有限元计算,得到了永磁电动机不同边界条件下的漏磁大小。计算结果与实验结果具有较高的吻合度,证明了有限元分析模型和理论计算方法的正确性。