Flux Permanent Magnet Synchronous Machine Research Articles

The Financial Aspects behind Designing a Wind Turbine Generator

This article investigates the construction of a wind power generator requiring the lowest possible cost. The proposed model is an Axial Flux Permanent Magnet (AFPM) Synchronous Machine, which contains two iron rotors and a coreless stator between them, constructed from resin. The scientific contribution relates to the coupling of economic and technical parameters, which will clarify the feasibility, i.e., a wind turbine construction capable of producing approximately 3.5 KW, using a simple mill and a generator of nominal rotor speed 100 rpm. Such studies are few in international literature and mainly concern low levels of rotor speed in relation to the produced output power. For the generator dimensioning, analytical equations are used, while the type and the dimensions of the magnets are determined, before the start of dimensioning. The authors carried out research in the international market, ending up with specific cost-effective magnets, while trying to adjust the remaining dimensions and materials of the machine based on these cost-effective magnets and the aforementioned nominal values of the generator. The machine, whose dimensions are derived by analytical equations, was simulated and analyzed using the Two-Dimensional Finite Element Method (2D-FEM) and the Three-Dimensional Finite Element Method (3D-FEM), for comparison purposes. Moreover, an economic analysis of the generator and its individual parts was conducted. Finally, a novel idea for reducing the total generator cost is proposed, by replacing the rotor disks with rings. The investigation revealed that analytical equations can predict with satisfactory accuracy the generator’s parameters. In addition, as permanent magnets are the most expensive materials in the construction, their predetermination using low-cost magnets can reduce the construction cost. Finally, the proposed concept of a ring-shaped rotor instead of a disk rotor, provides a cost reduction of up to 20%.

An analytical formula for back EMF waveform of a counter‐rotating dual‐rotor non‐slotted axial flux permanent magnet synchronous machine

AbstractFractional slot concentrated winding (FSCW) permanent magnet (PM) machines are gaining more attention for low‐speed applications because of their great advantages. This paper proposes a new structure for an FSCW double rotor axial flux PM synchronous machine (DRAFPMSM) with counter‐rotating rotors. In addition, an analytical formula for the Back EMF waveform of the proposed structure is presented. The accuracy of the formula is investigated by designing a 40 W sample machine. The rotors of this machine rotate with speeds of 600 and 428 rpm in opposite directions. The Back EMF of the sample machine is calculated using the suggested formula. In addition, the finite element method (FEM) is used to determine the Back EMF waveform. Comparison of the obtained results confirms that the new formula yields the Back EMF precisely such that the results well match to those of FEM. The effect of the relative position of two rotors on the Back EMF waveform is investigated using the proposed formula. In addition, the optimum relative position of two rotors for minimizing the Back EMF THD of the case study machine is determined.

Proposal of Torque-Correct-by-Construction Optimization Method for Axial Flux Machines

We propose an innovative optimization method for axial flux machine that keeps the output torque constant in the process of weight reduction. A concept of framework is introduced that provides guidance for optimization design on how to choose and redesign the relevant parameters. Unlike the conventional algorithms that search candidates in sample space, new designs with reduced weight are directly determined by following the developed optimization strategy using two-dimensional finite element analysis (FEA). The torque error is restricted by a maximum allowable error introduced in the framework. A single-sided axial flux permanent magnet synchronous machine is used as a starting design. A total of 29 new designs are derived with gradually varying optimization variables. The optimization trend and limit are investigated with respect to the redesigned parameters as well as the resulting weights, which provide an overview for selecting optimal design. At last, the torque of every design is verified by both two-dimensional and three-dimensional FEA. The effectiveness of proposed method is demonstrated by the result that the weight is significantly and continuously reduced as the independent optimization variable increases while the torque error remains in a small extent.

Research on Electromagnetic System of Large Capacity Energy Storage Flywheel

A large capacity and high power flywheel energy storage system (FESS) is developed and applied to wind farms, focusing on the high efficiency design of the important electromagnetic components of the FESS, such as motor/generator, radial magnetic bearing (RMB) and axial magnetic bearing (AMB). Firstly, a axial flux permanent magnet synchronous machine (AFPMSM) based on soft magnetic composite material (SMC) is designed. Then, considering the structure of FESS and machine, a permanent magnet biased radial magnetic bearing (PMRMB) and a HALBACH axial passive magnetic bearing (PMB) is proposed which have the advantages of low power consumption and large bearing capacity, then the analyses are carried out according to the load capacity requirements. Finally, the flywheel prototype is fabricated and tested. The experimental results verify the relevant theoretical analysis, and finally can achieve stable and reliable operation.

Leakage Flux Adjustment and Flux Field Optimization for Coreless Axial Flux Permanent Magnet Synchronous Machine Based on U-shaped Iron

Leakage Flux Adjustment and Flux Field Optimization for Coreless Axial Flux Permanent Magnet Synchronous Machine Based on U-shaped Iron

Stall Torque Performance Analysis of a YASA Axial Flux Permanent Magnet Synchronous Machine

There is a trend to go towards low gear-ratio or even direct-drive actuators in novel robotic applications in which high-torque density electric motors are required. The Yokeless and Segmented Armature Axial Flux Permanent Magnet Synchronous Machine is therefore considered in this work. In these applications, the motors should be capable to deliver high torque at standstill for long periods of time. This can cause overheating of the motors due to a concentration of the losses in a single phase; hence, it becomes necessary to derate the motor torque. In this work the influence of the slot/pole combination, the addition of a thermal end-winding interconnection and the equivalent thermal conductivity of the winding body on the torque performance at standstill will be studied both experimentally via temperature measurements on a prototype stator, and via a calibrated 3D thermal Finite Element model. It was found that both a good choice of the slot/pole combination and the addition of a thermal end-winding interconnection have a significant influence on the torque performance at standstill, and allow up to 8% increase in torque at standstill in comparison to a reference design.

Introducing Analytical Formulas for Calculating Back EMF of the Contra-Rotating Double-Rotor Axial Flux Permanent Magnet Synchronous Machine

Back electromagnetic force (back EMF) is one of the most significant performance characteristics of the machine which significantly affects the machine current, efficiency, power factor, and power angle. Studies showed that the precise analytical formulas to calculate the back EMF of Counter-rotating dual rotor axial flux permanent magnet synchronous machines (CRDR-AFPMSMs) were not presented so far. While by helping the analytical formulas, back EMF is calculated faster than the finite element method (FEM). Therefore, the novelty of this article is calculating the back EMF of CRDR-AFPMSMs considering its harmonic components. To fulfill this goal, Maxwell’s equations are used. The back EMF waveform obtained from the proposed formulas is compared with the results of FEM. Comparing the results confirms that the obtained results from the finite element (FE) simulation and analytical formulas are in good accordance. Besides, the shifting technique is used to reduce harmonic components of the back EMF. By helping proposed formulas and shifting techniques, the Total Harmonic Distortion (THD) of back EMF has decreased from 12.12 to 4.88%.

Fault-Tolerant Fuzzy Logic Control of a 6-Phase Axial Flux Permanent-Magnet Synchronous Generator

The objective of this paper is to propose the real-time implementation of a fault-tolerant strategy based on fuzzy logic controller (FLC) for a Six-Phase Axial Flux Permanent Magnet Synchronous Machine (6P-AFPMSM) for electrical energy production. This type of machine, suitable for high-power applications, is highly affected by the harmonics of the inductances and the electromotive force (emf) compared to the classical three-phase radial flux machine, which will influence the controller parameters of the machine. The proposed control strategy based on FLC is independent of the system model and guarantees the robustness of the process against disturbances and parameter variations of the model. An experimental comparison between FLC and a classical PI controller confirms the efficiency and the robustness of the proposed controller in healthy and faulty conditions with one open phase.

Power Density Boosting Techniques for Reconfigurable Integrated Modular Motor Drives

The electric drive power density and fault tolerance capability are of fundamental importance in many applications such as aerospace and traction applications. The modularization and the physical integration of the electric motor and the power converter components can lead to a high power density and a high fault tolerance drive system. The power density of a highly modular and integrated drive based on an axial flux permanent magnet synchronous machine and GaN converter is investigated in this paper. Several power density boosting techniques are provided and investigated using CFD simulations. These techniques incorporate optimization of the converter topology, the geometry of the shared cooling structure of the electric machine and the power converter and optimal selection of the materials in the path of heat transfer from the machine and the power converter to the cooling ambient. The power density of the reference integrated design is increased from 1.12 kW/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$l$</tex-math></inline-formula> to 2.14 kW/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$l$</tex-math></inline-formula> . The CFD computations are validated by extensive measurements on a modular integrated setup.

A Novel Multi-Layer Structure for Axial Flux Machines

In an axial flux machine (AFM), an effective air-gap area is a ring form of which the size is decided by the outer and inner diameter of the stator. The inner diameter is usually not small, which leaves a relatively large inner space unused because the slot size has to keep uniform radially for current density. This article proposes a multi-layer structure that adopts concentric rings consisting of multiple layers instead of the conventional single layer. A conventional single-sided axial flux permanent magnet synchronous machine (AFPMSM) is introduced as a baseline design with 110 kW output power and 350 mm outer diameter. Through transforming this baseline design, the benefit of this new structure has been revealed with three different investigations in this article: 1) the output power per mass can be improved; 2) the compactness (output power in a limited space) can be increased; and 3) the constant power speed range could be significantly extended with a new type inverter (only design specification of the new inverter given), in which no additional technique of flux modulation required. The proposed multi-layer structure bypasses the issue that the area of a single ring cannot be enlarged due to the limitation of inner diameter. The air-gap area can be extended to the complete inner radial space for generating electromagnetic force. Besides, two factors, i.e., the number of layers and the coordination between multiple layers, make the performance of AFM highly customizable for different design objectives.

A Rotor Cooling Enhanced Method for Axial Flux Permanent Magnet Synchronous Machine With Housing-Cooling

This paper focuses on the rotor thermal design of the axial flux permanent magnet synchronous machine (AFPMSM) with housing water-cooling. By adapting the effect of disc rotor self-ventilation, an enhanced cooling method has been innovated to optimize the temperature distribution of the rotor in AFPMSM. Two scenarios will be created to compare their influence on cooling enhancement of rotor with the diverse types of fins, the annular fin and the rectangular fin, each will be installed separately to the internal surface of housing. There is a significant effect by using this method in all types of AFPMSM with housing cooling, especially for multi-rotor ones. The results of CFD show that the effectiveness of annular fins is essentially enhanced, with 25% more heat dissipation achieved.

Design and Analysis for Multi-Disc Coreless Axial-Flux Permanent-Magnet Synchronous Machine

The multi-disc axial flux permanent magnet synchronous machine (AFPMSM) can provide high fault tolerance capability in applications requiring high reliability. Firstly, a topological structure of coreless AFPMSM is proposed, the magnetic circuit and the air-gap flux intensity are discussed in detail to improve stable operation of machine in this paper. The relationship between air-gap flux density and the parameters of rotor are clarified respectively based on finite element algorithm (FEA). Furthermore, the winding structure and power driver topology with fault tolerance are presented. And the 3D FEA analyzes the operation characteristics and stress of the machine. Finally, the prototype is manufactured. The results are demonstrated that the torque output and fault tolerance performance is better.

Design and analysis of a novel AFPM with counter-rotation dual rotors based on non-linear magnetic circuit model

This paper presents a nonlinear iterative magnetic equivalent circuit (MEC) model for a novel counter-rotation dual-rotor axial flux permanent magnet synchronous machine (CRDR-AFPMSM). The proposed machine mainly consists of two rotors with opposite rotation directions, two sets of concentrated windings and a stator core sandwiched in between the two rotors. The model takes into account of the nonlinear characteristics of the saturable permeance in the stator core, and the permeance matrix is updated by an iterative procedure to accurately illustrate its nonlinear feature. The air gap flux density, back electromotive force (EMF) and torque are predicted by the model. Based on the nonlinear model, the thickness of the stator yoke is determined. All of the results obtained by the proposed model match with finite element analysis (FEA) results closely, thus the validity of the proposed MEC model is verified.

Design Optimization of a Low Speed Small Scale Modular Axial Flux Permanent Magnet Synchronous Generator for Urban Wind Turbine Application

Small wind turbines can generate clean energy in diverse locations, from urban centers to rural areas without access to the main grids. This study proposes design optimization of an axial flux permanent magnet (AFPM) synchronous machine for small scale portable applications. At first, a fast, accurate and pragmatic hybrid analytical model is proposed for performance prediction of the machine. The proposed model is then used as a basis for a direct search optimization process with factual constrains and objective functions to improve the machine in terms of efficiency, weight and to ease the manufacturing process. 3 Dimensional Time Stepping Finite Element Method (3-DTSFEM) is utilized to validate the accuracy and effectiveness of the proposed model and optimization methodology. Output characteristic of the machine from both analytical model and 3-DTSFEM are compared to each other that proves the functionality of the proposed study.

Development of Mathematical Models in Explicit Form for Design and Analysis of Axial Flux Permanent Magnet Synchronous Machines

This article proposes a methodology for the design of double-sided coreless axial flux permanent magnet synchronous machines, which is based on a developed model for calculating the axial component of the magnetic flux density in the middle of the distance between opposite permanent magnets, which also represents the middle of the stator. Values for different geometric parameters represent the input data for the mathematical model in explicit form. The input data are calculated by using a simplified finite element method (FEM), which means that calculations of simplified 3D models are performed. The simplified model consists of two rotor disks with surface-mounted permanent magnets and air between them, instead of stator windings. Such a simplification is possible due to similar values of permeability of the air and copper. For each simplified model of the machine the axial component of the magnetic flux density is analyzed along a line passing through the center of opposite permanent magnets and both rotor disks. Values at the middle of the distance between the opposite permanent magnets are the lowest and are therefore selected for the input data at different stator, rotor disks and permanent magnets (PM) thicknesses. Such input data enable the model to consider the nonlinearity of materials.

An Integrated Modular Motor Drive With Shared Cooling for Axial Flux Motor Drives

In this article, a circumscribing polygon integrated modular motor drive topology with shared cooling for the power converter and the electrical machine is proposed and benchmarked with the nonintegrated version. The proposed topology is applied on an axial flux permanent magnet synchronous machine. The topology is capable of mechanically mounting the power converter, sufficiently cooling both the power converter and the electrical machine, and combining both of them into the same housing. The mechanical and the thermal design are done to ensure thermal decoupling between the power converter and the motor winding, and to provide a low thermal resistance from the power converter and the electrical machine to the ambient. Due to the limited space available for the power converter module, wide bandgap semiconductor technology is chosen for the implementation of the converter module, thanks to their small package size and low power losses. A highly modular, integrated, and compact drive is achieved compared to the nonintegrated one. A computational fluid dynamics (CFD) model is developed for one module of the proposed integrated drive to evaluate the maximum current that can be injected by one converter module without exceeding the junction temperature limit of the switches and the maximum winding temperature. An experimental setup is built to validate the results of the introduced multiphysics models.

Back-EMF Analysis of a Variable Flux Machine for Different Magnetization States

This article presents the effect of different magnetization pulse widths and methods on the back electromotive force (EMF), no-load losses, and minimum inverter rating at different operating conditions of a variable flux permanent magnet synchronous machine (VF-PMSM/VFM). Precise information of the back-EMF helps to estimate the cogging torque and torque ripple. An accurate determination of the core loss leads to a better efficiency estimation and machine design. An experimentally determined minimum inverter rating reduces the cost of the motor drive system. An adaptive nonlinear filter is used to estimate the VFM back-EMF during the motoring mode. The VFM is often demagnetized and remagnetized by injecting a current pulse to achieve the high-speed and high-torque requirements. The sudden injection of a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current pulse will change the magnet flux linkage and back-EMF harmonics. In this article, harmonics present in the machine back-EMF due to different magnetization and demagnetization current pulse widths and magnetization methods are analyzed. Besides, the quality of the back-EMF for different speeds and machine no-load losses are presented for different magnetization levels. The minimum inverter current rating is determined for magnetizing current and magnetizing current at full load considering the minimum pulse amplitude and width to magnetize the VF-PMSM.

Coupled electromagnetic and thermal analysis of an axial flux permanent magnet synchronous machines with printed circuit board winding

Axial flux permanent magnet synchronous machines (AFPMSMs) with printed circuit board (PCB) windings take on different electromagnetic and thermal performance characteristics when compared to the traditional radial flux permanent magnet synchronous m

Stator Winding MMF Analysis for Variable Flux and Variable Magnetization Pattern PMSMs

This article analyzes the stator winding magnetomotive force (MMF) in machines to establish a general guideline for active magnetization change techniques used in variable flux permanent magnet synchronous machines and variable magnetization pattern permanent magnet synchronous machines. In this article, the spatial and time harmonics in the stator winding MMF are analyzed to build guidelines for machine topologies and the magnetizing current trajectories for the active magnetization change technique. The proposed guideline about slot pole combinations and magnetizing current pulses are verified through 11 examples from the existing literature, numerical simulation, and experiments.

Analysis of Winding MMF and Loss for Axial Flux PMSM With FSCW Layout and YASA Topology

This article takes 12-slot/10-pole axial flux permanent magnet (PM) synchronous machine (AFPMSM) with fractional-slot concentrated windings and yokeless and armature (YASA) topology as the research object. Winding magnetomotive force (MMF) of three-phase double-layer layout is analyzed by three kinds of methods, which are star diagram method, winding function method, and holographic spectrum method. The analysis results of finite-element method (FEM) show that the three methods are effective and consistent in analyzing winding MMF. Comparative analysis of iron loss density and B–H magnetizing curves of four typical iron materials are studied. B–H hysteresis loops of silicon steel sheet and soft magnetic composite are measured by magnetizing and measuring equipment to validate iron core per unit mass. The three-dimensional FEM is used for analyzing eddy-current loss in PMs considering radial segmentation. Finally, an AFPMSM prototype is manufactured adopting YASA topology and segmented PM. Load experiments show that solid–liquid coupling computational fluid dynamics model can precisely predict temperature distribution of AFPMSM. Improved cooling jacket is beneficial to afford large current load.