Axial Flux Permanent Magnet Motor Research Articles

Investigation and Comparison of Different Calculation Methods for AC Copper Loss of Flat Copper Wire in Axial Flux Permanent Magnet Motor

Investigation and Comparison of Different Calculation Methods for AC Copper Loss of Flat Copper Wire in Axial Flux Permanent Magnet Motor

Axial Flux Permanent Magnet Motor Topologies Magnetic Performance Comparison

Axial flux permanent magnet motors have attracted increasing attention due to their compact topology and high torque density. Many topological variations have arisen over time; however, limited research has directly compared the differences in magnetic performance of these topologies. This paper carries out a comprehensive investigation, employing both analytical and 3D finite element analyses, to compare the magnetic performance of three topologies: yokeless and segmented armature (YASA), axial flux internal rotor (AFIR), and offset AFIR. The findings reveal that each topology offers specific advantages for different applications. The YASA topology excels in minimizing core losses; the AFIR configuration achieves the highest torque density; and the offset AFIR topology shows the highest efficiency. The offset AFIR topology appears to offer advantages for a wide array of applications due to its higher power factor and lower permanent magnet loss, leading to reduced costs for converter design and cooling system design.

Experimental verification and electromagnetic analysis of axial flux permanent magnet motor using the subdomain method

This study investigates a subdomain method for performing the characteristic analysis of an axial flux permanent magnet motor (AFPM). Initially, the AFPM was simplified for the analytical model and analysis regions were defined to apply the subdomain method. Subsequently, a general solution was derived for the governing equations of each analysis region using the variable separation method. Subsequently, the undetermined coefficients of the general solution were obtained from the matrix using appropriate boundary conditions, and the magnetic flux density in the air-gap region was derived based on the defined magnetic vector potential. Finally, the induced voltage and electromagnetic torque of the analytical model were calculated. The analytical results were verified using the finite element method and the experimental results.

Comprehensive investigation on the slot leakage inductance of axial flux permanent magnet motor with novel slot shape

Comprehensive investigation on the slot leakage inductance of axial flux permanent magnet motor with novel slot shape

Research on a Novel Hybrid Axial Transverse Flux Permanent Magnet Motor with Compound Rotor

Research on a Novel Hybrid Axial Transverse Flux Permanent Magnet Motor with Compound Rotor

Comprehensive Analysis of Dual-Rotor Yokeless Axial-Flux Motor with Surface-Mounted and Halbach Permanent Magnet Array for Urban Air Mobility

A dual-rotor yokeless and segmented armature (YASA)-type axial-flux permanent magnet (AFPM) motor with a surface-mounted permanent magnet (SPM) array type was developed for urban air mobility (UAM) aircraft in this work. The proposed AFPM motor had rated and peak output powers of 75.5 and 104 kW, respectively, with rated and peak rotational speeds of 1800 rpm. To achieve a high torque, a cobalt–iron alloy core material was used for the stator core. The prototype AFPM motor, developed by KSEP in the Republic of Korea, was successfully manufactured and verified through experimentation. Additionally, the thermal stability of the winding and permanent magnets (PMs) was confirmed with a water-cooling system. A structure analysis of the proposed AFPM motor was conducted due to the detachment of an uneven air-gap length in the prototype AFPM motor. An output performance comparison based on core materials for the stator and rotor was carried out to explore the material cost reduction. Subsequently, the design for performance improvement by applying a Halbach permanent magnet (HPM) array type was investigated for further research.

Analytical Calculation and Low-Order Component Optimization of Axial Electromagnetic Force for an Axial Flux Motor

The low-order high-amplitude component of axial electromagnetic force is the leading cause of electromagnetic vibration and noise of axial flux permanent magnet (AFPM) motors. In this paper, based on the analytical calculation of the axial electromagnetic force for a 20-pole 24-slot AFPM motor, the low-order axial electromagnetic force component is weakened by optimizing the motor’s electromagnetic structure. First, the three-dimensional (3-D) structural model of the motor is equated to a two-dimensional (2-D) analytical model, which is used to calculate the magnetic field generated by each of the armature winding and permanent magnet. Then, combined with the Maxwell tensor method, the axial electromagnetic force waveform is further obtained, and the target low-order high-amplitude component is extracted by 2-D Fourier analysis. Finally, taking this axial electromagnetic force component minimization as the target function of optimization, considering the output torque and ripple as constraints, the genetic algorithm is used to search for the optimal point by varying the structural parameters of the motor. The results show that the target low-order high-amplitude component of the axial electromagnetic force of the optimized motor is effectively suppressed, and the output torque ripple decreases with slightly increased torque amplitude, which provides a practical method for vibration and noise reduction of AFPM motors.

Analytical Modeling of Slotless Axial Flux Permanent Magnet Motor With Equidirectional Toroidal Winding

This study proposes a two-dimensional (2D) analytical model (AM) of slotless axial flux permanent magnet (AFPM) motor, which includes two submodels of armature winding (AW) and permanent magnet (PM) magnetic fields. It can reveal the operating mechanism of equidirectional toroidal winding (ETW) armature magnetic field in the theory and quantitatively analyze its AW and PM magnetic fields. The proposed AM is characterized in that AW magnetic field submodel is established only based on the current density distribution of the effective conductors on one side of a single toroidal coil considering its width and thickness. First, based on the proposed equivalence principle, the analytical submodels of AW and PM magnetic fields of AFPM motor with ETW are established separately, and the formulas of back EMF and torque of the motor are derived. Second, the electromagnetic performance of a slotless AFPM motor with ETW is studied by the proposed 2D AM, including the waveforms of AW and PM magnetic fields, phase back EMF and torque, which are verified by the finite element model. Finally, a prototype of AFPM motor with ETW is manufactured and tested in open-circuit and on-load conditions, which verifies the accuracy of the proposed AM.

Innovations in Axial Flux Permanent Magnet Motor Thermal Management for High Power Density Applications

For aerospace applications, power density is a major driving force in the design of electrified powertrains. At the forefront is the challenging design of electric motors with high efficiencies, torque, and power capabilities. Due to its high performance, the Axial Flux Permanent Magnet (AFPM) Motor is expected to be one of the leading technologies to meet the demands of these industries. Finding the balance between the cooling system’s effectiveness and subsequent parasitic losses is key to utilizing these performance benefits. Single stator double rotor topologies achieve the best torque density and lower stator losses, however are more challenging to cool as the stator is in the center of the motor. Single stator single rotor and double stator machines are less challenging to cool but typically have lower power density. Rotor air cooling is discussed including the effectiveness of blades, meshes, and vents which can be optimized to prevent demagnetization. Stator cooling is critical as many machines maximize current density producing a large amount of heat. The chosen strategy depends on the machine topology and can be accomplished by several strategies, including jackets, fins, channels, immersion cooling, hollow coils, and heat pipes.

Quantitative comparison of low-cost electrical machines with soft magnetic composite and ferrite magnet materials

Because of its special structure and manufacturing process, the soft magnetic composite (SMC) material has shown its advantages over silicon sheets, including magnetic and thermal isotropy, low high-frequency core loss, low material wastes during its manufacturing process, etc.. Considering the price of SMC raw material can be very cheap in the future, it is an ideal material for developing the low-cost electrical machine. Combined with SMC cores and low-cost ferrite magnets, some electrical machines with SMC and ferrite magnets for low-cost applications were developed in the past decades, which include the transverse flux flux switched permanent magnet motor (TFFSPMM), axial flux claw pole permanent magnet motor (AFCPM), axial flux vernier motor (AFVM), dual rotor axial flux permanent magnet motor (DRAFM) and axial radial flux permanent magnet motor (RAFM). To better utilize SMC material, all these machines are designed following the design guidelines of SMC machines. Though both of them with good performance for low-cost applications, it is necessary to know the main advantages of each machine. The main target of this paper is to compare these machines quantitatively. For obtaining the comparison results fairly all these machines are optimized by using the sequential robust Taguchi method. Finally, it can be seen that the AFVM and TFFSPMM are with relatively high torque ability and the DRAFM is with high efficiency and power factor ability.

Circulating and Eddy Current Losses in Coreless Axial Flux PM Machine Stators With PCB Windings

Printed circuit board (PCB) stators in coreless axial flux permanent magnet (AFPM) machines have been proposed, designed, and studied for use in multiple industries due to their design flexibility and reduction of manufacturing costs, volume, and weight compared to conventional stators. This paper investigates mechanisms and methods of approximating open circuit losses in PCB stators within example wave and spiral winding topologies for a dual rotor, single stator configuration using 3D FEA, analytical hybrid techniques and experiments. The effect of rotor magnet shape, end winding, and active conductor geometry on eddy currents is studied, and some mitigation techniques are proposed. Through stator equivalent circuit analysis, circulating current losses caused by mechanical abnormalities and magnetic circuit asymmetry are assessed. Possible strategies and schemes to minimize circulating current losses are also described. The trade-off between stator loss components and some practical design considerations are outlined in detail. The open circuit power losses of a prototype coreless AFPM motor were experimentally tested using multiple example PCB stators and emulated rotor asymmetries, with the findings being comparable to the FEA and hybrid analytical methods results.

Semianalytical Model of Multiphase Halbach Array Axial Flux Permanent-Magnet Motor Considering Magnetic Saturation

This paper proposes a nonlinear semi-analytical model (SAM) of the multi-phase Halbach array axial flux permanent magnet motor (AFPMM) to speed up the computation of its magnetic field. Compared to the existing analytical models, the proposed nonlinear SAM can directly consider magnetic saturation to obtain more accurate results. To this end, the multi-phase Halbach Array AFPMM is equivalent to several 2-D models by the Quasi-3D method under the Cartesian coordinate system. Then, the nonlinear SAM is developed by using the convolution theorem and the fast Fourier factorization. The proposed nonlinear SAM is studied on a five-phase Halbach array AFPMM with different rotors, and the nonlinear finite element (FE) model and experiment verify its effectiveness. The proposed SAM is computationally efficient and accurate, and it is also applicable to other types of multi-phase Halbach array PM electrical motors in Cartesian coordinates.

Pole shape design of ring winding axial flux permanent magnet used in a direct‐drive electric boat for cost‐efficient cogging torque alleviation

AbstractThe recently introduced Ring Winding Axial Flux Permanent magnet Motor (RW‐AFPM) is inspired by the yokeless structure of Yokeless and Segmented Armature (YASA) AFPMs and the partitioned‐phases configuration of transverse flux motors. Its potential application for rim‐driven electric ships propulsion has been examined in the previous studies and, here, it will be studied for ultra‐light direct‐drive electric boats. Owing to their specific structural features, the relatively large cogging torque of RW‐AFPMs seems to be a significant challenge for such applications. On the other hand, as investigated in previous studies, cogging torque reduction methods, such as conventional skewing, seem unsuitable for this type of machine. Thus, this paper will address the cogging torque issue via a comprehensive pole shape analysis. The results will be useful for all kinds of partitioned‐phases topologies that have high specific torque capability but suffer from large cogging effects. All analyses are performed via 3D‐FE models, the accuracy of which is pre‐verified through experiments.

A Study on Optimal Design Process of Dual Rotor Axial-Flux Permanent Magnet Synchronous Motors

The core design elements of the motor for the co-robot joint are miniaturization and high torque. In this paper, a dual rotor axial-flux permanent magnet (DRAFPM) motor is proposed to improve the performance of robot joints. DRAFPM motors have the advantage of reducing iron loss and minimizing volume because they can remove stator yoke. When designing a motor with the same volume, it can be designed to increase the height of the fixed ruler by the thickness of the yoke of the fixed ruler and increase the number of turns. In the case of existing axial-flux permanent magnet (AFPM) motors, the shape of the three-dimensional structure is limited by radial laminating of stator. Therefore, considering the production of 3D printing, the shape of stator shoe is designed. The optimal design problem of DRAFPM motor consists of real and integer design variables. In addition, due to the structural characteristics of DRAFPM motors, 3D finite element analysis (FEA) is required, so it takes a long time to interpret. Therefore, this paper proposes an efficient optimal design process to optimize the remaining real design variables after prioritizing the integer design variables. The proposed optimization process is applied to the DRAFPM motor for robot joints, and the optimal design plan satisfying the design function is derived from various design variables to prove the validity of the optimization process.

Demagnetisation optimisation of ring winding axial flux permanent magnet motor by modifying the load line of the magnet

AbstractRecently the new topologies of the permanent magnet (PM) motor attract a lot of attention. These newly introduced PM motors are not mature in design aspects and suffer from different perspectives. Therefore, it is necessary to develop a common design procedure to overcome these drawbacks. One of the common problems with newly introduced PM motors is the phenomenon of irreversible demagnetisation (ID) at high temperatures. So, a solution to this problem will be presented. The recently introduced ring winding axial flux PM (RWAFPM) motor is considered as a case study. First, a modified approach for modelling ID is introduced. Then, the effect of rotor geometry parameters on the ID of the RWAFPM motor is discussed. Finally, developed multi‐level multi‐objective design optimisation considering ID is presented based on the developed Taguchi method.

Rotor Air-Friction Loss and Thermal Analysis of IPM Rotors for High Speed Axial-Flux Machine

This paper focuses on the temperature rise of high-speed disc rotor considering the air-friction loss for an axial flux permanent magnet (AFPM) motor with double rotors and sandwiched stator. The air-friction loss and the heat transfer coefficient on the rotor surface at different speed are obtained based on the formula method and Fluid-Thermal coupling analysis. The rotor temperature distribution based on the coupling analysis of temperature and fluid field is obtained considering various losses and the impact of heat dissipation of air flowing in the motor cavity. Finally, the temperature variation of rotor disc considering the rotating speed is presented for the AFPM motor in this paper. The heat dissipation mechanism of rotor disc for the AFPM motor are revealed. It provides a significant guideline for the cooling design and the efficiency enhancement of high speed AFPM motor.

Review on Thermal Behavior and Cooling Aspects of Axial Flux Permanent Magnet Motors–A Mechanical Approach

With the increasing demand for high-energy density motors for applications such as electric vehicles and aircraft propulsion, axial flux permanent magnet motors are promising. However, utmost care should be taken when designing an axial flux permanent magnet motor with a higher torque density because of thermal effects. To enhance the reliability and overall performance of a motor, efficient thermal management is important, because the torque density is restricted by maximum temperature. Therefore, this study comprehensively reviews different techniques used for the thermal modeling of motors. Computational fluid dynamics, the lumped parameter method, and finite element analysis were used to calculate the total heat transfer inside the motor. Various heat enhancement techniques for an axial flux permanent magnet motor have been presented, including core cooling (water jacket cooling, air cooling, and oil cooling) and winding cooling (direct slot cooling, end winding cooling, and fins). Finally, two case studies of an 8kW AFPM motor and a 65kW AFPM motor with a cooling arrangement are discussed.

Research on Modeling Method for Eccentric Axial Force of Axial Flux Permanent Magnet Motor with Single-Rotor–Single-Stator Structure

Research on Modeling Method for Eccentric Axial Force of Axial Flux Permanent Magnet Motor with Single-Rotor–Single-Stator Structure

A Review of Axial-Flux Permanent-Magnet Motors: Topological Structures, Design, Optimization and Control Techniques

Axial-flux permanent-magnet (AFPM) motors are a kind of important motor with compact structure, high power density and high torque density. In this review, the progress of AFPM motors and their key technologies are analyzed and described, with emphasis on the topological structures, design and optimization methods and control techniques. Based on these analyses, the main findings of the review are the following: (1) the yokeless and segment armature (YASA)-type motors have great potential for development; (2) the multi-objective optimization design theories can be integrated and applied to optimize the design of AFPM motors; and (3) optimal control and sensorless control have important value in improving system reliability and reducing cost. Finally, highlights and prospects are provided for further advancing AFPM motors.

Analytical Performance Prediction of a New-Structured Solid-Rotor Line-Start Axial Flux Permanent Magnet Motor

The Axial Flux Permanent Magnet (AFPM) motors have recently attracted more attention in various applications due to their special outstanding potentials. However, two major problems have already restricted their usage, which are the lack of starting torque and their probable instability. These problems have caused the AFPM motors to be energized so far necessarily via expensive and complicated power-electronic drives, even when are desired to operate in the constant-speed condition. Alternatively, the better and less expensive solution to these problems is to provide the Line-starting capability through modifying the motor structures. Therefore, this paper studies a Line-start Non-slotted AFPM motor with a new proposed structure. The parameters of the electrical equivalent circuit and the principal performance characteristics of the motor are extracted through establishing a detailed analytical model. Finally, the performance of the newly developed structure and the validity of the established analytical model have been successfully verified through implementing the model in MATLAB and comparing the results with those of Finite Element Analysis (FEA) and experiment on a fabricated prototype. The results demonstrate the accuracy of the analytical model and appropriate performance of the motor in terms of direct start-up and synchronization.