Axial Flux Permanent Magnet Machine

In this paper, it’s mentioned about the design model for the one of the most appropriate motor for electric vehicles which is called as axial flux permanent magnet brushless dc motor. It is clarified why that kind of motor is favoured instead of  others and discoursed the basic design specs by taking account of the literature studies.The position of axial flux permanent magnet brushless dc motor in the electric machinery is showed and the regarding points of designing these kind of motors are pointed out. The road map of designing aspects are extracted step by step, from the determining of physcical parameters to building of a prototype.

This paper presents a dc-bus voltage control technique for a new power conversion topology feasible for parallelintegrated permanent magnet (PM) wind generation systems. This technique is based on a master-slave hysteresis control scheme in order to solve discrepancy problems that could happen between the controllers. A three-phase semicontrolled rectifier topology is proposed here as an effective interface circuit between each wind generator and the dc-bus. The proposed system provides interconnection extension ability of multiwind converter units sharing the same dc-bus and more economic utilization of the wind generator; by ensuring unity power factor operation. More advantages include voltage disturbance compensation capability, robustness: since a short circuit through a leg is not possible and high efficiency: due to the reduced number of switching elements. The rectifier topology concept, the principle of operation, the control scheme, and test results are presented. The developed technique is also implemented on a 12 kW parallel-connected PM laboratory setup in order to confirm the effectiveness of the proposed system. Index Terms-Permanent magnet generators, power factor correction, three-phase ac-dc rectifiers, voltage control, wind energy generation.

Abstrak Tujuan dari penelitian ini adalah merancang dan membuat generator fluks aksial putaran rendah serta mengamati grafik kinerja karakteristik yang diperoleh dari output generator. Penelitian ini merupakan jenis penelitian kualitatif. Penelitian yang dilakukan memiliki fokus pada disain sketsa perancangan dan pembuatan obyek komponen generator fluks aksial. Untuk mendapatkan data primer dan data sekunder, peneliti menggunakan teknik observasi, studi pustaka, serta teknik pengukuran dan pengujian. Tingkat performa generator dengan kemampuan sebagai prototipe atau purwarupa pada hasil akhir dari penelitian ini adalah pada putaran 800 rpm dengan frekuensi rata-rata 80 Hz generator dapat membangkitkan tegangan 128 VAC dengan nilai arus 24,5 mA. Kesimpulan penelitian ini adalah generator fluks aksial multi cakram 1 fasa untuk putaran rendah dapat dirancang dengan spesifikasi 6 buah stator dan 7 keping rotor berbahan aluminium menggunakan magnet neodymium (NdFeB) sebanyak 12 kutub. Masing-masing stator terdapat 6 buah kumparan kawat tembaga dengan diameter 0,6 mm memiliki jumlah lilitan rata-rata sebanyak 100 lilitan. Nilai perbandingan dari hasil perhitungan dan pengukuran pada generator tersebut adalah 5,69 % dan dikatakan telah mendekati nilai tingkat akurasi yang baik. Pada kecepatan 250 rpm nilai tegangan ketika sebelum diberi beban adalah 36,4 VDC dan pada saat diberi beban turun menjadi 16,46 VDC. Nilai faktor regulasi tegangan DC generator tersebut adalah 54,81 %. Drop voltage tersebut disebabkan karena generator tidak dilengkapi perangkat stabilizer tegangan. Kata Kunci: Generator Fluks Aksial, 1Fasa, Multi Cakram, Neodymium Magnet (NdFeB).

The aim of this paper is to find the best concentrated windings layouts for high pole number permanent-magnet (PM) machines. Pole and slot numbers are varied from 4 to 80 and 6 to 90 respectively. Among all the pole/slot combinations, those giving the highest winding factors are provided. Harmonics in the magneto-motive force (MMF), torque ripple and radial magnetic forces

In this paper, pulsating torque components of permanent magnet machines and pulsating torque minimization techniques are discussed for axial flux surface-magnet disc-type PM machines. The pulsating torque analysis describing general instantaneous electromagnetic torque equation and torque ripple factor is briefly provided in order to analyze torque ripple component. Detailed finite-element analyses focusing on the minimization of cogging and torque ripple components using several techniques are also given. A detailed comparison of the two techniques is also illustrated in this paper.

Axial flux motors have many advantages according to conventional motors. But, as it's known in general, the most important reason not to use axial flux motors as much as radial flux motors, is fabrication difficulties. In this paper, it's shown how to prototype an axial flux permanent magnet motor. Because of that, the difficulties are identified after prototyping job of the axial flux motor. Results that are caused by these difficulties are written. Physical advantages of axial flux motor type is established with this application. A single rotor, single stator axial flux permanent magnet brushless dc motor is produced to prove all of these.

This paper presents a gearless wheel motor drive system specifically designed for fuel cell electric and hybrid electric vehicle propulsion application. The system includes a liquidcooled axial flux permanent-magnet machine designed to meet the direct-drive requirements. The machine design implements techniques to increase the machine inductance in order to improve machine constant power range and high-speed efficiency. The implemented technique reduces machine spin loss to further improve efficiency. The machine design also optimizes the placement of magnets in the rotor to reduce cogging and ripple torque. An original cooling system arrangement based on the use of high thermal conductivity epoxy joining machine stator and liquid-cooled aluminum casing allows the very effective removal of machine power loss. Design details and experimental results are presented.

The design of direct-drive wheel motors must comply with diameter restrictions due to housing the motor in a wheel rim and allow the achievement of very high torque density and overload capability. Slotless axial-flux permanent magnet machines (AFPMs) prove to be the best candidate for application in electric vehicles as direct-drive wheel motors, as in comparison with conventional machines they

In modeling axial field machines, three-dimensional (3-D) finite-element method (FEM) models are required in accurate computations. However, 3-D FEM analysis is generally too time consuming in industrial use. In order to evaluate the performance of the axial flux machine rapidly, an analytical design program that uses quasi-3-D computation is developed. In this paper the main features of the developed program are illustrated. Results given by the program are verified with two-dimensional and 3-D finite element computations and measurements. According to the results, it is possible to evaluate the performance of the surface-mounted axial flux PM machine with reasonable accuracy via an analytical model using quasi-3-D computation.

This paper presents a new control scheme for wide speed range operation of interior permanent magnet synchronous motor drives, where both torque and stator flux linkage are directly controlled. The proposed scheme possesses some attractive features when compared to the conventional current-controlled drives. Current controllers followed by pulsewidth modulation or hysteresis comparators and coordinate transformation are not used. This eliminates the delays through these networks and offers the possibility of dispensing with the rotor position sensor for the electronic commutator, if the initial rotor position is known only approximately. The scheme incorporates all the usual control regimes, such as the maximum torque per ampere operation in constant torque region, the flux-weakening region, and operates the drive within the voltage and current limits of the motor/inverter. The control scheme has been verified by simulation and experimental tests with a prototype interior magnet motor. This paper describes the scheme in detail, followed by results of its implementation.

In this paper a new flux-switching permanent magnet (FSPM) machine with 12 stator poles and 14 rotor poles is investigated, and compared to a machine with the same stator but 10 rotor poles. Two prototypes are studied by both finite element method (FEM) analysis and experimental measurements. The results show that the 12/14 pole prototype can provide about 7-12% higher torque, the torque ripple reduces from 8.5% to 5.1% and its synchronous inductance is also 15% higher. After optimization, the FEM simulation results show the 12/14 pole machine could provide 19% higher torque than the 12/10 pole machine and the torque ripple is further reduced to 2.3%.

An axial-flux permanent-magnet machine (AFPM) topology with coreless winding is proposed for generator units required aboard ships, aircraft, or hybrid electric vehicles. In the proposed AFPM configuration, the winding consists of rhomboidal-shaped coils encapsulated in fiber-reinforced epoxy resin. The coils have a double-layer arrangement to leave space for a cooling water duct being used to remove heat directly from the interior surface of the winding. The overall machine structure has high compactness and lightness and, due to the lack of the iron core, generator operation with power output at 400 Hz can be accomplished with high efficiency and acceptable voltage regulation. This paper discusses the basic design and construction of AFPM generators with coreless winding and experimental results taken from a 16-pole machine prototype rated 230 N1m, 3000 r/min are finally reported.

The axial-flux permanent-magnet machine (AFPM) topology is suited for direct-drive applications and, due to their enhanced flux-weakening capability, AFPMs having slotted windings are the most promising candidates for use in wheel-motor drives. In consideration of this, this paper deals with an experimental study devoted to investigate a number of technical solutions to be used in AFPMs having slotted windings in order to achieve substantial reduction of both cogging torque and no-load power loss in the machine. To conduct such an experimental study, a laboratory machine was purposely built incorporating facilities that allow easy-to-achieve offline modifications of the overall magnetic arrangement at the machine air gaps, such as magnet skewing, angular shifting between rotor discs, and accommodation of either PVC or Somaloy wedges for closing the slot openings. The paper discusses experimental results and gives guidelines for the design of AFPMs with improved performance.

El estudio eléctrico de un aerogenerador superconductor para bajas velocidades de viento, se

puede desglosar en dos etapas: diseño eléctrico y construcción. Para desarrollar el diseño eléctrico del

aerogenerador, es necesario comprender ciertos conceptos de estos; la parte eléctrica principal del

aerogenerador es el rotor y el estator el cual es el generador de una FEM y por el otro lado los materiales

necesarios para su construcción tomando en cuenta las condiciones de operación de las máquinas eléctricas

superconductoras. En el presente trabajo, se mencionan los componentes principales de una maquina

eléctricas y los materiales necesarios para la construcción de prototipos que nos sirvan como referencia para

poder innovar en un futuro en otros aerogeneradores superconductores.

Axial flux permanent magnet motors having a dual air-gap configuration have been designed and constructed to achieve high power density and used in industries interestingly and specially in the system of driving electrical vehicles. In this paper, the equation related to the design and dimensions of double-sided slotted axial flux synchronous motor with internal stator (TORUS) will be investigated. Then, an optimum design based on genetic algorithm with the purpose of increasing power density is presented. Two-dimensional finite-element analysis (FEM) is used to demonstrate these optimization and its results will be presented. Finally, it presents the resultant back emf waveform and current for a 1.0 kW, 48 V, 50 Hz, 4-poles/15-slots TORUS slotted axial motor prototype, based on our optimization techniques. KEYWORDS Axial Flux PM Motors (AFPM), Power Density, Genetic Algorithm and Finite Element method (FEM)

We designed and tested a new axial flux permanent-magnet machine (AFPM) with field weakening capability. This paper provides a summary of key design features, optimization, and test results of an AFPM prototype. The proposed field weakening method is based on the control of the d-axis component of the armature reaction flux. The paper focuses on the air-gap flux control capability of the topology.

In this paper, we present a new tubular permanent-magnet linear machine with square-shaped cross section and derive its corresponding analytical model by solving Maxwell equations and applying the superposition theorem. The analytical field solution is necessary for obtaining an analytic form of the machine parameters and variables such as the self-and mutual inductances of the windings, the thrust force, and the windings electromotive force (EMF). These provide a valuable tool for tubular machine analysis, design, and optimization. In order to achieve maximum force density, we optimized the design parameters of the proposed machine using the analytical model. We used finite-element analysis and experimental results to demonstrate the validity of the developed analytical model. Again using the Fourier series of the cogging force and its harmonic analysis, in this paper, we introduce two techniques for cogging force reduction in the new tubular linear permanent-magnet machine. The first technique reduces the cogging force due to interaction between the permanent magnets and the stator teeth, and the other reduces the cogging force due to finite length of the armature. These techniques are straightforward, and their implementations in the tubular linear permanent magnet machine with square cross section are easy. We investigated the effectiveness of the proposed techniques in cogging force reduction by 3-D finite-element analysis and experimental measurements.

This paper presents a gearless wheel motor drive system specifically designed for fuel cell electric and hybrid electric vehicle propulsion application. The system includes a liquidcooled axial flux permanent-magnet machine designed to meet the direct-drive requirements. The machine design implements techniques to increase the machine inductance in order to improve machine constant power range and high-speed efficiency. The implemented technique reduces machine spin loss to further improve efficiency. The machine design also optimizes the placement of magnets in the rotor to reduce cogging and ripple torque. An original cooling system arrangement based on the use of high thermal conductivity epoxy joining machine stator and liquid-cooled aluminum casing allows the very effective removal of machine power loss. Design details and experimental results are presented.

There are two topologies for slotted double-sided axial flux permanent magnet generator (AFPG). Choosing an AFPG with high power density is an important parameter in applications. Hence, power density Evaluation between double-sided AFPM generators topologies is necessary. In this paper, the sizing equations of axial flux slotted one-stator-two-rotor (TORUS) and two-stator-one-rotor (AFIR) type PM generators is presented and comparison of the TORUS and AFIR topologies in terms of power density is illustrated. Finally a high power double-sided AFPG is introduced in the paper.

Permanent magnet synchronous machines are known as a good candidate for hybrid electric vehicles due to their unique merits. However they have two major drawbacks i.e. high cost and small speed range. In this paper an optimal design of a permanent magnet machine is presented. A reduction of permanent magnet material for a constant torque and an extension in speed and torque ranges are chosen as the optimization aims. For this purpose the analytical model of the permanent magnet synchronous machine is derived and the appropriate design algorithm is devised. The genetic algorithm is then employed to optimize some machine specifications. Finally the finite element method is used to validate the designed machine.

This paper investigates the impact of different operational temperatures on the performance of a surface permanent magnet (SPM) machine with neodymium-iron-boron (NdFeB) magnets for electric drive applications. The field distribution of the machine for various temperatures is depicted and a comparison of the field distribution in the air gap and the machine output characteristics is performed. On a second step the effect of rotor skew is investigated.

Permanent magnet synchronous machines are known as a good candidate for hybrid electric vehicles due to their unique merits. However they have two major drawbacks i.e. high cost and small speed range. In this paper an optimal design of a permanent magnet machine is presented. A reduction of permanent magnet material for a constant torque and an extension in speed and torque ranges are chosen as the optimization aims. For this purpose the analytical model of the permanent magnet synchronous machine is derived and the appropriate design algorithm is devised. The genetic algorithm is then employed to optimize some machine specifications. Finally the finite element method is used to validate the designed machine.

This paper proposes a method to estimate the magnet temperature in surface permanent-magnet machines using high-frequency carrier signal injection. The injection of a high-frequency signal, superimposed on the fundamental excitation, allows the estimation of the stator high-frequency impedance, which is a function of both the stator and rotor impedances. The temperature of the magnets is shown to have a significant weight on the overall stator high-frequency impedance, from which it can be estimated. The high-frequency carrier signal is injected intermittently in order to minimize potential adverse effects on the normal operation of the machine. This paper first explains the physics behind the magnet temperature dependence. Then, the principles of the method, as well as its practical implementation, are discussed. Experimental verification of the method is provided.

This paper deals with the design solution adopted for a high-speed axial-flux permanent-magnet generator devoted to supplementing power in automotive 42 V electrical systems through a low-voltage multilevel neutral-point-clamped converter. The axial-flux permanent-magnet generator is suitably designed to be directly coupled with a radial turbo-expander which provides recovery of kinetic energy available from the exhaust gases of an internal-combustion engine. The multilevel converter is properly sized for systems having low voltage and high first-order harmonic frequency. The paper describes the proposed 4-kW power rating generating system and discusses various issues resulting from electromagnetic, thermal, and mechanical design of the high-speed axial-flux permanent-magnet generator. As well, investigations on modulation strategy, total harmonic distortion, and power losses are presented for the low-voltage neutral-point-clamped power electronic converter.

An axial-flux permanent-magnet machine (AFPM) topology with coreless winding is proposed for generator units required aboard ships, aircraft, or hybrid electric vehicles. In the proposed AFPM configuration, the winding consists of rhomboidal-shaped coils encapsulated in fiber-reinforced epoxy resin. The coils have a double-layer arrangement to leave space for a cooling water duct being used to remove heat directly from the interior surface of the winding. The overall machine structure has high compactness and lightness and, due to the lack of the iron core, generator operation with power output at 400 Hz can be accomplished with high efficiency and acceptable voltage regulation. This paper discusses the basic design and construction of AFPM generators with coreless winding and experimental results taken from a 16-pole machine prototype rated 230 N1m, 3000 r/min are finally reported.

Like any other permanent magnet machines, Interior permanent magnet (IPM) motors also have high efficiency. Because of their high efficiency along with good performance characteristic makes them suitable for electric drive with wide speed range. The conventional IPM machine has very little constant power range. Many attempts have been made to improve the range by modification of rotor configuration. In

Direct-drive traction motors devoted to railway applications must be designed in order to comply with both machine diameter restriction and achievement of very high torque density, as well as they should have substantial flux-weakening capability in order to be operated over the required constant-power speed range. Concerning to that, this paper deals with the original solutions adopted for design and construction of an axial-flux permanent magnet machine (AFPM) prototype rated 8000 N-m, 682 rev/min. For such a demonstrator machine a 4-stack AFPM structure is adopted in order to overcome the design restriction on the machine diameter, whereas very efficient cooling arrangement of the machine stator is accomplished by means of a water-cooled toroidal plate. The paper outlines the design characteristics and reports experimental results of the above-mentioned railway traction motor prototype.

The axial-flux permanent-magnet machine (AFPM) topology is suited for direct-drive applications and, due to their enhanced flux-weakening capability, AFPMs having slotted windings are the most promising candidates for use in wheel-motor drives. In consideration of this, this paper deals with an experimental study devoted to investigate a number of technical solutions to be used in AFPMs having slotted windings in order to achieve substantial reduction of both cogging torque and no-load power loss in the machine. To conduct such an experimental study, a laboratory machine was purposely built incorporating facilities that allow easy-to-achieve offline modifications of the overall magnetic arrangement at the machine air gaps, such as magnet skewing, angular shifting between rotor discs, and accommodation of either PVC or Somaloy wedges for closing the slot openings. The paper discusses experimental results and gives guidelines for the design of AFPMs with improved performance.

The application of concentrated windings in permanent magnet machines significantly reduces overall machine length, due to the elimination of end winding overlap making it more suitable for areas with space limitations. Efficiency is also increased due to the reduction of copper loss. In order to take full advantage of these benefits, optimization strategies have been implemented and its effects are

In designing new topologies for permanent-magnet machines based on rare earth magnets, it is necessary to diminish the undesired cogging torque. This paper presents a 3-D finite-element analysis to evaluate the effect of magnet shape and stator displacement on cogging torque reduction, for axial flux machines. It analyzes the final electromagnetic torque for the proposed configurations. Finally, it presents the resultant cogging torque waveform for a 5.0 kW prototype, based on our optimization techniques.

Based on the concept of power converter-fed machines (CFMs), an optimal machine design can be considered as the best match of the machine topology, the power electronic converter and the performance specification. To compare the power production potential of machines with various topologies with different waveforms of back EMF and current, a general purpose sizing equation and power density equation are needed to compare the main dimensions and power of such machines. In this paper, a general approach is presented to develop and to discuss these equations. Sample applications of the sizing and power density equations are utilized to compare the induction machine and the doubly-salient permanent magnet machine

This paper presents a method for estimating the magnet temperature in surface permanent-magnet (PM) synchronous machines during six-step operation. Six-step operation allows the maximum available dc-bus voltage to be applied to a machine, which maximizes its torque and speed range. This can be of importance in electric traction applications, including railway as well as electric and hybrid electric vehicles. However, six-step operation produces current harmonics that induce additional losses in the PMs and can therefore increase their temperature. An increase of magnet temperature can result in a reduced torque capability and eventually in a risk of demagnetization if excessive values are reached, with real-time rotor magnet temperature monitoring being therefore advisable. Six-step operation provides opportunities for rotor temperature monitoring from the electrical terminal variables (voltages and currents) of the motor. To achieve this goal, the rotor high-frequency resistance is...

This paper presents a gearless wheel motor drive system specifically designed for fuel cell electric and hybrid electric vehicle propulsion application. The system includes a liquidcooled axial flux permanent-magnet machine designed to meet the direct-drive requirements. The machine design implements techniques to increase the machine inductance in order to improve machine constant power range and high-speed efficiency. The implemented technique reduces machine spin loss to further improve efficiency. The machine design also optimizes the placement of magnets in the rotor to reduce cogging and ripple torque. An original cooling system arrangement based on the use of high thermal conductivity epoxy joining machine stator and liquid-cooled aluminum casing allows the very effective removal of machine power loss. Design details and experimental results are presented.

For the calculation of torque in brushless (BL) alternating current motors a local method is proposed, based on the Maxwell stress theory and the filtered contributions due to the harmonics of the magnetic vector potential in the motor air gap. By considering the space fundamental field only, the method can efficiently estimate the average synchronous torque for a variety or

This paper describes a project which addresses the use of a small segmented oscillating water column with three sections. The turbine utilizes cascaded Savonius rotors (one for each section), and this system is developed and tested for validation of the performance algorithms. This paper shows that the system is easily described using a simulation, while a small-scale wave-tank-based system is shown to generate electrical power. The system is suitable for a shoreline location such as a harbor wall, where waves are random and not orthogonal to the column. Conversion rates in the region of 20% are tabulated with an output of 25 W peak. This paper reports on the operation of the column with respect to the wave frequency and wavelength. The peak tip speed ratio of the turbine is investigated in the application and found to correlate with published data when the turbine operates in free (rather than ducted) airflow conditions. The turbine is fully characterized-the generator is a brushless permanent-magnet machine connected to a diode bridge rectifier and a variable load.

The variable-speed driven pump can result in significant energy conservation where reduced flow rates are required for long periods of time. In regard to adjustable-speed pump drives, one major contribution of this paper is the demonstration that a permanent magnet (PM) motor based on the slotless axial-flux permanent magnet machine (AFPM) topology can be a suitable candidate to advantageously compete with the induction motor for such a low-cost drive application. For the purpose of a cost comparison, the paper discusses design and construction of a prototype machine which has been conceived to replace a 1.2-hp induction motor being used in a standard adjustable-speed pump drive. Results taken from laboratory tests of the prototype machine are reported, together with an assessment of the machine manufacturing cost.

This paper discusses three-phase topologies for modulated pole machines (MPMs). The authors introduce a new three-phase topology, which takes advantage of mutual flux paths; this is analyzed using 3-D finite-element methods and compared to a three-phase topology using three single-phase units stacked axially. The results show that the new “combined-phase MPM” exhibits a greater torque density, while offering a reduction

In this paper, one new axially laminated-structure flux-switching permanent magnet machine (ALSFSPMM) with 6/7 (stator/rotor) poles is proposed. Different from the conventional flux-switching permanent magnet machine (FSPMM), the stator and rotor of ALSFSPMM are laminated parallel to the axial direction, which can make full use of PM flux linkage, decrease part magnetic saturation, and reduce the iron loss particularly in the range of high speed. By the 2-D model prediction of finite element algorithm (FEA), ALSFSPMM has lower cogging torque, stronger flux weakening ability, greater torque density, higher efficiency, etc., and hence it is an ideal candidate for the drive system of plug-in hybrid electrical vehicle (PHEV).