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Analysis of the Yokeless And Segmented Armature Machine
Abstract
This paper presents a new type of axial flux motor, the yokeless and segmented armature (YASA) topology. The YASA motor has no stator yoke, a high fill factor and short end windings which all increase torque density and efficiency of the machine. Thus, the topology is highly suited for high performance applications. The LIFEcar project is aimed at producing the world's first hydrogen sports car, and the first YASA motors have been developed specifically for the vehicle. The stator segments have been made using powdered iron material which enables the machine to be run up to 300 Hz. The iron in the stator of the YASA motor is dramatically reduced when compared to other axial flux motors, typically by 50%, causing an overall increase in torque density of around 20%. A detailed Finite Element analysis (FEA) analysis of the YASA machine is presented and it is shown that the motor has a peak efficiency of over 95%.
... Finally, the stator back yoke can be removed, as shown in Figure 3d. This structure is called the YASA type [14]. By removing the stator back yoke, the stator is constructed as a segmented structure, and a high fill factor and without a mechanical-reduction gear system was selected in this work. ...
... Finally, the stator back yoke can be removed, as shown in Figure 3d. This structure is called the YASA type [14]. By removing the stator back yoke, the stator is constructed as a segmented structure, and a high fill factor and Among AFPM motor topologies (Figure 2), the double-sided internal rotor (AFIR) and double-sided internal stator (TORUS) types exhibit a higher torque density compared to the single-sided structure [7,10]. ...
... Finally, the stator back yoke can be removed, as shown in Figure 3d. This structure is called the YASA type [14]. By removing the stator back yoke, the stator is constructed as a segmented structure, and a high fill factor and short end windings are feasible. ...
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.
... In this variant, the ferromagnetic core of the stator is broken down into separate individual segments [18,19]. This is why the structure is also referred to as segmented [20]. The individual teeth of the stator are no longer connected via a magnetic back iron, but are instead fastened to a polymer ring, e.g., with the aid of screws, a clamp or by adhesive [17]. ...
... The individual teeth of the stator are no longer connected via a magnetic back iron, but are instead fastened to a polymer ring, e.g., with the aid of screws, a clamp or by adhesive [17]. This arrangement also helps to reduce the stator weight and volume, its costs as well as the losses inside the core compared to conventional AFM structures [19][20][21]. ...
With the increasing electrification of the powertrain across all mobility applications, the requirements for electric motors are becoming more and more diverse: Depending on the application, the requirements for power and torque vary greatly while at the same time keeping costs, weight and installation space must be kept to a minimum. While the radial flux design has established itself for electric traction drives in the market, axial flux motors also provide great potential for vehicles with high torque requirements and small installation space. The axial arrangement of the components within this topology allows many degrees of freedom in product design, which results in many sub-variants of axial flux motors. However, there is a lack of a uniform and consolidated categorization of these variating design features in both scientific literature and industrial practice. In this work, the different design features of axial flux motors were identified based on an extensive as well as systematic literature research and categorized according to uniform characteristics. As a result, the complex variety of different axial flux motor variants is systematized and standardized, which lays the foundation for a uniform categorization of this motor topology.
... The last type is the axial-flux yokeless and segmented armature machine (YASAM). This topology was first proposed in [52], which is shown in Fig. 14(c). Unlike previous types, whose magnetic paths of two MPs are in parallel, the magnetic path of two rotors for the YASA type is in series, which makes the common yoke of the stator unnecessary. ...
... (b) VM[49]. (c)YASAM[52]. ...
Electrical machines based on dual mechanical port (DMP) structures are widely used to increase the overall efficiency and power factor, to increase the speed / torque, or to distribute or combine the energy from different ports flexibly. Today, dual mechanical port machines have increasing applications in the field of transportation electrification with the advantages of structural compactness, design flexibility and high efficiency. By analyzing from fundamental principles to advanced controlling strategies, this paper aims to provide a comprehensive overview of existing DMP topologies. In this paper, the pros and cons of all topologies are analyzed, and their challenges and future trends are discussed.
... These articles also provide a means to extract trends in EM technology that migrate to the production of EVs. Research studies by [11][12][13][14][15][16][17][18][19] have focused on advanced new EM design, construction, and control strategies, enabling higher torque density, minimal to zero use of rare earth materials, and reduced torque ripple and/or improved torque delivery for drivability, respectively. The direction of magnetic flux, which is traditionally radial in PMSMs, has been shown analytically [18,20,21], experimentally [7], and in the production of EMs [22,23] to provide benefits in torque and packaging. ...
... The direction of magnetic flux, which is traditionally radial in PMSMs, has been shown analytically [18,20,21], experimentally [7], and in the production of EMs [22,23] to provide benefits in torque and packaging. Similar to studies by [5][6][7][8], a historical perspective, from the early 2000s to the present (2023), on EMs is provided in terms of performance and packaging [9,11,17,18,20,24,25], showing PMSMs to comprise a majority of the topology and yield the highest performance and smallest packaging, which are or attributes are provided for select EMs and TRMs, and the section is concluded with a high-level overview of TRM parasitic losses and the selection of power flow and torque transfer mechanisms for efficiency. ...
A review of past, current, and emerging electric vehicle (EV) propulsion system technologies and their integration is the focus of this paper, namely, the matching of electric motor (EM) and transmission (TRM) to meet basic requirements and performance targets. The fundaments of EM and TRM matching from a tractive effort and a vehicle dynamics perspective are provided as an introductory context to available or near-production propulsion system products available from OEM and Tier 1 suppliers. Engineering data and details regarding EM and TRM combinations are detailed with a specific focus on volumetric and mass density. Evolutionary trends in EM and TRM technologies have been highlighted and summarized through current and emerging products. The paper includes an overview of the initial EV propulsion system’s sizing and selection for a set of simple requirements that are provided through an examination of three light-duty EV applications. An enterprise approach to developing electrified propulsion modules with suitable applicability to a range of light-duty EVs from compact cars to full-size trucks concludes the paper.
... Specifically, Axial Flux Permanent Magnet (AFPM) machines have gained great interest because they have the advantages of PMSM with high levels of torque densities (Nm/m 3 ) and specific torque density (Nm/kg) [5]. Among AFPM machines, the YASA topology (Yokeless And Segmented Armature) stands out regarding high torque density and high efficiency [6]. ...
... With the voltage waveform, the FFT (Fast Fourier Transform) is performed in order to obtain the contribution of the fundamental component of the phase backemf E a1 . The ψ pm is then determined according to equation (6). ...
This work addresses the dynamic modeling and the drive of a multiphase YASA-type electric machine for use within electric traction. The main technical aspects of the machine, which can be fed with three or five phases depending on the electrical connection of its windings, are presented. The dynamic model of the machine for the two different electrical connections (three or five phases) is given in the synchronous reference frame and the parameters of the lumped model are obtained through experimental tests. In order to consider the vehicular application, standard driving cycles are used to serve as a reference for the speed whereas vehicular dynamics are considered to define the load torque to be developed by the machine. Afterward, field orientation control (FOC) is implemented for the machine to operate with three or five phases and simulations were carried out to show that the dynamic behavior is similar in both cases. Experimental tests validated the model and the FOC for the machine with both electrical connections. In addition, the reference curves of the driving cycle were satisfactorily followed, indicating the possibility of using the multiphase YASA machine with the control developed in vehicular traction applications.
... The central stator is made of a spiral of electrical steel sheet. This topology was chosen in advance of YASA topology [8,9] because of ease of its manufacture and better mechanical strength. Since the distance between machine slots varies with the radius, in the first step the stator stack was manufactured as a raw part without slots. ...
The paper deals with design of a five phase axial permanent magnet synchronous machine. The analytical design is verified by finite element analysis of designed topology. A prototype of designed machine is manufactured and measured in no-load state and under various loads.
... Axial flux motors, or axial gap, as shown in Figure 18, have gained increasing attention in the electric vehicle (EV) industry due to their unique geometry and performance characteristics. Unlike traditional radial flux motors, axial flux motors have a disc-shaped structure where the magnetic flux flows parallel to the motor's rotational axis [262]. The stator and rotor are arranged face-to-face in an axial flux motor. ...
The global reliance on electric vehicles (EVs) has been rapidly increasing due to the excessive use of fossil fuels and the resultant CO 2 emissions. Moreover, EVs facilitate using alternative energy sources, such as energy storage systems (ESSs) and renewable energy sources (RESs), promoting mobility while reducing dependence on fossil fuels. However, this trend is accompanied by multiple challenges related to EVs' traction systems, storage capacity, chemistry, charging infrastructure, and techniques. Additionally, the requisite energy management technologies and the standards and regulations needed to facilitate the expansion of the EV market present further complexities. This paper provides a comprehensive and up-to-date review of the state of the art concerning EV-related components, including energy storage systems, electric motors, charging topologies, and control techniques. Furthermore, the paper explores each sector's commonly used standards and codes. Through this extensive review, the paper aims to advance knowledge in the field and support the ongoing development and implementation of EV technologies.
... 1 Introduction AXIAL flux permanent magnet (AFPM) motor with yokeless and segmented armature (YASA) is a single stator, double rotor motor with the advantages of compact structure and high torque density [1] . It is suitable for applications having strict requirements for size and weight, such as electric vehicles and wind power generators [2][3] . ...
The slot shape of yokeless and segmented armature (YASA) motor differs significantly from the traditional ones due to its dual slot openings. This paper proposes an analytical method for determining the slot leakage inductance of the novel slot of the YASA axial flux permanent magnet (AFPM) motor. A general analytical formula for calculating the slot leakage inductance component within a single YASA slot is derived and the phase slot leakage inductance of a YASA-AFPM motor is further yielded based on its unique winding distribution. It reveals that the coil-side width has significant influence on the slot leakage inductance component while the pole-slot combination has apparent influence on the number of slot leakage inductance components of the phase inductance. Additionally, the relationships between coil-side width, pole-slot combination and slot leakage inductance are revealed analytically. Finally, the slot leakage inductance of a 20-pole-24-slot AFPM-YASA motor is calculated by the proposed method, and the results are in agreement with those obtained by the finite element method (FEA), verifying the accuracy of the proposed method.
... A cost effective AFM with SMC/steel lamination sheet core and 14 poles was presented in [78], higher efficiency was obtained in the machine and smear of iron particles was removed on the SMC surface by the means of a chemical process using phosphoric acid solution. A yokeless and segmented armature topology motor with SMC and has 10 poles was designed in [79] and found that the machines have higher torque density of 20% compared with other motors and the iron loss in the stator decreased by 50% and peak efficiency of 96% . ...
i Abstract-The introduction of compacted insulated iron powder in electrical machines design makes their manufacturing process easy together with high rates of production and the machine parts made from it are stable dimensionally compared to conventional laminated steel. The research work presented in this thesis was carried out with the main aim to improve the overall performance of a three-phase Axial Flux Machine (AFM) using Soft Magnetic Composite (SMC). To realise it, the machine was redesigned in a way to benefit from the unique properties of the material such as low eddy current loss at high frequency, isotropic magnetic properties and simple manufacturing process. Due to the three-dimensional (3D) nature of the SMC material and AFM structure, 3D Finite Element Analysis (FEA) was carried out for accurate prediction of performance and extensive simulation results were provided. Higher fill factor up to 70% was achieve by compacting the pre-formed coils on a bobbin before sliding onto the tooth for final assembly, which offered a significant improvement in performance. AC winding loss analysis was performed due to open-slot stator winding configuration and the higher frequency of operation resulting in skin-depths of the same order of size as the typical conductor diameters. A method of AC winding loss reduction was introduced using a single steel lamination sheet to shield the windings from stray fields due to the open-slot stator construction which encourage an elevated AC loss at AC operation. Moreover, this approach is easy to implement for this machine topology and does not require the use of more complex twisted and Litz type conductors. To validate the 3D FEA, a prototype machine was built which ultimately resulted in 6 machines being tested without and with steel lamination sheet during this PhD. The measured result which includes the back EMF, full load voltage, torque, power and losses are thoroughly presented and agreed with the 3D FEA very well. Depending on lamination type, it is shown that the AC winding loss reduced by up to 48.0%, total loss reduced by up to 31.7%, this method has disadvantages of minor reduction of up to 3.5%, 5.8% and 2.8% in the peak back EMF, torque and output power respectively. The efficiency has increased by up to 10.3%. The research studies signify the viability of designing and producing a highly efficient AFM with SMC and has the potential for mass production, this thesis makes significant contribution by implementing a simple novel method for AC winding loss reduction using steel lamination sheet to shield the stray flux due to open-slot stator winding construction.
... Researchers have focused on improving the output torque performances of AFPM machines [2]. The yokeless and segmented armature AFPM machines remove the stator yoke, which reduces the stator mass and increases the torque density [3]. As a result, yokeless and segmented armature AFPM machines are very suitable for the in-wheel drive system [4]. ...
The axial flux permanent magnet (AFPM) machines with the parallel magnetic circuit (PMC) rotor can effectively improve its torque density. The PMC rotor consists of two sub‐rotors, radial Halbach array permanent magnet (PM) and tangential PM. The magnetic fields generated by two sub‐rotors are not in the same 2‐D analytical planes. In this paper, an equivalent analytical model of PMC‐AFPM machines is proposed to solve this problem. The radial Halbach array PM rotor is equated to the axial Halbach array PM rotor based on the equivalent transformation principle. The exact subdomain models of equivalent axial Halbach array PM rotor and tangential PM rotor are built respectively and then superimposed to obtain the magnetic field distribution. The electromagnetic characteristics of the PMC‐AFPM machine under no‐load and load conditions are calculated by the proposed analytical model and compared with calculations of the finite element model (FEM). The results verify the accuracy of the equivalent analytical model. The comparative analysis of the AFPM machines with PMC rotor and tangential PM rotor verifies the advantage of PMC rotor configuration to improve the torque density. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.
... The NN type features the primary flux circulating circumferentially in the stator yoke linking with a Toroidal Gramme ring winding and corresponds to the machine in reference [6], while the NS type directs the main flux axially through the stator linking with windings of either the distributed double-layer type or tooth type. The yokeless and segmented armature (YASA) motor makes use of the NS topology to remove the stator yoke (backing iron) but still retains the stator teeth, thereby improving the torque-to-weight ratio compared to conventional AFIR motors [8,9]. A general diagram illustrating the YASA topology is presented in Figure 1a. ...
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.
... The axial flux machines are categorized in numerous different topologies based on its stator and rotor arrangements. For example, dual rotor single stator [12], [13], dual stator single rotor [14], [15], multi stator multi rotor [16], [17], toroidal stator, NS and NN rotor [18], [19], Yokeless And Segmented Armature (YASA) etc [20]- [22]. Among them, the YASA stator machines are getting much attraction nowadays thanks to its high slot fill factor, short end winding, reduced joule losses and improved efficiency [23]- [25]. ...
The demand for Axial Flux Permanent Magnet(AFPM) brushless DC machine is expanding in electric mobility sector owing to its high power density and compact size. However, the axial flux PM machine requires the magnets to be inset on the rotor core for more robustness and reliability. In this paper, the effects of varying depth of the inset-magnet on the airgap magnetic flux density distribution and the dynamic torque response of the machine are analyzed. A parametric analysis is performed on the machine which leads to an optimum value of the inset-magnet depth for best dynamic performance. In order to carry out the analyses, a 1 kW AFPM BLDC machine with18-slot 20-pole combination is designed and investigated using3-D finite element analysis based software. Finally, the steady state performance of the designed machine is reported for the optimum inset-magnet depth
... Based on the traditional torus motor, the entire stator was replaced with segmented stators fixed on the casing, and the stator yoke was removed. Furthermore, as shown in Figure 13, square coils were used to efficiently utilize the slot space to achieve a high fill factor, shorten the axial length of the motor, and further reduce the weight [49]. Consequently, the YASA motor had approximately 50% less stator weight, exhibited a 20% increase in torque density, and reached 95% efficiency. ...
Axial flux permanent magnet synchronous motors (AFPMSMs) have been widely used in wind-power generation, electric vehicles, aircraft, and other renewable-energy applications owing to their high power density, operating efficiency, and integrability. To facilitate comprehensive research on AFPMSM, this article reviews the developments in the research on the design and control optimization of AFPMSMs. First, the basic topologies of AFPMSMs are introduced and classified. Second, the key points of the design optimization of core and coreless AFPMSMs are summarized from the aspects of parameter design, structure design, and material optimization. Third, because efficiency improvement is an issue that needs to be addressed when AFPMSMs are applied to electric or other vehicles, the development status of efficiency-optimization control strategies is reviewed. Moreover, control strategies proposed to suppress torque ripple caused by the small inductance of disc coreless permanent magnet synchronous motors (DCPMSMs) are summarized. An overview of the rotor-synchronization control strategies for disc contra-rotating permanent magnet synchronous motors (CRPMSMs) is presented. Finally, the current difficulties and development trends revealed in this review are discussed.
... The torus type includes popular AFPM variants, such as the coreless machine, yokeless and segmented armature (YASA) machine, as well as the toroidal winding machine. More information about these variants can be found in [13], [16]. ...
Axial flux permanent magnet machines (AFPM) are popular for applications that benefit from high torque density and an axially compact form factor, such as in-wheel traction drives. Although the radial flux permanent magnet machine (RFPM) and the AFPM work based on the same underlying principle, the differences in their geometry introduce complexities in analysis of the AFPM. In this paper, the different AFPM design variants, their sizing approaches, computationally efficient design optimization techniques, and manufacturing techniques reported in literature are reviewed. In addition to classical AFPM machines, emerging variants and research opportunities with potential to push the boundaries of electric machine technology are reviewed. These include bearingless AFPMs, magnetically geared AFPMs, and combined radial-axial flux machines.
... As shown in [49]- [52], SMC can offer significant improvements in performance and power density, given the possibilities for mass reduction, wide frequency range of application, low losses, among others features. The YASA topology, also referred to as Internal Segmented Armature (ISA), was first presented by [53] in 2007. The YASA topology is an enhancement of the SSDR machine type, where an attempt to optimize the N-N and N-S constructions led to a design where the stator yoke (back-iron) was completely removed, eliminating with it the re-circulation of magnetic flux between neighboring poles. ...
... This paper explained the importance of combined cooling to achieve the cooling requirements. Woolmer et al. [14] studied the yokeless motor and found it increased the torque density and overall performance of the motor. Lamperth et al. [15] developed technology based on axial flux topology. ...
The cooling of E-machines was investigated using phase change material (PCM). The PCM is widely used in the cooling of electronic components because of its heat-absorbing and cooling properties. In this study, PCM OM35 (50:50) and OM35 (60:40) were used for the cooling of E-Machines, which are commonly known as electric vehicle motors. Three different configurations, viz. no rib, two ribs, and four ribs, were studied to understand the impact of thermal behaviour on bracket cooling. The ribs were added in between the brackets to enhance the heat transfer. Numerical simulations were performed using the volume of fluid multiphase analysis approach to model the behaviour of phase change inside the brackets for 18 KW E-Machines. Based on the study, a four rib configuration showed good performance compared to no rib and two rib configurations, and heat transfer improved by 6%. Heat transfer is thus improved by increasing the number of ribs placed between the brackets. The cyclic heat load was applied to the best performing ribs to study the impact of different PCM materials OM35 (50:50) and OM35 (60:40).
... The shorter end windings in the YASA topology improve the torque density of the motor [6], [7]. Additionally, this topology reduces core losses by replacing the stator yoke with an additional rotor [5], [8], [9]. Grain-oriented electrical steel (GOES) is employed for the stator teeth, which primarily experience axially directed flux in the YASA topology. ...
This paper presents and evaluates a dual rotor axial flux permanent magnet motor for electric aircraft applications. Several features, including grain oriented electrical steel, Halbach arrays, and wires with rectangular cross-sections, are used to improve torque density and efficiency. A novel winding arrangement is used to mitigate interturn short-circuit faults. Rather than simply optimizing the motor by itself, this paper evaluates the tradeoffs between motor performance and its interfaces with the drive, thermal management system (TMS), and mechanical structure. This information can be used along with similar analyses of these subsystems to select the design with the system-level optimal performance. The paper uses finite element simulations to characterize tradeoffs between active mass, efficiency, fundamental frequency, power factor, axial forces on the rotors, and cooling surface area. Several designs exceed 95% efficiency at takeoff with less than 8 kg of active mass. While high pole counts, a large outer radius, and short stator teeth tend to optimize the magnetic performance at takeoff, this can reduce cruise efficiency, reduce the surface area through which the TMS can extract heat, increase the fundamental frequency the drive must supply, increase the structural mass required to support the rotors, and introduce complexity to manufacturing process. Further analysis for a selected design reveals that the power factor can be significantly improved with a minimal torque penalty via field weakening, due to significant saturation in the stator teeth.
The yokeless and segmented armature (YASA) machine's compact structure, high efficiency, and high torque density make it an ideal choice for electric vehicle in-wheel applications. The stator cores of YASA machines are available in different materials and geometries. This paper presents a comparative study of YASA machines with different stator cores to determine their advantages and disadvantages for electric vehicle in-wheel applications. First, YASA machines with radial lamination silicon steel (RLSS) stator cores and soft magnetic composite (SMC) stator cores are introduced. A new combined lamination silicon steel (CLSS) stator core, consisting of two tangential laminated shoes and a radial laminated bar, is also proposed. The main parameters of YASA machines with different stator cores for electric vehicle in-wheel applications are listed. Then, the electromagnetic performance, including efficiency, torque density, flux weakening capability, and torque/power characteristics, are comprehensively compared based on 3-D finite element analysis (FEA). Finally, the guideline for the stator core selection of YASA machines for electric vehicle in-wheel applications is given.
This paper investigates the influence of randomly distributed additional air gaps (AAGs) between stator teeth and back-iron on cogging torque in 12-slot/10-pole modular permanent magnet machines by using Taguchi method. It has been observed that with uniform AAGs, a maximum cogging torque exists, while non-uniform AAGs significantly affect cogging torque, particularly resulting in the worst-case scenario with the highest cogging torque due to random non-uniform AAG distributions. In comparing uniform and non-uniform AAGs, two key findings are: (a) main harmonic order of pole number of cogging torque in nonuniform AAGs is much lower than that of least common multiple of slot and pole numbers in uniform AAGs; (b) amplitude of cogging torque in non-uniform AAGs is much higher than that in uniform AAGs. Hence, special attention should be paid for controlling non-uniform AAGs in mass production. The correctness of the results is validated by experiments based on the prototype in mass production.
This article focuses on modelling and validating a groundbreaking magnetorheological braking system. Addressing shortcomings in traditional automotive friction brake systems, including response delays, wear, and added mass from auxiliary components, the study employs a novel brake design combining mechanical and electrical elements for enhanced efficiency. Utilizing magnetorheological (MR) technology within a motor–brake system, the investigation explores the influence of external magnetic flux from the nearby motor on MR fluid movement, particularly under high-flux conditions. The evaluation of a high-magnetic-field mitigator is guided by simulated findings with the objective of resolving potential issues. An alternative method of resolving an interaction between an electric motor and a magnetorheological brake is presented. In addition, to test four configurations, multiple absorber materials are reviewed.
Yokeless and Segmented Armature (YASA) axial flux permanent magnet (AFPM) motors have been found as the highest power density candidate for various axial flux topologies, especially with concentrated winding flat wires. However, this winding configuration produces AC losses that limit efficiency gains. This article primarily discusses the AC eddy current losses calculation of flat wire armature winding and efficiency optimization by matching a perfect tradeoff of AC and DC winding losses by selecting cross profile specifications of flat wire, as well as the axial size of coils distance from the air-gap side. A hybrid analytical– finite element analysis (FEA) method for rapidly calculating eddy current losses of the rectangular cross-section wires is induced and applied for the YASA AFPM motor based on the tangential and axial flux leakage distribution in slots. The specification of flat wire directly affects the AC and DC losses of the windings. Certainly, the axial position of the coil affecting the eddy current loss is also considered. According to the study, two winding structures that can effectively reduce eddy current losses are acquired and the results are also verified. The calculation of winding losses and optimization of flat wire specifications are implemented and validated on the studied 12-slot 10-pole YASA AFPM motor, rated at 35 kW, with open slots by measuring efficiency. Meanwhile, the accuracy of 3-D FEA is further verified.
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This paper presents the design and performance of an integrated magnetorheological fluid brake axial flux permanent magnet (IMRFB-AFPM) machine with two switchable operation modes: rotation and brake modes while the machine has two kinds of windings: armature winding in axial stators and braking winding in radial stator. In rotation mode, this machine is equal to a conventional AFPM machine with high torque density. When switching to brake mode, MR fluid is excited by braking winding and applies large damping stress to the rotor to brake it. This paper illustrates the machine topology, operation principles, and design flow of the proposed machine. Then, this paper analyzes the torque generation mechanism in two modes and applies parameters optimization to improve the torque capability of each mode. Due to the independence of the magnetic flux path, the parameters optimization is divided into two parts: AFPM part and IMRFB part. After the optimization process, the electromagnetic performances of the optimal IMRFB-AFPM machine are analyzed by finite element (FE) analysis. Finally, a prototype machine with the optimal geometric parameters is manufactured and verified experimentally. The experiment results agree well with FE analysis results, validating the feasibility and practicability of the proposed design.
Zusammenfassung
Axialflussmaschinen eignen sich mit ihrer scheibenförmigen Bauweise gut dazu, eine hohe Drehmomentausbeute in Bezug auf das eingesetzte Aktivmaterial zu realisieren. Gleichzeitig erlaubt es der planare Aufbau, den Eisenkreis modular und möglichst einfach herstellbar zu gestalten. In diesem Beitrag wird eine Maschinenvariante vorgestellt, deren Eisenkreis aus U‑Jochen mit UI-30-Kernblechen und Steckspulen aufgebaut ist. Solche genormten Bleche mit 30 × 40 mm Außenmaß und 30 × 10 mm Nutausschnitt werden normalerweise zum Bau von Transformatoren eingesetzt. Vorteile dieses Maschinendesigns sind einfache Herstellbarkeit und Skalierbarkeit über die Anzahl der U‑Joche. Nachteile sind Wirbelstromverluste in den Magneten der Rotorscheibe, was den nutzbaren Drehzahlbereich aufgrund erhöhter Magnettemperaturen einschränkt. Da sich mit den UI-30-Kernblechen ebenso eine PMSM-Radialflussmaschine mit Außenläufer herstellen lässt, erfolgt ein direkter Vergleich der für beide Maschinenvarianten aufgebauten Prototypen anhand von Messdaten. In Bezug auf das Drehmoment ist die Radialflussmaschine im Vorteil, während die Axialflussmaschine in Bezug auf Rotorverluste, Materialbedarf und Herstellbarkeit besser abschneidet.
In this paper, electromagnetic performances of radial-flux dual-rotor (DR) fractional-slot concentrated-winding permanent magnet (PM) machines with series and parallel magnetic circuits are compared based on the optimised designs using finite-element analysis based genetic algorithm. It is found that under the same copper loss, the series magnetic circuit DRPM machine has higher output torque and lower iron loss due to yokeless structure. The influences of critical design parameters on both machines, e.g., PM thicknesses and pole arcs, inner and outer split ratios, and stator tooth width, are also investigated. It shows that both machines tend to sacrifice the inner rotor in order to enlarge the slot area, and the outer rotor makes a major contribution to the resultant torque.
Este trabalho desenvolveu a construção de geometrias modeladas através de Elementos Finitos (FEM) ante a construção dos núcleos do estator de um motor do tipo fluxo axial, este tipo de máquina que, compõe-se de materiais ferromagnéticos, produzidos a partir da metalurgia do pó. O núcleo, comumente construído de chapas laminadas, norteia a possibilidade dos materiais SMC’s (Soft Magnetic Composites) como alternativa ao laminado de grão não-orientado. Desta forma, o modelo computacional vem a levantar os comportamentos e geometria da máquina. Foi utilizado o software ANSYS ELETRONICS, de maneira a efetuar a simulação e, validar os parâmetros apurados das caracterizações, visando futura aplicação a uma máquina elétrica de fluxo axial do tipo YASA (Yokeless and Segmented Armature). Como resultados, desenvolveram-se núcleos e, demais geometrias visando-se a validação do uso da tecnologia e confirmação de parâmetros tridimensionais, a partir das caracterizações, o qual auxiliará na composição total do estator da máquina elétrica, tem-se que, para região de 7500 A/m as variações de B ficaram entre 1,5 e 1,42 T, para Somaloy® 1P, 1,55 e 1,25 T, para Somaloy® 3P, e, 1,42 e 1,35 T para Somaloy® 5P.
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.
In this paper a Lumped Parameter Thermal Network (LPTN) is proposed for a Yokeless and Segmented Armature (YASA) axial flux permanent magnet (AFPM) machine. A simulation model is used to examine the machine in isolation, with an Integrated Motor Drive (IMD), and the machine and IMD with a remote heat sink connected using heat pipes. Losses from electrical and magnetic Finite Element Modelling (FEM) are used as inputs to the model. Introduction of the IMD is found to reduce the power rating of the machine by 27%. This performance can be returned by utilising a remote heat sink configuration to enable enlargement of the heat sink by twice the original volume.
Axial flux permanent magnet (PM) machines are being developed for many applications due to their attractive features. An extensive literature exists concerning the design of a variety of types of axial flux PM machines. An overview of axial flux, slotless and slotted various PM machines are presented in this paper. Machine structures, advantages and features of the Axial Flux PM machine (AFM) are clarified. Several interesting novel axial flux machine structures are also covered from a variety of perspectives.
Two different external-rotor-internal-stator TORUS type axial flux PM machines can be derived based on the direction of the flux. In the first type of the TORUS machine, magnet driven flux enters the stator and travels circumferentially along the stator core while, in the second type, the flux enters the stator and travels axially along the machine axis of rotation. The major differences between the two topologies are the direction of the magnet driven flux, the winding arrangement and the thickness of the stator yoke. In this paper, the sizing equations are derived for both types of TORUS machines. Based on the sizing analysis, optimum design is achieved for minimum ripple torque and maximum torque density. Furthermore, finite element analysis (FEA) of both TORUS structures are investigated to get an insight in 3D field distribution, flux directions and paths in different parts of the machines for different load conditions. Minimization of the cogging and ripple torque components of the TORUS concept machines are displayed using 3D FEA for the insight in pulsating torques, ripple torques and cogging torques. Finally the comparison of the TORUS topologies are made in terms of flux densities, cogging and ripple torques and the results are illustrated in the paper.
Purpose – To design a high power density machine, an automatic design method is proposed. Hopefully, automatic design method uses only the requirements (torque and speed) and the information about sources (voltage and current). Design/methodology/approach – To calculate the volume, a necessary flux density and an inductance are calculated by the permeance method. All mechanical parameters, stator diameter, teeth width, turn number and so on, realize the necessary flux density and an inductance, and these parameters are expressed as a function of a rotor diameter. By using both conditions of current density and copper loss, a rotor diameter which realizes the minimum volume can be obtained. Findings – As a result of an optimum design, 50 kW SPMSM is realized only into 2[L] spaces, which copper loss is only 500[W], 1 percent of the maximum output. Moreover, 50 kW axial flux type machine is realized only into 1.3[L] spaces. Accurate comparison is possible by only optimum designs because these have the solutions of the same conditions. In a comparison result, a volume of the axial flux machine is less than that of the radial flux machine, because the radial flux type cannot utilize the large rotor diameter. Thus the axial flux type motor is suitable to the high torque machine. Research limitations/implications – In this research, the length of the coil end and the iron loss, are ignored, because an axial length of stator is much longer than a coil end especially for the high power motor, and the iron loss estimation has not been established. Practical implications – By using this method, it is possible to perform the automatic design. If a designer inputs only the requested torque, speed and device information, an automatic calculation will be done, and a designer can automatically get a motor structure. Originality/value – Although some papers can calculate the mechanical parameters which realize only torque, all requirements, torque, speed and power are satisfied in this paper. In addition, an optimum point of the volume is theoretically obtained. In industrial applications, because the power range is very important, especially for electric vehicles and so on, this paper provides more compact and more powerful machines.
This paper presents the design of two permanent magnet machines for a novel propulsion system for hybrid electric vehicles called the Four Quadrant Transducer (4QT). The presented machines are designed for a medium-sized passenger car with front wheel drive. It is therefore essential that the machines are compact, since the available space in the engine compartment is very limited. The first machine has a 3D-flux topology and uses Soft Magnetic Composites (SMC), i.e. iron powder, as the core material. The core is segmented in 48 parts, which individually consists of teeth and a rounded back. A rectangular conductor is toroidally wound around the back of each segment resulting in short end-windings and a high slot fill factor of 0,78. The second electrical machine design includes features that are unique for its power class, e.g. a segmented core with grain-oriented silicon iron teeth and rectangular copper conductors. The result is a slot fill factor of 0,74, a high fundamental winding factor for a tooth winding of 0,95, a cogging torque close to zero and high efficiency. Electromagnetic analyses of the proposed machines are performed with analytical calculations and by using the 3D-and the 2D-finite element methods, including torque ripple and eddy current calculations. A laboratory prototype has been built.
This paper presents a new type of axial flux motor, the segmented armature torus (SAT) topology. The SAT motor has no stator yoke, a high fill factor and short end windings which all increase torque density and efficiency of the machine. Thus, the topology is highly suited for high performance applications. The LIFEcar project is aimed at producing the world's first hydrogen sports car, and the first SAT motors have been developed especially for the vehicle. A laboratory prototype has been built and some preliminary results presented. The peak torque density of the drive is 18 Nm/Kg