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Journal ArticleDOI

Fractional-Slot Concentrated-Windings Synchronous Permanent Magnet Machines: Opportunities and Challenges

01 Jan 2010-IEEE Transactions on Industrial Electronics (IEEE)-Vol. 57, Iss: 1, pp 107-121
TL;DR: This paper will cover the theory and design of FSCW synchronous PM machines, achieving high-power density, flux-weakening capability, comparison of single- versus double-layer windings, fault-tolerance rotor losses, parasitic effects, compared of interior versus surface PM machine, and various types of machines.
Abstract: Fractional-slot concentrated-winding (FSCW) synchronous permanent magnet (PM) machines have been gaining interest over the last few years. This is mainly due to the several advantages that this type of windings provides. These include high-power density, high efficiency, short end turns, high slot fill factor particularly when coupled with segmented stator structures, low cogging torque, flux-weakening capability, and fault tolerance. This paper is going to provide a thorough analysis of FSCW synchronous PM machines in terms of opportunities and challenges. This paper will cover the theory and design of FSCW synchronous PM machines, achieving high-power density, flux-weakening capability, comparison of single- versus double-layer windings, fault-tolerance rotor losses, parasitic effects, comparison of interior versus surface PM machines, and various types of machines. This paper will also provide a summary of the commercial applications that involve FSCW synchronous PM machines.
Citations
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Journal ArticleDOI
TL;DR: The analysis suggests that the dual (or triple) three-phase PMAC motor drive may be a favored choice for general aerospace applications, striking a balance between necessary redundancy and undue complexity, while maintaining a balanced operation following a failure.
Abstract: This paper presents an overview of motor drive technologies used for safety-critical aerospace applications, with a particular focus placed on the choice of candidate machines and their drive topologies. Aircraft applications demand high reliability, high availability, and high power density while aiming to reduce weight, complexity, fuel consumption, operational costs, and environmental impact. New electric driven systems can meet these requirements and also provide significant technical and economic improvements over conventional mechanical, hydraulic, or pneumatic systems. Fault-tolerant motor drives can be achieved by partitioning and redundancy through the use of multichannel three-phase systems or multiple single-phase modules. Analytical methods are adopted to compare caged induction, reluctance, and PM motor technologies and their relative merits. The analysis suggests that the dual (or triple) three-phase PMAC motor drive may be a favored choice for general aerospace applications, striking a balance between necessary redundancy and undue complexity, while maintaining a balanced operation following a failure. The modular single-phase approach offers a good compromise between size and complexity but suffers from high total harmonic distortion of the supply and high torque ripple when faulted. For each specific aircraft application, a parametrical optimization of the suitable motor configuration is needed through a coupled electromagnetic and thermal analysis, and should be verified by finite-element analysis.

779 citations


Additional excerpts

  • ...Where multiple single-phase lanes are chosen, PM motor drives are designed to have multiple, isolated, single-phase windings, each driven by independent H-bridge power converters [18], [53], as shown in Fig....

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Journal ArticleDOI
TL;DR: A comparison between interior PM and surface-mounted PM (SPM) motors is carried out, in terms of performance at given inverter ratings, showing that the two motors have similar rated power but that the SPM motor has barely no overload capability, independently of the available inverter current.
Abstract: Electric vehicles make use of permanent-magnet (PM) synchronous traction motors for their high torque density and efficiency. A comparison between interior PM and surface-mounted PM (SPM) motors is carried out, in terms of performance at given inverter ratings. The results of the analysis, based on a simplified analytical model and confirmed by finite element (FE) analysis, show that the two motors have similar rated power but that the SPM motor has barely no overload capability, independently of the available inverter current. Moreover, the loss behavior of the two motors is rather different in the various operating ranges with the SPM one better at low speed due to short end connections but penalized at high speed by the need of a significant deexcitation current. The analysis is validated through FE simulation of two actual motor designs.

404 citations


Cites background from "Fractional-Slot Concentrated-Windin..."

  • ...Most of the more recent research in this field has been devoted to motors with nonoverlapping windings, either with SPMs [4], [5] or IPMs [6], [7], although such IPM machines are often very similar to SPM ones for magnet layout and for having rather a low saliency....

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Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the magnetic gearing effect in SFPM machines with different stator/rotor pole combinations, winding configurations, and stator lamination segment types by a simple magnetomotive force-permeance model, and validated by finite element (FE) analysis.
Abstract: In this paper, switched flux permanent magnet (SFPM) machines are analyzed from the perspective of the air-gap field harmonics. It is found that the modulation of the salient rotor to PM and armature reaction fields in SFPM machines is similar to that of the iron pieces to those fields in the magnetic gear and magnetically geared machine. The magnetic gearing effect is analyzed in SFPM machines with different stator/rotor pole combinations, winding configurations, and stator lamination segment types by a simple magnetomotive force-permeance model, and validated by finite-element (FE) analysis. Different from fractional-slot surface-mounted PM machines in which the working air-gap field harmonic generates 95% of the average electromagnetic torque, 95% of the average electromagnetic torque in SFPM machines having ps stator pole pairs and n r rotor poles are contributed by several dominating field harmonics, i.e., rotating ones with |kn r ± (2i - 1)p s | pole pair (k = 1, i = 1, 2, 3) and static ones with (2i - 1)ps pole pair (i = 1, 2, 3). The FE predicted average static torques in SFPM machines are validated by measurements on prototype machines.

228 citations


Cites background from "Fractional-Slot Concentrated-Windin..."

  • ...As well known, in fractional-slot SPM machine, there are many air-gap field harmonics mainly caused by the slot effect [23] and nonsinusoidal armature MMF distribution determined by nonoverlapping concentrated winding layout [24]–[26], resulting in severe parasitic effect, such as eddy-current loss and torque ripple [27]–[30]....

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Journal ArticleDOI
TL;DR: In this article, an analytical subdomain model is presented to compute the magnetic field distribution in surface-mounted permanent magnet motors with semi-closed slots, which accurately accounts for armature reaction magnetic field and mutual influence between the slots.
Abstract: This paper presents an analytical subdomain model to compute the magnetic field distribution in surface-mounted permanent-magnet (PM) motors with semi-closed slots. The proposed model is sufficiently general to be used with any pole and slot combinations including fractional slot machines with distributed or concentrated windings. The model accurately accounts for armature reaction magnetic field and mutual influence between the slots. The analytical method is based on the resolution of two-dimensional Laplace's and Poisson's equations in polar coordinates (by the separation of variables technique) for each subdomain, i.e., magnet, air gap, slot-opening, and slots. Magnetic field distributions, back-EMF, and electromagnetic torque (including cogging torque) computed with the proposed analytical method are compared with those issued from finite-element analyses.

218 citations


Cites background from "Fractional-Slot Concentrated-Windin..."

  • ...Fractional-slot PM machines with concentrated windings present several advantages such as short end turns and hence a low copper losses, high power density, and low cogging torque [21]....

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Journal ArticleDOI
TL;DR: In this paper, the authors provide details of the design, analysis, and testing of an advanced interior permanent magnet (PM) machine that was developed to meet the FreedomCAR 2020 specifications.
Abstract: Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis, and testing of an advanced interior permanent magnet (PM) machine that was developed to meet the FreedomCAR 2020 specifications. The 12-slot/10-pole machine has segmented stator structure equipped with fractional-slot nonoverlapping concentrated windings. The rotor has a novel spoke structure/assembly. Several prototypes with different thermal management schemes have been built and tested. This paper will cover the test results for all these prototypes and highlight the tradeoffs between the various schemes. Due to the high machine frequency (~1.2 kHz at the top speed), detailed analysis of various loss components and ways to reduce them will be presented. In addition, due to the high coolant inlet temperature and the fact that the machine is designed to continuously operate at 180 °C, detailed PM demagnetization analysis will be presented. The key novelty in this paper is the advanced rotor structure and the thermal management schemes.

209 citations

References
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Book ChapterDOI

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01 Jan 2012

139,059 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a synthesis of the structures of three-phase machines with concentrated windings, and a comparative analysis of the performances of the original and traditional structures is performed by using a field calculation software.
Abstract: The windings concentrated around the teeth offer obvious advantages for the electrical machines with radial air-gap, because the volume of copper used in the end-windings can be reduced. The Joule losses are decreased, and the efficiency is improved. These machines are still limited to applications of sub-fractional power and they generally present a reduced number of phases. In the three-phase machines, the concentrated winding is too often restricted to a winding with a short pitch of 120 electrical degrees, i.e., to a winding with performances reduced compared to the traditional structures. But there is a significant number of three-phase structures which can support a concentrated winding if the number of poles is increased. In this article, the authors present a synthesis of the structures of three-phase machines with concentrated windings. (1) In the first part, the structures with a regular distribution of the slots are presented. A systematic method is proposed to determine the windings and the performances are discussed. (2) In the second part, the authors present original structures of three-phase machines with concentrated windings which use an irregular distribution of the slots. A specific method to identify these structures is described, and a comparative analysis of the performances of the original and traditional structures is performed by using a field calculation software.

596 citations

Journal ArticleDOI
01 Nov 1994
TL;DR: In this article, the theoretical and practical limitations to the field-weakening performance of surface permanent magnet, synchronous reluctance and interior permanent magnet motors when driven from an inverter with a limited volt-ampere rating were examined.
Abstract: The paper examines the theoretical and practical limitations to the field-weakening performance of surface permanent magnet, synchronous reluctance and interior permanent magnet motors when driven from an inverter with a limited volt-ampere rating. It is shown that the 'optimal' field-weakening performance consists of an infinite constant-power speed range but is limited to an inverter utilisation of about 0.7. The new concept of the interior permanent magnet parameter plane is introduced. This graphically illustrates the effect of varying the drive parameters on the shape of the field-weakening characteristic. The interior permanent magnet parameter plane is used to show that there are three types of optimal field-weakening designs. When practical factors and considerations are taken into account, the optimal high-saliency interior permanent magnet motor design is the most promising for applications requiring a wide field-weakening range. A 7.5 kW design was built and a constant-power speed range exceeding 7.5:1 was demonstrated.

515 citations


"Fractional-Slot Concentrated-Windin..." refers background in this paper

  • ...weakening, for both SPM and IPM machines, occurs when the characteristic current Ix equals the rated current IR [41], [42]....

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Journal ArticleDOI
TL;DR: In this article, the authors presented some design considerations for synchronous machines characterized by a fractional number of slots per pole per phase, which is a smooth torque, due to the elimination of periodicity between slots and poles.
Abstract: This paper presents some design considerations for synchronous machines characterized by a fractional number of slots per pole per phase. The main advantage of this configuration is a smooth torque, which is due to the elimination of periodicity between slots and poles. A second advantage is a higher fault-tolerant capability, making the machine able to work even in faulty conditions. However, the fractional-slot configuration presents a high content of MMF harmonics that may cause an unbalanced saturation and thus an unbearable torque ripple. A method to design fractional-slot machines is illustrated in this paper, including double-layer and single-layer windings. The analytical computation is extended to determine the harmonics of MMF distribution. Their effect is highlighted in isotropic as well as anisotropic machines. Finally, some considerations are reported to avoid unsuitable configurations

402 citations

Proceedings ArticleDOI
01 Jun 2003
TL;DR: In this article, the authors describe methods for designing high performance permanent magnet machines with concentrated windings, including both single and double-layer configurations of concentric windings and verify their theory using FEM analysis.
Abstract: The torque to MMF ratio of a permanent magnet machine with concentrated windings is normally much lower than for the more traditionally used distributed windings. BLDC and AC machines with concentrated windings usually have a slot pitch of only 2/3 the length of the pole pitch, which results in a poor fundamental winding factor of 0,866. This can be compared to the ideal winding factor of one, which can easily be acquired using distributed windings. However, by choosing better combinations of the pole and slot numbers for a machine with concentrated windings, the winding factor can be substantially increased. Moreover, it is also possible to achieve low cogging torque without skewing, simply by selecting appropriate combinations. The presented theory includes both single- and double-layer configurations of concentrated windings. The theory is verified by using FEM analysis. This paper describes methods for designing high performance permanent magnet machines with concentrated windings.

399 citations


"Fractional-Slot Concentrated-Windin..." refers background or methods in this paper

  • ...In [4], Magnussen and Sadarangani presented a method for...

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  • ...These include high-power density, high efficiency, short end turns [3], [4], high slot fill factor particularly when coupled with segmented stator structures, low cogging torque, fluxweakening capability, and fault tolerance....

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