Littérature scientifique sur le sujet « Fractional-Slot Non-Overlapping »

Permanent magnet synchronous machines with non-overlapping concentrated fractional-slot windings present certain improved electrical characteristics compared to full pitch windings configurations. This paper describes the design process and construction of two 10-pole permanent magnet synchronous motors, featuring full-pitch and fractional-pitch windings. The paper compares these two configurations in terms of performance and efficiency. Both motors have been designed for direct-drive applications with low speed and high efficiency capability and are intended to be used as a traction drive in an electric prototype vehicle. The proposed motors have external rotor configuration with surface mounted NdFeB magnets. The electromagnetic characteristics and performance are computed and analyzed by means of finite elements analysis. These results are finally compared with the experimental measurements on respective prototypes.

This paper presents study of a multi-slice subdomain model (MS-SDM) for persistent low-frequency sound, in a wheel hub-mounted permanent magnet synchronous motor (WHM-PMSM) with a fractional-slot non-overlapping concentrated winding for a light-duty, fully electric vehicle applications. While this type of winding provides numerous potential benefits, it has also the largest magnetomotive force (MMF) distortion factor, which leads to the electro-vibro-acoustics production, unless additional machine design considerations are carried out. To minimize the magnetic noise level radiated by the PMSM, a skewing technique is targeted with consideration of the natural frequencies under a variable-speed-range analysis. To ensure the impact of the minimization technique used, magnetic force harmonics, along with acoustic sonograms, is computed by MS-SDM and verified by 3D finite element analysis. On the basis of the studied models, we derived and experimentally verified the optimized model with 5 dBA reduction in A-weighted sound power level by due to the choice of skew angle. In addition, we investigated whether or not the skewing slice number can be of importance on the vibro-acoustic objectives in the studied WHM-PMSM.

An analytical subdomain model is employed in this paper for predicting the magnetic field distributions in a three-phase double-stator permanent magnet synchronous machine (DS-PMSM) during open-circuit and onload conditions. Due to the stator cores are located in the outer and inner parts of the motor, the DS-PMSM construction is quite complex. The rotor magnets are positioned between these two stators. The stator inner radius, stator outer radius, slot opening, magnet arc, magnet thickness, inner and outer air-gap thickness and number of windings turns will directly influence the motor performance in DS-PMSM. The analytical subdomain model employed in this paper has a significant advantage as a rapid design tool since it is capable of precisely predicting the performance of DS-PMSM while requiring less computational effort. The analytical model was initially created using the separation of variables technique in four subdomains based on the Poisson’s and Laplace’s equations: inner air-gap, inner magnet, outer magnet and outer air-gap. Applying the appropriate boundary and interface conditions yields the field solutions in each subdomain. Besides, the fractional DS-PMSM with different number of slots between outer and inner stators to rotor poles can result in low cogging torque and non-overlapping winding configuration. The analytical results are validated by Finite Element Analysis (FEA). The slotted air-gap flux density, back-emf, and output torque have all been evaluated as electromagnetic performances. The results demonstrate that the suggested analytical model is capable of accurately predicting the DS-PMSM performance.

This thesis investigates the electromagnetic performance of the fractional-slot interior permanent magnet (IPM) and salient-pole synchronous reluctance (SynR) brushless AC machines having non-overlapping concentrated windings, the SynR machines being excited by bipolar AC sinusoidal currents with and without DC bias. The analyses are validated by finite element calculations and measurements. The PM machines with modular stators are often employed to improve the electromagnetic performance and ease the manufacture process, particularly stator winding. The influence of uniform and non-uniform additional gaps between the stator teeth and back-iron segments on the electromagnetic performance of fractional-slot IPM machines having either un-skewed or step-skewed rotors and different slot openings, viz. open slot, closed slot and hybrid slot (sandwiched open and closed slots), is investigated. The influence of load conditions on cogging torque and back-emf waveforms and the effectiveness of rotor skew on the minimization of the cogging torque, thus the torque ripple, are also examined. It is found that the additional gaps have a negligible influence on the average output torque, but significantly increase the cogging torque magnitude, while their non-uniformity can cause a large increase in both the peak and periodicity of cogging torque waveform, which in turn makes the skew method ineffective. The magnetic cross-coupling level and the sensitivity of cogging torque to manufacturing limitations and tolerances strongly depend on the slot opening materials. The cogging torque magnitude is significantly increased by load, while its periodicity also changes with load which makes the rotor skew less effective unless the machine is skewed by one cogging torque period on load. The electromagnetic performance of the SynR machines under AC sinusoidal bipolar excitation with and without DC bias is investigated and compared for three different winding connections, such as asymmetric, symmetric and hybrid. In general, the SynR brushless AC machines with DC bias excitation exhibit significantly higher torque density than those without DC bias. Comparing with the asymmetric and symmetric winding connections, their hybrid counterpart results in significantly larger mutual inductance variations. Consequently, it results in significantly larger output torque, since such torque is produced by the variation of both the self and mutual inductances. In terms of torque ripple, the symmetric winding connection leads to the best performance. On the other hand, at significantly larger current densities, the hybrid winding connection become more suitable, since it exhibits large average output torque and relatively low torque ripple.

Technological advances in the aerospace industry have improved aircraft efficiency and reduced the cost of air transport, leading since 1960 to a continuous growth of the worldwide air traffic. Today it is postulated that also into the foreseeable future both the passenger and cargo air traffic will continue to growth, increasing the CO2 air transport emissions. In this contest, there are many environmental as well as commercial pressures on aircraft manufacturers to improve performances of future aircraft in terms of safety, air pollution, noise and climate change. To achieve these goals, it is necessary revisiting the whole aircraft architecture system, with the introduction of new technologies for performing key functions on aircraft. Today the conventional civil aircraft are characterized by four different secondary power distribution systems: mechanical, hydraulic, pneumatic and electrical. This implies a complex power distribution nets aboard, and the necessity of an appropriate redundancy of each of them. In order to reduce this complexity, with the aim to improve efficiency and reliability, the aerospace designer community trend is towards the `More Electric Aircraft (MEA)' concept, that is the wider adoption of electrical systems in preference to the others. This solution involves an increase of the aircraft electrical loads and, as a consequence, heavy implications for the on-board electrical generation systems are predictable. The resulting increase of the electrical power requirements encourage the research of alternative solutions rather than simply scaling up existing technologies such as generators driven by gearboxes. To address these challenges, many studies are in the direction of the so called `More Electric Engine (MEE)', in which the electrical machines are integrated inside the main gas turbine engine to generate electrical power, start the engine and guarantee safety generation in case of a critical on-flight failure. In this way the mechanical gearbox which connects the actual generators to the aeroengine shaft can be eliminated. The MEA and the MEE concept can be considered as an evolutionary implementation of the `All Electric Aircraft (AEA)', in which all the aircraft on-board systems are supplied in an electrical form. The MEE concept will involve important mechanical and thermodynamic implications in the aeroengine design, making necessary a preliminary system analysis on today conventional aeroengine, in order to evaluate the integration feasibility with the actual mechanical and environmental constraints. The electrical machines can be integrated inside the engine in some different positions, either in the front part before the combustion chamber, in particular in the low-pressure or in the high-pressure compressor stages, or in the rear part of the engine, in the tail-cone zone. In the frame of the GREAT2020 (GReen Engine for Air Transport in 2020) project co-founded by Regione Piemonte, aimed to the development of new eco-compatible aircraft engines for the entry into service in 2020, the MEE concept focus is on the evaluation of the most suitable solution between four possible integration positions in the front part of the today conventional two-shaft GEnx turbofan engine. The rotational speeds and the maximum available volumes are respectively imposed by the shaft connection and by the available spaces inside the aeroengine. In the purpose of the MEE concept on which the work presented in this dissertations is based, in order to evaluate the less critical solution between the proposed, a trade-off study conducted on preliminary electromagnetic design has been performed considering both radial and axial flux surface mounted permanent magnet synchronous machines. The comparison of the different solutions have been done on the base of same sizing indexes. Due to the particular application in which the electrical machine integration is involved, in order to evaluate impact on the whole system performance, a wider trade-off study concerning the overall aeroengine system has been done by the aerospace company Avio, partner of the GREAT2020 project. The focus of the work presented in this dissertation, is the development of appropriate tools to perform a preliminary electromagnetic design of radial and axial flux, surface mounted, permanent magnet synchronous machines with three-phase distributed and single-layer fractional-slot non-overlapping concentrated windings. In particular, this latter winding topology has been considered for its specific application for its shorter end-winding connections respect to the distributed layout, and for their high fault tolerant capability due to the electrical and physical separation between the phases which reduces the possibility of a fault propagation. Regarding the radial flux topologies, both inner and outer rotor machine structures have been considered; for the axial flux machines the single-stage (one stator and one rotor) as well as the multi-stage structures, obtained connecting on the same axis more than one single-stage structure, have been considered. The developed general purpose tools are based on simple geometrical approach using conventional design equations. The geometrical dimensions are computed starting from the design specifications and material utilization indexes imposed by the designer. The implemented codes would be a useful tool for the electrical machine designer in order to quickly define a preliminary electromagnetic design starting from a fresh sheet of paper. The conducted comparisons with commercial software have proved the validity of the tools for the conducted MEE trade-off study; however, in a prototype design aimed to the construction, detailed analysis using commercial software available on the market and Finite Element Method analysis have to be done in order to verify and improve in details the preliminary electromagnetic design obtained by the implemented codes.