1,721,066 research outputs found
Design and development of permanent magnet synchronous machines shaft-line embedded in aeronautic engines
No full textTechnological 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 code
Electrical Machines for High-Speed Applications: Design Considerations and Trade-offs
No full textThe high-speed electric machines are gaining attention in several different applications, and the development of advanced materials, electronic components and control algorithms is pushing ahead the technological speed limits. In the electromagnetic sizing of high-speed machines the mechanical and thermal involvements are so tight to make necessary to deal with all the different aspects at the same time. The paper aims to summarize and discuss the electrical as well as the mechanical aspects involved in the high speed machine design, highlighting the main issues and the trade-offs that the designer has to consider. Furthermore the correlation between volume reduction and the speed increase, based on commercial high-frequency roto-stator units, is presented to
Off-Line Efficiency Mapping of Induction Motors Operated in Wide Torque-Speed Ranges
Full text linkIn the context of a progressive component virtualization for energetic assessments in variable speed and load operations, this paper presents a methodology for computing the efficiency maps of three-phase induction motors. The proposed approach is based on the conventional machine equivalent circuit to quickly obtain a set of efficiency maps at different machine temperatures and supply voltage levels. The well-known no-load and locked-rotor tests are used to determine the motor parameters at different frequencies and voltages, taking into account the machine nonlinearities and the iron losses. The approach has been validated on an 11 kW, 4 poles, 50 Hz induction motor tested in different operating conditions
Fast Computation of the No-Load Characteristic for Wound Field Synchronous Propulsion Motors
Full text linkWound field synchronous machines are gaining attention as an interesting permanent magnet-free alternative for propulsion applications. The third degree of freedom introduced by the rotor current makes the electromagnetic design of these machines not trivial. Hence, dedicated and fast analysis tools are necessary to predict the machine behavior. This paper presents a fully analytical procedure for the computation of the no-load characteristic of salient-pole wound field synchronous machines. The procedure considers the iron saturation and includes the magnetic shunt of the stator slots. The distortion of the air gap flux
density waveform introduced by the teeth saturation and the rotor saliency are considered. The procedure has been experimentally validated using a 4 poles, 100 kW peak power wound field synchronous motor
Map-based Simulation Model for Energetic Assessment of Electric Propulsion Systems
No full textThe electric propulsion systems modeling is a necessary tool for the evaluation of performance and onboard energy source requirements in electrically propelled aircraft. This paper presents a map-based simulation approach for energetic assessment of electric propulsion units, suitable for general aviation applications. The energetic analysis of the propulsion system relies on multidimensional maps to include the nonlinearities of the components, and the system dynamics is simulated by means of numerical integration. Additionally, the proposed approach considers the effects of electric machine temperature variations through a first-order thermal model. The developed model has been numerically validated in a simulation environment using the specifications of a commercial general aviation fuel aircraft
Accurate Induction Machines Efficiency Mapping Computed by Standard Test Parameters
Full text linkThe extensive electrification process that is taking hold in several applications makes increasingly necessary the virtualization of electric components for energetic and performance assessments during the system design stage. For this purpose, this paper proposes a straightforward methodology for computing the efficiency maps of induction machines operated in wide torque-speed ranges. The modeling approach is based on the induction machine equivalent circuit defined in the rotor dq coordinates. The procedure allows computing a set of efficiency maps at different machine temperatures and supply voltage levels, both for motor and generator operation modes. The equivalent circuit parameters at different frequencies and voltages are determined by means of the well-known no-load and locked-rotor tests, thus including in the modelling the machine nonlinearities, skin effect and the iron losses. The proposed methodology has been validated on a 10 kW, 4-pole induction machine. The comparison between computed and experimental efficiency maps for different operating conditions, confirm the validity of the proposed methodology
Magnetic Behavior and Loss Assessment of Additively Manufactured Fe-Si alloys
No full textThis study deals with the production and characterization of soft magnetic materials produced by means of additive manufacturing technologies. In particular, the laser-powder bed fusion has been used developing different silicon-iron alloys. The focus is to provide the BH magnetization trends, as well as the specific losses, for a wide range of supply frequency of a set of additively manufactured soft magnetic materials. Ad hoc specimens, including 'as build' and 'annealed' samples, have been tested in order to address the complete scenario about their applicability in advanced electrical machines. Consequently, the present document has to be considered as a reference where the readers that do not have the possibility to print or test soft AM materials can find useful data to start the designs and simulations of their own applications
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