Electromagnetic launch systems for civil aircraft assisted take-off

This paper considers the feasibility of different technologies for an electromagnetic launcher to assist civil aircraft take-off. This method is investigated to reduce the power required from the engines during initial acceleration. Assisted launch has the potential of reducing the required runway length, reducing noise near airports and improving overall aircraft efficiency through reducing engine thrust requirements. The research compares two possible linear motor topologies which may be efficaciously used for this application. The comparison is made on results from both analytical and finite element analysis (FEA)

Synchronous reluctance motors with fractional slot-concentrated windings

PhD ThesisToday, high efficiency and high torque density electrical machines are a growing research interest and machines that contain no permanent magnet material are increasingly sought. Despite the lack of interest over the last twenty years, the permanent magnet-free synchronous reluctance machine is undergoing a revival and has become a research focus due to its magnet-free construction, high efficiency and robustness. They are now considered a potential future technology for future industrial variable speed drive applications and even electric vehicles. This thesis presents for the first time a synchronous reluctance motor with fractional slot-concentrated windings, utilizing non-overlapping single tooth wound coils, for high efficiency and high torque density permanent magnet-free electric drives. It presents all stages of the design and validation process from the initial concept stage through the design of such a machine, to the test and validation of a constructed prototype motor. The prototype machine utilizes a segmented stator core back iron arrangement for ease of winding and facilitating high slot fill factors. The conventional synchronous reluctance motor topology utilizes distributed winding systems with a large number of stator slots, presenting some limitations and challenges when considering high efficiency, high torque density electrical machines with low cost. This thesis aims to present an advancement in synchronous reluctance technology by identifying limitations and improving the design of synchronous reluctance motors through development of a novel machine topology. With the presented novel fractional slot concentrated winding machine design, additional challenges such as high torque ripple and low power factor arise, they are explored and analysed - the design modified to minimise any unwanted parasitic effects. The electrical and electromagnetic characteristics of the developed machine are also explored and compared with that of a conventional machine. A novel FEA post-processing technique is developed to analyse individual air-gap field harmonic torque contributions and the machines dq theory also modified in order to account for additional effects. The developed machine is found to be lower cost, lower mass and higher efficiency than an equivalent induction or conventional synchronous reluctance motor, but does suffer higher torque ripples and lower power factor. The prototype is validated using static and dynamic testing with the results showing a good match with finite element predictions. The work contained within this thesis can be considered as a first step to developing commercial technology based on the concept for variable speed drive applications.Financial assistance was provided by was provided by the UK Engineering and Physical Sciences Research Council (EPSRC) in the form of a Doctoral Training Award and additional financial assistance was kindly provided by Cummins Generator Technologies, Stamford, UK, through industrial sponsorship of this wor

Leakage Inductance of a Prototyped Single Tooth Wound Synchronous Reluctance Motor

This paper explores the inductance characteristics present in single tooth wound synchronous reluctance motors, specifically the stator leakage inductance. Despite the nature of the single tooth design resulting in increased air gap harmonic content, having has consequences for the machines' design, performance & operation, the topology has been shown previously to be competitive for high efficiency drives. A key design constraint in the design of synchronous reluctance motors is maximizing the direct axis inductance and minimizing the quadrature axis inductance for a high saliency ratio. The effect of increased leakage inductance on this saliency ratio is explored with emphasis placed on design aspects of such single tooth wound synchronous reluctance motors. It is shown that careful design of the machine is required to maximize the saliency ratio in this machine topology and that the dominant leakage inductance component is the air gap harmonic leakage

Advances in the Field of Electrical Machines and Drives

Electrical machines and drives dominate our everyday lives. This is due to their numerous applications in industry, power production, home appliances, and transportation systems such as electric and hybrid electric vehicles, ships, and aircrafts. Their development follows rapid advances in science, engineering, and technology. Researchers around the world are extensively investigating electrical machines and drives because of their reliability, efficiency, performance, and fault-tolerant structure. In particular, there is a focus on the importance of utilizing these new trends in technology for energy saving and reducing greenhouse gas emissions. This Special Issue will provide the platform for researchers to present their recent work on advances in the field of electrical machines and drives, including special machines and their applications; new materials, including the insulation of electrical machines; new trends in diagnostics and condition monitoring; power electronics, control schemes, and algorithms for electrical drives; new topologies; and innovative applications

On the Influence of Increased Stator Leakage Inductance in Single Tooth Wound Synchronous Reluctance Motors

This paper explores the leakage inductance of a single tooth wound synchronous reluctance motor and its influence on motor performance. It is shown that the stator leakage inductance heavily influences the true saliency ratio in synchronous reluctance motors and a large stator leakage inductance has a serious detrimental impact on the operating power factor. It is also shown through analytical and FEA analysis that synchronous reluctance motors with single tooth windings suffer an inherent high stator leakage inductance that is dominated the air gap harmonic leakage component, derived from the significant stator MMF harmonics experienced with this winding type. This explains for the first time the experimental results showing a low operating power factor compared to a distributed wound machine. Measurement of the stator leakage inductance is attempted on a prototyped machine and the standardized method is found to be lacking when single tooth windings are employed

On the design of a low cost high performance traction motor with ferrite magnets

PhD ThesisPermanent magnet motors with rare earth magnets are amongst the best candidates for high performance applications such as automotive. However, due to their cost and risks relating to security of supply, alternative solutions such as ferrite magnets have recently become popular. In this thesis the two major design challenges of using ferrite magnets for a high torque density and high speed application, namely their low remanent flux density and low coercivity, are addressed. It is shown that a spoke type design may overcome the torque density challenge due to a simultaneous flux concentration and reluctance torque possibility. Furthermore, the demagnetization challenge can be overcome through careful optimization of the rotor structure, with the inclusion of non-magnetic voids on the top and bottom of the magnets. To meet the challenges of the high speed operation an extensive rotor structural analysis has been undertaken, during which electro-magnetic as well as manufacturing tolerances are taken into account. In this thesis, the impact of the motor stack length and level of magnetic saturation on the demagnetization risk are studied based on 3-Dimensional Finite Element (3D FE) simulations and a proposed lumped circuit model. It is shown that reducing the stack length can significantly enhance the demagnetization resistance, with the effect being more pronounced for designs with a higher level of magnetic saturation. To benchmark the practicality of the concept, a previously presented high performance ferrite based design is modified by using a 30% weaker grade of ferrite magnet whilst shortening the stack length. It is shown that the demagnetization withstand capability of the design was significantly enhanced and exceeded the short circuit requirement with a good safety margin. The fir tree based spoke type rotor comprises of two sections: a) the ferromagnetic rotor pole to provide the path for the magnetic flux, and b) the non-magnetic rotor support to provide the structural integrity. In this thesis, the Multiphysics and cost implications of the rotor support material, as part of a high performance ferrite magnet traction motor, are analysed, and an optimal selection with respect to those criteria is proposed. The performance of the design based on the proposed rotor support material is validated by electromagnetic and structural testing of three sets of customized prototypes. Based on the analysis, the proposed rotor support material was shown to, significantly, boost the cost competitiveness of a low cost ferrite motor for a high volume production. ii As an alternative design to the proposed fir tree based rotor, a magneto-structurally optimized single piece rotor topology targeting the same EV application requirements is designed and compared against the fir tree based rotor performance. It is shown that an optimally designed single piece rotor design can meet about 80% of the power density of a fir tree rotor design at the cost of ~3 percent lower efficiency. Furthermore, the single piece rotor design may have better demagnetization resistance during severe faults. With regards to the performance per manufacturing costs, it was discussed that the single piece rotor design may match the fir tree solution, and the competitiveness may boost for designs with less severe structural requirements such as those with lower top speed requirement. With regards to the stator design, distributed and concentrated windings may have both advantages and disadvantages when considering manufacturing cost, slot fill factor, the contribution factor of reluctance torque and parasitic effects. Furthermore, the trend toward high speed operation of the traction motors may increase the AC loss effects in the windings, contributing to the motor deficiencies and risk of thermal failure. In this thesis, the performance of a high speed ferrite motor with a distributed and concentrated wound stator, and with regards to torque and power performance as well AC loss effects is assessed. The thermal capability of the windings under peak torque conditions and cyclic loading, as well as the intermittent and continuous performance of the full scale prototype design based on the proposed distributed aluminium wound stator is presented. The theoretical findings have been supported by a series of electromagnetic, thermal and structural testing of a custom built small scale prototype as well as a final full size prototype. The electromagnetic torque and power density is evaluated based on static and full dynamic testing, while the demagnetization withstand capability has been validated using current injection method. The structural testing includes an over-speed rotor spinning at 18000 rpm, as well as a fatigue testing under numerous cyclic loading. The thermal test validations include the evaluation of the aluminium windings temperature rise under the peak load, the reliability assessment under the cyclic load variation, and, finally, an investigation of the intermittent and continuous electromagnetic performance as well as windings temperatures of a fully assembled prototype. To conclude, a comparison of the proposed ferrite traction motor against the industrially available state of the arts is provided, based on which the merits of the PhD thesis findings and the competitiveness of the disclosed design in terms of the performance per cost is highlighted.Jaguar Land Rover and the innovate UK consortium under the Evoke-E project, Grant 110130

Design and prototyping methods for brushless motors and motor control

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010."June 2010." Cataloged from PDF version of thesis.Includes bibliographical references (p. 109).In this report, simple, low-cost design and prototyping methods for custom brushless permanent magnet synchronous motors are explored. Three case-study motors are used to develop, illustrate and validate the methods. Two 500W hub motors are implemented in a direct-drive electric scooter. The third case study, a 10kW axial flux motor, is used to demonstrate the flexibility of the design methods. A variety of ways to predict the motor constant, which relates torque to current and speed to voltage, are presented. The predictions range from first-order DC estimates to full dynamic simulations, yielding increasingly accurate results. Ways to predict winding resistance, as well as other sources of loss in motors, are discussed in the context of the motor's overall power rating. Rapid prototyping methods for brushless motors prove to be useful in the fabrication of the case study motors. Simple no-load evaluation techniques confirm the predicted motor constants without large, expensive test equipment. Methods for brushless motor controller design and prototyping are also presented. The case study, a two channel, 1kW per channel brushless motor controller, is fully developed and used to illustrate these methods. The electrical requirements of the controller (voltage, current, frequency) influence the selection of components, such as power transistors and bus capacitors. Mechanical requirements, such as overall dimensions, heat transfer, and vibration tolerance, also play a large role in the design. With full-system prototyping in mind, the controller integrates wireless data acquisition for debugging. Field-oriented AC control is implemented on low-cost hardware using a novel modification of the standard synchronous current regulator. The controller performance is evaluated under load on two case study systems: On the direct-drive electric scooter, it simultaneously and independently controls the two motors. On a high-performance remote-control car, a more extreme operating point is tested with one motor.by Shane W. Colton.S.M

Experimental assessments of a triple redundant 9-phase fault tolerant PMA SynRM drive

Fault tolerant machine drives are key enabling technologies in safety critical applications. The machine drives are expected to exhibit high performance in healthy conditions and accommodate as many faults as possible, namely open circuit or short circuit in the machine and inverter or even an inter-turn short circuit. This paper aims to assess a triple redundant 9-phase (3x3-phase) permanent magnet assisted synchronous reluctance machine (PMA SynRM) drive by comprehensive experimental tests under both healthy and fault conditions on a 35kW machine drive prototype. The healthy performance, fault behavior, fault detection and fault mitigation strategy are presented and assessed by extensive tests which demonstrate that the machine drive exhibits high performance and excellent fault tolerance with simple and cost-effective implementation. Therefore, the proposed machine drive has proven to be a practical candidate for safety critical applications

Electro-thermal design and optimization of high-specific-power slotless PM machine for aircraft applications

A 1 MW high-frequency air-core permanent-magnet (PM) motor, with power density over 13 kW/kg (8 hp/lb) and efficiency over 96\%, is proposed for NASA hybrid-electric aircraft application. In order to maximize power density of the proposed motor topology, a large-scale multi-physics optimization, which is not favorable for current electrical machine software, is needed to obtain the best design candidates, which is not favorable for current electrical machine software. Therefore, developing electromagnetic (EM) and thermal analytical methods with computational efficiency and satisfactory accuracy is a key enabling factor for future multi-physics optimization of motor power density. This dissertation summarizes the efforts of developing an electro-thermal analysis and optimization scheme of the proposed motor for aircraft applications. Component hardware tests including windage loss, fan performance, full-scale stator temperature and litz-wire were conducted to validate the proposed prediction methods and provide calibrations in the motor design analysis. Furthermore, slotless litz wire winding geometry and strand size are optimized with the developed electro-thermal modeling including transposition effects. After gaining confidence in the developed electro-thermal models, an optimization design toolbox is built for the hybrid-electric engine systems study. The first application study is in partnership with Rolls Royce's Electrically Variable Engine Project to study thermal management system integration effects on motor sizing. The second study is in collaboration with Raytheon Technologies to study motor transient performance with phase change materials integration, which can be tailored to a hybrid-electric engine mission profile

Damage analysis of internal faults in flux concentrating permanent magnet motors

Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 67-68).by Francis R. Colberg.M.S.Nav.E