Advancing the design and modelling processes for high performance electrical machines

The implementation of an integrated oil pump and drive motor (where no mechanical coupling between the motor and pump is required) is a very attractive solution for various industries, especially where high performance requirements are important, such as for the aerospace industry. As in many applications, high power density and high efficiency are very important design objectives. However, to achieve such objectives while keeping the overall weight of the electrical machine to minimum values is very challenging and requires an optimal machine design with a detailed knowledge of power losses. To address these aspects, this thesis aims to improve the machine performance through accurate modelling by considering often overlooked aspects during the development process of electrical machines. To achieve this goal, the first stage of the project involved the analysis, design and optimisation of a high performance, high power density electrical machine for directly-coupled pump application. The second stage has shown how accurate machine models that include the effects of machining processes required to produce the finished product (e.g. the stator core) and the effects of in-active component (e.g. rotor endcaps), can be achieved and used to provide a more accurate estimation for the machine performance than with the traditional methodologies. A prototype machine based on the first stage of this project is manufactured and experimentally tested. This machine was then used as a vessel for the second stage of the work. The main contribution of this work is the investigation and verification of the effects on the accuracy of design models due to 1) the detrimental effects of machining processes of the stator core and 2) the detrimental effects of leakage fluxes flowing in the inactive materials/components of the machine. This knowledge is then used to inform the future machine designer on how to take into consideration these aspects during the design of electrical machines

Influence of rotor endcaps on the electromagnetic performance of high speed PM machine

Surface-mounted permanent magnet (SPM) machines are preferred for high-speed aerospace applications over induction and switched reluctance machines, since they combine the advantages of high torque density and efficiency. Also, in aerospace applications, where low rotor weight and inertia are essential requirements, a permeable hollow shaft is proposed to replace the need for rotor back-iron and reduce the overall rotor weight. For rotor mechanical integrity, a retaining sleeve is commonly used, leading to thicker magnetic airgap. Furthermore, when permeable rotor endcaps are applied, an increase of the magnetic end leakage occurs, i.e. end-effect. In this paper, the influence of the rotor endcaps on the mechanical and electromagnetic performance of a high-speed SPM machine is investigated through 3D-finite element analyses (FEA). Also, different endcap thickness and different rotor shaft materials are investigated and compared in this work. Finally, a prototype of the SPM machine under study has been manufactured and tested. The comparison between simulation and experimental results is presented and discussed

Design and losses analysis of a high power density machine for flooded pump applications

This paper describes the design process of a 10 kW 19000 rpm high power density surface mounted permanent magnet synchronous machine for a directly coupled pump application. In order to meet the required specifications, a compact machine, with cooling channels inside the slots and flooded airgap, has been designed through finite element optimization. For high power density, high speed machines, an accurate evaluation of the power losses and the electromechanical performance is always extremely challenging. In this case, the completely flooded application adds to the general complexity. Therefore this paper deals with a detailed losses analysis (copper, core, eddy current and mechanical losses) considering several operating conditions. The experimental measurements of AC copper losses as well as the material properties (BH curve and specific core losses), including the manufacturing process effect on the stator core, are presented. Accurate 3D finite element models and computational fluid dynamics analysis have been used to determine the eddy current losses in the rotor and windage losses respectively. Based on these detailed analysis, the no load and full load performance are evaluated. The experimental results, on the manufactured prototype, are finally presented to validate the machine design

Considerations on the Development of an Electric Drive for a Secondary Flight Control Electromechanical Actuator

The more electric aircraft concept aims to improve the fuel consumption, the weight and both the maintenance and operating costs of the aircraft, by promoting the use of electric power in actuation systems. According to this scenario, electromechanical actuators for flight control systems represent an important technology in next generation aircraft. The paper presents a linear geared electromechanical actuator for secondary flight control systems, where the safety and availability requirements are fulfilled by replicating the electric drive acting on the drivetrain. Indeed, the architecture considered consists of two power converters feeding as many electrical machines coupled to the same mechanical system. The design of both the permanent magnet synchronous machine and the power converter are addressed. Preliminary results on the electric drive prototype are also provided and compared to the design requirements. Finally, the electromechanical actuator performance at system-level is evaluated in Dymola environment, analyzing different operating modes

Advancing the design and modelling processes for high performance electrical machines

The implementation of an integrated oil pump and drive motor (where no mechanical coupling between the motor and pump is required) is a very attractive solution for various industries, especially where high performance requirements are important, such as for the aerospace industry. As in many applications, high power density and high efficiency are very important design objectives. However, to achieve such objectives while keeping the overall weight of the electrical machine to minimum values is very challenging and requires an optimal machine design with a detailed knowledge of power losses. To address these aspects, this thesis aims to improve the machine performance through accurate modelling by considering often overlooked aspects during the development process of electrical machines. To achieve this goal, the first stage of the project involved the analysis, design and optimisation of a high performance, high power density electrical machine for directly-coupled pump application. The second stage has shown how accurate machine models that include the effects of machining processes required to produce the finished product (e.g. the stator core) and the effects of in-active component (e.g. rotor endcaps), can be achieved and used to provide a more accurate estimation for the machine performance than with the traditional methodologies. A prototype machine based on the first stage of this project is manufactured and experimentally tested. This machine was then used as a vessel for the second stage of the work. The main contribution of this work is the investigation and verification of the effects on the accuracy of design models due to 1) the detrimental effects of machining processes of the stator core and 2) the detrimental effects of leakage fluxes flowing in the inactive materials/components of the machine. This knowledge is then used to inform the future machine designer on how to take into consideration these aspects during the design of electrical machines

Intralobar pulmonary sequestration in elderly woman: a rare case report with emphasis on imaging findings

Intralobar pulmonary sequestration is a rare malformation that predisposes to recurrent respiratory infections. It is difficult to diagnose unless a more extensive directed investigation (to the vasculature and pulmonary parenchyma) is take on. Failure to diagnose and treat this condition can lead to recurrent pneumonia and fatal hemoptysis. Most cases are diagnosed before the age of 20 years. In this report, we present an extremely rare case of elderly woman with initial diagnosis of intralobar sequestration, and to our knowledge, this case represents the oldest diagnosed patient in the literature