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

Considerations on the effects that core material machining has on an electrical machine's performance

An often-overlooked aspect during the development process of electrical machines, is the validity and accuracy of the machine material properties being used at the design stage. Designers usually consider the data provided by the materials supplier, which is measured on material in an unprocessed state. However, the fact that the machining processes required to produce the finished product (e.g. the stator core) can permanently vary the material properties is very often neglected. This paper therefore deals with and investigates the effects that such processes can have on the overall machine performance. To do this, three sets of material data, based on 1) the materials suppliers’ data, 2) materials data based on conventional characterization methods and 3) materials data based on test samples that include the manufacturing processes, are used to develop three versions of the same baseline machine. The results of these three machines are then compared and the resulting variations of the machine’s performance presented and described. The chosen baseline machine is a high performance and relatively high speed, aerospace, electrical machine. Special attention is focused on the efficiency maps of the machine as this aspect is highly dependent on the material properties that are the most sensitive to manufacturing processes such as the material’s anhysteretic BH curve and its specific core loss

Axial eccentric SynRel and SPM Motors analytical models validation using 3D finite element

This paper deals with the uniform and non-uniform axial eccentricity analyses of the surface mounted permanent magnet and synchronous reluctance machines. The analyses are carried out using an analytical model for each considered machine. Being the axial eccentricity a 3D physical phenomenon, the standard sliding approach used in the analytical models has been validated through accurate 3D FE simulations. The results presented in this paper verify the effectiveness of the analytical approaches quantifying the results deviations respect to the computational expensive 3D FE simulations. The results also confirms that synchronous reluctance machines show higher radial forces compared to the surface permanent magnet machines for the same eccentricity level, main geometry and operating condition

Trade-off analysis and design of a high power density PM machine for flooded industrial pump

This paper presents the trade-off analysis and design of a high power-density machine for industrial pump applications. The developed permanent magnet synchronous machine drives an electric, oil flooded pump. Different slot/pole combination and winding configuration have been investigated in order to identify the optimal combination that satisfies the electromagnetic and thermal constraint while keeping the losses as small as possible. Several strategies such as the use of the Cobalt iron material for the stator core lamination and the adoption of Halbach array have been investigated in this work to improve the performance capabilities of the designed machine. The electromagnetic performances have been evaluated by using a finite element method. Thermal behaviour has been determined using a lumped parameter network. The outcome of the thermal analysis helped to identify the optimal cooling configurations. The final results are presented highlighting the achieved design targets

Thermal management of a permanent magnet motor for an directly coupled pump

A high speed permanent magnet motor is designed for a flooded industrial pump. Oil in the pump is used to cool the motor. Due to the limitation of space and mass requirement for the application, thermal management is one of the main challenges. This paper describes the thermal management optimization process and design of the machine. Different cooling strategies are applied to cool the machine and Computational Fluid Dynamics (CFD) is used to predict and improve the cooling performance. The machine has been designed and is currently being manufactured

Design and optimization of a high power density machine for flooded industrial pump

This paper presents the design optimization procedure of a high power-density, permanent magnet synchronous machine for industrial pump applications. The designed machine drives an electric, oil flooded pump. In order to achieve higher torque-density, a fractional slot machine (8 poles, 9 slots) with double layer (concentrated) winding has been selected after a preliminary trade-off study, which considered several slot/pole combinations and winding configurations. The developed machine provides low torque ripple and short end windings, which contribute to lower axial length and higher efficiency. The electromagnetic performances have been evaluated by using finite element method and the lamination geometry has been optimized through a genetic. The final results are presented highlighting the achieved design targets

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

Comparative study of permanent magnet-synchronous and permanent magnet-flux switching machines for high torque to inertia applications

This paper investigates the capability of both permanent magnet synchronous machine (PMSM) and permanent magnet flux switching (PMFS) machine to provide high torque to inertia ratio for applications with demanding response in terms of acceleration and fast dynamic. The PMSM has higher torque density and efficiency among different electrical machines. However, the presence of the permanent magnets can increase the rotor inertia. Thanks to its passive salient-pole rotor, PMFS machine is a suitable solution for those applications requiring lower inertia. This paper provides a comparative analysis between the PMSM and PMFS machines considering the torque to inertia ratio, the challenges of a flooded air gap and dimensional constraints. The electromagnetic performances of both machines have been evaluated by means of finite element method and a detailed sensitivity analysis is carried out for stator and rotor geometry

Eccentric reluctance and permanent magnets synchronous machines comparison

This paper deals with a comparative study between reluctance (REL), permanent magnet assisted reluctance (PMAREL), and surface mounted permanent magnet synchronous machines with rotor eccentricity. Static, dynamic, and combined eccentricity cases are considered. For the sake of generality, this comparison is carried out at different levels of airgap flux density, as different current angles, different permanent magnet (PM) materials, and different number of magnetic poles. Additionally, different stator windings arrangements, i.e, distributed and fractional slot concentrated windings are taken into account. Besides, different rotor geometries of REL and PMAREL machines are included. As a case of study, 36-slot machine is analyzed, considering three flux barriers per pole, however, the study can be applied to any machine geometry. Due to the structural criticality of the rotor iron ribs of the REL machines, the impact of the eccentricity on the mechanical stress acting on those ribs and the deformation of the rotor is studied

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