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Torsional tests were conducted to investigate the influence of service temperature on torsional property of composite/steel hybrid structures. In the experiment, two types of lightweight hybrid composite‐metal shafts were tested at both room temperature and various elevated temperatures up to 150°C, including hybrid shafts with and without a metal core. Consequently, the torsional stiffness of the two hybrid shafts at different temperatures was calculated based on the recorded angular deformation‐torque curves. The experimental results revealed a significant decrease in the torsional stiffness of the hybrid shaft without metal core as the increase of service temperature, while the torsional stiffness of the one with metal core remained almost unchanged, especially at high temperatures. In addition, a finite element model was proposed to predict the torsional behavior of the hybrid shafts at different service temperatures. In the model, an empirical equation was introduced, and micromechanical method was adopted to determine the temperature‐dependant elastic properties of composite material and adhesive layer in the hybrid structure. Then, the predicted torsional property was compared to the experimental results for model verification. Highlights: Two types of hybrid composite‐metal shafts are designed and manufactured.Torsional tests are conducted at both room and elevated temperatures up to 150°C.A finite element model applicable to shaft at various temperatures is proposed.The temperature‐dependant property is characterized by an efficient equation. [ABSTRACT FROM AUTHOR]

Electric machines are widely employed in a variety of sectors, including automotive and aerospace industry. With the rising trend towards electrification in aviation, electric machines with increased power density and efficiency are becoming key enabling technologies, requiring the development of innovative design procedures. In this study, a preliminary design procedure for Surface Mounted Permanent Magnet Synchronous Machines (SPMSMs) intensively cooled by means of oil channels placed in the stator slots is proposed. The analytical derivation of SPMSM sizing equations, including the sub‐domain model and optimisation algorithm will be reported in detail. Indeed, both the electromagnetic and thermal equations of the machine are considered for the derivation of the sizing tool. As a result, the latter allows to capture variation of the machine design not only in terms of mechanical demands, such as power and speed, but also in terms of coolant characteristics, and can be effectively employed to perform trade‐off studies at a preliminary design stage. The proposed design tool will be used for a specific case study: The design of a high‐speed machine for an aerospace hydraulic actuator. The accuracy of the proposed design tool is validated for different parameters by comparing the results to experimental measurements performed on an existing 8‐pole 9‐slot prototype SPMSM. [ABSTRACT FROM AUTHOR]

PAPER 3: An H-TYPE ARCHITECTURE FOR ELECTRIC/HYBRID-ELECTRIC AIRCRAFT PROPULSION SYSTEMS In this study a novel H-type hybrid-electric aircraft propulsion architecture is proposed to address the issues associated with the radial electric propulsion architecture. Public and political pressures for environmental improvements are driving a wave of current interest in all-electric and hybrid-electric aircraft. These emerging new aircraft propulsion systems bring with them the promise of net-zero emissions and greatly reduced noise profiles. [Extracted from the article]

This paper evaluates various modes of transport against the dual requirements of Net‐Zero carbon emissions and user convenience, in particular, speed of travel and cost of transportation. Results show that when operated across a whole country, battery‐powered ePlanes have the lowest energy use as measured by well‐to‐wing efficiency of other high‐speed transport systems such as the UKs HS2 and conventional diesel rail systems. This condition may not hold for extremely high passenger numbers per hour as seen in metropolitan areas with high density populations. Various proposed disruptive technologies lower cost of ownership when combined with changes in the transport paradigm that has rarely been explored in other papers. [ABSTRACT FROM AUTHOR]

High‐speed permanent magnetic machine (HSPMM) is attracting more attention due to its high power density, compact size, small rotating inertia, and rapid response capability. However, the design of the HSPMM rotor is a non‐linear, multi‐physics coupled process that makes it difficult to build an accurate mathematical model for optimisation. This study proposes a multi‐objective optimisation method based on the multi‐physics surrogate model (MPSM). This method uses an MPSM to replace the finite element model (FEM) for optimisation, which can effectively solve the problem of non‐convergence and time consumption of the traditional FEM in the optimisation process. Finally, a 1.1 MW, 18,000 r/min HSPMM is produced and related experiments are carried out; the feasibility of the method proposed in this study for HSPMM optimisation is verified. [ABSTRACT FROM AUTHOR]

Interior permanent magnet synchronous machines (IPMSMs) with V‐shaped permanent magnet (PM) rotors are widely used as traction motors in electric vehicles because of their high torque density and high efficiency. However, the V‐shape IPMSMs have the disadvantages of inevitable torque ripple due to the non‐sinusoidal air‐gap flux density distribution and the utilisation of the reluctance torque. In this study, with the aim of improving the torque ripple characteristics, a modified V‐shaped IPMSM rotor configuration with bridges extended inwards towards the pole centre is proposed to generate a more sinusoidal air‐gap flux density waveform. The proposed topology, referred to as 'Type C' within this study, is compared with baseline rotor configuration references, namely 'Type A' which is a conventional V‐shaped PM rotor, as well as 'Type B' which is a related configuration with a mechanically non‐uniform air gap. The analysis results show that the rotor 'Type C' exhibits significant advantages in terms of reducing cogging torque, torque ripple and radial force, without incurring additional air‐gap friction losses. Finally, a prototype of the IPMSM with the proposed rotor configuration is manufactured and tested, verifying the predicted benefits experimentally. [ABSTRACT FROM AUTHOR]

The substantial heat generation in modern electronic devices is one of the major issues requiring efficient thermal management. This work demonstrates a novel concept for the design of thermally conducting networks inside a polymer matrix for the development of highly thermally conductive composites. Highly ordered hexagonal boron nitride (hBN) structures are obtained utilizing a freeze‐casting method. These structures are then thermally sintered to get a continuous network of BN⊥–BN⊥ of high thermal conductivity in which a polymer matrix can be impregnated, enabling a directional and thermally conducting composite. The highest achieved thermal conductivity (K) is 4.38 W m−1 K−1 with a BN loading of 32 vol%. The effect of sintering temperatures on the K of the composite is investigated to optimize connectivity and thermal pathways while maintaining an open structure (porosity ≈ 2.7%). The composites also maintain good electrical insulation (volume resistivity ≈ 1014 Ω cm). This new approach of thermally sintering BN⊥–BN⊥ aligned structures opens up a new avenue for the design and preparation of filler alignment in polymer‐based composites for improving the thermal conductivity while maintaining high electrical resistance, which is a topic of interest in electronic packaging and power electronics applications. [ABSTRACT FROM AUTHOR]

In this article, the qualitative theoretical derivation, together with finite element analysis and experimental studies are presented to investigate the unbalanced magnetic pull (UMP) as well as the rotor vibration characteristics. Differently from previous studies, this study focuses on the UMP/vibration not only under the normal and the conventional radial rotor eccentricity conditions but also for three‐dimensional (3D) hybrid static air‐gap eccentricity (SAGE) cases which are composed of both the radial SAGE and the axial SAGE. The detailed UMP expressions before and after each SAGE, are first deduced based on the analysis of the magnetic flux density variation. Then, the 3D finite element calculation and the experimental study are carried out on the CS‐5 prototype generator which has two poles and a rated speed of 3000 rpm in order to validate the proposed theoretical analysis. It is shown that the DC component and the even harmonics of the radial UMP/vibration, especially the second harmonic, increase under the SAGE conditions. Specifically, the increment of the radial SAGE increases both the radial and the axial UMPs/vibrations, while the growth of the axial SAGE increases the axial UMP/vibration but meanwhile reduces the radial UMP/vibration. [ABSTRACT FROM AUTHOR]

Electric drive systems with long feeder cables connecting inverter and machine are used for oil exploration, mining, remote operated vehicles, industrial, and aerospace applications. Though this topology has the advantage of providing a better operating environment and easier serviceability for the inverter if the machine is located in an inhospitable and inaccessible environment, it does come with its own drawbacks. Steep‐fronted switched voltages and cable‐machine surge impedance mismatch can lead to high‐amplitude, high‐frequency (HF) voltage oscillations along the feeder cable, at the machine terminals, and throughout the machine's stator windings. These[AQ ID=Q1] effects can cause high‐electromagnetic interference, corona discharge, insulation failure in the feeder cable and machine's stator windings, common‐mode, differential‐mode, and bearing currents. This study discusses the HF issues relating to electric drive systems with long cable feeders. HF models for feeder cable and machine to analyse these phenomena are presented. The effects on long feeder cable loading on inverter switching characteristics are discussed. Methods to mitigate high‐amplitude and HF oscillations in such systems are shown. [ABSTRACT FROM AUTHOR]

This paper proposes a novel winding layout for the electric machines with fractional-slot concentrated windings (FSCW) using a stator shifting concept, with which all the non-working harmonics can be completely cancelled or significantly reduced and the non-overlapping winding can be kept. First, the basic winding layout with a 24-slot 14-pole machine to reduce the significant 1st sub-harmonic will be presented for machines with single-layer (SL) windings. From this, a novel double layer (DL) winding layout using the stator-shifting concept will be introduced. By adopting two SL winding sets with a 105° mechanical angle shift with respect to each other, it is not necessary to use overlapping windings. With this configuration, the 1st sub-harmonic will be completely cancelled and the parasitic 5th harmonic will be significantly reduced. Hence, the rotor losses, specifically magnet loss will be significantly reduced. Finally, two PM machines with different DL winding layout, namely, conventional 12-slot 14-pole and 24-slot 14-pole machine, will be designed and compared to validate the advantages of this winding topology. [ABSTRACT FROM AUTHOR]

Here, a typical small low-voltage totally enclosed fan-cooled (TEFC) motor (output power ∼10 kW) has been studied using computational fluid dynamics. The complexity of the end-winding geometries, often consisting of several insulated copper strands bound together, provides a challenge to the modelling and analysis of heat transfer and fluid flow phenomena occurring in the end region, which typically is an area of most interest for thermal management. Approximated geometries are usually employed in order to model the end windings to reduce the analysis time and cost. This paper presents a comparison of two cases, a typical simplified geometry and a more realistic geometry of end windings, and uses these cases to highlight the challenges and impact on predicted heat transfer. A comparison of the two models indicate that the different representations of end winding geometries can affect the heat dissipation rate through the outer housing by up to 45%. [ABSTRACT FROM AUTHOR]

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer have been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, while ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure. [ABSTRACT FROM AUTHOR]

For safety‐critical applications, electrical machines need to satisfy several constraints, in order to be considered fault tolerant. In fact, if specific design choices and appropriate control strategies are embraced, fault‐tolerant machines can operate safely even in faulty conditions. However, particular care should be taken for avoiding uncontrolled thermal overload, which can either cause severe failures or simply shorten the machine lifetime. This study describes the thermal modelling of two permanent magnet synchronous machines for aerospace applications. In terms of the winding's layout, both machines employ concentrated windings at alternated teeth, with the purpose of accomplishing fault‐tolerance features. The first machine (i.e. Machine A) adopts a three‐phase winding configuration, while a double three‐phase configuration is used by the second one (i.e. Machine B). For both machines, the winding temperatures are evaluated via simplified thermal models, which were experimentally validated. Copper and iron losses, necessary for the thermal simulations, are calculated analytically and through electromagnetic finite‐element analysis, respectively. Finally, two aerospace study cases are presented, and the machines' thermal behaviour is analysed during both healthy and faulty conditions. Single‐phase open‐circuit and three‐phase short‐circuit are accounted for Machines A and B, respectively. [ABSTRACT FROM AUTHOR]

In order to accurately estimate the temperature rise for high‐power high‐speed permanent magnet machines (HSPMMs), a novel temperature calculation method considering the non‐linear variation of material properties with temperature is proposed based on multi‐physics co‐simulation analysis. According to the theory of computational fluid dynamics and heat transfer, the computation model of fluid–solid–heat coupling heat transfer is established, and the coupled field is calculated using finite volume method with fundamental assumptions and corresponding boundary conditions. With the influences from temperature gradient and water flow rate considered, the heat transfer coefficients of water pipe surfaces are obtained by the application of the inverse iteration method. Thus, HSPMM temperature and fluid field can be simulated numerically by the finite volume methods, while the spatial temperature distributions for the machine main components are analysed in this study. The 1.12 MW, 18,000 rpm HSPMM is prototyped with experiments conducted on it, while the test data are then compared with the calculated results, which validate the correctness of the solution method of the coupled field. [ABSTRACT FROM AUTHOR]

This study proposes a modified modulated model predictive control (MMPC) scheme to control an open-end winding induction motor drive using an asymmetric source dual inverter with one floating bridge. The control algorithm uses a modulation algorithm within the cost function optimisation scheme to avoid variable switching frequency. The voltage of the floating capacitor is regulated utilising predefined redundant switching sequences as well as the voltage vector location is identified to improve calculation time. The proposed MMPC scheme enhances the output performance with comparison to the model predictive control scheme. Experimental results are presented to verify theory and simulation results. [ABSTRACT FROM AUTHOR]

In this study, electrical machine technologies are compared comprehensively for a hybrid turbocharger used with a high‐power marine engine. It is required for the machine to operate in a thermally aggressive environment, with turbine exhaust temperatures in excess of 600°C. Furthermore, it is required to both generate from the extra exhaust energy (turbo‐compounding) at high‐engine loads as well as a motor for low‐engine loads during slow steaming. The application investigated translates to a machine featuring both high‐power (150 kW) and high speeds (25–50 krpm), together with a considerable constant power–speed region. In this study, induction machines (IM), permanent magnet machines and switched reluctance machines are compared taking into account a number of aspects including the thermal performance, torque ripple, converter volt–ampere rating, and cost. In light of the technical and market requirements, the IM featuring new materials is prototyped and tested for the application in a representative environment. [ABSTRACT FROM AUTHOR]

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 study, 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. 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. [ABSTRACT FROM AUTHOR]

With increased need for high power density, high efficiency and high temperature capabilities in aerospace and automotive applications, integrated motor drives (IMD) offers a potential solution. However, close physical integration of the converter and the machine may also lead to an increase in components temperature. This requires careful mechanical, structural and thermal analysis; and design of the IMD system. This study reviews existing IMD technologies and their thermal effects on the IMD system. The effects of the power electronics position on the IMD system and its respective thermal management concepts are also investigated. The challenges faced in designing and manufacturing of an IMD along with the mechanical and structural impacts of close physical integration is also discussed and potential solutions are provided. Potential converter topologies for an IMD like the matrix converter, two-level bridge, three-level neutral point clamped and multiphase full bridge converters are also reviewed. Wide band gap devices like silicon carbide and gallium nitride and their packaging in power modules for IMDs are also discussed. Power modules components and packaging technologies are also presented. [ABSTRACT FROM AUTHOR]

The paper proposes a fast dynamic mathematical model to evaluate the performances of saturated permanent magnet synchronous machines (PMSMs) under stator winding's inter‐turn fault. The parameters of the model can be determined using only manufacturer's data of the healthy machine. Two surface mounted PMSMs have been considered to investigate the validity of the proposed approach; with distributed and concentrated winding. It has been shown that the proposed model predicts the fault current with a reasonable accuracy compared with the non‐linear finite elements analyses and to the experimental results. This model can be incorporated in a global simulation environment of power electronic of electrical device since the computation time is very short. [ABSTRACT FROM AUTHOR]

This paper evaluates the capability of saliency tracking to assess the health condition of permanent magnet synchronous motor (PMSM) drives operating under non‐stationary conditions. The evaluated scheme is based on saliency tracking methods, which are associated to the accurate sensorless control of AC drives without zero speed limitations. In this work two representative saliency tracking architectures are evaluated: high frequency (HF) injection, and PWM transient excitation. Although a monitoring approach based on HF injection was previously reported, a comparative study to evaluate the most representative saliency tracking schemes to assess health condition in drives was still missing. The aim of this work is to fill out this gap by evaluating and comparing two saliency‐based monitoring schemes (one based on HF‐injection and the other based on PWM transient excitation) to evaluate their performance in the presence of inter‐turn winding faults. Simulation and experimental results are presented which confirm that both schemes offer excellent detection capabilities and that are suitable for drives operating under nonstationary conditions including standstill operation. [ABSTRACT FROM AUTHOR]

This study proposes a monitoring scheme based on saliency tracking to assess the health condition of permanent magnet synchronous motor drives operating under non‐stationary conditions. The evaluated scheme is based on the INFORM methodology, which is associated to the accurate sensorless control of PM drives without zero speed limitation. The result is a monitoring scheme that is able to detect faults that would be very difficult to evaluate under non‐stationary conditions. A relevant aspect of the proposed scheme is that it remains valid for full speed range, and can be used for standstill operation. In addition, the approach is insensitive to the inverter non‐linearities which enhance the detection capabilities further respect to similar topologies. In this study the proposed approach is evaluated numerically and experimentally in the presence of incipient winding faults and inter‐turn short circuits in a PM conventional drive. The obtained results show quick response and excellent detection capabilities not only in the detection of faults, but to determine their magnitude which is vital to avoid further degradation. [ABSTRACT FROM AUTHOR]

This study presents a systematic study on turn-turn short circuit (SC) fault and ways to manage them to provide a basis for comparison of the various options available. The possible methods to reduce the likelihood of the winding SC fault and the fault mitigation techniques related to such faults are discussed. A finite-element analysis of a surfacemounted permanent magnet machine under application of different mitigation techniques during a turn-turn fault is presented. Both machine and drive structural adaptations for different fault mitigation techniques are addressed. Amongst the investigated fault mitigation techniques, the most promising solution is identified and validated experimentally. It is shown that the shorting terminal method adopting vertical winding arrangement is an effective method in terms of the implementation, reliability and weight. [ABSTRACT FROM AUTHOR]

This study is the first in a series dedicated to investigating the airflow and thermal management of electrical machines. Owing to the temperature dependent resistive losses in the machine's windings, any improvement in cooling provides a direct reduction in losses and an increase in efficiency. This study focuses on the airflow which is intrinsically linked to the thermal behaviour of the machine as well as the windage power consumed to drive the air through the machine. A full computational fluid dynamics (CFD) model has been used to analyse the airflow around all major components of the machine. Results have been experimentally validated and investigated. At synchronous speed the experimentally tested mass flow rate and windage torque were under predicted by 4% and 7%, respectively, by the CFD. A break‐down of torque by component shows that the fan consumes approximately 87% of the windage torque. [ABSTRACT FROM AUTHOR]