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This paper compares two variable reluctance permanent magnet machines – a flux reversal and vernier hybrid variant. The machine, which is being developed in conjunction with Mocean Energy, is required to operate at very low speed. The paper describes the application and electrical topology development, with a focus on the optimization routine used. Results show there is a conflict between peak torque and cogging torque, but also that the peak induced voltage and cogging torque are highly dependent on and sensitive to the rotor tooth width, rather than if the machine is vernier or flux reversal type.

One possibility for onboard electricity generation in a hybrid vehicle is a free piston engine incorporating an integrated linear generator. This paper presents the modelling and development of the linear engine generator concept, where a linear electrical machine is physically integrated within a free piston engine. Details and results of a multi-physics simulation of this concept are given, with a focus on the design of the electric machine. It is shown that a short translator design can result in the highest power density. This also gives the opportunity for integrating the electric machine physically within the compressor. Details of a prototype demonstrator of the resulting generator-compressor are given.

This article presents a comprehensive review of the modern thermo-conductive materials that have potential to improve the heat extraction in electrical machines by conduction. Currently, there is a significant interest in thermal design and analysis of electrical machines as the demand for high power/torque density is substantially raised in applications such as marine, aerospace, e-mobility and rail. Thermal design engineering has become very important to develop smaller and more efficient electric motors, therefore electrical machine designers need to be more informed with the recent development in novel thermo-conductive (insulation) materials. Such developments can provide enhanced thermal characteristics for high power dense electrical machines. It is reported that high voltage electrical insulations can have more sophisticated thermal properties with the recent advancements in materials science. This study aims to inform electrical machine designers with and without a thermal background about recent thermo-conductive materials. Thus, a profound understanding can be gained in thermally conductive materials for the use of numerous applications in electrical machines for which thermal management is a crucial aspect of the overall multi-physics design and optimization process. WOS:000597178100001 Q1 Q2

In low-speed applications, variable-reluctance permanent magnet machines are often proposed due to their efficient use of magnet material and high torque density. This becomes even more important in large linear applications, where the translator is longer than the stator. Often, however, very low power factors are experienced by this class of machines. This paper proposes a V-shaped flux concentrated version of a consequent pole linear Vernier hybrid permanent magnet machine and compares it to a surface-mounted magnet variant. Using finite-element analysis validated by two laboratory prototypes, it is shown that the flux-concentrated version increases the airgap flux density, which potentially leads to an improvement in the force density and efficiency or can be used to increase the operating power factor.

This work presents a new wave energy converter power take off (PTO) system that combines two recent developments in drive train technology, the consequent pole linear vernier hybrid permanent magnet machine and the linear magnetic gear. The combined system is fully realised in three-dimensional finite element method and compared to a similar direct drive machine. While the resulting system is lighter, reducing the active material mass by 30%, and more efficient, the system requires larger amounts of high cost permanent magnet material and increased PTO complexity. It is summarised that while such a system could be recommended in certain conditions, it is not viable for general application.

Wave Energy Converters (WECs) generally use a Mechanical Power-Take-Off (MPTO) involving hydraulics or gearing to optimise the extraction of energy from the incoming waves before converting it into electrical energy via a high speed rotating generator. This simplifies the design of the Electrical Power Conversion System (EPCS). Further, it facilitates the use of mechanical energy storage such as hydraulic accumulators to reduce the peaky nature of the power flow and allows the WEC resonant frequency to be tuned for maximum energy capture. This work compares two power electronic converter topologies for an Electrical PTO (EPTO). This EPTO is intended to replace the aforementioned MPTO and generator with a Permanent Magnet Linear Machine (PMLM) directly coupled to the WEC. The compared topologies comprise either a Current Source Converter (CSC) or a Voltage Source Converter (VSC) as the generator interface working in combination with a DC-DC converter and an Energy Storage System (ESS). The principle differences between the two topologies are explored and losses are evaluated in a modular EPCS working with a WEC. Wide-bandgap power electronic switches are assumed for both topologies over a range of switching frequencies. The evaluation concludes that the CSC topology is advantageous at higher switching frequencies.

This article proposes a new topology of double-sided linear Vernier permanent magnet (LVPM) machine with segmented translator structure. A combination of a typical Halbach array consists of two horizontally magnetised permanent magnets (PMs) sandwiched between a salient iron tooth and adjacent vertically magnetised PM pole with the aim of improving its electromagnetic performance. The coreless partitioned translator contributes to a significant reduction in mass and the associated cost. With the aid of finite element analysis (FEA), two LVPM machines with the same PM, and stator volume have been investigated, analysed, and compared. The results imply that the proposed LVPM is capable of producing higher force density, while it exhibits lower cogging force and force ripple compared to its counterpart.

In some wave energy converters, there is a need for linear electrical machines where all the active parts are mounted on the stator. For this reason the linear Vernier hybrid machine has been investigated. In other research, it is analyzed in 2D and assumed to have a flat cross section. In this paper a cylindrical version of the Vernier hybrid machine is presented and analyzed. A geometrical model is used to investigate potential mass savings of the cylindrical version, and a finite element analysis design study is used to demonstrate a potential improvement in performance. A proof of concept laboratory scale model has been built and tested to validate the predictions.

This paper considers the use of transverse flux machines (TFMs) as an alternative to radial flux machines (RFMs) in an in-wheel application for an electric vehicle. The base motor is an existing outer rotor surface-mounted permanent magnet machine with fractional slot concentrated windings and liquid cooling. Two topologies of TFM are compared against this base machine. The first topology is a mutual flux path (TFM-MP), while the second is a claw pole machine (TFM-CP). First, the proposed TFM topologies are studied using FEA to understand the torque capability of both topologies. Second, a comparison between two different pole numbers of each topology is compared with the performance of the benchmarking machine (BMM). The machines will be compared in terms of torque density, losses, efficiency, and power factor (PF). Finally, it is presented as a comparison on the torque capabilities when constraining the magnet mass. It is shown that the TFMs selected can deliver higher torques than the base motor during continuous operation, but have failed to deliver the required overload torque. Furthermore, low PF and low efficiency make these machines unsuitable for the application of this in-wheel traction motor.

In this study, a linear synchronous machine is compared with a linear transverse flux machine. Both machines have been designed and built with the intention of being used as the power take off in a free piston engine. As both topologies are cylindrical, it is not possible to construct either using just flat laminations and so alternative methods are described and demonstrated. Despite the difference in topology and specification, the machines are compared on a common base in terms of rated force and suitability for use as a generator. Experience gained during the manufacture of two prototypes is described.

Wave energy converters (WECs) generally use a mechanical solution such as hydraulics or gearing to optimise the extraction of energy from the incoming waves prior to converting it into electrical energy via a high-speed rotating generator. This simplifies the electrical power conversion system (EPCS) design and facilitates the use of mechanical energy storage such as springs, compressed air, or hydraulic accumulators. The naturally peaky nature of the WEC power can thus be reduced and there is potential to tune the resonant frequency of the WEC. The potential design of a current source converter (CSC) for an integrated low-speed direct-drive power take-off (PTO) for a WEC is described here. Silicon carbide (SiC) devices which enable high switching frequencies with a beneficial reduction in passive component dimensions are considered. Issues such as fault tolerance, protection, and parasitic inductance are investigated leading to an improved layout proposal.

Different topologies of Vernier permanent magnet (PM) machines have been proposed for direct drive low-speed applications due to their high thrust and power density. However, this type of machine can suffer from low power factor (PF). In this study, a flux concentrated doubly salient linear permanent magnet machine with V-shape PM arrays is proposed and compared to a consequent pole (CP) type machine. Using the configuration of V-shaped PMs allows the flux to be concentrated in iron spacers located between two pieces of PMs. This feature is shown to result in an improvement of the airgap flux density, which allows a reduction in electrical loading and hence an improvement in power factor. In order to achieve a fair comparison, two doubly salient linear permanent magnet machines with different PMs’ configurations have been analysed and compared using transient FEA. The investigated machines have the same overall machine and, crucially, magnet volume. The results confirm that the proposed V-shape machine is capable of higher thrust force, higher no-load back EMF and can achieve a higher PF of 42% compared to the consequent pole machine, while it consumes the same amount of the PM material.

Compression of windings is known to give thermal and performance benefits. The aim here is to investigate how the health of stator winding insulation systems are influenced by on-tooth coil pressing. A set of compressed coils have been aged by exposing them to high temperatures. Winding insulation resistance (IR) was monitored during this process to experimentally validate whether compressed coils remained healthy in terms of electrical insulation. In this case, a single stress (i.e. temperature) model is used to predict the reliability of the compressed coils. Accelerated life tests have been conducted to inspect the life expectancy and thermal endurance of the compressed stator coils. The employed statistical model (Arrhenius-Weibull) demonstrates that on-tooth coil pressing reduces the life expectancy dramatically due to reduced turn to ground wall insulation dielectric strength.

This paper presents the testing of an in-wheel permanent magnet Halbach array machine developed for automotive traction. A machine with a Halbach array rotor is experimentally compared to results from a surface mount variant with the same magnet mass and the finite element analysis (FEA) simulations done during its design. A battery emulator and dynamometer is used to mimic the performance in a vehicle. The Halbach version is shown to require between 6% and 15% less current to deliver the same torque across the operational speed range and delivers 20.6% more power during the continuous operation. High static cogging torque was found during testing and an approach to its solution is shown.

This paper discusses the development of a new topology of cylindrical transverse flux linear machine for use with a free piston engine. Despite its three-dimensional flux path, the stator of this topology can be made from regular laminated components and only the translator includes soft magnetic composites. The design development is discussed, including alternative winding and fabrication techniques. Finite element analysis, results of a laboratory prototype, and numerical-reluctance analysis are all used to give insight into the machine characteristics. By using flux and flux linkage factors, the tradeoff between force requirement and power factor is explored. It is shown that the power factor of this topology will generally vary from 0.89 to 0.6, which compares well with other transverse flux machines.

This paper discusses the development of linear vernier hybrid machines for use in wave energy converters. A number of topology options are explored to reduce magnet usage and improve performance for use as a linear generator. Consequent pole, V-shape, and Halbach arrays are designed for a target 25 kW specification. A discussion of overall cost of energy produced is used to justify using efficiency and power factor to asses fixed magnet mass topology variants. A power factor improvement from 0.38 to 0.72 is presented. Physical integration of the electrical machine into wave energy converters is considered including flooded experimental results of thermal behavior and polymer bearing wear.

During the 1999 community survey of Australian tree-kangaroos by the Tree Kangaroo and Mammal Group of the Atherton Tablelands, the well-known naturalist, John Young, submitted a detailed account of watching a tree-kangaroo for half an hour in the Iron Range rainforest of Cape York Peninsula in 1979. At the time this was treated by hard-nosed scientists as "needing confirmation", particularly as numerous earlier collecting expeditions had worked the area without the hint of a tree-kangaroo. John's report triggered a flurry of interest and has resulted in the collation of numerous "sightings" from the Peninsula and some targeted searches for the animal, but as yet no concrete evidence. So does the animal exist? Tantalising leads, but no hard evidence, have been found for the occurrence of tree-kangaroos in the region. We discuss the possibility that such a creature exists and what might be necessary to find it, and if it does occur what level of evidence is required.

In this paper, a permanent magnet alternator which presently relies on magnetic slot wedges is redesigned to give lower iron loss. The new segmented stator design is used as the basis for a validated loss study—comparing bonded lamination stacks with those held together with a punched notch. Segmentation is shown to improve the production process, reduce losses, and remove the need for wedges, while not significantly altering the acoustic performance. In the first series of prototypes, however, where notching is used to secure lamination packs, the process is shown to have adversely affected material properties of the nickel iron laminations and overall measured losses increased. In the second prototype, with thinner laminations and glued stacks, iron loss predictions and measurement agree and are less than the present slot wedge design.

This paper focuses on the improved thermal performance of electrical machines by increasing the conductor fill factor. A comparative design study of the integrated starter generator is used as a case study to investigate the mechanical, electrical, and thermal aspects of pressing coils. By performing quasi-static explicit dynamics simulations, deformation of insulation has been investigated. Magnet wires of 1.25 mm diameter are simulated and demonstrated to be compressible up to a 0.73 fill factor without observing insulation failure. Thermal conductivity enhancement of the stator windings at improved slot fill factor is investigated by performing steady-state finite element analysis thermal simulations and short-time thermal transient tests.

In the paper, a coupled dynamic model of the Linear Joule Engine and the embedded permanent magnet linear alternator is presented, which is the first dynamic model alike to bridge mechanical and electrical parts of linear engine generator, and provides better prediction of the performance. The detailed sub-model of the linear alternator responding forces eliminate any underestimation of their impact on the kinetics of the moving mass, i.e. piston, translator and rods, in turn, the electricity generation. The coupled model also enables an integrated design of the Linear Joule Engine and the linear alternator, which has the double acting piston in the compressor mounted with embedded permanent magnets to work as the translator, while the compressor cylinder bore is integrated with coils as the stator. It is predicted that the Linear Joule Engine Generator of the new design produces 1.8kWe with thermal efficiency of 34% and electrical generation efficiency of 30%.

Recently, the extraction of energy from the incoming waves has taken more importance in the energy generation based on renewable resources. However, most of the attention has been directed towards the Power-Take-Off systems more than in the interaction between several generating units. Consequently, in this work, there are presented and carefully analysed a novel topology of Interconnected Wave-Energy Converters (IWECs) and its associated control system. A representative set of data of a real wave frequency and height variation from the South Uist island, in Scotland, and a proof-of-concept simulation show that the energy requirements of the proposed IWEC are lower than those required for individual WECs.

Related plants are often hypothesized to interact with similar sets of pollinators and herbivores, but this idea has only mixed empirical support. This may be because plant families vary in their tendency to share interaction partners. We quantify overlap of interaction partners for all pairs of plants in 59 pollination and 11 herbivory networks based on the numbers of shared and unshared interaction partners (thereby capturing both proportional and absolute overlap). We test for relationships between phylogenetic distance and partner overlap within each network; whether these relationships varied with the composition of the plant community; and whether well-represented plant families showed different relationships. Across all networks, more closely related plants tended to have greater overlap. The strength of this relationship within a network was unrelated to the composition of the network's plant component, but, when considered separately, different plant families showed different relationships between phylogenetic distance and overlap of interaction partners. The variety of relationships between phylogenetic distance and partner overlap in different plant families probably reflects a comparable variety of ecological and evolutionary processes. Considering factors affecting particular species-rich groups within a community could be the key to understanding the distribution of interactions at the network level.

the aim of this paper is to investigate the integration of a tubular linear electrical machine with a linear free-piston combustion engine in order to create a single integrated free piston engine generator. The performance of the engine when coupled to a long and short translator electrical machine is discussed. To simulate the dynamic performance of the overall system, an integrated thermodynamic, mechanical and electromagnetic model is required. LMS Amesim software is used to model the thermodynamic engine and electromechanical finite element analysis is used for the electrical machine. The overall performance of an engine coupled to electrical machines with varying translator length is investigated. The performance of such a tubular generator is demonstrated by measurements on a 7-pole/6-slot prototype machine. The short translator generator design appears to perform better in terms of performance and capital cost, based on the dynamic simulation results of the system.

This paper reports on the results of a project to develop the drive train for a wave energy converter - consisting of a linear generator and a power converter. Two power converters and a number of small scale linear machines have been designed, built and tested in the laboratory. A variety of simulated and laboratory results are presented and a summary of project findings described.

This paper will investigate the use of a Halbach array in an in-wheel motor. It highlights the benefits of introducing a Halbach array to reduce the rotor-core-back depth and compares two different stator topologies for the application: a parallel teeth and a parallel slots.

In a free piston engine, the translator of a linear generator is coupled directly to the moving cylinder of a thermodynamic engine. For a linear machine to have a constant active area, either the translator or the stator must be oversized. The length of the translator effects its mass, which in turn effects the engine performance. This paper investigates the effect of translator length on the overall power density of a free piston engine coupled to a cylindrical permanent magnet machine.

This paper discusses a field weakening method for permanent magnet electrical machines. The proposed method can be an alternative to complex mechanical field weakening methods for safety critical applications. The developed concept is based on a split rotor in which a permanent magnet rotor is split into two parts to achieve two states of field excitation; either maximum flux output or the least flux output, depending on alignments between the rotor parts, having a degree of freedom to rotate on the shaft. The stator of the permanent magnet (PM) machine exposes two magnetic fluxes by the split rotor sections. Thus, the fixed nature of the PM excitation can be altered by this concept to achieve a wide speed range, which is a key concern in PM electrical machines at higher speeds. A number of 3D finite element (FE) simulations and a Simulink/Matlab model have been implemented to investigate the dynamic behavior of the system. Although it is challenging to computationally investigate the behavior of the split rotor at different operating conditions due to complex torque interactions, altering the relative angular position of the free-to-rotate rotor on a shaft, the proposed method might eliminate the complex implementation of mechanical field weakening apparatus for PM electrical machines. Thus, a PM machine with split rotor would be used over a wide speed range without excessive voltages at high speeds in fault tolerant aerospace applications.

This paper proposes a new method of speed amplification for a direct drive ocean wave energy converter. The relative speed of the stator and translator of a linear generator is doubled through a fixed pulley wheel mechanism. Analytical and simulation models of the system have been developed and simulated considering the mechanical damping and electrical damping coefficients. The models have been simulated in both the regular waves and irregular waves where hydrodynamic parameters for different heaving buoys are calculated from hydrodynamic boundary element analysis simulation using the ANSYS AQWA software. The relative displacement, output voltage and harvested power of the speed amplified wave energy converter system have been obtained in the frequency and time domains. The frequency and time domain models were validated through comparing the peak output power values at different frequencies. The generator parameters of electromagnetic coupling coefficient, or the power take-off (PTO) electrical damping coefficient and external resistance were studied to ensure an optimal wave-energy converter (WEC) design.

High performance electric motor designs with ferrite magnets have recently gained interest due to the high and volatile price of rare earth magnets. However, due to the relatively poor coercivity of ferrite magnets, these designs are highly susceptible to demagnetization, as a result of which accurate modelling and better understanding of this phenomenon is particularly important. In this paper, the impact of the motor stack length and level of magnetic saturation on the demagnetization risk are studied based on 3-dimensional finite element 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 theoretical findings have been supported by prototype testing.

Indirect interactions play an essential role in governing population, community and coevolutionary dynamics across a diverse range of ecological communities. Such communities are widely represented as bipartite networks: graphs depicting interactions between two groups of species, such as plants and pollinators or hosts and parasites. For over thirty years, studies have used indices, such as connectance and species degree, to characterise the structure of these networks and the roles of their constituent species. However, compressing a complex network into a single metric necessarily discards large amounts of information about indirect interactions. Given the large literature demonstrating the importance and ubiquity of indirect effects, many studies of network structure are likely missing a substantial piece of the ecological puzzle. Here we use the emerging concept of bipartite motifs to outline a new framework for bipartite networks that incorporates indirect interactions. While this framework is a significant departure from the current way of thinking about bipartite ecological networks, we show that this shift is supported by analyses of simulated and empirical data. We use simulations to show how consideration of indirect interactions can highlight differences missed by the current index paradigm that may be ecologically important. We extend this finding to empirical plant–pollinator communities, showing how two bee species, with similar direct interactions, differ in how specialised their competitors are. These examples underscore the need to not rely solely on network‐ and species‐level indices for characterising the structure of bipartite ecological networks.

In this paper, 28 slot − 18 pole and 24 slot − 20 pole permanent magnet alternators (PMA) with soft magnetic composite slot wedges are designed and compared. Power lane separation required due to fault tolerance requirements, means the proposed machines initially do not produce balanced phase voltage and currents, resulting in high ripple on the rectified power output. The alternators are optimised using 2-D finite element analysis (FEA) to get smoother DC power waveform. It is shown that the power ripple might be reduced by about 12%and un-balanced windings can be significantly balanced by thickening up the SMC slot wedges between the sub-machines. Furthermore, no load loss analysis has been conducted at rated speed and it is shown that 28 slot − 18 pole machine generates lower loss on no load condition compared to 24 slot − 20 pole single layer PMA.

Vernier hybrid machines (VHMs) are known for their simple salient translator structure and inherent magnetic gearing, making them a strong candidate for low-speed, high-force applications. As both the armature coils and the permanent magnets (PM) are mounted on the stator, linear versions of this machine are attractive for applications with a large stroke amplitude. In most configurations, single-sided or double-sided flat cross sections are utilized, giving a two-dimensional flux path. In this article, a cylindrical variant of the double-sided flat configuration is presented, where the flux path is now three dimensional. Three-dimensional finite-element analysis is used to design, analyze, and compare both flat and cylindrical topologies for a fixed PM mass and current density. Details and test results of a soft magnetic composite based laboratory prototype of the cylindrical VHM are given, which demonstrate the concept and validate the simulation results.

This paper proposes a new flux concentrated version of a consequent pole linear Vernier hybrid permanent magnet machine. The Vernier hybrid machine stator has alternatively magnetised adjacent magnets directly in contact with each other. A salient rotor then switches the direction of flux past the stator coils. Alternate magnets can be removed to make the consequent pole version, where inset rectangular magnets are magnetized in a common direction and separated by soft magnetic poles. In a flux concentrated consequent pole configuration, each magnet pole comprises of two magnets forming a V -shape. This topology hence possesses a combination of consequent poles, flux concentration and flux switching machine topologies. Magnetic flux concentration increases the airgap flux density, which potentially leads to an improvement of the force density and operating power factor. This paper compares the inset and V -shape consequent pole topologies using finite element analysis simulations. Both machines have the same dimensions, magnet volume, rated speed and current density. The simulation results imply that the V-shape machine offers higher electromagnetic performance. To confirm this, two linear prototypes are currently under construction, where the key parts that already produced are presented in this paper.

This paper compares a Halbach array to a more conventional surface mounted permanent magnet arrangement for an in wheel traction motor. Demagnetisation, physical air-gap and torque capability at continuous and overload operation is considered. Without increasing the machine operating space, using one transition per pole was found to increase rated torque by 5% and overload torque by 3 %. A second comparison was done using 3 transitions per pole and this topology was found to give an increase in the overload torque of 4%. Finally, a novel trapezoidal Halbach array arrangement has been proposed to reduce the demagnetisation of the transition magnets and increase their permeance coefficient.

This paper investigates methods of magnet mass reduction in linear flux switching permanent magnet (LFSPM) machines by introducing tapered consequent poles. Based on the finite element analysis (FEA) three different models are designed, investigated and compared. The obtained results indicate that by adopting the proposed tapered ferromagnetic poles a considerable saving of material cost and weight is obtained without sacrificing the machine performance.

In this paper a novel E-core Linear Variable Reluctance Vernier Hybrid Permanent Magnet (LVR-VHPM) machine with inherent magnetic gearing is proposed for use in the long stroke application of a wave energy converter. The proposed topology is a combination of a doubly salient flux reversal machine, a consequent pole machine and a surface mounted Halbach array Permanent Magnet (PM) machine. The stator teeth interact with horizontally and vertically magnetized PM and ferromagnetic poles in such a way as to maximize the flux density in the machine by minimizing flux leakage. The translator is segmented to ensure the most effective use of material for minimum mass. A performance comparison study between the novel LVR-VHPM machine, a baseline linear Vernier Hybrid Permanent Magnet (VHPM) machine, a linear Halbach VHPM machine and a linear Consequent pole VHPM machine is used to show that the best result is achieved by the combined topology. All four designs consist of the same double sided E-core stators, segmented translators and an equal magnet mass.

The modulated pole machine (MPM) is known to offer high torque density utilizing permanent magnets and a three dimensional flux pattern. However, their construction requires a departure from conventional coil wound teeth formed of lamination stacks which can be a challenge. In this paper three construction techniques for MPM stators are compared: pure soft magnetic composite, pure lamination and a hybrid of the two. Simulation and practical knowledge of the build of each of these machines, including torque capability and mechanical tolerances is presented and discussed. Using the methods proposed here, it is shown that the pure laminate MPM machine has the potential to offer the greatest torque per kg of active material, yet it is the hybrid machine which delivers the highest absolute torque.

More electric is a platform being widely adopted by the current generation of aircraft. It offers significant benefits in terms of fuel savings and flexibility of airframe design but relies on the development of torque dense machines. This paper documents the development of an air-cooled transverse flux machine for use in short-haul aircraft to improve on-ground operational efficiency. If its potential is to be realized, this topology of the machine comes with a new set of manufacturing challenges. Two competing machine layouts with different approaches toward their fabrication are discussed. Experimental results and experiences gained from overcoming the challenges of building the machines are presented. A combined phase topology with soft magnetic composite core-back is shown to give a better rated torque, whereas a separate phase bent lamination concept gives better overload capability.

This paper proposes a new topology of a Linear Veriner Hybrid Permanent Magnet (LVHPM) machine with E-core stators and a segmented chamfered translator, which is shown to give mass reduction and better magnetic flux path compared to existing designs. Linear Permanent Magnet (PM) generators have the capability to reduce the number of moving parts, providing a simpler mechanical drive train when used as an all-electric direct drive power take-off for wave energy converters. The translator can be directly connected to a heaving buoy, or similar, to translate linear motion from the ocean waves into electricity. In this paper, the electromagnetic performance including magnetic flux, back EMF, cogging, thrust force, thrust ripple as well as force density of the new segmented chamfered translator design is analyzed in Finite Element Analysis (FEA). The proposed design is compared with two different models and shown to produce the best performance among those models.

This paper describes the thermal modeling approach of a permanent magnet alternator (PMA), developed to investigate the quantitative effect of thermal paste added into the machine end winding region. A thermal lumped parameter network is proposed to investigate the principal heat flow paths for a flange mounted alternator. The thermal model is implemented in Simulink, which allows many different heat paths to be easily combined. Since addition of a thermal paste introduces new axial heat flow by conduction paths between the stator windings and frame, the developed thermal network considers the detailed heat flow paths when thermal paste is present. Experimental results are presented which validate the results.

This paper describes the effect of alternative power conversion techniques on the performance of a Linear Alternator driven by a Joule Cycle-Free Piston Engine for electrical power generation. The design of a tubular Longitudinal Flux machine with axial magnets is performed using 2-D axisymmetric FEA modelling with transient solver to extract the rated power for three power conversion scenarios: Resistive Loading, Grid Interface, and Unity Power Factor Controlled Converter. The design study is carried out for a specific engine operating force and velocity, taking into consideration geometrical constraints for a compact system. Results are presented and discussed emphasizing the effect of the power conversion method on the idealized resultant machine physical and performance parameters.

Wave energy conversion can be simplified by using direct drive linear generators which may improve reliability. Numerous topologies of direct drive linear generators have been proposed in the last few decades such as the linear vernier hybrid permanent magnet (LVHPM) machine. However, the cost of this kind of machine is driven by the quantity of permanent magnet (PM) material. This paper proposes a linear vernier hybrid permanent magnet machine with consequent pole and concentrated windings for wave energy converters, which requires less magnet material for comparable performance. The key of the proposed design is the modular stator where the unbalanced magnetic circuit caused by consequent pole can be eliminated. Based on finite element analyses (FEA) the present machine is capable of higher thrust force, higher back EMF and lower cogging force as well as force ripple compared to that of a baseline LVHPM machine.

Ecological communities are composed of many species and an intricate network of interactions between them. Because of their overall complexity, an intriguing approach to understanding network structure is by breaking it down into the structural roles of its constituent species. The structural role of a species can be directly measured based on how it appears in network motifs – the basic building blocks of complex networks. Here, we study the distribution of species’ roles at three distinct spatio-temporal scales (i.e. species, network, and temporal) in host–parasitoid networks collected across 22 sites over two years within a fragmented landscape of oaks in southern Finland. We found that species’ roles for hosts and parasitoids were heterogeneously distributed across the study system but that roles are strongly conserved over spatial scales. In addition, we found that species’ roles were remarkably consistent between years even in the presence of disturbances (e.g. species turnover). Overall, our results suggest that species’ roles are an intrinsic property of species that may be predictable over spatial and temporal scales.

This paper focuses on the improved thermal performance of electrical machines by increasing the conductor fill factor. A comparative design study of integrated starter generator (ISG) considering different pole/slot combinations and magnet topologies is used as a case study to fix slot dimensions. Compressed stator windings coupled with segmented stator structure are introduced to reduce copper losses of the optimized ISG. By performing quasi-static explicit dynamic simulations, deformation of insulation has been investigated regarding mechanical properties of the magnet wire enamels. It is noted that magnet wires at certain cross-sectional area can be compressed up to 0.72 fill factor without observing insulation failure. Thermal conductivity enhancement of the stator windings at improved slot fill factor is demonstrated by performing steady state and transient finite element thermal simulations.

This paper investigates the design of alternative permanent magnet linear machines for use as the generator in a free piston engine. All of the machines are of a modulated pole structure with three dimensional flux flows. In transverse flux machines such as these, the current flows in a different plane to the flux path, eliminating the usual conflict between electric and magnetic loading. For a linear machine, the mass of magnets used is sensitive to whether the magnets are mounted on the stator or translator. Hence this paper compares transverse flux machines with translator mounted magnets and flux switching machines with stator mounted magnets. A three dimensional finite element analysis of each topology is run through an optimization routine in order to investigate the magnet usage, power factor and other performance criteria. It is concluded that flux switching machine is uncompetitive due to the 65% flux leakage even with improved tooth structure, moreover the transverse flux machine is shown to perform better overall, giving a better power factor, better efficiency and lower translator mass as a whole flux switching machine is not match for free piston engine applications.

Electric motors are becoming increasingly utilized in aircraft, replacing traditionally mechanical or hydraulic auxiliary systems to realize improvements in mass, control and efficiency. Aerospace motor design has the unique characteristic that mass and, therefore, torque density is of critical importance. For low maintenance, non-safety critical components, which are only used for short durations of the flight cycle, efficiency also becomes less important, whilst eliminating an external cooling circuit and gearbox will further benefit mass constraints. This paper considers the design of a high torque density machine in order to meet a specification for an aerospace application with a stringent mass target. As mass is reduced, thermal capability becomes critical and detailed thermal models, along with simulation results, are presented for operational characteristics.

This paper discusses three-phase topologies for modulatedpole machines (MPMs). The authors introduce a new threephasetopology, which takes advantage of mutual flux paths; thisis analyzed using 3-D finite-element methods and compared to athree-phase topology using three single-phase units stacked axially.The results show that the new “combined-phase MPM” exhibitsa greater torque density, while offering a reduction in thenumber of components. The results obtained from two prototypesare also presented to verify the concept; the results show that the“combined-phase” machine could provide both performance andconstructional benefits over prior MPM topologies.

Human alterations to natural systems have resulted in a loss of biological diversity around the world. Amphibian population losses have been more severe than those of birds and mammals. Amphibian population declines are likely due to many factors including habitat loss, disease, contaminants, introduced species and ultraviolet-B (UVB) radiation. The effect of UVB, however, varies widely among species and can vary within populations of the same species or at different life-history stages. This variation has often led to opposing conclusions about how UVB affects amphibians. We used meta-analysis techniques to explore the overall effects of UVB radiation on survival in amphibians. We also used recently developed factorial meta-analytic techniques to quantify potential interactions between UVB radiation and other stressors on amphibians. Ultraviolet-B radiation reduced survival of amphibians by 1.9-fold compared with shielded controls. Larvae were more susceptible to damage from UVB radiation compared with embryos, and salamanders were more susceptible compared with frogs and toads. Furthermore, UVB radiation interacted synergistically with other environmental stressors and resulted in greater than additive effects on survival when 2 stressors were present. Our results suggest that UVB radiation is an important stressor in amphibians, particularly in light of potential synergisms between UVB and other stressors in amphibian habitats.