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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]

Sensorless drives of interior permanent magnet synchronous motors (IPMSMs) find a broad range of applications due to their inherent benefits. In practical electrified propulsions, the IPMSM drives are usually working in highly utilized conditions where the performance and stability could deteriorate. Without considerable compensation, this vulnerability causes the existing phase-locked loops (PLLs), estimators, or observers to lose the synchronization with the rotor position. To achieve better performance and reduce the estimation error, in a PLL-type framework for sensorless control, a position error observer (PEO) utilizing the current errors as correction terms plays the role of the phase detector. A reduced-order extended state observer (ESO) is presented to form the loop filter with a switched nonsmooth feedback structure. The outstanding property of the PEO and nonsmooth ESO is verified through experiments. The results demonstrate its strong adaptability for model uncertainties and disturbances along with the quick convergence speed and minimal oscillation. [ABSTRACT FROM AUTHOR]

In transportation vehicles, the installation of force sensors for electromechanical brake systems causes cost issues and implementation difficulties. The elimination of the sensor is highly demanded. The main vulnerability of the existing force estimators is that the algorithms either rely on shifting characteristic curves or empirical data to determine the major quantities. Hence, they are less capable of dealing with initialization offset errors, fast-changing dynamics, and uncertainties. This article presents a novel super-twisting observer to accurately estimate the clamping force on the basis of a dynamic torque-balance model. In this observer, an extended state is defined on top of a super-twisting algorithm. The observer gains are computed through a smooth Lyapunov function to guarantee the fast convergence. It is experimentally validated that the observer enhances the performance required by the antilock braking systems in comparison with conventional methods. [ABSTRACT FROM AUTHOR]

A close functional and structural integration of passive elements is required to improve the power density of motor drives. Such power-dense motor drives are prerequisites in aerospace and automotive applications. This article presents a permanent magnet motor with an integrated filter inductor, which not only eliminates inductor losses but also removes its associated weight and volume. The motor with an integrated filter uses motor's inherent magnetics in order to use it as a filter inductance instead of adopting an external inductor option, which is traditionally placed outside the motor. A vector-controlled model, taking modulation and switching effect into account, has been developed by using MATLAB/Simulink tool. To experimentally validate the concept of the motor with an integrated filter inductor, the winding connections of an existing motor are modified. The comparative analysis, between the traditional and integrated motor drive systems, is carried out in terms of the magnitude of switching component, total system losses, weight, and volume. The total losses in the motor with integrated filter are reduced by 34.2% at 2100 r/min and 3-N·m load, when compared to the motor with traditional filter inductor, whereas, its weight and volume in the motor with integrated filter inductor are eliminated completely. [ABSTRACT FROM AUTHOR]

This paper presents a validation of the novel motor-shaped rotational inductor. To validate the concept, 12 slots 2 poles rotational inductor is tested at different supply frequencies and rotor speeds. Experimental results have shown that the iron losses reduce as the rotor speed increases to the synchronous speed of the stator supply. The performance of the integrated rotational inductor is also compared with traditional EE core inductor in terms of total losses, synchronous inductance, copper resistance, and total harmonic distortion (THD). The total loss-to inductance ratio of the rotational inductor is reduced by 22.5% when rotor is rotating at 18 kRPM and supply frequency is held at 300 Hz. A significant reduction in copper resistance-to-inductance is also noticed when supply frequency is varied from 0 Hz to 20 kHz. Furthermore, the synchronous inductance and voltage and current's %THD of rotational inductor is found to be superior to EE core inductor. [ABSTRACT FROM AUTHOR]

This article describes the development of an exact analytical model for predicting magnetic field distribution within active parts of a dual-rotor (DR) permanent magnet (PM) synchronous machine with a Halbach array. The model is based on the accurate solution of Laplace’s and Poisson’s partial differential equations (PDEs) using a method of separation of variables. The model also allows the calculation of the DR machine flux linkage, back electromotive force (bEMF), and electromagnetic torque at on load and cogging torque at a no-load condition. The model can be used at the initial stage of designing a DR PM machine for the estimation of electromagnetic parameters and the optimization of machine geometry. [ABSTRACT FROM AUTHOR]

Annealing (at multiple cooling rates) and quenching (with tempering) was performed on specimens of cast steel of varying composition. The aim was to devise a method for selecting the steel with the highest permeability, from any given range of steels, and then increasing the permeability by heat treatment. Metallographic samples were imaged using optical microscopy to show the effect of the applied heat treatments on the microstructure. Commonly cast steels can have DC permeability altered by the careful selection of a heat treatment. Increases of up to 381% were achieved by annealing using a cooling rate of 6.0 °C/min. Annealing was found to cause the carbon present in the steel to migrate from grain boundaries and from within ferrite crystals into adjacent pearlite crystals. The migration of the carbon resulted in less carbon at grain boundaries and within ferrite crystals reducing the number of pinning sites between magnetic domains. This gives rise to a higher permeability. Quenching then tempering was found to cause the formation of small ferrite crystals with the carbon content of the steel predominately held in the martensitic crystal structures. The results show that with any given range of steel compositions the highest baseline DC permeability will be found with the steel that has the highest iron content and the lowest carbon content. For the samples tested in this paper a cooling rate of 4.5 °C/min resulted in the relative permeability of the sample with the highest baseline permeability, AS4, increasing from 783 to 1479 at 0.5 T. This paper shows how heat treatments commonly applied to hypoeutectoid cast steels, to improve their mechanical performance, can be used to also enhance electromagnetic properties of these alloys. The use of cast steels allows the creation of DC components for electrical machines not possible by the widely used method of stacking of electrical grade sheet steels. [ABSTRACT FROM AUTHOR]

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]

In electrical machines, a higher torque/force density can usually be achieved by increasing the current density in the windings. However, the resulting increase in copper losses leads to higher temperatures in the coils, particularly in the center of the slots where the thermal resistance to the ambient/cooling surfaces is highest. In this paper, a novel, simple technique is presented in which a higher thermal conductivity path between the center of the slot and the cooling arrangement is created, thus increasing the heat flow away from the slot center. A lumped-parameter thermal model is presented and used along with finite-element analysis to investigate the effectiveness of the proposed technique. The lumped-parameter model is also used for optimizing the high conductivity path for maximum air-gap shear stress and to obtain a compromise between the reduced slot area and the improved temperature distribution. Experimental validation is then presented to compare the predicted results with the measured results on a purposely built instrumented setup. [ABSTRACT FROM AUTHOR]

In safety critical aerospace applications, fault-tolerant drives can help reach the necessary system reliability levels without replicating the entire drive system and thus minimizing the overall system weight. Machine selection and design for fault tolerance has to be considered at an early stage to ensure optimal performance at a system level. This paper looks at the fault-tolerant properties of permanent-magnet flux-switching machines (PMFSMs) and proposes a new configuration able to fulfill the fault-tolerant requirements. PMFSMs have the distinct property of having a robust rotor construction with the permanent magnets embedded in the stator while having their operational characteristics similar to those of synchronous permanent-magnet machines. While these machines have numerous inherent advantages for achieving a high power density, in their basic form, they are not tolerant to short-circuit winding failures. This paper will look at a novel stator structure able to achieve a 1-p.u. winding inductance and will subsequently look at design iterations to maximize the torque density. [ABSTRACT FROM AUTHOR]

This paper looks at the requirements and challenges of designing a permanent-magnet (PM) motor for a directly driven electromechanical actuator for aerospace applications. Having a directly driven system, the intermediate gearbox is eliminated, bringing advantages in terms of lower component count and reduced jamming probability. The design of a low-speed high pole number PM motor will be investigated as a potential solution. The main goals of the design are a high level of actuator integration in order to minimize weight and volume, fault tolerance, and high reliability. The design will be tailored to the requirements of a typical midspoiler actuation system for a large civil aircraft. [ABSTRACT FROM AUTHOR]

A detailed magnetic reluctance-based computational model of an induction machine, into which a traditional rotor-flux-orientated vector control scheme has been grafted, is used to examine the influence of saturation of both main and leakage flux paths upon vector-controlled drive performance. Individual machine teeth, windings, and conductors are incorporated, as is pseudo-3-D modeling of skew. The cross-saturation effect is there- fore determined from the basic dimensional and winding design data of the machine. Effective compensation methods can then be derived for practical implementation. Direct rotor flux orientation and magnitude control is used to ensure that inaccuracies in a machine-parameter-based vector control scheme are not reflected in the results for cross saturation. Results for a 15-kW four-pole induction motor with rotor skewed one stator slot pitch show that skew leakage flux is predominantly responsible for cross saturation. The skew leakage flux is shown to heavily saturate one end of the machine and to reduce the air gap flux density at the other. At 200% rated load current, this equates to an 11% reduction in direct axis flux if isd is kept constant. To compensate for this reduction, a 27% increase in isd would be required. [ABSTRACT FROM AUTHOR]

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]

An introduction is presented in which the editor discusses various reports within the issue on topics including current technologies for high-speed electrical machine applications, a novel motor topology with a lateral stator used for drilling, and use of amorphous laminations on induction motor.

Sensorless control technologies based on rotor saliency may not operate well due to the effect of magnetic saturation. In this work, a rotor backend (RB) is attached to an existing rotor structure of a permanent magnet synchronous motor (PMSM) to enhance anisotropic features. The geometry of the RB is further optimized to achieve greater current amplitude induced by the RB saliency modulation. The phase sequence direction of the modulation is not electrically synchronized with the rotor reference frame. A fractional slot/pole combination is selected and analyzed to strengthen the saliency modulation signal. Hence, the sensorless techniques will be immune to saturation effect in highly exploited machines. Both low and high-speed performance of the proposed method is verified through the experimental tests. It is demonstrated that the position estimation using saliency modulation of the RB is unaffected by machine saturation due to its electrical asynchronous property. [ABSTRACT FROM AUTHOR]

High-speed permanent magnet machine (HSPMM) design is considered with particular attention paid to machine electromagnetic, thermal, and mechanical analyses. In this article, a 140-kW, 15 000 r/min HSPMM is designed with its power losses evaluated at first. Afterward, the machine temperature distribution is obtained based on computational fluid dynamics modeling. HSPMM is prototyped with experimental tests conducted to verify the calculation results. Mechanical strength analysis is performed for the HSPMM rotor structure with pole filler by finite-element method for the rotor at three operational conditions, while the influences from sleeve parameters on rotor strength are comprehensively studied for the HSPMM rotor at the most challenging condition. In this article, stator auxiliary slotting is extensively researched to reduce the rotor eddy current loss with little effects on machine output torque. The air gap flux density for HSPMM with auxiliary slotting is analytically predicted, while the working mechanism is illustrated in-depth. The effects from auxiliary slot dimensions, numbers and positions, on machine performances are further proposed and investigated. The experimental tests also validate the reduction of HSPMM rotor eddy current loss by the application of auxiliary slotting. [ABSTRACT FROM AUTHOR]

A nonlinear third-order extended state observer (TESO) is proposed for the rotor position and speed estimation for sensorless interior permanent magnet synchronous motor drives. The disturbance observation bandwidth of the proposed observer is expanded by deploying a gain optimization method. The measurement noise excited in the control loop is suppressed effectively by substituting the previous high gain configuration. Experimentally, both the steady-state and transient performance of the TESO are verified on testing rigs. In comparison with the performance of a conventional linear extended state observer, the TESO has a better capability of disturbance observation and noise suppression in a wide operating range. [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]

The long and enduring history of utilization of the wound-field synchronous generator in a large number of applications makes it one of the most known and consolidated electrical machine technologies. Thus, its design, modeling, and analysis processes have been widely exploited and implemented through various and different methods, including the equivalent circuit approach. When a damper cage is embedded within the rotor of the synchronous generator, its theoretical analysis becomes quite complicated. Thus, today numerical tools are being used. In this paper, an alternative way of modeling symmetric damper cages of salient-pole synchronous generators is presented. The proposed approach is embedded in the circuital model of the generator. A hybrid analytical–numerical model is implemented, permitting to accurately predict the voltage waveforms of the generator with excellent accuracy, however, at a lower cost of computational resources than the pure numerical method. A case study of an off-the-shelf 400 kVA machine is considered to develop and validate the proposed technique. The results are compared with the corresponding finite-element and experimental evaluations for validation purposes. [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]

High-speed permanent magnet synchronous machine (PMSM) can provide high power density and high efficiency, which is often highly desirable in high performance applications. A multi-physics optimization program based on the multi-objective genetic algorithm was developed in this paper, to achieve a tradeoff solution between the electromagnetic, mechanical, and thermal aspects. First, the parametric electromagnetic model was modeled based on the finite-element method, and then a thermal network model and an analytical mechanical model to determine the thickness of the magnet and the sleeve were developed and merged within a design cycle of the machine, in an effort to attain the target performances of 20 kW/kg at 20 000 r/min for a 2 MW PMSM. Optimization results indicated that a final design with eight poles and 48 slots could obtain a comprehensive performance between power density and efficiency, and the performance satisfied all the requirements. [ABSTRACT FROM AUTHOR]

Active power filters (APF) are used to improve power quality and are commonly connected in parallel with the load at the point of common coupling. They are used to compensate for harmonics from nonlinear loads, for reactive power compensation, and/or balancing mains currents. This paper will investigate the effect of using an APF to improve the output power quality of a simplified synchronous generator (SSG) with distorted back EMF. A MATLAB/Simulink model for the SSG is built to simulate all the system, the APF, and the proposed generator. Using an APF, simulation, and experimental results show significant improvements in generator output current and reduced the total harmonic distortion in the system. [ABSTRACT FROM AUTHOR]

This paper investigates high-speed surface PM machine design for portable turbo-generator applications. The rotor radius is fixed to achieve certain optimal characteristics of the magnet retention mechanism. The objective of this paper is to design and select the stator. The stator designs are populated by different slot/pole combinations, winding arrangements, and over a range of possible stack lengths. However, the design is constrained by physical diameter, stack length, and electrical volt–ampere constraints. A large number of preliminary machine designs do not satisfy the specified turbo-generator torque/speed requirements under the given volt–ampere constraints and therefore it is ineffective to perform finite element analysis on all preliminary design variations. In order to establish the feasibility of a machine design to fulfill the specified turbo-generator torque/speed requirements, the concept of inductance-limits is presented and then linked with stator design parameters. By application of this analysis strategy, a confined optimal set of stator designs are obtained and are subjected to detailed finite element simulations. A final machine design is selected and fabricated. Experimental results are presented for the validation of the final machine design. [ABSTRACT FROM AUTHOR]

The traditional generating set is usually comprised of a classical, wound-field, salient-pole, or cylindrical rotor synchronous generator, excited by a separate smaller machine, via a rotating, uncontrolled diode rectifier. The effects of the commutation processes of the diode bridge are often overlooked and neglected. However, due to the uncontrolled nature of this process, the rectified voltage available at the main generator's rotor terminals can be significantly lower than the expected value. This is especially true for low-to-medium power rated systems. In this paper, a detailed investigation of these aspects is done and an accurate voltage drop prediction model is then proposed. The model is validated with finite-element analysis and with experimental results for a particular low–medium rated generating system in the 400 kVA power range. The validated tool is then integrated into an innovative design tool, which first performs an analytical presizing procedure and then utilizes a genetic algorithm approach to identify an optimal excitation system design, aimed at minimizing the voltage drop ensuing from the diode commutations, with minimum impact on the overall efficiency. [ABSTRACT FROM AUTHOR]

This paper is concerned with the use of conical induction machines. Such machines are extremely valuable when apart from the rotational torque output; an axial translation of the rotor is also required. The inherent attraction between the stator and rotor of any machine combined with the geometry of a conical machine will provide the required axial movement. However, when applied to aerospace applications, where reliability is very important, then full monitoring of the axial position is required. In this paper, an innovative approach aimed at monitoring and controlling the axial translation of a conical induction machine is proposed and investigated. In order to increase the system reliability and also decrease component count as demanded by the application, the methodology is a sensor-less technique based on an innovative variant of the high-frequency injection approach. In this paper, the technique has been fully investigated and experimentally validated on a purposely built instrumented test-rig. [ABSTRACT FROM PUBLISHER]

The general effects of implementing skewing techniques in electrical machines are well known and have been extensively studied over the years. An important aspect of such techniques is related to the identification of optimal methods for analyzing and modeling any skewed components. This paper presents a fast, finite-element-based method, able to accurately analyze the effects of skew on wound-field, salient-pole synchronous generators in a relatively shorter time than the more traditional methods. As a vessel for studying the proposed technique, a 400 kVA alternator is considered. Analytical and theoretical considerations on the benefits of skewing the stator in the generator under analysis are preliminary carried out. A finite-element model of the machine is built and the proposed method is then implemented to investigate the effects of the skewed stator. Comparisons against more traditional techniques are presented, with focus on the analysis of the voltage total harmonic distortion and the damper bars’ currents. Finally, experimental tests are performed at no-load and on-load operations for validation purposes, with excellent results being achieved. [ABSTRACT FROM PUBLISHER]

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]

This paper proposes a novel Continuous Quantum Immune Clonal Optimization algorithm for thermal optimization on a 117 kW high-speed permanent-magnet generator (HSPMG). The proposed algorithm mixes the Quantum-Computation into the Immune-Cloning-Algorithm and causes better population diversity, higher global searching ability, and faster convergence which is approved by simulation results. Then, the improved algorithm is applied to seek an optimized slot groove and improve HSPMG thermal performance, where the 3-D fluid-thermal coupling analyses are processed with a multiobjective optimal group composed of the highest temperature and temperature difference. Both the proposed algorithm and the obtained conclusions are of significances in the design and optimization of the cooling system in electric machines. [ABSTRACT FROM AUTHOR]

Early detection of incipient faults in ac drives is one of the most difficult challenges for condition monitoring, especially for faults related to insulation degradation of the windings. In low power motors, the insulation degradation is principally due to the steep voltage variations caused by the voltage source converters that drive the machines. In the last years, with the coming to market of new no-Si based power devices, which achieve great values of dv/dt, fast tracking of electrical fault has became a topic of primary importance. In this paper, a new method to detect the presence of incipient faults in ultrareliable electric machines is presented and compared with a previous solution. The different methods were extensively evaluated by means of experimental results. It is shown that potential winding faults can be detected at an early stage of fault inception and thus measures can be taken to limit propagation. [ABSTRACT FROM PUBLISHER]

This paper investigates the influence of a constant carrier phase shift on the DC-link capacitor harmonic current of cascaded converters used in fuel-cell and mild-hybrid electric vehicles. In these applications, a DC-DC converter can be adopted between the battery and the motor drive inverter in a cascaded structure, where the two converters share the same DC-link. Since the DC-link capacitor of such a system represents a critical component, the optimization of the converter operation to limit the current stress and extend the lifetime of the capacitor is an primary objective. This paper proposes the use of a carrier phase shift between the modulations of the two converters in order to minimize the harmonic current of the DC-link capacitor. By harmonic analysis, an optimal carrier phase shift can be derived depending on the converter configuration. Analytical results are presented and validated by hardware-in-the-loop experiments. The findings show that the pulse width modulation carrier phase shift between the interleaved boost converter and the voltage source motor drive inverter has a significant influence on the DC-link capacitor current and thus on its lifetime. A case study with two-cell and three-cell interleaved boost converters shows a possible DC-link capacitor lifetime extension of up to 390%. [ABSTRACT FROM AUTHOR]

With the increased development of electrical subsystems onboard modern transportation platforms, e.g., more electric aircrafts or more electric ships, the need for electric generation systems has increased. Since many motors require electric starting capability, the application of the starter/generator has been the focus of several studies. The peculiarity of such a system is its requirement for high torque at low speed (for the starting) as well as an extended operation range during the normal generation operations. This mismatch between maximum torque and speed comes at the expense of the power density of the electronic converter, which needs to be designed for the worst case situation and, due to the electric machine optimization, often requires field weakening operations. A new winding reconfiguration is proposed to achieve speed extension and provide more potentiality for high-speed applications. This work compares different power trains in terms of efficiency current stress for electric machines. Hardware-in-the-loop results are adopted to verify the practical implementation of the control systems. [ABSTRACT FROM AUTHOR]

In this article, we present a comprehensive analysis on the thermal response characteristics of the stator winding insulation under static air-gap eccentricity (SAGE) conditions in synchronous generators. Different from previous studies, this article not only takes into account the interactions of both the core-loss-caused heat and the copper-loss-caused heat but also investigates the thermal degrading distribution regularities due to SAGE. The whole work is based on the qualitatively theoretical analysis, the finite-element analysis, and the experimental validation on a nonsalient synchronous generator. The study shows that SAGE will significantly make the temperature rise, resulting in uneven temperature distribution and intensifying the thermal responses, such as the thermal deformations, stresses, and strains, of the insulation. The nose part and the joint between the line winding and the end winding on the smaller air-gap side are the two most dangerous positions. [ABSTRACT FROM AUTHOR]

This article describes a novel analytical methodology for eddy current losses simulation in the windings of permanent magnet synchronous machines. The methodology is based on subdomain modeling technique in conjunction with solving of ordinary differential equations system. The main advantage of the proposed method is high accuracy and significant reduction of simulation time in comparison with finite-element modeling (FEM) technique that is frequently used for eddy current loss modeling. The proposed model allows fast and accurate evaluation of proximity and skin effect in conductors in time domain for an arbitrary current waveform and machine duty cycle. The main difference from previously presented analytical methods is the possibility to evaluate losses for a wider range of conductors geometries, regardless their shape, dimensions, location in the stator slots, and rotor speed. The main contribution and novelty of the proposed analytical approach is simultaneous implementation of subdomain modeling technique and strands segmentation concept followed by the eddy current effect representation through the equivalent circuit. This approach allows reducing the computational time while keeping the accuracy close to the FEM result. The proposed model was compared to FEM, using different types and sizes of conductors and also validated experimentally. [ABSTRACT FROM AUTHOR]

This paper presents a model predictive control technique applied to a dual-active bridge inverter where one of the bridges is floating. The proposed floating bridge topology eliminates the need for isolation transformer in a dual inverter system and therefore reduces the size, weight, and losses in the system. To achieve multilevel output voltage waveforms, the floating inverter dc-link capacitor is charged to the half of the main dc-link voltage. A finite-set model predictive control technique is used to control the load current of the converter as well as the floating capacitor voltage. Model predictive control does not require any switching sequence design or complex switching time calculations as used for space vector modulation; thus, the technique has some advantages in this application. A detailed analysis of the converter as well as the predictive control strategy is given in this paper. Simulation and experimental results to validate the approach are also presented. [ABSTRACT FROM PUBLISHER]

Future transportation challenges include a considerable reduction in pollutant emissions at a time when significant increase in demand is predicted. One of the enabling solutions is the electrification of transport systems as this should lead to improved operability, fuel savings, emission reduction, and maintenance. While state-of-the-art technology has demonstrable benefits there needs to be considerable advancement to meet future transportation affordability and emission targets. Primarily, electrical drives need an improved power density, an increased reliability, and a reduced specific cost. For this reason, integrated modular motor drives (IMMDs) present an attractive solution. Modularity leads to redundancy and easier integration. This paper presents a novel speed-drooped control system applied to motors fed by modular paralleled converters. This control technique allows precise speed regulation and power sharing among different segments showing improved fault tolerance and reliability. The design procedure and the power sharing dynamic have been presented and analyzed by means of MATLAB/Simulink and validated in a 3-kW experimental rig, showing good agreement with the expected performances. [ABSTRACT FROM PUBLISHER]

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 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 surface‐mounted 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 paper presents a study of the effects that the shoe shape of the teeth of electrical machines has on the performance and losses. This is done by considering a concentrated wound, high-speed permanent magnet generator. The paper investigates the influence of the tooth shoe shape on the machine magnetic circuit and the losses distribution based on analytical and finite-element analysis (FEA). A shape coefficient K {t} is proposed to provide an optimized design reference. A comprehensive analytical tool able to study the variations of the machine performance parameters is proposed. The deduced optimization function is normalized using the non-equilibrium relative weighting method, and then, it is processed via a genetic algorithm to achieve the optimized design. FEA is used to validate the proposed analytical tool and the optimum design. [ABSTRACT FROM AUTHOR]

In high performance electric machines, the increase of fundamental frequency leads to additional losses in the winding due to parasitic effects such as the associated skin and proximity effects. In the first part, this paper presents an investigation into accurate modelling of AC losses in the winding using numerical methods and their experimental verification. Then, using experimental motorette setups, this research provides a comparative study between fixed strand positioning and fixed conductor shapes on the AC losses in the winding. It is shown that the exact position of strands in the conductor is not a critical factor; however, it is very important to control the conductor shape inside the slot. In the final section of this paper, an investigation into the relationship between AC losses in the winding and copper filling factor is presented. It is shown experimentally that counter-intuitive design choices such as using a lower copper fill factor and thicker strand diameters may be beneficial in achieving the highest overall efficiency. [ABSTRACT FROM AUTHOR]

This article proposes a modular approachto the power sharing control of permanent magnet synchronous bearingless machine. The selected machine topology features a winding layout with phases distributed into nonoverlapping three phase groups, a solution whose twofold aim is to increase the fault tolerance and to allow for the radial force generation. The three phase subwindings are supplied by standard three-phase inverter, leading to a modular system architecture. A throughout explanation of the methodology used to develop the control algorithm is presented considering the torque and force control in combination with the power sharing management of the machine. Special emphasis is placed on validating the modeling hypotheses based on a finite element characterization of the machine electro-mechanical behavior. The proposed control strategy is also extended to cater the possibility of one or more inverters failure, thus validating the intrinsic advantage of the redundancy obtained by the modularity of the system. An extensive experimental test campaign is finally carried out on a prototyped multi three-phase permanent magnet synchronous drive. The obtained results validate the bearingless power sharing operation in healthy and faulty scenarios, both at steady state and under extreme transient condition. [ABSTRACT FROM AUTHOR]

Cable-driven parallel mechanism has been widely studied due to its advantages of fast response and large workspace. The structural uncertainties in the system often introduce internal disturbance and unavoidably influence its motion precision. Generally, to reduce the influence, robust control is adopted and the boundary of the disturbance is regarded as a fixed value given by rough estimation. This method often causes large vibration of the motion component, which certainly compromises the dynamic performance of the system. Therefore, to solve this problem, a variable boundary analytical scheme based on the decoupling of control law and internal disturbance is proposed in this article. Specifically, sufficient condition for the solvability of disturbance boundary is proved by the boundedness of the structural matrix error. Then, the disturbance boundary is modeled analytically, so that its particular value can be determined with respect to the system status. Following that, a robust adaptive control algorithm based on the variable boundary of disturbance is developed. It is verified that the tracking error is globally uniformly bounded. The experimental results show that the proposed control method can effectively reduce the tracking errors and attenuate the tension chattering compared with the conventional robust adaptive control scheme with a roughly estimated boundary. [ABSTRACT FROM AUTHOR]

The automated design of synchronous reluctance (SyR) motors based on multiobjective genetic optimization and finite-element analysis is considered in this paper. Three types of barrier shapes are considered, all described by an effective limited set of input variables. The three solutions are investigated to establish which of the geometries can give the best torque output and also which one represents the best compromise between output performance and computational time. The analysis presented in this paper shows that SyR motors designed automatically can give a good performance and can be designed in a reasonable time, and it is also shown that not all design degrees of freedom are useful in terms of motor performance. Two prototypes of automatically designed machines have been fabricated and experimentally compared with a third prototype designed according to state-of-the-art design principles. [ABSTRACT FROM PUBLISHER]

The automatic design of synchronous reluctance (SyR) machines is considered in this paper by means of finite-element analysis and multiobjective optimization algorithms (MOOAs). The research focuses on the design of the rotor geometry, which is the key aspect of the SyR machine design. In particular, the performance of three popular MOOAs is analyzed and compared in terms of quality of the final design and computational time. A procedure to minimize the computational burden of the optimized design process is introduced and applied to a three-layer and a five layer rotor. Two prototypes experimentally demonstrate the feasibility of the design procedure. [ABSTRACT FROM AUTHOR]

In an interior permanent magnet synchronous motor (IPMSM) with segmented skewed poles, the armature reaction magnetic field (AR-MF) changes nonlinearly due to the saturation of the rotor magnetic barrier. Meanwhile, this varies under different excitation currents. As a result, it is difficult to be calculated by means of analytical methods. In this paper, the calculation model of AR-MF of IPMSM is first established by vector superposition method, without considering the saturation effect of rotor and the slotting effect of stator. In the second step, the virtual magnetic field of the rotor is introduced to quantitatively calculate the influence of local inhomogeneous saturation on the AR-MF. The latter is derived by combining both the subdomain method and equivalent magnetic circuit method. The complex relative permeance is also introduced to establish the AR-MF accounting for the stator slotting effect. To validate the AR-MF calculation method proposed, an 8-pole 48-slot IPMSM with segmented skewed poles is considered as a case study, showing a comparison by both with finite element (FE) results and the electromagnetic torque measured on a test bench. The model proposed in this paper shows high accuracy and fast computation with respect to FE analysis. [ABSTRACT FROM AUTHOR]

This paper analyzes the electromagnetic torque (EMT) fluctuation characteristics in synchronous generators under rotor interturn short-circuit (DRISC) fault. The novelty of this paper is that the DRISC fault is proposed based on the intermittent interturn short circuit existing in the actual operation and compared with the static rotor interturn short-circuit (SRISC) fault. In the work, by studying the influence of DRISC with different positions and different short-circuit degrees, the fluctuation characteristic of the EMT is analyzed and verified. The results show that when the DRISC5% fails, the location is in slot 3, the amplitude of first harmonic decreases by 7.2%, second harmonic amplitude increases by 33.4%, third harmonic decreases by 4.3%, and fourth harmonic increases by 26.8%. As the degree increased and positioned away from the large tooth of the DRISC, the overall EMT amplitude and reverse pulse increased, first and third harmonics decreased, and second and fourth harmonics increased. [ABSTRACT FROM AUTHOR]