The surface-mounted permanent magnet synchronous motor has found widespread use across various sectors, owing to its outstanding characteristics of torque density, efficiency and ease of control. These features, particularly crucial in the aviation field, make this type of machine highly desirable, especially in fixed-speed applications such as single-speed starter-generators. Additional performance metrics usually required nowadays in transportation are the sustainability and the overall environmental impact of components and systems. In this context, this paper proposes the design of a surface-mounted permanent magnet synchronous motor for a fixed-speed starter-generator, emphasizing all these different performance requirements. The design process is based on finite element (FE) optimizations, achieving a number of possible optimal configurations from an electromagnetic point of view, but giving then priority to the most environmentally friendly solutions. The outputs under examination are efficiency, power density, total harmonic distortion, torque ripple, copper and permanent magnet quantities, and temperatures. A motor characterized by a power density exceeding 2,3 kW/kg, 98% efficiency, and reduced copper and permanent magnet content is obtained.

The rapid increase in electric vehicle (EV) adoption underscores the urgent need for advanced charging infrastructure and strategies. This survey provides a comprehensive examination of battery charging, with a particular focus on control and optimization dimensions. It meticulously reviews a variety of control methods and optimization techniques, addressing critical factors such as charging efficiency, battery longevity, safety protocols, thermal management, and cell balancing. By enhancing our understanding of these crucial aspects, this paper not only highlights the current state of battery charging control and optimization but also sets the stage for future research and developments in this dynamic field.

This paper describes a new fault-tolerant control technique for over-actuated uncertain linear systems that compensates for actuator faults and failures using an output integral sliding mode-based control allocation strategy. An observer-based fault estimation unit is first proposed to estimate the system states and the actuator’s effectiveness level. Based on the estimated state’s information, a nominal virtual control law is created to achieve the desired specification of the perturbed system. A nonlinear output integral sliding manifold is incorporated with the nominal virtual control law that provides resilience to the closed-loop system against the uncertainty caused by the actuator’s faults and failure, states estimation error, and fault estimation error. Finally, depending on anticipated actuator efficacy from the fault estimation unit, the control allocation reroutes the virtual control input signals among the redundant actuators. A small-gain theorem is used to demonstrate the augmented closed-loop system stability. The observer and controller gains are synthesized using the linear matrix inequality technique. Finally, simulations on an aircraft system are performed to verify the efficacy of the suggested FTC technique. Compared with the existing work, the proposed approach is better able to handle actuator redundancy in faulty conditions and cater to the fault estimation error up to a certain level.Note to Practitioners—The aim of this paper is to address the reliability issues of industrial systems that contain sufficient input redundancy and are particularly designed to tolerate the faults and failures issues during the system operation. Existing fault-tolerant control schemes based on control allocations have limitations in terms of effective utilization of actuator redundancy, handling of fault estimation error, and applicability of reconfigurable control law. In this paper, we developed a fault-tolerant control strategy that is capable of addressing all the aforementioned concerns. The output integral sliding mode control-based control allocation scheme, proposed in this paper, is applicable to the class of over-actuated systems. The reconfiguration of fault-tolerant control law based on the estimated states and fault information is capable to cover a wider class of faults and failures while maintaining robustness against the system dynamics and uncertainty. The control reconfiguration is equally applicable to the class of systems that contains both rank-deficient and in-deficient input distribution matrices. The proposed scheme assumed the bounded external disturbance, therefore in future work, the adaptive law will be incorporated with sliding mode controller and results will be extended to a generalized class of affine nonlinear systems.

In this paper, the AC copper losses are investigated and mitigated for different permanent magnet synchronous motor designs. AC copper losses can represent a substantial share of the total loss in electrical machines. In an application such as aerospace, it is more demanding to optimise all aspects of the motor design. Recently, different approaches to modelling the AC copper losses have been proposed. This paper utilises simulation software to quantify the expected AC losses from six different propulsion motor designs. The motor designs are then modified to reduce the AC winding losses. Using two-dimensional finite element analysis, the motor slot openings are modified such that an optimum design with reduced losses is achieved. The paper considers distributed, fractional slot and concentrated windings, and the results show promising reductions across these different winding configurations.

Coaxial magnetic couplings are an attractive alternative to traditional mechanical machine couplings which bring several desirable advantages but are limited by their relatively low torque density and torque to mass ratio. The optimum magnetic design of a coaxial magnetic coupling possesses a significant volume of inactive material due to the radius of the permanent magnet arrays. In this paper, the torque density of a coaxial magnetic coupling is increased by up to 82% by utilizing a second set of permanent magnet rings to form a double coaxial magnetic coupling. The proposed design enhancement achieves the aim of reducing the total volume of the coupling, whilst maintaining the same mass and peak torque transmission capacity.

One of the advantages of multiphase machine is the capability of fault tolerance. Variety of post-fault control methods based on hysteresis, proportional-integral (PI), proportional resonant (PR) and model predictive controller (MPC) have gradually been developed. Due to simple structure and decoupling of reduced-order matrix, it is used as an alternative to the Clarke matrix in the healthy mode when the fault happens. Although a lot of control methods adopted a reduced-order matrix as the basic derived technology, the performance of controllers is different, and they need to be compared in term of specific applications in fault tolerance. For this propose, the paper deals with the steady-state and dynamic performance of four current control methods, hysteresis control, PI control, PR control and model predictive control in open-circuit fault. The results shows that the PR control method has low torque ripple, copper loss and derating in healthy and post-fault stage, and the MPC control method has low torque ripple in fault stage and fast response capability after applying fault-tolerant methods.

The thermal lifetime assessment of electrical machines' insulation systems is generally performed at the design and prototyping stages. Hence, the insulation system's thermal endurance curve (or temperature index) can be extrapolated, allowing the machine designer to tune lifetime prediction models and / or qualify a market-ready prototype, according to technical standards. The whole thermal evaluation process usually relies on accelerated thermal aging tests carried out on appropriate specimens, and an extensive economical effort could be needed. In this paper, a methodology relying on the Weibull statistical distribution and the geometrical size factor (i.e. statistical enlargement law) is analyzed for evaluating the machine's thermal life by using simple twisted pair as specimen. The obtained results are also experimentally validated against data collected on a different specimen's layout, namely random wound coils, confirming the feasibility of the analyzed approach.

Health monitoring has gained a massive interest in power systems engineering, as it has the advantage to reduce operating costs, improve reliability of power supply and provide a better service to customers. This paper presents surrogate methods to predict the electrical insulation lifetime using the neural network approach and three curve fitting models. These can be used for the health monitoring of insulating systems in electrical equipment, such as motors, generators, and transformers. The curve fit models and the supervised backpropagation neural network are employed to predict the insulation resistance trend of enameled copper wires, when stressed with a temperature of 290 °C. After selecting a suitable end of life criterion, the specimens' mean time-to-failure is estimated, and the performance of each of the analyzed models is apprised through a comparison with the standard method for thermal life evaluation of enameled wires. Amongst all, the best prediction accuracy is achieved by a Backpropagation neural network approach, which gives an error of just 3.29% when compared with the conventional life evaluation method, whereas, the error is above 10% for all the three investigated curve fit models.

This paper presents an enhanced modulation technique for dual converters with isolated supplies. This unified modulation technique is applicable for any positive voltage ratio between the isolated supplies. The modulation technique enhances the quality of converter output voltage. The effectiveness of the proposed technique is validated and results are presented for an open-end winding induction motor to demonstrate the advantages.

The development and validation of an advanced two-level Voltage Source Back-to-Back Converter model, considering its multi-physics operation, is presented in this paper. Based on a set of input parameters, the proposed model evaluates the converter in terms of input current ripples, transient performance, losses, and total volume. The model is discussed separately in three parts: modulation and control analysis, semiconductor loss estimations and heatsink sizing, and passive components sizing, i.e. for the boost inductors and DC-link capacitor. The performance analysis and loss calculations are verified to be accurate using time-domain simulations and experimental loss measurements. Due to its computational efficiency and accuracy, the proposed model is suitable for use within an optimization design environment.

This paper focuses on evaluating the energy and power requirements of a specific aircraft on-board electric taxiing (ET) system. The developed model of the investigated system is used to determine the requisites for a typical taxiing profile mission of a Boeing 737-400. Besides the derivation of the specifications, the comparison of batteries and electrochemical capacitors is outlined in the light of viable candidates for a local energy storage system (LESS). It is estimated that LESS should be sized for capacity of 19kWh and peak power of 81kW. The paper is concluded with a comparison and discussion on LESS topologies.

Electrical motors are required to perform reliably for a certain number of hours/cycles. Assuming the insulation breakdown as the predominant source of failure, then the lifetime of an electrical machine can generally be said to correspond to that of its weakest insulation sub-system. Among all the insulation stressing factors, thermal aging is a primary source of progressive deterioration, and, eventually, failure. In order to guarantee a satisfactory lifetime, motors are designed to have thermal operational points which are always lower than their insulation thermal class. However, this design choice does not allow to maximize the exploitation of the insulation lifetime capability. Technical standards report methods for the thermal qualification of electrical machines based on accelerated thermal aging tests. Such assessment, despite enabling the insulation lifetime estimation, might require several thousand hours of testing. This paper, therefore, proposes and validates a new methodology which considerably shortens the thermal qualification of electric motors.

The classical, wound-field, synchronous generator is currently enjoying a revamped interest in its design and development, partly due to the ever-increasing requirements in terms of power quality standards, efficiency and power density and partly due to advances in materials and manufacturing techniques. Also, the significant improvements in the computational resources allow the utilization of modern design techniques and tools. Apart from the design of the machine itself, another area of interest is the system-level optimization. The proposed project is aimed at renewing the power electronics and the control logics in power generating sets featuring the popular brushless configuration. An industrial small-to-medium size power generating set is taken as case study. The considered platform is first analyzed at system-level, by modelling in detail all of the components comprised in it. Then, focus is given to the automatic voltage regulator. A faster, more flexible and more efficient system is proposed, based on a 4-quadrant DC-to-DC converter which permits to improve the dynamic response of the excitation system.

Typically, electrical machines feature rotor and stator winding configurations and core structures which comply with both simplicity and cost requirements. Such constraints limit the design search space and degrees of freedom, thus leading to exploit and implement only standard symmetrical layouts which therefore represent by far the most common choice. In this paper, the potential of adopting non-symmetrical windings and geometries in electrical machines is discussed. The perceived benefits are first detailed and then proven by applying the concepts to two case studies, namely a squirrel-cage induction machine and a salient-pole synchronous machine.

The more-electric aircraft initiative represents an important technology step-change for the aircraft industry. The reduction of both fuel consumption and environmental impact are leading to alternative solutions for actuating the flight control surfaces. The traditional hydraulic systems, are progressively being replaced with electrically powered actuators. In this scenario, electromechanical actuators are gaining an ever-increasing importance as enabling technology for next generation aircraft. This paper presents the design and testing of a permanent magnet synchronous motor driving a linear geared electromechanical actuator for commercial aircraft. The experimental results are discussed throughout the paper and compared to the finite element ones obtained at the design stage. Finally, the machine is integrated into the mechanical drivetrain and the electromechanical actuator performance is evaluated through experimental tests carried out on a purpose-built mechanical demonstrator for achieving a high technology readiness level.

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

This paper proposes an analytical model that considers the torque characteristics and results in an optimum geometry for dual-stator synchronous machines with permanent magnets. The distribution of the magnetic field in the air gap is obtained by solving Neumann's problem by using Green's function. The results of the study shows that the dual-stator topology of synchronous machine with permanent magnets can achieve up to 1.7 times more torque when compared to conventional machine with radially magnetized magnets. This effect is achieved due to more efficient using of the volume of the machine. The analytical model presented in the paper allows fast but accurate optimization of the machine's geometry and is used to achieve an optimal design for the considered application.

This paper presents an extensive study on the electromagnetic and structural influences of the end barrier shape of a Synchronous Reluctance Machine (SynRel). One of the most challenging tasks in designing these machines is to achieve a smooth torque and a mechanically robust structure, especially when high operating speed range is required. Several papers have already addressed the electromagnetic design problem related to the choice of the flux barriers thicknesses and positions. However a comprehensive work on the influence of the end part of the flux barrier on the electromagnetic and structural performance has not been yet presented. In this work two end barrier shapes are considered and optimized using the same methodology. Then the optimized machines have been deeply analyzed in terms of torque, torque ripple and rotor von Mises stress distribution. Furthermore, with the aim to further investigate the influence of such end barrier shape, a detailed sensitivity analysis is presented. In conclusion, general guidelines for the structural and electromagnetic design of such end barrier shape are drawn.

This paper is focused on the electromagnetic and structural design of high-speed synchronous reluctance (HS-SyR) machines. Both design aspects are equally taken into account due to high speed requirements. Two design procedures, both based on multi-objectives stochastic optimization algorithms (OA) and Finite Element Analysis (FEA), are presented and compared in terms of computational time and quality of the final result. The first design procedure combines an electromagnetic FEA with an analytical rotor structural design. The second procedure evaluates both electromagnetic and structural performance using FEA simulations within the optimization. The former approach needs a structural refinement stage of the rotor geometry. The latter gives rotor designs ready for manufacturing at the cost of increased computational resources. The two approaches have been investigated considering the rotor design of an 80.000 rpm SyR motor for aeronautical applications. Finally, a sensitivity analysis has been performed to identify which variables most affect structural performance and which parameters need tighter manufacturing tolerances.

In this paper, the optimization process of a rotational Electro-Mechanical Actuator (EMA) for an Aerospace application is presented. Specifically, the EMA is designed for the extension and retraction of a landing gear. The main aim of the optimization process is the minimization of the overall weight of the system whilst maintaining the system dependability. Since the EMA is composed of different, interacting subcomponents, it is necessary to adopt a system level, design approach. The work reported here will show how the motor weight is influenced by the gear ratio and the DC-Link voltage in such an EMA. The result of this analysis is the optimum configuration of the drive-train gear ratio, which minimizes the EMA's weight. This paper pays particular attention to the motor design approach.

Wide-bandgap devices are under the spotlight of scientific research as they exhibit great performance in terms of efficiency and temperature operation. However, to fully exploit their characteristics, dedicated driving circuits are needed. High-power gate-insulated switching devices exhibit important input capacitance; when fast switching speeds are demanded, high-current pulses are needed to drive the gate terminal. This is particularly true for wide-bandgap devices, capable of lower transition times than conventional silicon devices. The proposed circuit is a voltage controlled resistor, which output can drive wide-bandgap devices. Design criteria, as well as simulation results, are presented.

In safety critical applications, such as for the aerospace industry, where fault tolerant systems are mandatory, the ability of an electric actuator to detect a malfunctioning and eventually operate in faulty conditions is of paramount importance. This paper is concerned with the fault tolerance operation of a linear actuation drive, consisting of a tubular, linear motor controlled and driven by a high performance matrix converter for an aerospace application. The aim of this work is thus to propose and validate techniques addressing specific faulty operation conditions. The main points of interest addressed in this paper are the operation of the position sensor and operation during a fault on one of the phases of the motor. An Extended Kalman Filter is adopted for the double goal of improving the measured data of the position sensor and to continuously monitor its condition. On the other hand, the TLPM motor is operated under the assumption of a total fault of a single phase. In this work the modification to the Field Oriented Control (FOC) with only two phases is described, and the results are compared to those of the healthy machine. Theoretical analysis, simulations and experiments confirms the feasibility of the described strategies.