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.

Wide-bandgap (WBG) power semiconductor devices have acquired more and more interest in power circuits, since they allow to operate at higher switching frequencies and temperatures compared to the conventional silicon-based devices, while also improving efficiency and power density. In electric drive applications they can produce significant electrical stress at the machine terminals due to their inherently elevated voltage gradients (dv/dt), hence resulting in a reduced lifetime of the entire system. Voltage overshoot at the electrical machine terminals depends on many factors, such as voltage dv/dt, cables type and length, electrical machines input impedance etc. In this paper, a novel control based on a recent multilevel drive architecture is presented. This control is able to minimize the voltage overshoot at the terminals of an electrical machine independently form the system layout, increasing the overall reliability and lifetime of the winding’s insulation system.

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.

This work provides an analysis of the impact on AC losses in hairpin conductors, provided by different values of resistivity. Starting from some specific stator geometries, the optimal resistivity which minimizes the AC losses is calculated for each configuration through both analytical and finite element (FE) methods, considering a frequency range typical of automotive applications. Possible applications and conditions where a higher resistivity material, such as aluminum, can be adopted, are discussed. The main sources of discrepancies between the analytical and simulative approach are also discussed.

This work discusses the modelling approach adopted for the estimation of the voltage distribution within hairpin windings of electrical machines. The physical phenomena and the major contributors to the occurrence of the uneven voltage distribution are first described. Then, the equivalent circuit used to predict the voltage distribution is presented in detail. The circuital parameters employed in the equivalent circuit are estimated via finite element electrostatic and electromagnetic analyses. Finally, a numerical tool is used to solve the differential equations describing the equivalent circuit above mentioned. Simulation results are illustrated and discussed. The phenomena under investigation are applied to a pre-defined reference system, consisting of slot motorettes.

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 use of wide band gap devices in power converters is becoming more and more popular since they enable operations at higher switching frequencies, voltages and temperatures compared to traditional power semiconductors, while also improving the efficiency. However, in electric drives, they also tend to increase voltage overshoots at motor terminals and to produce uneven voltage distributions across stator windings, due to their high rate of voltage change over time (dv/dt). In order to mitigate these issues, passive filters can be employed. The aim of this paper is to give an overview of possible solutions based on passive filters, analyzing the main advantages and drawbacks. A comprehensive, qualitative comparative study is carried out taking into account common mode currents reduction, power losses, costs, dimensions and reliability.