Electric drive systems encounter significant challenges in mitigating motor shaft voltage and bearing currents, primarily due to common-mode voltage (CMV) effects. While many studies have explored pulse width modulation (PWM) strategies to reduce CMV, the majority have focused on low-frequency domain analysis. This paper evaluates the high-frequency performance of the electric drive system considering various PWM techniques, including Space Vector PWM (SVPWM), various discontinuous PWM (DSPWM) methods, Active Zero-State PWM (AZSPWM), Remote-State PWM (RSPWM), and Near-State PWM (NSPWM). To ensure the applicability of the study, a detailed electric drive system model (including inverter, cable, and motor models) has been implemented and simulated. Moreover, a comparative analysis is conducted across a wide motor speed range (500 rpm to 3000 rpm), analyzing CMV dynamics, motor line-line voltage, shaft voltage, and total harmonic distortion (THD) of motor current. From the results, AZSPWM, RSPWM, and NSPWM demonstrate superior CMV and shaft voltage mitigation, making them suitable for reducing bearing current, while SVPWM offers the best current quality. The findings provide insights for selecting appropriate PWM strategies at different operating conditions. The simulation was conducted using MATLAB software, and the data was post-processed using ModeFRONTIER.

This paper proposes a novel brushless electrically excited synchronous machine that employs inductive wireless transfer of rotor excitation power through the air gap. The magnetic parts of the machine fulfill the excitation function on top of the torque production, thusly achieving similar compactness as brushed electrically excited synchronous machines. Moreover, the machine is compatible with conventional traction inverters. The excitation power can be controlled by adjusting the injected stator current harmonics and a full decoupling between the excitation and torque production function is ensured. A proof of concept has been demonstrated on a radial flux prototype machine.

This paper presents a multi-material topology optimization (TO) to efficiently utilize rare-earth permanent magnet (REPM) material and improve the machine performance. The proposed approach employs a density-based TO method to optimize the multi-material distribution inside the rotor domain. The TO algorithm optimally redistributes air, silicon-steel, and REPM. The objective function of the TO is to maximize the average torque of the IPM motor while constraining the material volume of both silicon-steel and REPM to below that utilized in the conventional design. The results demonstrate that multi-material TO is a highly effective strategy for developing a new generation of sustainable electric machines. The topology optimized configuration achieved an approximate 4% increase in torque density while reducing the amount of REPM used by 12.5%. Moreover, the amount of silicon steel required for the optimized rotor is 9% lower than the conventional design.

When an electric drivetrain is ordered for deployment under load conditions different from those encountered during its design and testing phases, it is crucial to evaluate its performance beforehand. However, the experimental validation of the efficiency of an electric drivetrain for a new load profile is time-consuming and costly. This article proposes a digital twin approach to estimate the efficiency of an entire drivetrain for a new load profile—one that has not yet been tested on the physical asset. The parameters of the digital twin are determined through a system-level optimization study, utilizing measured data from the load cycles in the time domain. Utilizing this digital twin, the efficiency of the drivetrain is estimated for a new load profile. Subsequently, experimental validation is conducted. The results demonstrate that the proposed approach is accurately assessing drivetrain performance in terms of efficiency for new load profiles, facilitating informed decision-making in deployment scenarios.

This paper delves into the development of on-board EV chargers with the purpose of using the energy of the vehicle-roof photovoltaic panels and merging charging and driving modes power converters. In pursuit of this objective, a novel high step-up coupled inductor-based DC-DC converter is proposed, which enables the proposed charger to use the PV panel energy in an efficient way. From utility grid point of view, a bridgeless AC-DC converter is considered that is able to operate in continuous and discontinuous conduction modes (CCM and DCM), providing the chance to achieve natural power factor correction in DCM operation in addition to control the power factor in CCM operation. The sources participate in charging process via the proposed dual-input single-output SEPIC based DC-DC converter. In addition to the charging mode, in which the battery is charged using grid and/or PV panel, the proposed charger can deliver energy from the battery and PV panel to the motor drive system during driving mode. It should be noted that the buck-boost structure of the proposed converter enables the control system to manage the power sources and load efficiently according to their characteristics. All stages of the proposed multifunctional multiport on-board charger are analyzed thoroughly and simulation results are given to validate the analysis.

Practical optimization of the rotor layer thicknesses and arrangement in a 100 krpm axially laminated anisotropic synchronous reluctance machine (ALAsynRM) for a micro-gas turbine generator is presented. The machine utilizes practically available rotor lamination thicknesses that can maintain the rotor's mechanical integrity at this speed. As straight metal sheets are used, a two-pole rotor is favorable from the manufacturing point of view. The rotor is manufactured from S355 and Inconel 600 sheets by vacuum brazing which does not allow any fine geometric details like semi-closed rotor slots and despite geometric limitations, in practice only allowing the selection of different layer thicknesses, the machine performance can be good. The targeted application for this machine is a micro-gas turbine generator. The possibility of using e.g, a permanent magnet-assisted ALAsynRM instead can be disregarded considering the cost, difficulty of manufacturing, and reducing the dependence on rare-earth materials. The ALAsynRM optimal rotor layer combination is formed when magnetic and non-magnetic layers alternate. The effect of the arrangement of various rotor layers and their thickness on the overall performance of the ALAsynRM is also indicated.

In switched reluctance motors, the stator can be seen as comprising a stator yoke and a modular tooth-coil construction. Each module consists of a concentrated winding wound around a steel pole. In the conventional driving technique, depending on the number of the stator poles, a number of coils are connected together and driven from one asymmetric H-bridge. Another possible driving technique is the modular one in which each stator coil is driven by a separate asymmetric H-bridge. In this way, the fault tolerance of the drive is highly enhanced. In this paper, three modular driving techniques are proposed, simulated and compared to the conventional one. The difference between the three modular techniques is in the number of turns per stator coil and the DC-link voltage compared to the conventional one. The first technique maintains both the number of turns per coil and the DC-link voltage, the second one maintains the number of turns per coil while halving the DC- link voltage and the last one maintains the DC-link voltage and doubles the number of turns per coil. All the techniques are applied on a 6/4 SRM machine. The technique that maintains the DC-link voltage and doubles the number of turns shows superior performance in terms of the drive efficiency and the converter power density but results in the highest torque ripple. The technique that halves the DC-link voltage achieves a low torque ripple and an efficiency equal to the conventional technique. The converter is designed using SiC technology to enable higher switching frequency capability so that, a smaller DC-link capacitance can be obtained and a high drive efficiency as well.

Various cutting techniques are in use as part of the manufacturing process of electrical machines such as laser cutting, punching, electrical discharge machining and waterjet cutting. The cutting process degrades the magnetic material near the cut-edge. This degradation results in lower magnetic permeability and higher core-loss density. This paper studies the effect of three different cutting techniques namely punching, waterjet and laser cutting on the magnetic properties of the grain oriented electrical steel sheets. A standard Epstein test confirms the different magnitude of degradation depending on the cutting technique. Further, a loss model based on the measurement results has been applied to the yokeless axial flux machine. The comparative analysis shows the superiority of the punching and water-jet cutting techniques over laser cutting which resulted in more than 150% increase in the core losses. Other machine performance parameters such as generated EMF and torque remain unaffected by the cutting method.