In this paper, the results obtained from lab tests on twisted pairs subjected to different voltage waveforms and atmospheric conditions are used to propose how to modify the IEC Std. 60034-18-41. The goal is to make the standard suitable for the More Electrical Aircraft (MEA). The results show that it is initially necessary to screen out materials through simple tests. The enhancement factors for temperature can be modified to consider reduced pressures and temperatures using a simple model. The aging enhancement factor can be reduced considering the reduced sensitivity of the partial discharge inception voltage (PDIV) at low pressures on the enamel thickness. Eventually, reference will be made to the drive discussed in Part I of this series to draw conclusions about the likelihood of partial discharge inception in a random wound stator and how to reduce it by modifying either the inverter or the stator insulation. Reference to a random wound motor is made throughout the paper.

The arrival on the market of new power devices based on wide bandgap semiconductors has raised a relevant interest due to their superior properties compared to conventional technologies. On the other hand, these devices are inherently characterized by high rates of voltage changes over time, which may result in reliability challenges in electric drives adopting them. In fact, dangerous voltage overshoots at the motor terminals and uneven voltage distributions within the machine windings may occur. These phenomena can trigger a high insulation stress and partial discharges and, as a consequence, they may concur to the premature failure of the dielectric materials. This paper proposes a flexible and comprehensive modelling approach for the accurate analysis and estimation of both voltage overshoots and voltage distributions in a typical converter-cable-motor system intended for more electric aircraft applications. The modelling results are validated against experimental measurements carried out on a physical prototype comprising a wide bandgap-based converter, a connecting cable and an electrical machine stator. The findings are then used in the companion papers (part II and part III) to investigate the dependence of partial discharge phenomena on these voltage waveforms, highlight reliability challenges in modern ±270 V DC bus voltage drives for the more electric aircraft and discuss solutions.

In the last years, hairpin windings are amongst the most studied and implemented winding topologies to increase torque and power densities of electrical machines, especially in the traction field. However, their main drawback remains the elevated ohmic losses generated at high frequency operations. Recently, hairpin windings with segmented conductors have been proposed to overcome this challenge, but an analytical model to predict the losses in such unconventional winding is missing, as well as a critical analysis on the extra manufacturing complexities needed. In this paper, first a simple analytical formulation for the estimation of AC losses in segmented hairpin conductors is proposed, developed and validated at various operating frequencies, both through finite element analyses and experimental measurements. Then, an in-depth analysis of the main advantages and disadvantages of this winding topology is proposed with the aim at providing guidelines and recommendations for their practical realization, adopting standard methodologies for their connection and transposition.

The widespread diffusion of electric vehicles poses new challenges in the field of fault diagnostics. Past studies have been focused mainly on machines designed for industrial applications, where the operating conditions and requirements are significantly different. This work presents a review of the most recent studies about fault diagnosis techniques in electrical machines feasible for traction applications, with a focus on the most adopted approaches of the last years and on the latest trends. Considerations about their applicability for electric vehicle purposes, along with some areas that require further research, are also provided.

The widespread diffusion of electric vehicles poses new challenges in the field of fault diagnostics. Past studies have been focused mainly on machines designed for industrial applications, where the operating conditions and requirements are significantly different. This work presents a review of the most recent studies about fault diagnosis techniques in electrical machines feasible for traction applications, with a focus on the most adopted approaches of the last years and on the latest trends. Considerations about their applicability for electric vehicle purposes, along with some areas that require further research, are also provided.

Transportation electrification roadmaps are pushing for a step-change increase in power densities of electric drives, leading to rapidly growing developments of high-switching frequency wide bandgap (WBG) semiconductor-based inverters. Meanwhile, induced high dV/dt can challenge the reliability of the stator winding insulation system. This study provides guidelines to mitigate the winding voltage stress through the implementation of an improved modular hairpin winding (HW) layout featuring a multibranch design, reconfigurable by simply reconnecting phase terminals and neutral points. This enables comparison of voltage distributions across different winding layout patterns. A high-frequency electrical lumped parameter network for the prediction of voltage stress distribution is further adopted, and validated through experimental tests carried out on different configurations. The downselected configuration reduces by 35% the maximum interturn voltage. Furthermore, sensitivity analyses at different rise times revealed that improvement could be limited to only 10%–15% when rise times are in the range of tens of nanoseconds. Under these conditions, the first series turns connected to the inverter side are very sensitive to sudden voltage spikes and experience the highest voltage stress, even though they have fewer connecting conductors between them and adjacent layers. In general, the article provides reliability-oriented HW design guidelines that address the integrity of the insulation system.