Bearing currents and associated high frequency effects in permanent magnet machines - improved computational and experimental methods

在向零碳社会过渡的过程中，电机变得越来越重要，尤其是在交通运输的脱碳方面。它们在电动和混合动力汽车中的应用已经在迅速加速，未来小型和支线飞机也将采用混合动力推进系统。电机几乎总是与电力电子控制器结合使用，电力电子控制器向机器施加高频电压脉冲序列来控制电流，从而控制速度或转矩。结合起来，机器及其相关控制器提供了一个高效和高度可控的传动系统解决方案。然而，由控制器产生的高频开关并非没有缺点，其中一个最大的问题是高频寄生电流可以流过机器轴承，除非在设计和安装中采取预防措施。轴承中的这些寄生和意外电流导致润滑膜的恶化和轴承滚动部件的表面损坏。这种轴承损坏反过来可能导致在使用中的电机发生灾难性和意外故障。导致轴承电流的各种现象是复杂的，在许多情况下，人们知之甚少，目前采取的预防措施是初步的，并损害了性能的其他方面。拟议的研究计划调查了永磁电机中的高频电容和感应效应，特别关注高频轴承电流的创新建模和测量方法。这将为通过改进设计和模拟减少轴承电流奠定基础，提高可靠性和安全性，从而进一步促进交通电气化。这在混合动力航空推进系统中尤为重要，因为基于对物理现象的稳健和严格理解的最高水平的可靠性对于采用新技术至关重要。

Electrical machines are becoming ever-more important in the transition to a zero-carbon society, particularly in the decarbonisation of transport. Their use in electric and hybrid vehicles is already accelerating rapidly with hybrid propulsion also on the horizon for future small and regional aircraft. Electrical machines are almost always used in conjunction with power electronic controllers which apply a high frequency voltage pulse train to the machine to control the current and hence the speed or torque. In combination, the machine and its associated controller provide an efficient and highly controllable drive-train solution. However, the high frequency switching produced by the controller is not without its drawbacks, one of the most problematic being that high frequency parasitic currents can flow through the machine bearings unless precautions are taken in design and installation. These parasitic and unintended currents in the bearings lead to deterioration of the lubrication film and surface damage to the rolling parts of the bearings. This bearing damage could in turn cause catastrophic and unexpected failure of the electrical machine in service. The various phenomena which result in bearing currents are complex and, in many cases, poorly understood and the precautions which are adopted at present are rudimentary and compromise other aspects of performance. The proposed research programme investigates the high frequency capacitive and inductive effects in permanent magnet machines with a particular focus on innovative modelling and measurement approaches for high frequency bearing currents. This will lay the cornerstone for bearing current mitigation through improved design and simulation, enhancing reliability and safety and hence promote further electrification of transport. This is of particular importance in hybrid aerospace propulsion systems where the highest levels of reliability based on robust and rigorous understanding of physical phenomena is essential for the adoption of new technology.