Influence and mechanism of ablation pits on the electrical contact stability of conductive slip rings

Conductive slip rings, essential components in rotary electrical systems, often experience contact instability due to surface ablation because of electrical arc discharge. This study examines how the position of ablation pits influences contact stability within slip rings, highlighting their detrimental impact on electrical performance. By integrating multiscale characterization, it explores the structure, composition, and properties of ablation pits formed under operational conditions. The findings aim to deepen the understanding of their effects and identify strategies for mitigating their impact.

To investigate the positional dependence of ablation pits and their impact on electrical contact stability, this study employs a comprehensive multitechnique approach. The surface topography and morphology of the ablation pits are characterized using surface profile measurements. This technique provides high-resolution data on pit depth, width, and overall surface texture. Nanoindentation tests evaluated hardness and elastic modulus variations across different pit regions within the ablation pits, identifying localized changes caused by arc discharge. Raman spectroscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analyses examined the chemical and structural alterations within the pits. Raman spectroscopy detected molecular-level alterations, such as the presence of graphitic or disordered carbon, whereas SEM-EDS offered data on elemental compositions. Conductive atomic force microscopy (C-AFM) measured electrical conductivity variations across different pit regions, linking material changes to the slip ring performance. By combining these techniques, the study provides a thorough examination of the effects of ablation on the mechanical, chemical, and electrical properties of the slip ring material.

The results demonstrate a clear positional dependence of the ablation pit characteristics, with significant variations in morphology and material properties across different regions. Surface profiling showed that pits in the central area were deeper and more defined than the outer regions that appeared shallower. Nanoindentation results indicated high hardness and elastic modulus in the pit center and inner ring regions, suggesting localized transformation of the material owing to high-temperature arc discharge. Conversely, the outer regions exhibited low hardness, indicative of extensive material degradation. Raman spectroscopy results highlighted the presence of disordered and graphitic carbon deposits in the inner and central regions of the pits, further contributing to high local conductivity. These findings were supported by C-AFM measurements, which confirmed considerably increased conductivity in the central and inner regions owing to carbonaceous deposits formed during the discharge process. Finally, SEM-EDS analysis reveals compositional gradients within the pits, with high concentrations of carbon and oxygen near the center and copper depletion toward the edges, suggesting complex interactions between copper, carbon, and oxygen during ablation.

Ablation pits introduce mechanical and electrical heterogeneities, remarkably influencing contact stability. The positional differences in pit properties are directly linked to the arc discharge process, driving localized surface modifications and material transformations. The study highlights the complex interplay among mechanical properties, electrical conductivity, and material composition within the ablation pits, offering valuable insights into the mechanisms underlying contact instability in conductive slip rings. The results improve the understanding of surface ablation and inform material design and operational strategies for mitigating its adverse effects. Addressing the challenges posed by ablation pits plays a key role in advancing the performance and reliability of conductive slip rings in demanding, high-performance applications.