Multi-field analysis of transient force during current-carrying pantograph–catenary separation

Transient force jumps are observed during current-carrying separation of the pantograph–catenary (PAC) system, which can induce the current collection performance and operational reliability. However, the physical origin of such transient forces remains unclear. Existing studies predominantly interpret PAC separation from mechanical contact or electromagnetic perspectives, with insufficient discrimination of the coupled electromagnetic, thermal, and interfacial phase-transition effects under current-carrying conditions. To address this issues, current-carrying tensile separation experiments were conducted in this study. Electromagnetic simulations, arc thermal analysis, and analytical modelling were combined to systematically quantify the potential sources of additional force during PAC separation. Viscous force models for molten interfaces and a necking–fracture model for semi-solid metallic bridges were further established. Experimental results show that aluminium strip exhibit pronounced transient additional force peaks during current-carrying separation, which increase monotonically with current amplitude, whereas no comparable phenomenon for carbon strip under identical conditions, indicating a material dependence. Quantitative analysis demonstrates that the electromagnetic Ampère force is limited to 0.01–1 N and contributes negligibly to the force. Arc thermal simulations indicate that the arc temperature is sufficient to induce interfacial melting in aluminium materials, while remaining below the phase-transition threshold of carbon materials. Further results show that the semi-solid metallic bridge necking–fracture model is consistent with the experimental additional force, with a maximum relative error below 10%. This study identifies the dominant mechanism responsible for transient force jumps during current-carrying PAC separation, and provides experimentally validated physical models for failure mechanism decomposition in complex current-carrying contact interfaces.