Vacuum contacts: analysing contact lifespan for enhanced performance in grids

This study evaluates contact erosion in vacuum circuit breakers (VCBs) using two contact designs: Axial Magnetic Field (AMF) and Transversal Magnetic Field (TMF). Six test series were conducted under sinusoidal currents up to 45 kArms and contact separations of 45 mm. Results reveal distinct charge distribution characteristics; AMF contacts generated diffuse arcs, leading to concentrated erosion in the middle of the contact surfaces, as confirmed by charge evaluation, microscopy images and high-speed camera (HSC) observation. In contrast, TMF contacts produced rotating, constricted arcs, resulting in a more uniform erosion distribution. Notably, both designs demonstrated resilience to varying gaps, indicating their suitability for higher voltage applications. The charge estimation technique utilized served as a performance indicator, allowing for comparative analysis of different contact geometries.