The performance of engineering components and structures is strongly influenced by the interaction between design, manufacture and materials. This paper presents the fracture of copper lamellas from a circular collector. The investigated circular collector, having 315 copper lamellas, is one of the main parts of an electric motor. The fracture of the copper lamellas was observed in normal operation. This unexpected fracture required an investigation of the fracture origin, in order to improve the initial design. The numerical results of the Finite Element Analysis on the stress field in the copper lamellas for the operating regimes, and the stress concentration effects are shown. A study of crack initiation, based on Notch Stress Intensity Factor approach was performed in order to estimate if the conditions of crack initiation are meet. Finally a study of crack propagation will present comparatively the numerical obtained crack path against the one observed in-service.