Effect of Prismatic Rotor Slots on the Thermal Performance of an Axial-Flux Eddy Current Brake

Prismatic radial slots machined into the aluminum rotor disk of an eddy current brake (ECB) increase the convective cooling area, but their effect on steady-state temperature has not been quantified systematically. This paper presents a two-dimensional polar finite difference thermal model, coupled with a one-dimensional pin-fin shaft model through an iterative energy balance loop, to evaluate 12 slotted disks for an axial-flux ECB with double-sided excitation, eight poles, and a rated speed of 3000 min−1. Four slot counts (N = 12, 24, 36, 48) and three bridge subdivisions (single, double, triple) are compared with a solid disk under the same 400 W Joule heat load, which the excitation current holds constant for every disk; the effect of the slots on the loss distribution is not modeled. The model predicts a solid disk peak temperature of 165.5 °C, which the best slotted configuration (48 slots, triple subdivision) reduces to 130.8 °C, a 34.7 °C (21.0%) reduction. Slot count is the dominant design variable: increasing N from 12 to 48 lowers the peak temperature by 21.9 °C (14.2%), while bridge subdivisions contribute only 0.6–1.4 °C. At N = 48, slot-wall convection carries 37.0% of the heat. These are numerical predictions; the ranking survives variations in the face convection, slot width and heat load, and of the slot-wall convection down to one third of its estimate.