Numerical Investigations on the Effects of Slot Openings on Friction Losses in the Air Gap of Electrical Machines

In this paper, the effect of slot openings on air gap losses of electrical machines is shown. Computational Fluid Dynamics simulations are used for the calculations, which are validated on literature with a smooth air gap. Due to the slot openings, there is an increase in air friction losses in the air gap. The losses are up to 60% greater than with smooth air gaps. The increase in losses was determined for a selected air gap geometry.