Analysis of axial windage loss in air gap of high-speed motors under high Taylor number

Abstract In the field of ultra-high-speed motors, windage loss rises rapidly with increase rotational speed, and even becomes main part motor loss. However, most researches are based on empirical formulas, which has a narrow scope application. These formulas could not guarantee accuracy when calculating large Taylor number flow in high-speed air gap, especially under axial ventilation condition. This paper focuses interaction between vortices flow, analyses influence behaviour non-axial ventilation. First, another form friction coefficient related to rotation speed is proposed using dimension analysis. Second, scale estimated how it affects discussed. Finally, deceleration experiment taking 250krpm induction used verify model.