Loss measurement method of windage and bearing losses in high-speed traction motors for electric vehicles

The rising speeds of automotive traction motors have significantly increased the proportions of windage and bearing losses (collectively termed mechanical losses). These losses are influenced by multiple factors, such as rotor stiffness, surface roughness, and assembly process. However, previous studies have shown the difficulty of precisely characterizing these factors and finding their relationships with motor losses. Therefore, it is necessary to get reliable estimations using experimental measurements rather than relying solely on simulations or theoretical analyses. However, testing a real rotor for bearing loss introduces substantial windage loss simultaneously. This paper introduces an innovative method for measuring windage and bearing losses in high-speed electric machines based on the principle of controlling variables. The windage losses at different speeds can be obtained by taking the difference between pairs of rotors with the same bearing loss. The bearing losses are determined by subtracting the windage loss components from the total mechanical losses of the rotors.