Research on windage losses of smooth rotor supported by active magnetic bearings in a vacuum chamber

Abstract

In order to study the windage losses caused by the friction between fluid and rotor surface in high speed rotating machines, a series of rundown experiments are performed in a vacuum chamber. By means of an evacuation method, the windage losses are extracted by subtraction operation between specified pressure and near absolute vacuum. The windage losses separated with existing separation models for large gap are compared to the extracted values with evacuation method and the results show big disagreements. For this reason, a modified separation model considering the skin effect and gas state is presented for rotating electrical machines simultaneously including both large and small gap. Using the modified separation model, the results show good agreements with the extracted values. In contrast to the evacuation method, the new model provides a way to quickly assess windage losses in electrical machines, where vacuuming is not obligatory any more.