Numerical investigation of the air-gap flow heating phenomena in large-capacity induction motors

The thermal characteristics of a large-capacity induction motor were investigated with an air-gap flow temperature that is higher than the stator and winding temperatures. Air-gap flow heating phenomena were defined and classified into three states: under-heating, over-heating, and super-heating. A non dimensional temperature was suggested to predict the corresponding air-gap flow heating state of a motor. Based on the non-dimensional temperature, the over-heating state is inevitable for a motor with a capacity above 50 kW, and the super-heating state is inevitable for a motor with a capacity above 100 kW. Furthermore, the effects of the over-heating and super-heating states of the air-gap flow on the stator and windings were investigated. Under these two states, the cooling of the stator by the air gap flow was diminished. Additionally, the winding temperature increased because of the discharged air-gap flow. (C) 2017 Elsevier Ltd. All rights reserved.