The influence of additional loss on rotor surface heat transfer coefficient and temperature field of large air-cooled hydro-generator

In this paper A 250MW air-cooled hydro-generator is taken as the analysis example, the additional loss in rotor while machine rated operating is calculated. Based on this, the distribution of the heat transfer coefficient on surface of exciting windings is determined and the 3D steady temperature field is studied. The influence of varied additional loss on the distribution of the rotor heat transfer coefficient, as well as temperature field, is studied. It is observed that the calculated value of additional loss is close to the designed value and the error is less than 2%. When the additional loss add 10%, the value of heat transfer coefficient on rotor surface changes, but the whole variation trend is the same as before.