Evaluation of Equivalent Core Length in Synchronous Machines with Radial Ventilation Ducts for Industrial Applications

Radial ventilation ducts are applied to stator or rotor core inside synchronous machines about 1MW and over in industrial applications. The radial ducts have a positive effect on reducing temperature rise in windings. As some part of main magnetic flux flows the radial ducts, called fringing effect, main design variables such as terminal voltage, synchronous reactance, and equivalent core length can be changed significantly.In this paper, the equivalent core length using several calculation methods is calculated and applied to a 2-D finite element analysis. A 3-D finite element analysis is performed considering actual core length. The appropriate method is verified that the voltage and core loss between results of the analysis and the factory test are compared.