Abstract- This article deals with the calculation of the circulating current distribution and the resulting ohmic losses in a large synchronous generator. Circulating currents are produced by voltage differences induced between parallel strands in a bar that cause high ohmic losses in high-power synchronous generators. In this paper, three different cases are assumed for the armature end winding structure, and a 3D finite element model is adopted to calculate the effectiveness and resulting losses of these cases. As mentioned below, using an appropriate transposition in the slot area, both the main and leakage flux within the machine are the same for all transposed strands in the active part and consequently the voltage difference induced in each strand in a bundle is negligible. However, currents flowing in the terminal winding of the generator produce a leakage flux in the slot region which causes currents flowing in the strands and consequently electrical power losses in the machine. Index Terms: Synchronous Generator, Slot Region, Terminal Winding, Circulating Current, Finite Element Method.I. INTRODUCTIONCirculating currents are produced by voltage differences induced between parallel strands in a bar due to the different magnetic flux of the link. In large synchronous generators with high power density, Roebel bars are used for stator windings where the strands of a bundle are completely transposed into the slot region by a different arrangement. Using this procedure, the overall physical position of each strand in a package is the same. Therefore, both the main and leakage flux are the same for each strand of each bundle and consequently the voltage difference induced in each strand is negligible. Anyway, the current... half of the article......gren X, Lijian T, Dangun Z, Yi and circuit equation method”, IEEE Trans Magn 1990;26:497–500.[5] K. Takahashi, M. Takahashi, and M. Sato, “Calculation Method for Wire Current Distribution in the Armature Winding of a Turbine Generator,” Electrical Engineering in Japan, vol. 143, n. 2, 2003 Translated from Denki Gakkai Ronbunshi, vol. 122-D, no. 4, April 2002, pp. 323–329.[6] Hitachi, Ltd., Japan MA Mueller, “Design and Performance of a 20 kW, 100 RPM Switched Reluctance Generator for a Direct Drive Wind Energy Converter,” IEEE International Conference on Electric Machines and Drives, page( e): 56-63, 2005 .[7] J. Haldemann, “Transpositions in Stator Bars of Large Turbogenerators” IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 19, no. SEPTEMBER 3 2004