抄録
In the stator windings of large rotating machines such as the turbogenerators and the hydrogenerators, the conductor bars are divided into strands to reduce the eddy current loss due to the leakage magnetic flux which are mainly induced inside the slot. Moreover, in the case of the strands which are shorted in the most end of the stator bar, inter-strand circulating current is induced due to the leakage flux and it causes additional heating. Therefore the strands are usually transposed in the stator core region and sometimes in the end region in the generators of large output. In order to enhance the efficiency of the generator and/or to avoid the additional heating, it is important to evaluate the loss in each part of the machine and the circulating current loss should also be calculated precisely to evaluate the effect of transposition. In this paper, magnetic field analysis method using multi-slice finite element method is proposed to calculate the circulating current in the stator bar which includes strands transposed in the coil end region. Then circulating current loss analyses of transposed stator bars are performed and the effect of the transposition is discussed for some variations of transposition. The end transposition "90-360-90" is the most effective for the coilend internal leakage flux and circulating current loss increase for "0-360-0" case is reduced to around 3/5 by the coilend transposition and it is around the same level as "0-450-0" case.
