Calculation Method of Circulating Current in Parallel Armature Windings in Consideration of Magnetic Circuit

Recently, the capacity of turbo generators used in power plants is increasing in order to keep up with the growth of electric power consumption in the world. Turbo generators are consequently experiencing problems, including increasing electromagnetic force, temperature rise of armature coils, etc., as we try to increase the armature current to keep pace with the capacity increase. One way of avoiding these problems is to increase the number of parallel armature windings for decreasing the armature current per coil. However, the circulating current in the parallel windings is generated by the difference of the linkage flux of each winding, when the number of parallel windings is not a divisor of pole numbers. In this paper, we propose a simple method to calculate the circulating current by using a magnetic circuit in the design phase. We confirmed the proposed method has a similar accuracy and faster performance in comparison with the finite element method (FEM) analysis. And then we applied the proposed method to a calculation of the circulating current in 2- and 4-pole generators and considered the factors affecting the circulating current.