Research on Intrinsic Shaft Voltage in Permanent Magnet Synchronous Wind Generators with Sectionalized and Overlapped Stator Laminations

The stator laminations of large permanent magnet synchronous wind generators are often sectionalized and overlapped, which will cause the magnetic circuit asymmetry. The resulting asymmetric magnetic flux around the shaft yields intrinsic shaft voltage along the shaft. The shaft voltage will cause electric corrosion of the bearing and endanger the security of system. In this paper, the shaft voltage of a 5.57 MW permanent magnet synchronous wind generator with sectionalized and overlapped stator laminations is calculated through analytical method and finite element method. The results show that when the number of overlapped layers is the same, the voltage amplitude with symmetrical overlapping is much smaller than that of asymmetrical overlapping. It is necessary to properly match the sectionalized stator and the number of overlapped layers combination. In a certain range, the larger the rotating speed, the larger the shaft voltage amplitude; The shaft voltage amplitude of the generator under loaded condition is larger than that under no-loaded condition.