Analysis of Field Harmonics of Pole-Changing Pumped Storage Machines in View of Distribution Factor

ABSTRACT

The rotor poles in conventional pumped storage machines are with different sizes and unequal distribution. It contains both Integral and fractional harmonics. A synthetic distribution factor of poles are introduced in this paper to evaluate the effects of construction parameters on harmonics (such as the positions, dimensions and the turn ratio of large and small poles and the length of air gap). A unified formula for calculating integral and fractional harmonics are derived also. The results, which were checked with the FEM for typical rotor models of pole-changing pumped storage machines, show that the method introduced in this paper can be used not only to calculate the magnitude of harmonics but also to propose a method to suppress some undesired harmonics.