Multiple Multiphase Combined Star–Polygon Winding Analysis

In order to improve the efficiency and to reduce the field amplitudes of spatial harmonics influencing noise and vibration of electrical machines, three- and five-phase combined star-polygon windings have been suggested in the literature. Besides, the efficiency of an electrical machine is dependent on the fundamental winding factor and the noise/vibration level is related to the winding factors of some higher/lower harmonics. However, there is no systematic method to calculate the winding factor of each spatial harmonic for a multiple topology. This paper deals with proposing different topologies of multiple series multiphase combined star-polygon windings and accordingly with the calculation methods of winding factors for all spatial harmonics and the harmonic leakage factor. The results of winding function approach and symmetrical components of electromotive forces (EMFs) are perfectly in compliance with each other, provided that the fast Fourier transform (FFT) analysis is sufficiently accurate. The results obtained from measurements on an unskewed electrically excited synchronous machine are applied for validating the results given by the sum of EMFs and the proposed calculation formula. The sum of EMFs, considering just one set of a multiple topology, can give the same results as the proposed winding analysis methods for the fundamental or the slot harmonic winding factors.