Calculation of Synchronous Torques and Radial Magnetic Forces for Pole-Changing Winding Using the 3//Y / 3//Y Method

During the elaboration of pole-changing winding for induction motors using the 3//Y/3//Y method for close ratio it has been ascertained that the winding causes the unavoidable occurrence of even harmonics. The impact of these harmonics has been previously investigated only for asynchronous torques. In this paper, the impact exerted on synchronous torques and radial magnetic forces will be investigated. Analytic calculation is provided. Short formulas, missing so far, have been found. The results are demonstrated via quantified examples for an unfavorable situation. It is proven that in case the rotor slot number is chosen in accordance with the general recommendations found in the literature, the impact of the even harmonics, for subject winding, is insignificant on the synchronous torques and moderate on the radial magnetic forces.