The Use of Combined Star–Triangle Windings in Three-Phase Electric Motors: A Refined Analysis

Abstract: The use of combined star–triangle windings in three-phase electric motors can reduce differential scattering, inductive resistance, additional losses, and electromagnetic noise from higher spatial harmonics of the magnetic field. The employment of combined windings with a doubled number of parallel structures makes it possible to change the number of parallel branches of the winding in a larger range. In practice, the theoretical advantages of combined windings are not always achievable in three-phase electric motors, since conditions of parallel operation should be fulfilled for effective joint operation of the star–triangle windings. Failure to comply with the conditions leads to degraded efficiency of electric motors. The combined windings in three-phase electric motors should be selected based on a refined electromagnetic analysis. An algorithm for calculating combined windings with a serial connection of star–triangle windings is proposed. The refined harmonic analysis of magnetomotive forces, differential scattering, and the distribution of magnetic field induction in the gap confirmed that the influence of higher spatial harmonics is decreased when using combined windings. Due to the enhanced starting torque and the reduced effect of higher spatial harmonics of the magnetic field, direct start of an electric motor with a combined winding occurs faster and with lower speed pulsations during acceleration. © Allerton Press, Inc. 2024. ISSN 1068-3712, Russian Electrical Engineering, 2024, Vol. 95, No. 3, pp. 165–174. Allerton Press, Inc., 2024. Russian Text The Author(s), 2024, published in Elektrotekhnika, 2024, No. 3, pp. 2–12.