Analysis of three-phase induction machines with combined Star-Delta windings

Combined Star-Delta windings in electrical machines result in a higher fundamental winding factor and cause a smaller harmonic content. This leads to lower I²R losses in the stator and the rotor winding and thus to an increased efficiency. In this paper, a calculation method is presented to determine these I²R losses for three-phase induction machines with combined star-delta windings. An important calculation tool is the field damping factor in order to consider the rotor´s influence on the magnetic field excited by the stator. As the magnetomotive force in the star and delta winding is different, more harmonic contents are generated, but with rather load amplitudes. The method presented here also considers the additional harmonic content by determining the corresponding winding factors.