@inproceedings{KastenHofmann, author = {Kasten, Henning and Hofmann, Wilfried}, title = {Optimal number of strands in electrical medium-frequency machines}, series = {The XIX International Conference on Electrical Machines - ICEM 2010, Rome, Italy}, booktitle = {The XIX International Conference on Electrical Machines - ICEM 2010, Rome, Italy}, publisher = {IEEE}, isbn = {978-1-4244-4174-7}, doi = {10.1109/ICELMACH.2010.5608252}, pages = {1 -- 6}, abstract = {The conductors of rotating electrical machines run through slots. The conductor will often be divided into many strands in order to reduce the current displacement losses. However, a high number of strands also results in a higher volume for the wire enamel so that the slot space factor and the conductor cross-sectional area will be reduced. A smaller conductor cross-sectional area is the reason for higher ohmic winding resistance and copper losses. Therefore the copper losses are minimal at a certain number of strands. Additionally, higher numbers of strands reduce the thermal conductivity, so that thermal aspects should also be considered. This paper provides a theoretical foundation for the dimensioning of the strands.}, language = {en} } @inproceedings{KastenHofmann, author = {Kasten, Henning and Hofmann, Wilfried}, title = {Electrical machines with higher efficiency through combined star-delta windings}, series = {2011 IEEE International Electric Machines \& Drives Conference (IEMDC), Niagara Falls, ON, Canada}, booktitle = {2011 IEEE International Electric Machines \& Drives Conference (IEMDC), Niagara Falls, ON, Canada}, publisher = {IEEE}, isbn = {978-1-4577-0061-3}, doi = {10.1109/IEMDC.2011.5994806}, pages = {1374 -- 1379}, abstract = {Combined windings have higher fundamental winding factors and produce smaller harmonic contents. Therefore, the efficiency can be increased without any additional active mass. This paper presents specifics of the combined windings. Special topics are the higher efficiency in comparison to machines with the same size and classical windings, design and calculation of combined windings, winding technique and experimental results of a 30 kW standard asynchronous motor.}, language = {en} } @article{KastenHofmann, author = {Kasten, Henning and Hofmann, Wilfried}, title = {Wirkungsgradsteigerung durch kombinierte Wicklungen}, series = {Antriebstechnik}, volume = {52}, journal = {Antriebstechnik}, number = {1}, pages = {22 -- 25}, language = {de} } @inproceedings{KastenHofmann, author = {Kasten, Henning and Hofmann, Wilfried}, title = {Combined stator windings in electric machines with same coils}, series = {2012 XXth International Conference on Electrical Machines, Marseille, France}, booktitle = {2012 XXth International Conference on Electrical Machines, Marseille, France}, publisher = {IEEE}, isbn = {978-1-4673-0142-8}, doi = {10.1109/ICElMach.2012.6349848}, pages = {103 -- 108}, abstract = {The idea of combined windings is very old, but only a few motor windings have been built with them until today. Recently some releases were cast out about this topic, because the combined winding reduces the copper losses. The international claim IEC 60034 for more efficiency to reduce greenhouse gases pushes the factories to look for new ways of reducing the losses in electrical machines. A way to save energy is to build up asynchronous machines with copper cast rotors. Combined windings are a further possibility and avoid the higher costs caused by the copper rotor. A further application of combined windings is the high speed drives. Combined windings can be built up to generate a very small harmonic content so that the losses of permanent magnet rotors and its temperatures decrease. A problem of combined windings is that two kinds of coils will be needed. This paper shows a way to create one layer combined windings with only one sort of coils. By using this windings the higher costs will be narrowed. Examples of combined windings will be compared with conventional windings about copper losses and harmonic content.}, language = {en} }