Optimal number of strands in electrical medium-frequency machines

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.