Current distribution within multi strand windings for electrical machines with frequency converter supply

The current distribution within multi strand windings is investigated for transient current and voltage supplies. The difference in losses between transient and sinusoidal waveforms is elaborated. Therefore, a wide range of frequencies as well as different kinds of transient waveforms has been investigated. The definition of the skin depth is no longer sufficient. A new parameter is required for transients, which is related to time. This parameter will be defined and called “skin time”. A numerical method is developed based upon a finite element transient calculation. The method is applied to the winding as well as to the core. A comparison with measurements verifies the approach described.