AC Loss Calculation for Litz Wire Windings in Electrical Machines

High-frequency operation of electrical machines leads to excessive AC losses in the windings due to skin and proximity effects. To mitigate these losses, multistrand windings or Litz wire windings can be employed. This paper explores the applicability of the direct finite element (FE) method and two computationally efficient approaches—the homogenization technique and the FE-based dB/dt technique—for predicting Litz wire AC losses in electrical machines. Experimental validation is conducted using a motorette model with different configurations. Based on the dB/dt technique, a fast sweep method is proposed for AC loss calculation across various Litz wire specifications. This method efficiently scales with variations in working points, enabling the optimal design of Litz wire over a working cycle to minimize winding losses in a computationally efficient manner.