Fast Analytical Loss Model for Litz Wire in Transformers With Arbitrary Winding Arrangements

The commonly used 1-D field loss models fail to predict eddy current losses of litz wire (LW) in transformers with medium/high voltage, sectioned windings, multiwindings, etc., where the magnetic fields in the core window are 2-D. This article presents an accurate and fast loss model for LW in transformers with arbitrary winding arrangements. In the proposed model, the 2-D spatial RMS value of magnetic fields for each turn is used in the loss calculation. By both numerical and experimental results, the accuracy of the proposed model is verified to be less than 6%, which is much better than other state-of-the-art loss models, e.g., the squared field derivative (SFD) and the mirror image method (MIM), of which the error is up to 50%. The calculation time of the proposed model is as fast as MIM but is more than 20 times faster than SFD.