Introduction to Litzopt

Purpose

Litzopt is a free Matlab-based tool that can optimize high-frequency inductor and transformer designs by minimizing material costs and power losses.

Motivation

Litz wire is typically used when operating frequencies are high enough to degrade the performance of magnetic components (10 kHz-1 MHz). The primary mechanism by which litz wire improves efficiency is by reducing eddy-current losses (see the references for more detail). LitzOpt offers an array of design alternatives, ranging from expensive, very low loss-designs to high-loss, low-cost designs. Typically, all of the LitzOpt design alternatives vastly decrease costs or losses relative to standard rule-of-thumb designs, and many of them offer improvements in both cost and loss. The algorithm used in LitzOpt is explained in detail in "Easy-To-Use CAD Tools for Litz-Wire Winding Optimization." This and related papers can be downloaded here.

Capabilities

LitzOpt can be used to minimize winding loss in transformers with multiple windings, sinusoidal or arbitrary waveforms, and one-, two- or three-dimensional field geometry. Current waveforms for each winding can be specified as piecewise linear or sinusoidal. LitzOpt can calculate the magnetic field integral over the windings with a one-dimensional field calculation or a two-dimensional field calculation. Optimization accounting for three-dimensional field effects requires the user to perform a numerical field solution with any third-party finite element or other numerical field solution software. To simulate, the user is to model the entire region of the windings as regions of uniform current density to simplify calculations (see 'Obtaining the Squared Field'). The required magnetostatic field simulation is far more computationally efficient than a full-blown field simulation and all that is to be computed is the spatial integral of squared flux density over the winding cross-sections (considered as regions of uniform current density).

LitzOpt begins with a fixed number of turns, core geometry, and winding configuration and optimizes the number and diameter of strands. LitzOpt assumes that the wire is small compared to a skin depth (d < δ).

LitzOpt M-File

In addition to this web-based version, which runs the calculations on our web server, you may download the MATLAB code to run on your own computing system. The downloadable version is for use with MATLAB Version 5 or later (by Mathworks). The two have similar capabilities, but the downloadable version allows the user to view the source code and adapt it to non-standard cases.

To download LitzOpt for use with MATLAB on your own system, click the link below. The litzopt.m file must be placed on the Matlab path in order to run it from the Matlab command window.