Simulating Magnetic Core with FEMM and LUA Scripts for DRV421 Designs
Learn how to estimate inductance and magnetic gain of magnetic cores without cutouts for DRV421 designs using FEMM software. Understand the basics of Finite Element Method Magnetics (FEMM) and how LUA scripts can control functionality. Follow step-by-step instructions to run scripts and input parameters for accurate simulations.
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Presentation Transcript
Magnetic Cores with no cutout for DRV421 designs with FEMM Simulating magnetic core using FEMM and LUA scripts to estimate inductance and Magnetic Gain Javier Contreras Scott Vestal 1 TI Information Selective Disclosure
Installing FEMM FEMM can be downloaded from the official website. http://www.femm.info/wiki/HomePage. 2 TI Information Selective Disclosure
Finite Element Method Magnetics (FEMM) Basics FEMM uses a Finite Element method to solve electromagnetics problems. Nodes connected by line segments and arcs to define boundary conditions as well as regions containing different materials and current distributions. FEMM then generates a mesh within this problem s geometry, which it uses to solve for the magnetic field distribution within the boundaries. 3 TI Information Selective Disclosure
Finite Element Method Magnetics (FEMM) Basics LUA allows all the functionality of FEMM to be controlled through scripting and make drawing a core and changing parameters quicker and not having to redraw a core in FEMM Scripts attached are used to get an estimate of magnetic core s inductance in the secondary coil and the core s magnetic gain. Parameters are used in the DRV421 System Parameter Calculator 4 TI Information Selective Disclosure
Magnetic Core PCB DRV421 The script attached will draw the core seen. Download script and save where you would like all your FEMM Magnetic Core simulations saved. Core Air Gap Windings Primary Conductor 5 TI Information Selective Disclosure
Run Script From FEMM Click Open a Lua Script Navigate to location of the scipt Build_Magnetic_CoreNoCutout.lua and select it. Follow the next slides for description of the input parameters. 6 TI Information Selective Disclosure
Input Parameters for Script File Name This is the name of the file created and saved. It will be save in the folder that contains the script. Note: file name must include .fem extension Core_Depth (dc) This is how much depth in the simulation there is. This is the axis that is not shown in FEMM since this is only a 2D drawing. 7 TI Information Selective Disclosure
Input Parameters for Script Cont. Core Inside Radius (ri) Core Outer Radius (ro) Air Gap (a) 8 TI Information Selective Disclosure
Input Parameters for Script Cont. Primary Radius (r) Core Permeability 14000 (Iron) 83000 (Mu Metal) 9 TI Information Selective Disclosure
Input Parameters for Script Cont. Number of Turns- Secondary Coil number of windings. Winding Angle ( ) 10 TI Information Selective Disclosure
Input Parameters for Script Cont. PCB Height (hP) PCB Width (wP) Distance from Core (yD) DRV421 Height (hD) is a constant 11 TI Information Selective Disclosure
Script outputs Filename.fem file with the drawing of the Magnetic Core with input parameters. i. A current on the compensation coil. Compensation current is 1? # ?? ????? . The current is used to calculate the inductance and magnetic core gain. ii. Primary current is zero. 12 TI Information Selective Disclosure
Script outputs Cont. Filename.ans (answer) file that shows the magnetic field on and surrounding the magnetic core with current on the compensation coil as described in previous slide. 13 TI Information Selective Disclosure
Script outputs Cont. Lua Outputs. 1. Inductance(H) 2. Core Magnetic Gain (Tesla/Amp) 3. Sensor Location (X,Y) 0.4 mm from top of DRV421 14 TI Information Selective Disclosure
