Will it Blow? Joule Heating in a Fuse on a Circuit Board, Chapter 1

A classic multiphysics coupling is joule heating, also called resistive heating or ohmic heating. This video resource is the first in a three-chapter series that will see how you can effectively simulate joule heating in a fuse and answer the question: "Will it blow?"

Transcript

00:00:06 in this video I'd like to demo how you can use comel multif physics to model dual heating so we got this fuse sitting on a simple circuit board I intend to run a current of 15 amps from left to right in this picture so from the pink patch up to and through the fuse and down through the Via to the ground plane or rather I'll assign a 15 amp input current to the patch and ground to the

00:00:30 ground plane and console will find out the rest for us this includes the resulting Jewel Heating and temperature increase the question will hopefully be able to answer by the end is Will It Blow now the fuse is effectively just an aluminum thread running through a vacuum tube aluminum has a melting point of 933 Kelvin so what the question boils down to in the end is whether or not the

00:00:56 temperature in the thread will exceed 933 Kelvin we will also find the voltage drop across the circuit and a whole lot of other interesting results now let's bring up console on our left there is the model builder which is where we'll spend most of our time modeling so far there isn't much in here but we'll constantly be

00:01:19 adding things by the end of the session it will contain a complete record of the model we got a graphics window as you can see in some message bars as well the model wizard right here in the center takes you through the first steps of each model and right now it wants to know what space Dimension we will use I'll pick 3D and hit the next Arrow for the next choice there's the

00:01:43 physics and uh there's a whole lot of different kinds of physics here there's AC and DC currents and electromagnetic fields there's various kinds of Acoustics there's uh transport and chemical reactions etc etc remember that we want the fuse to heat up so we should find something in heat transfer under heat transfer I'll uh browse down to electromagnetic Heating

00:02:08 and finally Jewel heating Jewel heating just so happens to contain everything we'll need for this model but you can actually mix and match any number of interfaces if for example you want to model thermal expansion due to this heating you can add a structural mechanics interface either now or later on but for this model let's go for just duwel heating I'll hit the next Arrow

00:02:32 again and that brings us to the final step in the model wizard which is the study type selection you can select the time dependent study if you want to see how the temperature evolves with time you can do a frequency transient study if you want to keep the temperature is time dependent but look at AC instead of DC currents for now though we are only interested in the temperature after a

00:02:53 long time so let's select stationary and that's the final step in the model wizard I'll hit the finish flag now look at this the model builder has now been filled with nodes for definitions geometry materials physics that's jeel heating our case mesh study and results I'm going to go top down starting with geometry and just fill all

00:03:22 these notes with content so let's right click on the geometry node uh doing so I get various options for drawing such cylinder sphere and lots of other Primitives uh 2D Works planes and a little bit of everything but I can also choose to import the geometry and that's what I'll do console supports most common CAD formats after selecting fuse which is my geometry I'll just click the

00:03:48 import button and here it is let's set the wireframe button in here so that we can see what goes on on the inside and there's the fuse wire so we got geometry we'll need some materials you can create your own materials that's this first selection or you can use the ones from our built-in material library and I'll do that so let's pick as the first material

00:04:17 aluminum I'll right click on that and add it to the model now this being the first material that we're using in the model it will automatically apply everywhere and I don't quite want everything to be aluminum so I'll just hit this little broomstick and delete it now let's add aluminum only to those places where we want it to apply I'll select this wire leading up to the fuse

00:04:43 the heat sink of the fuse the actual fuse wire the second heat sink and finally the wire leading down to the circuit board those are now all aluminum the next material will be copper I'll find it right here I'll add it to the model and uh I would like copper to reside in the patch leading up to the fuse and the Via and finally in the ground

00:05:10 plane as the last material in our model I'd like to add a material called f fr4 and that's commonly used in circuit boards so this is what applies to the non-conductive parts of the circuit board right here right beautiful we got our materials and we have the geometry obviously so what's next well it's the physics