How do I calculate the Temperature rise in the Ferrite core?

Thread Starter

Manjesh Gowda

Joined Oct 19, 2020
83
Hello,

This question might seem basic but I would like to state it. I would like to calculate the operating/Rise temperature of the ferrite core of an inductor. I am modelling my own bobbins for the core so I need to decide on the material/filament to use for 3D printing which can take the temperature of the core without causing any damage or melting of the bobbins. I looked into it but could not get the answer I am looking for. Inductor specifications which might be useful for better understanding: E70 core N87 material, v= 450VRMS, I=40A, f=85khz, Litz wire for the windings, distributed air gap on each leg. I attach the datasheet as well. Please help me with this, any links or any articles would be great too. Thank you

https://www.tdk-electronics.tdk.com/inf/80/db/fer/e_70_33_32.pdf
 

Papabravo

Joined Feb 24, 2006
16,132
In order to calculate something you need a theory of the case.

Potential Hypothesis #1: the main source of heat is from the current dissipation in the wire.
We can find the resistance of the wire for a given length and by knowing the current through the wire we can compute the power consumption. Now we can assign some fraction of the power dissipated to each of the three sources of heat transfer: radiation, conduction, and convection. Conduction from the wire to the core is the one we are chiefly interested in.

This hypothesis should be easy to confirm and verify by experiment.

If that doesn't work for you we can proceed to alternatives.
 

BobaMosfet

Joined Jul 1, 2009
1,776
This may help-

Inductance Calculations
Author: Frederick W. Grover
ISBN-10: 048647440-2

At a primitive level the heating has more to do with the wire gauge of the inductor, the current through it, and EMF, than anything else. What is the heat dissipation value of each conductor material in C/W, and go from there.
 

MisterBill2

Joined Jan 23, 2018
8,760
If you know the frequency and power level and just want to be sure that you are not going to have a hot core problem you can look at the manufacturers listings of which materials have low loss at that frequency and also the size of the core needed for that power level at that frequency.That is much simpler than attempting to calculate the power lost in a core.
 

Thread Starter

Manjesh Gowda

Joined Oct 19, 2020
83
If you know the frequency and power level and just want to be sure that you are not going to have a hot core problem you can look at the manufacturers listings of which materials have low loss at that frequency and also the size of the core needed for that power level at that frequency.That is much simpler than attempting to calculate the power lost in a core.
Hey, I have already core in my hand! Just want to calculate how much it gets heated with the mentioned power level
 

MisterBill2

Joined Jan 23, 2018
8,760
That level calculates to be 450v x 40a=18000 watts. That is, iif 450 volts are developed across the choke at 40 amps. That is a whole lot of power. Heating of the wire will be due to resistance losses, heating of the core will be due to both magnetic hysteresis losses and eddy current losses . So you will need to calculate the amp turns and determine how close the choke is coming towards saturation. At that point you will need to know how your naterial woks at that frequency, unfortunately I can't help there.
 

Hymie

Joined Mar 30, 2018
976
I would think the answer to your question is with difficulty.
Normally the temperature is determined from measurement on a physical sample.
Bear in mind that once ferrite material reaches around 180⁰C it can suffer thermal runaway, so besides considering a maximum current, you need to take into account the maximum ambient temperature in which the inductor will be operating.
 
Top