Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

[SOLVED] Inductor temperature rise

Status
Not open for further replies.

bowman1710

Full Member level 3
Joined
Nov 8, 2014
Messages
183
Helped
6
Reputation
12
Reaction score
6
Trophy points
18
Activity points
1,604
Hi Guys,

What is the easiest way to calculate the temperature rise of an Inductor at a given DC current (e.g @ 40 deg the current would be ???A) I have calculated the DCR and the power loss at the max current but dont know how to transpose this information into temperature.

Thanks
 

KlausST

Super Moderator
Staff member
Joined
Apr 17, 2014
Messages
21,980
Helped
4,591
Reputation
9,196
Reaction score
4,808
Trophy points
1,393
Activity points
145,108
Hi,

sure, it depends on size and cooling.....
Is it potted or unpotted, air flow or vacuum, or water cooled?
In a box or not?

Klaus
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
50,020
Helped
14,496
Reputation
29,262
Reaction score
13,426
Trophy points
1,393
Location
Bochum, Germany
Activity points
287,099
The missing link is thermal resistance of inductor to ambient. Estimate numbers are given by core and inductor manufacturers, but the exact value depends on how the part is mounted.
 

bowman1710

Full Member level 3
Joined
Nov 8, 2014
Messages
183
Helped
6
Reputation
12
Reaction score
6
Trophy points
18
Activity points
1,604
sure, it depends on size and cooling.....
Is it potted or unpotted, air flow or vacuum, or water cooled?
In a box or not?

Well I have my toroid core

**broken link removed**

That will be fitted unpotted in a box with minimum air flow if at all.

The missing link is thermal resistance

I tried calculating this but didnt know how it related with the current

"Dividing the temperature rise due to Irms current (e.g. 40°C rise) by the power required to generate that rise (Power = DCR × Irms2):

Rth (in °C/W) = 40°C ÷ (DCR × Irms2)"

**broken link removed**
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
50,020
Helped
14,496
Reputation
29,262
Reaction score
13,426
Trophy points
1,393
Location
Bochum, Germany
Activity points
287,099
The coilcraft articel is assuming that you have a component with specified current rating and DCR. Knowing the temperature rise the rating is based on, you can calculate a Rth value.

But you are apparently making your own inductor and don't have respective data. So you can't "calculate" Rth.

You can either determine it by a measurement, or try to find Rth specifications for inductors using a similar core and winding size. I just checked the Epcos Ferrite tool, unfortunately it gives no thermal data for toroid cores.
 

malli_1729

Full Member level 5
Joined
Feb 13, 2007
Messages
253
Helped
48
Reputation
96
Reaction score
46
Trophy points
1,308
Location
INDIA
Activity points
3,287
Inductor will have DC and AC Losses. DC losses will depends on DCR of Inductor and the rms current flowing through it. AC Losses will depends on Frequency of operation, Core ..etc. Once we have DC and AC losses. Find out total losses. Most of the inductor datasheets will give Current Vs temperature rise characteristic. Check with WE they have an EXE which will give more details. or any mfg like Vishay/Coilcraft/cooper-busman etc
 

D.A.(Tony)Stewart

Advanced Member level 5
Joined
Sep 26, 2007
Messages
7,067
Helped
1,721
Reputation
3,441
Reaction score
1,725
Trophy points
1,413
Location
Richmond Hill, ON, Canada
Activity points
51,856
Well I have my toroid core

**broken link removed**

That will be fitted unpotted in a box with minimum air flow if at all.



I tried calculating this but didnt know how it related with the current

"Dividing the temperature rise due to Irms current (e.g. 40°C rise) by the power required to generate that rise (Power = DCR × Irms2):

Rth (in °C/W) = 40°C ÷ (DCR × Irms2)"

**broken link removed**

This formula works for low frequency ESR losses but does not include Eddy current losses in the core at high f.

Core and winding losses, and an estimate of the resulting temperature rise, can be calculated for Coilcraft’s power inductors using the web tool :
Thermal resistance will be greatly dependent on air flow. The wire is also thermally insulated with any electrical insulation.
 

bowman1710

Full Member level 3
Joined
Nov 8, 2014
Messages
183
Helped
6
Reputation
12
Reaction score
6
Trophy points
18
Activity points
1,604
Ok then guys,

I found this

**broken link removed**

which seemed to have all my answers.

Another thing, how do I know the Isat of the inductor I am making for a given DC, is there a way to calculate the current at which it will go into saturation?
 

T

treez

Guest
the isat you get by equation isat = (Bsat. Area.N) /L

where
Area = min core area cross section
N = number of turns
L = inductance

this equation is got by equating

V = L.di/dt

and

V = N.d(phi)/dt

..equate right hand sides and do B = PHI/AREA

I am assuming that you are using a standard ferrite with Bsat = 0.3T

But welcome to the subject of saturation/heating of ferrites, which is shrouded in industrial secrecy
 
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top