Message Board Thread - "Ferrite Rings"

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Ferrite Rings ns6ao 5/12/2010
I have used my FLIR E45 ThermaCam to take images inside robot control cabinets. The ferrite rings appear to be at much higher temperature as compared to the cables. The temperature difference between ferrite rings and cables is as high as 30-35 degrees in some cases.

I understand that ferrite beads act as a passive low-pass filter attenuating high frequency EMI/RFI electronic noise. So, it is possible that the absorbed energy gets converted to heat and dissipated by the ferrite. But, I'm a bit worried about their temperature going up to 50-60 degrees.

Any comments/views would be very much appreciated, thanks.

 
Re:Ferrite Rings jvoitl 5/12/2010
The first time I saw this many years ago I was a little surprised too. It is normal but one of those things you don't think about until you see it with an IR camera. The high frequencies induce a current into the rings which naturally generates some heat. As long as they were sized correctly there should be no problelm.
 
Re:Ferrite Rings ns6ao 5/13/2010
Thanks for your response.
 
Re:Ferrite Rings darrenc 6/2/2010
they are workng as a transformer in a way, i have seen them get to some really high temperatures in excess of 100°C what i recommended in when this happens is check any cabling for signs of insulation degradation as its likely to melt. having spoke to some inverter manufacturers they have recommended reducing cable length from machine to panel as the length of cable increases noise for the 'filter'to deal with
 
Re:Ferrite Rings Rudie 6/3/2010
I design high frequency power supplies for a living. We use ferrites in big quantities. We noticed this phenomenon on the measurements we did. The cores look very hot compared to the rest of the circuit. This normally raises a lot of concern from the owner of the equipment and a lot of explanation from the thermographer. Measuring the real temp with a thermocouple normally confirms that the temp is within limits. I think the core material is florescencing at that wavelength. I can’t confirm it before it hasn’t been tested in a spectroscope. Last year I presented a paper at the Inframation conference and then mentioned this problem (Paper 2009-039). The best is to mention this problem to who ever the moment you see a ferrite core in any equipment
 
Re:Ferrite Rings Hellmuth 6/3/2010
I can agree to some extend to all the comments below. Yes the core will heat-up as a result of the high frequencies that it need to supress, but if it reaches the temperatures that you measure then there is a problem. Have you confirmed the Emissivity of the core? I would also use a thermo couple or some other contact method to verify the temperature if possible.
 
Re:Ferrite Rings Karl 7/7/2010
ns6ao wrote:
used my FLIR E45 ThermaCam to take images inside robot control cabinets. The ferrite rings appear to be at much higher temperature as compared to the cables. The temperature difference between ferrite rings and cables is as high as 30-35 degrees in some cases.

I understand that ferrite beads act as a passive low-pass filter attenuating high frequency EMI/RFI electronic noise. So, it is possible that the absorbed energy gets converted to heat and dissipated by the ferrite. But, I'm a bit worried about their temperature going up to 50-60 degrees.

Any comments/views would be very much appreciated, thanks.

A small qestion about the measuring in this foto.
Emisivity in area and the spot, same ??
Ferrite and cabinet has different surface.
Do you know the enisivity on cabinetsurface and the ferrite?
You need also to take a new foto and be sure that object is in focus.
You can also use som thermostrips (Reatec). It is easy to use.
 
Re:Ferrite Rings Karl 7/7/2010
Karl wrote:
A small qestion about the measuring in this foto.
Emisivity in area and the spot, same ??
Ferrite and cabinet has different surface.
Do you know the enisivity on cabinetsurface and the ferrite?
You need also to take a new foto and be sure that object is in focus.
You can also use som thermostrips (Reatec). It is easy to use.
Sorry: I ment cables curface
 


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