magnetic properties of alumina (aluminum oxide) and induced current

Thread Starter

neorules33

Joined Apr 9, 2009
8
So aluminum is non magnetic as is alumina.
One is a conductor and one is an insulator.

My question is if alumina is exposed to high magnetic fields (rotating specifically) will an eddy current and thus heat get introduced into the ceramic?

I am looking for a light weight stiff substrate for rapid positioning and speed control of a large ultra lightweight servo.
Regular PCB material would work but I was wondering about alumina ceramics due some requirements of the structure.

And I have considered Kevlar and other non metallic substrates but alumina is better at reflecting heat.
Thanks
JC
 

ian field

Joined Oct 27, 2012
6,543
So aluminum is non magnetic as is alumina.
One is a conductor and one is an insulator.

My question is if alumina is exposed to high magnetic fields (rotating specifically) will an eddy current and thus heat get introduced into the ceramic?

I am looking for a light weight stiff substrate for rapid positioning and speed control of a large ultra lightweight servo.
Regular PCB material would work but I was wondering about alumina ceramics due some requirements of the structure.

And I have considered Kevlar and other non metallic substrates but alumina is better at reflecting heat.
Thanks
JC
Once or twice I've been known to clean the alumina insulator on spark plugs in the microwave.

Alumina is lossy enough at that frequency to glow red hot, the metal rod in the top insulator acts as a stub and picks up a fair bit of microwave energy. Sometimes a shower of sparks comes out the business end of badly fouled plugs - I assumed the voltage developed was sputtering the carbon deposits.
 

ian field

Joined Oct 27, 2012
6,543
No heat from eddy currents, so let rip with the rotating magnetic fields.

Not a good choice for high heat insulation. Good for high voltage


An informative advert
http://www.azom.com/article.aspx?ArticleID=4469
Spark plug alumina probably has closely specified thermal conductivity.

The heat grading of plugs is down to the design of the ceramic "nose insulator" - long and thin for hot plugs, short and stubby for cool plugs.
 
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