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Electrical Engineering/Calculating the field strength of a "Permanent Electromagnet"


Hello Cleggsan,

I hope this message find you genki, and that everything is daijoubu with you. If you are missing Japan at all, I would remind you that right now it is rainy season - terrible weather every day!

Recently I have been reading recently about Permanent Electromagnets, that is an electromagnet with a permanent magnet as the core material, and I have a question I was wondering if you could share some insight on.

On this website
it says "Permanent electromagnets have a permanent magnetic field, but when supplied with power, the magnetic field is neutralized."

I am wondering how the strength of magnetic field produced by the solenoid/electromagnet might be calculated in this situation.
Regarding the usual formula of
Magnetic field in Gauss/Tesla = permeability x turn density x current
I am wondering if we can apply this formula in this case. The magnetic field of the permanent magnet opposes the magnetic field generated by the coil. Would this fact change the formula we need to use to calculate the magnetic field of the coil? Would it change the permeability value?
If so, it seems like it would make a huge difference to the resulting magnetic field produced by the coil.

Any feedback would be much appreciated as always. I hope the weather is good where you are.

Best regards,

No, permeability would not be changed under normal situations. If the electrically induced field were sufficiently high it could saturate the permanent magnet to some degree and cause some change but I think that would be an extreme case.

In the case of the calculations it is likely there are so many variables that experimental results may be the best solution.  Some estimation can be done by using physical parameters but it is very easy to determine the neutral level with simple measurements with guass meter. Increasing the current in the electro coils until the neutral level is achieved would be a simple matter.

Weather is hot here in my section of the USA.  Very hot and not much moisture in the form of rain but humidity higher than normal.  Makes for discomfort when out of doors.

Glad to hear from you.  Genki-des.  Sayonara.  

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