need help designing and building electromagnet 1

[Gus2014]

I want to build a c frame electromagnet that will be powered with a variable dc source range of 3 to 24 volts. I need to create 200 gauss to 800 gauss in a 3/4" air gap. The c frame made of iron can be 2 inches on each side and maybe tapered down at the pole tops to help concentrate flux in air gap. Can somebody help me with this electromagnet?

 

[Gus2014]

Can I use a 15 volt battery with this application? Also, x can be 10.

 

[Skogsgurra]

I use a small quite decent B probe to measure magnetic fields. If you get yourself a few pieces of mild steel and of suitable size, then you can easily mock up something to start testing with. The probe I use is the i-prober 520. It works from DC up to several MHz and can be used either as a current probe or a field probe.

It works up to 2.5 mT - so you will not be able to use it all the way up to full field strength, but you can reduce the excitation current and check uniformity, it will be very much the same at 2.5 mT as it is for 20 - 80 mT. I see no risk that saturation cuts in at these levels.

Tip for improved uniformity: Use shims made from mild steel plate and arrange at the perimeter of the pole shoe faces. It makes it a lot easier to "mould" the field you want.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[logbook]

Can I use a 15 volt battery with this application?

The idea of the forum is to give help and advice, not to do it all for you.

I have given you a worked example with 0.5mm wire requiring 8.2V to operate at 1A.

Try working it out for more turns of thinner wire running at a lower current. Post your result and it can be checked.

Alternatively use a switched mode regulator so you can adjust the field without incurring excessive power loss.

 

[Gus2014]

I appreciate all the help, I will post my results

 

[waross]

On a DC magnet you will find that a greater number of turns will lower power consumption but will not make much difference to the strength. For greater magnetic field strength you must use either higher voltage or larger diameter wire.

Example:
The field strength depends on the number of Amp Turns. That's Amps time turns.
"I have given you a worked example with 0.5mm wire requiring 8.2V to operate at 1A."
Now double the number of turns of this wire. The resistance will be substantially doubled and the current will be halved.
Half the current through twice as many turns results in the same Amp Turns.
You may add a second coil with the same number of turns and run both coils in parallel for greater strength.

Bill
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"Why not the best?"
Jimmy Carter

 

[Gus2014]

The more options I have to get the desired results the better chance I have of achieving them. So, thanks for all this info.