Increasing Magnetic Field & Decreasing Heat

[SFSmith]

Hello, and thanks to anyone who helps.

I'm working on a project for school and am trying to get a small electromagnet to pull and repel a permanent magnet. It needs to pull and repel the magnet about 2 inches. Would using a Stronger permanent magnet help? The magnets in question are not much larger than one's index finger.

My question concerns building the electromagnet. I understand that increasing the coils and current can increase the field. I believe if the current is increased that it will get hotter, and in my case begin to melt my plastic insulation. So I am wondering how I would decrease the temperature of this. If I were to use more wiring would that help? Any suggestions would be great, Thx.

-SSmith

 

[biff44]

I am by no means a coil expert, but it seems to me that you want to have the magnetic field extend as far out as possible. I would try winding the coil on an iron shaft that is long, maybe 6"+ long. That way the fields will probably extend well out to 2" away from the end.

 

[logbook]

Well I have never tried anything like this either but 2 inches is a very long gap. How far away from this are you at the moment? I would think it probably only works over half an inch at most. The field drops off very rapidly with distance so if you can't even get half an inch at the moment then you have very little chance of succeeding.

Are you using AC or DC exitation? DC is going to be easier.

You need to think about the magnetic path. If teh magnetic field "flows" through iron then that is a good path. Air is really rubbish as a magnetic path. The trick is to make the iron core of the electromagnet wrap around and get close to the permanent magnet. Look at the ironwork design of pulling solenoids. The sliding core is surrounded by the ironwork. This is the only way you will get a high pulling/pushing force.

 

[IRstuff]

That sort of gap is not crossable without LOTS of current. We've built voice coil actuators with about 1/2-inch gaps, but we pay about a 4x penalty vs a 1/5-inch gap

TTFN

 

[SFSmith]

yes, thank you for your help. After 2 days of trying different things I actually never got over about half an inch like you said. I was using DC also, but it never really helped. I decided to change my project to something else, but thank you.