Drive electronics question

[jaydhall]

My first post, be gentle!

I have never designed with an electromagnet. I need to design a circuit that will allow me to adjust the magnetic force of the magnet. I was intending to use a constant current source which I can vary. I also do not want the iron part I am lifting to become magnetized, as I intend to use DC, so I was going to reverse the polarity on the magnet at a 250 Hz rate. Any input from you would be most useful.

Thanks!

 

[nbucska]

Conect a C || with L -- when you turn it off, it will
ring down and degauss itself.


<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[UKpete]

jaydhall, when you lift the iron component with the electromagnet you are of course magnetizing it to a degree. What happens when you release it depends on whether or not the iron falls away or whether it is still in contact with the electromagnet - it depends on your application.

If you release it and it falls away (as in a lifting magnet application), it will unavoidably retain some remanent flux density afterwards i.e. the level required to just hold it against the electromagnet at the instant of release.

If you release it and it is still in contact with the electromagnet (as in a magnetic chuck for example) then you have some control over the situation. As you imply, the technique in this case is to apply a decaying ac field so that the field in the iron also decays to zero.