DC Electro-Magnet Core Material Selection

[RobGer]

Hello All.
I require assistance in the selection of a suitable core material for my Electromagnet project. I’ve experimented with steel/iron of different properties and have found field strength varies considerably as expected. What properties effect field output ? i.e. Iron/silicon contect etc. My aim is to increase field output by best selection of core material.

DESCRIPTION
My Electromagnet comprises of a solid steel round bar for the center core, a flat steel top plate, and a U shaped steel bottom plate. Core dimensions are 280mm x 60mm Dia.
A wound coil is place around center post.
24V DC is supplied to energize coil and produce required field at top plate.

RESTRICTIONS & VARIABLES
Metal assembly dimensions, coil design and supply voltage are not changeable.
My only variable is steel/iron core and top and bottom plate material.
Core material must be machinable and strong. i.e. If hit with hammer wont break.
Once power is removed little or no residual field is required.

Assistance appreciated.

RobGer

 

[nbucska]

If you connect acap parallel, when the power is turned off,
it will ring and degouss itself. Watch onrush current !

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

 

[RobGer]

Thanks nbucska[b/].

I'll give your idea a try!

RobGer

 

[RHMagster]

Hello Robger,

There are materials that can help in increasing the output but usually this only required if you are already saturating the material used.

Low carbon steel saturates at around 18 kOe.

If you are saturating your current material you may try Magnetic Iron which saturates at a higher level. Approx 20 kOe. Permadur (if I spelled correctly) is a name brand of material that could help, again, only if you are generating enough field to saturate normal CRS. These materials are more expensive though. In any event, look for the lowest carbon material in CRS (to keep cost down) and that may help give you what you require.

By the way, ringing demag, as mentioned by nbucska, will help eliminate the residual magnetics in the steel. Be sure of the ring time is adequate to fully degauss the steel. This can be done by calculation or by capacitive bridge.

 

[MagneticIronGuy]

Hello Robger,

I am a supplier (for 20+ years) of low carbon (C1002)electromagnetic strip & Rod. I am sure I can help. We currently inventory .250" thru 6.00" diameters. Let me know if I can help.

Sincerely,

Lloyd lloyd@cmispecialty.com

 

[Warpspeed]

Not sure if a solid steel core will ring too well, the induced eddy current would damp it out pretty quickly I am thinking.

However, a cylindrical core rolled from thin steel strip may serve several purposes. It would be decent material, it would have extremely low eddy current loss (for the ringing trick), and it would already have a hole through the middle for mounting.

Question for Mag Iron Guy, I know commercial wound and cut steel cores are readily available, including toroids, but can they be wound with a very small centre hole ?

I have an application for something like this myself.