INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Powerful electromagnet

Powerful electromagnet

(OP)
Im trying to build a powerful electromagnet with a field strength of a 1 Tesla or neat it. While planning... one concern to me is the input power required. What could be the range from?

I'll be using a high permeability core that saturates beyond 1 Tesla. Is it possible?
An electromagnet that requires less than 5 kW, with a field of 1 Tesla or a value very near.
Can anyone please share their experiences in designing & building previous project/product? The difficulties and everything.
I'm open to any options. As long as it fits the requirements of a field of 1 Tesla or near it, however using a power input of less than 5 kW.

RE: Powerful electromagnet

(OP)
Is this practical?

RE: Powerful electromagnet

What is the shape/volume that you are trying to create this field? In small regions, nearly every commercial solenoid produces fields in excess of 1T with only a few watts of input power. Also, how uniform does the field need to be? Can't answer the question without a lot more problem definition.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Powerful electromagnet

Size is the key.
traditionally high field units are built using high purity iron for the core, Cu foil for the windings (better than wire), and then higher saturation material for the tapered pole pieces.
We has a large unit that pulled about 7kW, it reached 1.25T or so, over about a 4" diameter area with a 0.5" air gap.
Of course it was about 4'x4'x4' in size.......

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Powerful electromagnet

I guess your core is 80Ni-Fe with a Bs about .8 T. The problem is that when it is saturated, the core will act like air. Recommend to use Ni50-Fe material as the core which has a Bs of 1.6 T and still with high permeability.
For a solenoid, B is proportional to N.I.µ/l (N.I amper turn, µ permeability of core, l -length of solenoid), as long as N.I keeps the same, the B is independant to diameter of solenoid. however, to keep the same N.I, bigger diameter needs longer wire, so higher resistance, and so larger watts.

RE: Powerful electromagnet

(OP)
Thank you for the help & reply!

Im trying to achieve a powerful magnetic field that can act on "magnetic objects" 20 mm away. Size, material, etc... Does not matter. All that matters is using the least amount of power(5KW MAX) and achieving a magnetic field of 1 Tesla,
+ I forgot.
The core must be a soft ferromagnet that will have 0 remaining magnetic field when the current is off.

RE: Powerful electromagnet

(OP)
@dgallup, What do you mean with the small regions part? Could you clarify? Can these solenoids(I assume with iron cores i/e electromagnets...) act on objects form a distance?
It does not have to be fully uniform, anything about 70% will do.

RE: Powerful electromagnet

No they will not pull something from 20 mm. The typical solenoid has a stoke of maybe 0.1 mm. Easy to get well over 1T in a small air gap.

If you truly need 0 remaining magnetic field when the current is off you can stop right now, 0 is impossible. Small is possible.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Powerful electromagnet

That is why large electromagnets are wound with Cu foil, lower resistance than wire.
We used fairly thin foil (about 0.008") with 0.001" film between as insulation.
The core is low carbon iron that has been well annealed.
The saturation should be about 1.2, so design the coil to this field level.

If you need 1T, at 20mm you need to do some simple modeling.
Knowing that using 50/50 Fe/Ni as pole pieces you can reach 1.6T.
How large of a diameter will the pole piece need to be?
If it comes out 100mm diam then you can work backwards to the coil core diameter.
Then figure out how many amp turn it will take.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Powerful electromagnet

(OP)
@EdStainless
The size is not an issue, any size is fine. Most important factors is the power consumption, I'm hoping it could be low.

RE: Powerful electromagnet

The Amp turns depend mostly on the gauge of wire (or equivalent foil).
As the number of turns increases, the diameter and average length of turn often increase, but neglecting this factor for a moment, look at the basic effect of wire diameter and the number of turns.
A given magnet coil has 100 turns and draws 10 Amps. In an attempt to increase the strength of the magnet the number of turns is doubled. As a result the total resistance is doubled and the current drops to 5 Amps.
10 Amps through 100 turns equals 1000 Amp turns.
5 Amps through 200 turns equals 1000 Amp turns.
By the time you increase the turns to 1000 turns, the average turn length will have increased enough that the extra resistance may start to show a small but noticeable drop in magnet strength.
But then we may have another second order effect: Heat or lack of it.
I have seen field coils where the current drops 5% or more when the coil warms up.
If your coil runs cold with 10 Amps then there is nothing to be gained, however if it runs hot, the reduced current in increased turns will give a much cooler running coil and with the thermal coefficient of resistance of copper. The lower resistance may gain back some or all of the loss caused by the longer average turn length.
You will have to design a coil and run your own numbers to quantify the actual changes.
Bottom line:
The strength of an electromagnet up to saturation depends on Amp turns per inch of magnetic path.
Three ways to increase the strength:
1: Raise the voltage.
2: Rewind the coil with a larger gauge wire.
3: Shorten the length of the magnetic path.
Once you have the strength you want, decrease the losses by increasing the number of turns of the same size wire.
Remember.- The induction increases as the square of the number of turns. The high induction of a large number of turns may slow the response of the magnet on energization and either slow the response, generate an extremely high "inductive kick" or both on de-energization.

Bill
--------------------
"Why not the best?"
Jimmy Carter

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close