How to obtain the magnetic force?

In summary, the conversation discusses the process of obtaining the magnetic force between a coil and a permanent magnet, specifically a NdFeB magnet. The individual asking for help outlines their procedure, which involves calculating the number of turns and layers for the coil, as well as the wire length, resistance, and current. They also ask if the magnet's mass and B need to be considered in the calculation. Others in the conversation suggest using a Finite Element package to model the system and solve the problem experimentally.
  • #1
mmytu
3
0
How to obtain the magnetic force??

Hi ,

I didn't have any experience to design coil and permenent magnet .

Now i have to do one project using coil and magnet NdFeB. But i haven't got the maximum force. (need maxi force between 1300 to 2500)

I am doing the below procedure. Is it correct?
using DC supply 48V,
known value :core internal and external diamer, length
1. choose the wire size (From AWG spec)
2. calculate the number of turns / layer (turns/inches * core length)
3. calculate the number of layers (turns / inches * core thickess)
4. calculate total no of turns (Step 2 * Step 3)
5. calculate the wire length (using AWG spec's : ohm / km)
6. calculate the resistace and current.
7. calculate the B using (B = u0 * N*I/L)
8. calculate Force using (F=B*I*L(length of wire)).

Do i need to consider NdFeB magnet mass and B in this calculation? How can i get the force??

Anybody helps me?

Thanks in advance for the help.
 
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  • #2


What are your units of force?

And why is the core material hollow?

I assume you want the force between the perm magnet and electromagnet when they are aligned north to south.


You left out some specs.

What is your core material?
What is the shape of the NdFeB magnet and what is it's rating?
 
  • #3


I want the force between permenent magnet and electromagnet.

Force unit is Newton to design.

I considered that the core material is air core. Is it possible?

And then the shape of NdFeB is Ring Type.

Specification for NdFeB
Dimensions: 3/4" od x 1/2" id x 3/8" thick
Material: NdFeB, Grade N42
Magnetization Direction: Axial (Poles on Flat Ends)
Weight:*0.399 oz. (11.3 g)
Pull Force, Case 1:*16.30 lbs
Pull Force, Case 2:*21.12 lbs
Brmax: 13,200 Gauss
BHmax: 42 MGOe

Do i need to consider anything to get the maximum force?

Thank you Phark..:smile:
 
  • #4


There's no easy way to calculate the force; it depends on the axial component of the gradient of the net magnetic field produced by the two magnets.
 
  • #5


Thank you for your reply, Gokul :smile:

Do you mean that I need to find out the net magnetic field B produced by the permenent magnet and electromagnet (Coil)? How can I solve that one?

Now I am finding out the magnetic field B (z) at a distance from the center of a coil again.
So could I use Brmax for permenent magnet from NdFeB specification?

Any idea to solve this problem? :confused:
 
  • #6


Yes, you can make an electromagnet without a core. If it's a cylindrical in shape, it's called a solenoid.

As Gokul says, it's not an easy problem. If you can't put a problem in mathematical analysis down, and can do calculus you might find it interesting, otherwise there's always experimentation.

You could sum the contributions to the B field at an arbitrary point in space due to the solenoid. Treat the solenoid as the sum of rings of current. For a single layer solenoid this is easiest. You add up the contributions from a bunch of rings all having the same diameter. By add, I mean integrate. If the inner windings are much less in diameter than the outer windings, you will need to take that into account with a double integral.

Next you consider how the field acts on the neodymium magnet which you treat as bunch of magnetic dipoles. I'm not sure how this is done. Somehow we would need to figure out the dipole strength per unit volume of material given the specs of N42...

However it might help if you said what you had in mind with this project.
 
Last edited:
  • #7


mmytu said:
Any idea to solve this problem? :confused:
Yes, you would have to model the system on a Finite Element package (like COMSOL or ANSYS). You will not get anywhere close with paper and pencil.

The easier approach is to solve it experimentally.
 
  • #8


Gokul43201 said:
Yes, you would have to model the system on a Finite Element package (like COMSOL or ANSYS). You will not get anywhere close with paper and pencil.

If you were to apply finite elements, how would you model the perm magnet give the material data sheet?
 
  • #9
I don't know yet since I haven't done it myself, but I imagine packages like COMSOL and ANSYS have something built-in specifically for permanent magnets.

Edit: Yes, found these, so it should be doable:
http://www.it.comsol.com/showroom/gallery/1414/
http://www.comsol.com/showroom/gallery/78/
http://www.comsol.com/community/forums/general/thread/3155/
 
  • #10
Gokul43201 said:
I don't know yet since I haven't done it myself, but I imagine packages like COMSOL and ANSYS have something built-in specifically for permanent magnets.

Edit: Yes, found these, so it should be doable:
http://www.it.comsol.com/showroom/gallery/1414/
http://www.comsol.com/showroom/gallery/78/
http://www.comsol.com/community/forums/general/thread/3155/

Is this one of those $2000 packages that amatures aren't interested in?
 

1. What is the magnetic force?

The magnetic force is a fundamental force of nature that arises from the movement of electrically charged particles. It is responsible for the attraction or repulsion between magnets and the behavior of electric currents in the presence of a magnetic field.

2. How is the magnetic force created?

The magnetic force is created when charged particles, such as electrons, move through a magnetic field. This movement causes the particles to experience a force perpendicular to both the direction of their motion and the direction of the magnetic field.

3. What factors affect the strength of the magnetic force?

The strength of the magnetic force depends on the magnitude and direction of the magnetic field, as well as the velocity and charge of the moving particles. The distance between the particles and the strength of the magnetic field also play a role in determining the strength of the force.

4. How can I calculate the magnetic force?

The magnetic force can be calculated using the formula F = qvBsinθ, where q is the charge of the particle, v is its velocity, B is the magnetic field strength, and θ is the angle between the velocity and the magnetic field. This formula is known as the Lorentz force law.

5. How can I increase the magnetic force?

The magnetic force can be increased by increasing the strength of the magnetic field or by increasing the velocity and charge of the moving particles. Additionally, arranging multiple magnets in a specific configuration can also increase the overall magnetic force.

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