Calculate Magnet Strength for Lifting 75 kg Iron in 1 Second - Morten

[Ankhen]

Hi. Can somebody make a calculation for me?
how strong do a magnet need to be to lift a mass of 75 kg iron 1 meter straigth up in 1 second.
Best Regards morten

 

[Hesch]

how strong do a magnet need to be to lift a mass of 75 kg iron 1 meter straigth up in 1 second.

It cannot be calculated just like that, because it depends on the shape of the iron and the magnet ( actually the shape of the airgap ).

So correct answers could be 1T or 100T, depending on the shapes.

 

[Ankhen]

It cannot be calculated just like that, because it depends on the shape of the iron and the magnet ( actually the shape of the airgap ).

So correct answers could be 1T or 100T, depending on the shapes.

Hi Hesch and thanks
Can you explaine it a little more, perhapse with some calculations so I can understand it?

 

[Hesch]

Can you explaine it a little more

The attraction is not due to some "magnetic poles" inside the magnet, but due to magnetic energy density in the airgap between magnet and iron, which is:

E_dens = ½*B*H [ J/m³ ].

Thus the energy: E = E_dens*(volume of airgap) = E_dens*(cross section area)*(width) of airgap = E_dens*A*s.

The force: F = dE/ds = E_dens*A.

Is the width of the airgap 1m in the starting position, or are magnet/iron closed up all the way ?

 

[Ankhen]

The attraction is not due to some "magnetic poles" inside the magnet, but due to magnetic energy density in the airgap between magnet and iron, which is:

E_dens = ½*B*H [ J/m³ ].

Thus the energy: E = E_dens*(volume of airgap) = E_dens*(cross section area)*(width) of airgap = E_dens*A*s.

The force: F = dE/ds = E_dens*A.

Is the width of the airgap 1m in the starting position, or are magnet/iron closed up all the way ?

Can you calculate it with both airgap 1m and with the magnet/iron closed up.
It would really be a big help.
Do you have a email or facebook I can contact you? It seems like you know you way around this stuff,and I have some psysics-questions i prefer not to ask in a open forum

 

[Hesch]

Can you calculate it with both airgap 1m and with the magnet/iron closed up.

Say that the total area, A = 0.1m², then

F_dens = m*g / A = 7370 N/m² →

E_dens = ½*B*H = 7370 [ J/m³ ] →

B*H = B² / μ₀ = 14730 [ J/m³ ] → B = 0.136 T.

Now, if s = 1m, try to calculate the H-field needed ( B = μ₀ * H ). Then calculate the amount of ampere-windings needed using Amperes law:

∫_circulationH⋅ds = N * I.

You should use a ∩-shaped magnet.

 

[Hesch]

Then calculate the amount of ampere-windings needed

PS: You will need about 216000 ampere-windings by a distance = 1m ( × 2 airgaps ).