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How to calculate the pole area (Am), magnet length (Lm) and permeance coefficient (Pc)?
On the condition of absence of any coil excitation, the calculations of pole area (Am) and magnet length (Lm) follow below equation:
Remark:
Bg=the gap flux density Ag=the air gap area
Bm=the flux density at the operating point Lg=the air gap length
Hm=the magnetizing force at the operating point
How to calculate the flux density on a magnet¨s central line
1. For cylinder magnet
2. For rectangle magnet
3. For ring magnet
4. For magnet on a steel back plate
Respectively use the same equation of calculating flux density for cylinder magnet, rectangle magnet and ring magnet, and substitute ^2L ̄ for ^L ̄ in the each equation.
5. For identical magnets facing each other in attracting position,
The Bx value at the gap centre is the 2times value of Bx on condition of only one piece magnet exists. At a point ^p ̄, the value of Bp is the sum of B(x+p) and B(x-p), where (x+p) and (x-p) substitute for ^x ̄ in the equation of calculating Bx of individual magnet.
6. For identical, yoked magnets facing each other in attracting positions
Substitute 2L for L and follow the same procedure of calculating Bp or Bx of ^For identical magnet facing each other in attracting position ̄ Remark: The unit of dimensions can be any one but should be uniform.
How to calculate the attractive force?
The calculation of attractive force exerted by a magnet to a ferromagnetic material can follow the below equation:
Or we can follow below equation to approximately calculate the attractive force.
Remark:F=attractive force with unit in Newtons
B=flux density with unit in Tesla
Br=remanence with unit in Tesla
A=pole area with unit in cm2
The formula of approximately calculating attractive force is subject to magnet with straight line demagnetizing curve such as rare earth magnet and ferrite magnet, ^L ̄ kept within the bounds of normal and standard magnet configuration, and one pole of magnet tightly closing a flat and machined surface of steel.