Concerning permeability and relative permeability
Concerning permeability and relative permeability
(OP)
N5211
BHmax = 52 MGOe
Br = 14.5kG
Hci = 11.0 kOe
Hc = 10.6 kOe
U0 = .000001256636
I am working on a project with coils and electromagnets and the information above is from a B/H chart and the values for magnetic flux density and coercive force are for neodymium N5211 metal. I know that Br is the remaneant flux density of the metal and I'm not sure which if is that the number I should use to compute the permeability(mu)and also not sure which number for coerce force I need to use to get the correct magnitude, so here goes.
u=B/H=14.5/11.0(Hci)=1.318181818181818
u=B/H=14.5/10.6(Hc) =1.367924528301887
Relative Permeability(ur)=u/u0=1.31818/.000001256636=1048975.20045582 for Hci and
1088560.251337698 for Hc.
First is the numbers I used to compute the permeability the correct numbers to use to start with to calculate permeability of N5211?
Which numbers would be the correct numbers to plug into an equation to get the correct magnitutde, Hci or Hc? Any help from anyone would be greatly appreciated.
Thanks
neferkamichael
BHmax = 52 MGOe
Br = 14.5kG
Hci = 11.0 kOe
Hc = 10.6 kOe
U0 = .000001256636
I am working on a project with coils and electromagnets and the information above is from a B/H chart and the values for magnetic flux density and coercive force are for neodymium N5211 metal. I know that Br is the remaneant flux density of the metal and I'm not sure which if is that the number I should use to compute the permeability(mu)and also not sure which number for coerce force I need to use to get the correct magnitude, so here goes.
u=B/H=14.5/11.0(Hci)=1.318181818181818
u=B/H=14.5/10.6(Hc) =1.367924528301887
Relative Permeability(ur)=u/u0=1.31818/.000001256636=1048975.20045582 for Hci and
1088560.251337698 for Hc.
First is the numbers I used to compute the permeability the correct numbers to use to start with to calculate permeability of N5211?
Which numbers would be the correct numbers to plug into an equation to get the correct magnitutde, Hci or Hc? Any help from anyone would be greatly appreciated.
Thanks
neferkamichael





RE: Concerning permeability and relative permeability
your estimates of 1.31 to 1.36 are good and, by the way, are the relative permeability
for the units you have
you can use the average or either one, it won't make much difference
RE: Concerning permeability and relative permeability
Your modeling software will hopefully have the option of importing the 2nd quadrant curve, point by point. That is the only way to truly model its performance. If the software doesn't have this option, you'll have to ensure the magnet always operates above the knee of the curve.
RE: Concerning permeability and relative permeability
MagMike, how did ya come up with 1.02 if ya don't mind.
Appreciated the help, thanks.
neferkamichael
RE: Concerning permeability and relative permeability
I came up with 1.02/1.03 because magnetic modeling is my day job and I use and have catalogs from all the major NdFeB magnet producers. All of them list it as 1.02 to 1.03.
Please tell us you are not using NdFeB as the core of your electromagnet.
RE: Concerning permeability and relative permeability
So MagMike, for equations that call for relative permeability and I'm using SI unit is 1048975.20045582 the relative permeability?
Thanks for responding.
RE: Concerning permeability and relative permeability
RE: Concerning permeability and relative permeability
µ0 = 4π×10−7 V·s/(A·m) ≈ 1.2566370614...×10−6 H⋅m−1 or N·A−2 or T·m/A or Wb/(A·m)
in the SI system of units.
RE: Concerning permeability and relative permeability
That said, please realize the limitation inherent to your original question. N5211 is non-linear in the 2nd BH quadrant so its magnetic behavior can't be completely characterized by just Br, Hc and/or µ0. The slope of the BH curve is 1.02/1.03 (cgs units) until you reach the knee of the curve. To properly model N5211 you need to manually enter a number of B,H coordinates to account for the knee of the curve.
Finally an apology: I assumed the NdFeB was the core of an electromagnet based on Hacksaw's posting. His comment didn't help the conversation much.
RE: Concerning permeability and relative permeability
Because the relative permeability is on the order of 1.02-1.03.
Compare to iron - may be on the order of 1000 at 1T
=====================================
(2B)+(2B)' ?
RE: Concerning permeability and relative permeability
Force=(NxI)2xkxa/(2g2)
SI units
N=Number of turns=100
I=current in Amperes=1
Force=Newtons
k=permeability of a vacuum=.000001256636
a=area in meters=.004559991meters2(7.0682")
g=distance between electromagnet and ferromagnetic material in meters.=.0000254 meters(001")
If you do the math the answer is 44409.5147 Newtons = 9983.657lbsf.
Now my question is, is there really almost 10000 pounds of force between and air coil core with a radius of 1.5" and a metal plate at a distance of .001" between them? I've done the math over and over.
RE: Concerning permeability and relative permeability
Think on that one a bit...
Dan - Owner
http://www.Hi-TecDesigns.com