I am indebted to my colleague, Mr Tony Grainger, for the
JavaScript program which performs the calculations for this
page.
How to use this page:
An electromagnet consists of 2 basic parts;
an electric circuit (or coil) and
a magnetic circuit (or flux path).
An electric current in the coil induces a magnetic current (flux) in the magnetic circuit (
Magnetic potential = N x I ampere turns).
The program on this page brings together all the salient features of
both these basic parts and makes detailed calculations to inform your electromagnet
design.
Feel free to experiment.
You can type any numbers you like into the
input fields. The program will immediately make all the relevant calculations and present them in the "
Calculated Results"section.
At the same time both the geometry and the dimensions for
electromagnet cross section drawing will be automatically updated
.
Additional Calculated Results can be displayed if desired by clicking on the "
Details +/-" button. These additional results will not usually be needed but may be useful for advanced designers.
To reset the program to the default numbers just refresh (or reload) this web page.
The calculations assume that the coil is made from
copper wire (resistivity = 0.0171 Ωm at 20ºC) and that the magnet body is made from
mild steel SAE 1020.
The relationship between the magnetisation in the steel and the field strength
is non linear and cannot be represented by an equation. The curve is usually referred to as a
B-H curve.
The calculations on this page use a table lookup for the B-H curve followed by an
iterative method to obtain accurate results for the flux density
pertaining to the particular magnet configuration.
(See the magnetisation data here).
DESIGN PROCEDURE:
This section is being developed but you can use it now if you wish.
See also the
Coil Calculator.
[ 0, 0.000 ],
[ 10, 0.003 ],
[ 25, 0.007 ],
[ 50, 0.015 ],
[ 75, 0.026 ],
[ 108, 0.050 ],
[ 137, 0.100 ],
[ 160, 0.150 ],
[ 180, 0.200 ],
[ 200, 0.250 ],
[ 235, 0.350 ],
[ 285, 0.500 ],
[ 320, 0.600 ],
[ 365, 0.700 ],
[ 480, 0.900 ],
[ 560, 1.000 ],
[ 660, 1.100 ],
[ 800, 1.200 ],
[ 1000, 1.300 ],
[ 1150, 1.354 ],
[ 1550, 1.450 ],
[ 1840, 1.500 ],
[ 2250, 1.550 ],
[ 2800, 1.600 ],
[ 3450, 1.650 ],
[ 4350, 1.700 ],
[ 5500, 1.750 ],
[ 7707, 1.810 ],
[ 11863, 1.890 ],
[ 15839, 1.945 ],
[ 21076, 2.000 ],
[ 27281, 2.050 ],
[ 35288, 2.100 ],
[ 45642, 2.150 ],
[ 59046, 2.200 ],
[ 76412, 2.250 ],
[ 98907, 2.300 ],
[ 128000, 2.350 ],
[ 134764, 2.360 ],
[ 141880, 2.370 ],
[ 149364, 2.380 ],
[ 157235, 2.390 ]