Electromagnet Holding Force Calculator
SI
Imp
Imperial
Inputs
View results
Flux density at pole
(B)
Measured or estimated normal flux density at the working pole face.
T
Pole width
(w)
Effective rectangular pole contact width.
mm
Pole length
(l)
Effective rectangular pole contact length.
mm
Active poles
(n_p)
Number of pole faces carrying useful normal flux.
Contact factor
(k_c)
Derating for rough surface, paint, scale, air gap, thin backing steel, leakage and nonuniform flux.
%
Safety factor
(SF)
Holding force is divided by this value to estimate a safe working load.
Results
Default result
Edit inputs
Safe working load
(SWL)
458.4
N
Pass
103 lbf
Also computed
Derated holding force
(F_hold)
Pass
1,375
N
309.1 lbf
Equivalent held mass
(m_hold)
46.74
kg
Force per pole
(F_pole)
687.5
N
Magnetic pressure
(p_m)
0.573
MPa
Total pole area
(A)
4,000
mm²
Contact factor used
(k_c)
60
%
Safe working load vs Flux density (T)
Holding force scales with the square of flux density, so small field losses from gap, paint or rough contact can remove a lot of load capacity.
Safe working load vs Flux density (T)
0
500
1,000
1,500
0
0.5
1
1.5
2
design B
Flux density (T)
Safe working load (N)
Holding force scales with the square of flux density, so small field losses from gap, paint or rough contact can remove a lot of load capacity.
Method notes
3 notes
Holding force uses magnetic pressure p = B^2/(2*mu0), multiplied by total pole area and contact factor.
Safe working load divides the derated holding force by the entered safety factor.
Paint, rust, curved parts, thin backing steel, air gaps, vibration and sliding loads can reduce real holding force sharply. Test safety-critical lifts.
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