Electromagnet contact area vs. force
Electromagnet contact area vs. force
(OP)
I have a solenoid electromagnet whose cylindrical steel core protrudes out and has a chamfer at the end. When the core end contacts the mating part, the chamfer reduces the actual contact area by 1/2 (compared to the core diameter). I know pull force is dependent on core diameter, but is it dependent on the diameter of the contact area or of the core diameter within the solenoid? If I remove the chamfer (so that the contact diameter is the same as the core diameter, doubling the contact area) will I nearly double my pull force?





RE: Electromagnet contact area vs. force
I don't think it will double but the force will increase because you've reduced the air gap the flux will travel through.
I played with this calculator:-http://easycalculation.com/engineering/electrical/...
RE: Electromagnet contact area vs. force
Anyone care to run it through FEMM?
RE: Electromagnet contact area vs. force
RE: Electromagnet contact area vs. force
RE: Electromagnet contact area vs. force
One aspect of the system to consider: when the core contacts the mating part, is there still an airgap in another part of the circuit, or does it become a closed magnetic circuit?
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(2B)+(2B)' ?
RE: Electromagnet contact area vs. force
case 1. your core is not saturated: decreasing S by half increases B twice, F = c. (2B)^2 x (1/2 S)= 2 c B^2.S will increase twice.
case 2. core is saturated: decreasing S will not change B, F decreases simply by half
it also can be between case 1 and 2
other condistions, such as close or open circuit, limited size of pore pieces, air gap, can affect B, so affect F.
RE: Electromagnet contact area vs. force
Ok, so my coil parameters are as follows:
Coil Length (L): 17mm
Core Diameter (D): 4.75mm
# of Turns (N): 3,700
Current (I): .060 Amps
Core Material: 1110 Low Carbon Steel
Using the equation for Field Strength H = (N*I)/L = (3700*.060)/.017 or H = 13,059 A/m
Using the value of H in the B-H curve for 1010 Steel (don't have one for 1110), I get a B value of about 1.7T. And the point seems to be right at the knee of the curve, so its not saturated yet, but starting to make the turn.
Are my calculations correct?
If so, then my next question is, what alternate material can I use (instead of 1110 Steal) to increase the Flux B, thereby increase my clamping force? For example Carpenter Hiperco50 would produce a flux of over 2.2T and would be more saturated (so removing the chamfer would be more effective). I assume Hiperco50 is really expensive? What other material could give me significant improvement?
RE: Electromagnet contact area vs. force
RE: Electromagnet contact area vs. force
with an H field of 13,059A/m = 164 Oe, assuming a B of 1.7 T for 1110 steel is reasonable, which is close to saturation. if using annealed 1010 steel, the B could increase to 2.0T. A litle bit of chamfer can help to increase B at the contacting point, 1/2 area of chamfer is too much, sacrified too much of area.
With Hiperco 50, you can easily tget 2.2T at 164Oe. but if you have room to increase current or turn to increase the H field, you may want to go easily with this option.
RE: Electromagnet contact area vs. force
RE: Electromagnet contact area vs. force
I did manage to measure the B field within the empty solenoid with a probe and it came out to be 165 gauss. Not sure if it's correct since adding a steel core would bring it up hundreds of times, and that is too high once again.
In any case, even if I do have a field as low as 0.5 to 1 T, then the core's saturation would be at the lower steap side of the B-H curve. In this region, if I replace the 1110 Steel with 1006 Steel I would get around a 30-60% increase, according to the B-H data I have. If I replace the 1110 core with a Silicon Steel I would double the field.
Does this sound reasonable?
RE: Electromagnet contact area vs. force
you just missed the point. The H field inside the solenoid has nothing to do with the circuit, has nothing to do with what kinds of core materials used. when you measured the B field of 165 Gs, it is also H field of 165 Oe! with a steel core in it, the B field will increase to 165 + permeability x 165.
From the B-H curves attached, 165Oe (13200A/M) is close to saturtion for all the core materials. i.e. all three materials will give you a simlimar B field!
RE: Electromagnet contact area vs. force
The only part I need clarification is calculating the B field with the steel core in it. You said it would be 165 + Permeability X 165. Is that relative permeability? Relative MUr for 1010 steel is about 200 @ 165G, so .165 + (200 X .165) = 33.165T. Is it really that high inside the core?
RE: Electromagnet contact area vs. force
It is correct you measured B of 165 Gs using a Hall probe. Since in the air Gs = Oe, the H field generated by the solenoid is also 165 Oe.
at 165 Oe = 13,200 A/m, the steel is close to saturation, no way the relative permeability is 200, i guess it is about 100 @ 165, so the B is 165 Gs + 100x165 Gs = 16,665 Gs = 1.67 T.
RE: Electromagnet contact area vs. force
I've heard about that upper limit of 1.6T. I wonder why the data/result is off by that much in that region?
RE: Electromagnet contact area vs. force
never heard of 1.6T limit
RE: Electromagnet contact area vs. force
RE: Electromagnet contact area vs. force
TTFN

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RE: Electromagnet contact area vs. force
I said 100. so 100 x 165 = 16500 =1.65 T! 1T = 10,000 Gs, not 1000Gs
RE: Electromagnet contact area vs. force
So sorry. Thank you so much for all you help (and patience!)