Core permeability and electromagnet design
Core permeability and electromagnet design
(OP)
Core permeability and electromagnet design
How much of a benefit might a higher permeability core provide and how might I improve on my electromagnet design?
I have been working on a design that uses a DC electromagnet to actuate a small armature over a small airgap.
My resources have been very limited, but I'm attempting to take it to the next level by mainting the flux of the electromagnet while reducing the power draw of a small power input.
Specs:
Core: .5" x 3" 1006 steel (unannealed)
Coil: #22 AWG / 994 turns / 231' / 3.73 ohms / 1 1/4" x 1 7/8" final dimensions
Power: 9 volt battery
Cycle: .25 second pulse every 1 second
Considerations/questions:
Core
Material:
1. 1006/1018 steel/grade 2 hex bolt: Will all these materials offer similar performance?
2. 'Pure' iron: either 99.6% or 99.95%. Would 99.95% offer significant benefit over the 99.6%? Will these materials require annealing? What increase might they offer over #1?
4. Carpenter Electrical Iron
5. CMI-C: specialty magnet iron offering lower annealing times (1 hr. vs. 2hr. vs. Carpenter material)
6. Carpenter High Permeability 49 Alloy: higher permeability/flux density nickel alloy
7. Carpenter HyMu 80 Alloy: highest initial permeability but lower max. flux density
Considering the small input, what material might offer the best reduction in power input while still producing the same flux required to actuate the armature?
With the small input, saturation is not an issue, so the HyMu might offer the greatest benefit?
Is increasing the core diameter and/or length something to consider?
At how large a diameter might the windings/low power input might not affect the core interior?
I was recently told that an airgap will negate any benefits of a a high permeability core. I find this contrary to what I know/have read. ?
Coil
Winding dimensions:
It's my understanding that windings beyond 1/2" from the core will decrease efficiency as the windings begin adding more to resistance than they provide in additional flux.
And winding length. What length begins to just add resistance rather than flux? Diameter/length recommendations?
Any other recommendations?
Thanks for reading and look forward to any/all replies!!
P.S. attached is an excellent .pdf charting various material permeabilities in FEMM.
How much of a benefit might a higher permeability core provide and how might I improve on my electromagnet design?
I have been working on a design that uses a DC electromagnet to actuate a small armature over a small airgap.
My resources have been very limited, but I'm attempting to take it to the next level by mainting the flux of the electromagnet while reducing the power draw of a small power input.
Specs:
Core: .5" x 3" 1006 steel (unannealed)
Coil: #22 AWG / 994 turns / 231' / 3.73 ohms / 1 1/4" x 1 7/8" final dimensions
Power: 9 volt battery
Cycle: .25 second pulse every 1 second
Considerations/questions:
Core
Material:
1. 1006/1018 steel/grade 2 hex bolt: Will all these materials offer similar performance?
2. 'Pure' iron: either 99.6% or 99.95%. Would 99.95% offer significant benefit over the 99.6%? Will these materials require annealing? What increase might they offer over #1?
4. Carpenter Electrical Iron
5. CMI-C: specialty magnet iron offering lower annealing times (1 hr. vs. 2hr. vs. Carpenter material)
6. Carpenter High Permeability 49 Alloy: higher permeability/flux density nickel alloy
7. Carpenter HyMu 80 Alloy: highest initial permeability but lower max. flux density
Considering the small input, what material might offer the best reduction in power input while still producing the same flux required to actuate the armature?
With the small input, saturation is not an issue, so the HyMu might offer the greatest benefit?
Is increasing the core diameter and/or length something to consider?
At how large a diameter might the windings/low power input might not affect the core interior?
I was recently told that an airgap will negate any benefits of a a high permeability core. I find this contrary to what I know/have read. ?
Coil
Winding dimensions:
It's my understanding that windings beyond 1/2" from the core will decrease efficiency as the windings begin adding more to resistance than they provide in additional flux.
And winding length. What length begins to just add resistance rather than flux? Diameter/length recommendations?
Any other recommendations?
Thanks for reading and look forward to any/all replies!!
P.S. attached is an excellent .pdf charting various material permeabilities in FEMM.
Talk To Other Members
RE: Core permeability and electromagnet design
I assumed the 1.875 dimension was the coil OD and the 1.25 dimension the coil height. You should have a 17.75w coil with about 1956 amp-turns, correct?
To reduce the effect of total wire length and resistance you might wind a larger diameter wire part way through the coil. But that will make the diameter grow faster. I don't know of any rule concerning 1/2 inch thickness of coil. One simply works with whatever thickness it works out to be.
Your coil would get very hot if you were running continuous. However with a 25% duty cycle it looks, maybe, okay. Have you calculated the inductance and rise time of the coil. Can it see peak current at 9VDC in 0.25 seconds? That will change with the linkage to the core.
Mike
RE: Core permeability and electromagnet design
My apologies, the final coil dimensions are:
1.25" Diameter x 1.875 Length
The airgap is 1/8" and the armature is 1.5"x1.5"
The inductance is 6.625 mH
The power draw as read by meter:
5V @ 2A = 10W (with a fresh 9V battery)
994T x 2A = 1988 AT
Wire gauges of #30 AWG, #28, #26, #24 and #22 have been tested. The #22 performs the best. As max. current of the 9V battery (2A) is achieved with #22, larger size wire beyond this/smaller resistance won't offer any benifits?
Tx