Phil Newell was an early director at Virgin Records, designed and set up the first Virgin Studio in Oxfordshire [having designed and built much of the equipment himself]. He started up a seaplane taxi service on the Scottish West Coast and qualified as a commercial pilot and Master Mariner. Later he set up and ran the tonmeister faculty at Southampton University. Although he may not pass SY's strict criteria he does know what he is doing!
I'm not sure yet. I made a copper foil inductor to test Ls/Rs, but had problems preventing turn to turn shorts...the foil and kapton were both .5 inches width, it was a pita to do.
Litz wire inductors can remain linear throughout the audio band. Those, I've measured extensively.
Edit: I've attached one graph. The only caveat I can point out is the slight bump in the litz coil in the 10 to 20 Khz range, I suspect that capacitance is playing a role there. the coil was potted using an alumina filled epoxy, so has a relative permittivity of between 4 and 6. I also put this in my gallery.
jn
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I have been disappointed with commercial foil coils as well. Engineered litz coils had much higher Q at the target cut off frequency. Mine were bobbin wound and not potted. Cheaper too.
Funny you brought up the solenoid winding as I was going to ask about your opinion on that. I have made and have had made solenoid wound inductors and wondered what if any disadvantage there was to using them. They use much less wire than an air core wound inductor so you would think the dcr would be much lower but wondered if there was any reason besides marketing not to do that?
Pretty much what i have found when meauring their inductance vs freq for standard AC coils , pretty nonlinear across its bandwidth. laminate core is pretty stable but power limited. When in development foil type dont lend itself to value changes making them pretty limited unless you have multiple values ...
I have tried making my own foil inductor what a PITA ...
I'm not clear on your terminology. By solenoid, do you mean wire around magnetic material?
Any time you wind an inductor, you enhance the fields. That enhancement is gonna rear it's ugly head at some point, so further enhancement by using permeability is going to bite ya when the copper is near the metals.. I don't know which is better vs frequency, air core or iron based, when it comes to proximity effects and resistive nonlinearities. The tradeoff is probably some eeequation that is beyond me...
That's why I would go the easy route, and just litz it...and if ya use litz and a ferrite with very little eddy circulation, all the better.
jn
Okay,
I shouldn't have used that terminology. The center piece was not a magnetic material, was actually a piece of round wood dowel, 1/4" dia. with the wire wound on that rather than a large air core which turn for turn would use a much longer wire if the center diameter was something like an inch or more. At audio frequencies do we really need the large air core or does the small air gap make some other problem, again at audio frequencies?
I shouldn't have used that terminology. The center piece was not a magnetic material, was actually a piece of round wood dowel, 1/4" dia. with the wire wound on that rather than a large air core which turn for turn would use a much longer wire if the center diameter was something like an inch or more. At audio frequencies do we really need the large air core or does the small air gap make some other problem, again at audio frequencies?
I'm sorry, I should have been more specific.
When an iron core has to be used high bandwidth, it is typically made using thin sheets of iron, each insulated from it's neighbors to reduce eddy currents.
What thickness sheets comprised the glued structure that you've used in the past.
My non DC magnets use 1mm thick and .5mm thick. I made a hv transformer for a friend using an iron core of about 5 by 8 inch with about 1.5 inch by 1.5 inch section that was made using .001 inch thickness foil, that works totally cool to the touch at 20Khz and 1.5 kW of power.
Without trying to make or test anything, I also suspect that going with larger diameter would be best for solid copper wire, as it's the magnetic field energy density (and actually it's rate of change) that sideswipes the current centroid, causing the non linearity. For just solid wire, there will always be that tradeoff between DCR and AC nonlinear R. Litz stops that.
jn
Nope, component quality does not matter.
Component 'concepts' does..
Besides, I am currently winding a new testing inductor using near superconductor. You read that correctly, NEAR superconductor.
It was on the same shelf as the copper clad niobium titanium wire spool...6 inches away...Near enough?
jn
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