Air coupled inductors for power transfer applications
I'm new to electromagnetic simulation, at now I can use FEMM or Maxwell software to to EM simulation or other ones if someone have some other suggest.
I've to design a air coupled link to transmit power for recharge a movable unit, what I like to do is a fixed coil with inner diameter of approx 42 mm, outer diameter is not a problem, then I've to couple this coil (fixed with a moving part) with another one fixed to the plant which must send the power to the moving one.
Of course the charging stage is only when the moving part is into the homing position and in this situation the two coils are one inside the other.
What I need to simulate and then know is the best coil turn number for the primary and the secondary coil that is able to maximize the power trough the system. First coil can be powered by using a push-pull topology, on the secondary side we've a bridge and the battery charger circuit (a series of 5 cells of NiMeH coin battery in order to have 6.0 V).
Does anyone have try a similar simulation or setup? Could you please gimme some hint how to start? Referring the attached drawing of the system we need to optimize the diameter D2, d1, D1 and the length L, the only constrainst is about the inner diameter of the secondary coil that should be fixed to 42 mm.
Thanks to all that can give me some hint, help in that sense. All the info regarding this project should be free and I'll post all the final result if we're able to get it working.
Best regards
F.F. a.k.a. Powermos
Do you have a reason to use a particular frequency or are you just trying to minimize the coil effort? I think, in most cases the simulation will reduce to simple rotation symmetric AC magnetics. Self and mutual inductance of coils are the basic parameters, may be skin and proximity effect losses for power applications.
Simple rotation symmetric AC magnetic problems can be solved with free tools or e. g. Quickfield student version. It could also be solved analytically by integrating basic induction rules.
Technical magnectic power transmission solution are using cores to concentrate the field, this may be helpful also in your application. It may allow lower operation frequency and more simple electronic, also probably avoid thinking about RF regulations.
@FvM
thanks for reply, do you've some paper reference or link where I can take a look about the last proposal "Technical magnectic power transmission solution "?
About working frequency there is no problem, my only constraints is about the inner diameter of the secondary coil.
Thank again
F.F. a.k.a. Powermos
I've no literature at hand. I remember some design I saw previously. Do I understand right that your design is constrained to a coaxial arrangement with a cylindrical shape of the moving part? Could you also use an axial transmission direction at the bottom of the inner cylinder? It could easily use ferrite pot cores to concentrate the field then. How about the transmitted power requirement?
Moving the inner coil will change the mutual inductance. Grover has a book on all aspects of inductors.
The battery charging stage is when the system is into the homing position as I've show into the drawings, there is no moving element when the system is into the homing, of course the coupling will change when the module is going away from the primary coil and when this one is returning but this is not important because the charging will be done with the secondary coil stop into the primary one, as I've drawn.
Also we can think to done the charging with the two coils arranged in a axial way and not concentric as I've supposed now, there is no matter about the coil disposition, just one constrainte have to be taken in account, the inner diameter must be equal to 42 mm.
Thanks again
F.F. a.k.a. Powermos