Mutual Inductance WPT system of coaxial spiral coils
In general, the extraction of parameters of an EM system having a non-trivial geometry is obtained by measurement with field solver simulator tools, which intrinsically use iterative processes, instead of making a mathematical analysis that would hardly be able to give this result in the form of an explicit function for this parameter.
Can you suggest me some program that does this measurement?
There you go:
That was extracted from Optimal coil size ratios for wireless power transfer applications - IEEE.
Spiral coils are relatively simple geometries. However, the above formula is still an aproximation. FEM software must be used for more accurate results, as andre_teprom suggests.
I'm not very familiar with this segment of electronics, but the little I've seen from this tool I found it very powerful for a free sofftware and perhaps you could take some results with it..
For best transfer efficiency in WPT, only to find the coupling between two round coils is not enough.
Important factors are: the shape of the coils, the number of coils (you can have more coils in parallel), the turns spacing, the ferrite core used to improve magnetic coupling, the shape of the core to minimize the extraneous magnetic flux, etc.
You've got 4 ports.Download Sonnet EM simulator for free and find the couplings and other stuffs by simulation.
Calculation will give you an insight but simulation will be much more realistic.
www.sonnetsoftware.com
Exactly, although as usual we aim to be accurate in the modeling of the phenomenon, the mathematical complexity is always such that at certain stage we are tempted to simplify it with specific assumptions (eg: wire gap much smaller than coils distance, etc ...), which ends loosing part of the general characteristic of the solution.
I really like Sonnet, but this circular model is just too big (in memory requirement) to analyze in the free Lite version. You would need conformal mesh, and that is only available in Sonnet Professional.
Can you suggest an EM simulator tool just to measure coupling,loss of two inductors (wireless transmission) with distance, turns and frequency.
Sonnet Professional (the commercial version, not the free Lite) is fine. For my own work, I used ADS Momentum to optimize inductors for wireless power transfer (Qi).