I am just wondering on what are the factors affecting the inductance in a coil. Based on my experience, loop diameter, wire diameter, number of turns, and gap between turns will affect affect the inductance. However, I have not seen formula of calculating the inductance of a coil that involves all the affecting factors. Thanks for your reply.
Inductance could be given as variation of flux with variation of current (L= do/di). Flux development depend on reluctance offered by circuit, and reluctance depends on the factors you discussed. Increased gap between turn could increased reluctance or decreased the inductance.Hence before thinking of inductance, one, has to think of changing in offered reluctance of circuit... ..
Long gap between the turns means more lengthy coil and it means less inductance. On the other hand if you fix the length then long gap means less number of turns and it cause to decrease the inductance. In fact, inductance is inversely proportional to coil length and directly proportional to the square of the number of turns in the coil.
Please consider the following
1. The self and mutual inductance of two single coils will depend on the topology ,
medium and various dimensions , as well as boundary conditions.
2. An accurate determination of self/ mutual inductances in 1 above would require afield analysis .
3 However if some simplifying assumptions are made , say air cored/ magnetic core and we approximate the field pattern it should be possible to derive self and mutual inductances of the two coils. The formula would show that a larger distance between coils will reduce mutual coupling.or even gap between coil and core.
4. Armed with formula for two coils as in 3 , it should be possible to use circuit theory to workout the total inductance.
5 Not directly connected with q but a somewhat difficult problem to comprehend is to assume two elemental conductors carrying current and then to analyze the inductances.. Of course this is a theoretical situation as elemental currents with no closed loops are not allowed in circuit theory.
5 As an aside I think there are some classic formulas given in a book on Inductance calculation:
"Inductance Calculations (Dover Books on Electrical Engineering) Kindle Edition
by Frederick W Grover (Author) "
Good Luck
Cheers
if we assume that the shape of coil was a solenoid
By ignoring the effects at the edges of the solenoid, with μ0 is the permeability, N the number of turns, i the current and l the length of the solenoid.
L=µ*N²*A/l
l=(section of cable+gap) * N-1gap
section of cable could be defined according to the wire is covered or not(heat dessipation and maximum temperature),the maximum current and the conductive metal resistor .
generaly copper is used, you could find tables in the net for the section of cable.
maximum dV/dt defines inductor-wind’s gap or insulation.
Losses in the magnetic core defines core’s material.
Good Luck
Yes, of course - to some extent. The effect is even used for fine tuning In VHF/UHF circuits - just by compression/extension of the helical coil. The coil is an energy accumulator - it turns the electrical energy into magnetic field and vice versa. If the gap between adjacent turns is small, the magnetic bounding between turns is stronger and the inductance increase.
The more turns, the more inductance, yes, but only up to a limit since the more turns, the higher AC resistivity (Eddy+Skin+Proximity effects) and the worse is your I, your efficiency and your Q. Probably the shortest way is a bit of experimentation and good instrumentation though.
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