Talk:Resonant inductive coupling

Rename article

I think I'm going to move the article ["Resonant energy transfer"] to resonant inductive coupling or resonant transformer. It seems to be a better name; there's other resonant energy transfers that are not inductive.- Wolfkeeper 23:57, 12 November 2009 (UTC)

I agree. One method of "Resonant energy transfer" is "resonant inductive coupling." Two other methods of "Resonant energy transfer" are "Electrical conduction" by means of a "Terrestrial transmission line with atmospheric return circuit" and "Electrical conduction by means of a "Terrestrial single-conductor surface wave transmission line." Because the article or page "Resonant energy transfer" deals exclusively with the "Resonant induction method" it should be renamed or moved to "Resonant inductive coupling." -- GaryPeterson (talk) 16:42, 28 November 2010 (UTC)

I think that this phenomenon is similar with the micro power transformer magnetic characteristics. So It should be called "Synchronized Magnetic Phase Coupling". Please refer this URL[1]. --Neotesla (talk) 08:52, 15 June 2014 (UTC)

References

Could someone please change the source for reference 6. The maximum link efficiency had already been derived at least 4 years earlier in 'K. Van Schuylenbergh, R. Puers, "Inductive Powering - Basic Theory and Application to Biomedical Systems", 2009' and there is no reason why WiTricity's white paper should be the source. — Preceding unsigned comment added by 137.222.185.147 (talk) 11:42, 28 January 2015 (UTC)

Re-writing Coupling Coefficient subheading

The sub-heading 'Coupling Coefficient' needs re-writing. Simply look to the first sentence to see why:

"Well misunderstood, the coupling coefficient is often said to be the ratio of flux interlinking to the secondary coil, but it is a misunderstanding."

There's no reason at all to suggest a misunderstanding in an informative article, never-mind book-ending it like that.

The section is also unclear at points: "The coupling coefficient is fixed by the positional relationship between the coil and the coil."

and uses a lot of unexplained technical language: "the coupling coefficient does not change between when the system is in the resonance state and when it is not in the resonance state, but the ratio between the mutual flux and the leakage flux changes greatly."

There are also no citations anywhere in the section.

I would edit this myself, but I do not have sufficient experience to be able to explain these terms.

209.6.37.209 (talk) 15:55, 28 December 2016 (UTC)

I've removed that first sentence which is plain WP:WEASEL but I don't think it has helped much. The closest it ever comes to actually defining anything is "the coupling coefficient is the ratio to the component that becomes mutual inductance in the coil inductance". Not at all clear to me whether that is the same as the usual definition of M/root(L1L2). A ratio is a ratio between two things and "the component that becomes mutual inductance" is only one thing. SpinningSpark 00:30, 8 January 2017 (UTC)

The coupling coefficient in electromagnetism is the ratio of inductance. This is obvious by looking at the diagram of the equivalent circuit of the transformer and we can be easy understood by referring to the several formura. If necessary I will be possible to indicade a lot of literature. And the coupling coefficient does not directly indicate the magnetic flux ratio.118.236.168.22 (talk) 04:03, 8 January 2017 (UTC)

The ratio of what inductances? The self-inductances of the two windings? That's not going to give sensible results; the coupling coefficient won't change if you put one coil on the Moon and leave the other on Earth. So please, state this as a proper mathematical expression in terms of the measurables of the circuit, or else link to an online source that does so. Otherwise, I'm inclined to wipe the whole section and replace it with something that makes sense. The inductance article makes a much better fist of this. SpinningSpark 10:47, 8 January 2017 (UTC)

The description of the leakage factor which is in the article of the leakage inductance is not good at all. Very rudimentary mistakes were found. The dimensions of the physical quantity did not match in the formula. Inductance ratio is the ratio of mutual inductance and leakage inductance. First the following formula was shown.

σ_P = Φ_P^σ/Φ_M = L_P^σ/L_M

σ_S = Φ_S^σ'/Φ_M = L_S^σ'/L_M

The dimensions of the physical quantity[2] of the magnetic flux is,

kg m² s^-2 A^-1

The dimension of the inductance is,

kg m² s^-2 A^-2

Obviously the dimensions are different. So I reviewed it as follows,

$\sigma _{P}={\frac {\phi _{P}^{\sigma }}{\phi _{M}}}={\frac {L_{P}^{\sigma }i_{P}}{L_{M}i_{M}}}$

$\sigma _{S}={\frac {\phi _{S}^{\sigma }}{\phi _{M}}}={\frac {L_{S}^{\sigma }i_{S}}{L_{M}i_{M}}}$

The dimensions are now matched. And it became a general relational expression that appears in many textbook. Is it necessary to present any literature on this general formula?118.236.168.22 (talk) 11:40, 8 January 2017 (UTC)

I searched for a while, and I found a source which is simply described about the relation of inductance, winding current and flux.[3]

$\phi =LI$

118.236.168.22 (talk) 12:16, 8 January 2017 (UTC)

We don't seem to be getting any closer to a definition of coupling coefficient. SpinningSpark 14:36, 8 January 2017 (UTC)

If Cblambert does not Insist his own creation about the Leakage factor, the difinition of the coupling coefficient has no problem as follows,

Leakage_inductance#Leakage inductance and coupling coefficient

$L_{oc}^{pri}=L_{P}=L_{P}^{\sigma }+L_{M}$

where

$L_{P}^{\sigma }=L_{P}\cdot {(1-k)}$

$L_{M}=L_{P}\cdot {k}$

and

$L_{oc}^{pri}$ = Primary inductance

$L_{P}$ = Primary self-inductance

$L_{P}^{\sigma }$ = Primary leakage inductance

$L_{M}$ = Magnetizing inductance referred to the primary

Leakage factor is not related to coupling coefficient. In this article, it is sufficient to state that the value of the coupling coefficient does not change even if it resonates or does not resonate.118.236.168.22 (talk) 15:38, 8 January 2017 (UTC)

You keep banging on about leakage factor not being relevant. That is half the problem with this article, it talks about what is not relevant ahead of talking about what is, and never quite gets to the point.

You have not given a definition in terms of measurables. You have used coupling coefficient to define a new thing (magnetizing inductance) which is not a measurable. I prefer the explanation in the inductance article which defines mutual inductance and coupling coefficient in terms of the two-port voltages and currents. I think the best solution is to reduce the description here to a sentence giving the definition in the inductance article and link that as {{main article}}. There is no point in having the same thing described in detail in two places, especially as one of them is so badly done. SpinningSpark 16:48, 8 January 2017 (UTC)

At here, we need to think about the purpose of using the coupling coefficient. Even with the same content, the explanation will be different if it is described mathematically, academically or explained to the electronic design engineer. The above link to the coupling coefficient is not academic, but very practical. The important thing is that there is no theoretical contradiction between there. The coupling coefficient in this article have to be consistent with them, but furthermore it is necessary to adapt the expression and the explanation for the purpose of understanding wireless power transfer. As it is written by several writers, it is very coarse so far, but it will be a useful section by enriching links in this field.121.2.184.184 (talk) 01:58, 9 January 2017 (UTC)

"Magnetizing inductance referred to the primary" is written by another writer and I would like to write "Mutual inductance referred to the primary" if it is me.121.2.184.184 (talk) 02:22, 9 January 2017 (UTC)

What does that even mean? A transformer is a reciprocal device which leads to mutual inductance being numerically equal in both directions. There is no "referred to the primary". That phrase only has meaning for impedances that originate on the secondary and are transformed by the transformer ratio as seen from the primary. That does not apply to mutual inductance. Yes, you can use the coupling coefficient to divide the inductance into a part that couples and a part that does not (your comment about how these have been named really doesn't matter for this discussion) but that does not mean you can use that as a definition of coupling coefficient. Those inductances don't really exist, they are purely notional. You can't connect a voltmeter on the node between them because it doesn't actually exist. So I say just say in this article that you are notionally dividing the inductance by the coupling ratio and link to the inductance article for an explanation of coupling coefficient. The diagram has to go as well, marking the k fraction of the inductance as M (implying mutual) is just plain wrong. SpinningSpark 14:31, 9 January 2017 (UTC)

Probably I think that it is better to do it according to your thinking as to the correction of this part. I just wanted to correct the description that "the coupling coefficient is the fraction of the flux of the primary that cuts the secondary coil". Because it means that "the ratio of the effective flux reaching the secondary side of the total flux generated at the primary side".121.2.184.184 (talk) 16:43, 9 January 2017 (UTC)

Ratio of mutual flux and leakage flux

I have removed this from the article "but the ratio between the mutual flux and the leakage flux changes significantly. Specifically, mutual flux increases significantly when the system is in a resonant state." Why do we need to say this? The transformer coupling coefficient is defined purely in relation to the transformer, not the resonant circuits. It is defined under open circuit conditions (so there can be no question of resonance) and under open circuit conditions the ratio of leakage and mutual flux does stay constant with applied voltage. It can only get to be different if a load is applied. True, that load can be a resonating capacitor, but stating this in the section about the transformer is very misleading. SpinningSpark 16:38, 9 January 2017 (UTC)

You mentioned the description as "This leads to the voltage appearing at the secondary being less than predicted by the turns ratio of the windings.", but in WPT (wireless power transfer), it is the "Resonant inductive couplingIng" that there is a phenomenon that the voltage is higher than the predicted turns ratio.--121.2.184.184 (talk) 17:04, 9 January 2017 (UTC)

Not under secondary open-circuit conditions there can't, because there can't be any resonance in the first place. SpinningSpark 17:11, 9 January 2017 (UTC)

Then, it is better to supplement that a voltage higher than the voltage expected by the turns ratio appears on the secondary side when the system is in the resonance state.--121.2.184.184 (talk) 17:20, 9 January 2017 (UTC)

The diagram of Resonant coupling

The parallel capacitor Cs on the primary side has no meaning. It should be removed.--121.2.184.184 (talk) 17:37, 9 January 2017 (UTC)