Mutual inductance vs coupling coefficient - Electrical Engineering Stack Exchange most recent 30 from electronics.stackexchange.com 2019-08-24T22:25:22Z https://electronics.stackexchange.com/feeds/question/408234 http://www.creativecommons.org/licenses/by-sa/3.0/rdf https://electronics.stackexchange.com/q/408234 1 Mutual inductance vs coupling coefficient Raitis Bērziņš https://electronics.stackexchange.com/users/163315 2018-11-22T13:17:04Z 2018-11-22T19:52:15Z <p>Question regarding <a href="https://electronics.stackexchange.com/questions/213138/equivalent-inductance">this</a> and <a href="https://electronics.stackexchange.com/questions/308286/two-solenoid-coils-and-ferrite-rod-how-to-calculate-mutual-inductance-or-coupli">this</a> question about mutual inductance and coupling coefficient. </p> <p>I'm trying to analyse a two coil system: <a href="https://i.stack.imgur.com/VPQ7R.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VPQ7R.png" alt="enter image description here"></a></p> <p>It consists of two coils like in the picture with 2 cm air gap between them. </p> <p><a href="https://i.stack.imgur.com/B8mDD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/B8mDD.png" alt="enter image description here"></a></p> <p>I want to find out the mutual inductance and the coupling coefficient. I'm confused, because, from my understanding, to calculate the mutual inductance, we need to know the coupling coefficient:<br> <img src="https://chart.googleapis.com/chart?cht=tx&amp;chl=M%3Dk%5Csqrt%7BL1L2%7D" alt="enter link description here"> </p> <p>But to calculate the coupling coefficient, we need to know the mutual inductance. </p> <p>Experimentaly, how should I measure coupling coefficient and mutual inductance between these two planar coils?</p> https://electronics.stackexchange.com/questions/408234/-/408239#408239 2 Answer by Andy aka for Mutual inductance vs coupling coefficient Andy aka https://electronics.stackexchange.com/users/20218 2018-11-22T13:50:06Z 2018-11-22T14:05:40Z <blockquote> <p>Experimentaly, how should I measure coupling coefficient and mutual inductance between these two planar coils?</p> </blockquote> <p>You start by recognizing that with no load, and perfect coupling (100%), the output voltage from coil 2 is slightly less than the input voltage to coil 1. This is because the two inductances are not the same (24uH to 20uH) and this results in a turns ratio of 1.0954:1.</p> <p>In other words the square root of the inductance ratio is the voltage coupling ratio (turns ratio) when the two coils are perfectly coupled. So, with 1 volt p-p on coil 1, coil 2 produces 0.9129 volts p-p into an open circuit load.</p> <p>When the two coils are not perfectly coupled (say 50% coupling), coil 2 only receives 50% of the flux generated by coil 1 hence, the output voltage will be half of 0.9129 volts i.e. 0.4564 volts p-p.</p> <p>So, you can use the voltage level on coil 2 for predicting the coupling factor but, be aware of parasitic capacitance - if you are anywhere close to the natural resonant frequency of either coil you will get voltage magnification effects that ruin the ability to predict the coupling factor.</p> <p>Try and use the lowest frequency you can for this experiment and stay way-below resonances.</p> https://electronics.stackexchange.com/questions/408234/-/408307#408307 0 Answer by Pojj for Mutual inductance vs coupling coefficient Pojj https://electronics.stackexchange.com/users/178941 2018-11-22T19:52:15Z 2018-11-22T19:52:15Z <p>You can measure mutual inductance with only use of an LCR meter (or impedance analyzer). Use the following wiring while the coil position is fixed. Mutual inductance will be quarter of the difference between two readings.</p> <p><img src="https://i.stack.imgur.com/f1Qvp.png" alt="schematic"></p> <p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2ff1Qvp.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p>