Timeline for How do we define resonant frequency for a circuit, that has arbitrary combination of resistors,capacitors and inductors?
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28 events
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| Jun 13, 2019 at 4:10 | vote | accept | helloworld1e. | ||
| Jun 13, 2019 at 4:11 | |||||
| Jun 12, 2019 at 12:28 | comment | added | user136077 | @LvW He wanted general rule for arbitary RLC circuit. The resonat freq is 1/(2pi) times the imaginary part of a complex conjugate pole (not my invention and others have said it as the frequency of the decaying sinusoidal oscillation in the step or impulse response. Resonance is internal buildup of reactive power that happens as in-circuit flow between energy storing components. | |
| Jun 12, 2019 at 12:21 | history | edited | user136077 | CC BY-SA 4.0 |
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| Jun 12, 2019 at 11:51 | comment | added | LvW | Are you aware that in your answer - up to now - you did not give any DEFINITION of resonance resp. the resonance frequency? (Quote: "... then the resonance appears as a complex conjugate pole pair of the transfer function"). What does this mean? Instead, you gave some examples how to detect or measure or describe some special resonance effects (in case the circuit is oscillating, which is not always the case!). I think, the questioner has asked for a clear definition which allows to calculate the resonance frequency based on a particular the circuit and the known parts values | |
| Jun 12, 2019 at 11:24 | comment | added | user136077 | @LvW there's now more | |
| Jun 12, 2019 at 8:21 | comment | added | LvW | So what? Sorry to say but that is a useless comment without any new information. The electric equivalent of a crystal has "more reactive parts" - and what is the result? We have two resonant points - one serial and one parallel, based on the definition I have quoted! | |
| Jun 11, 2019 at 19:56 | comment | added | user136077 | @LvW That's useless definition for more complex RLC circuits than one L, one C + resistors. Resonance in one LC pair can make their common reactance zero, but there can be more reactive parts. | |
| Jun 11, 2019 at 13:50 | comment | added | LvW | Microwaves101.com: "The resonance of a RLC circuit occurs when the inductive and capacitive reactances are equal in magnitude but cancel each other because they are 180 degrees apart in phase. When the circuit is at its resonant frequency, the combined imaginary component of the its admittance is zero, and only the resistive component is observed." | |
| Jun 11, 2019 at 13:38 | comment | added | LvW | But the question was about the DEFINITION! How will you measure the pole frequency? You propose to use the "pole criterion"...What does this mean in relation to the definition of resonance? Please, be more specific...how do YOU define the resonance case? | |
| Jun 11, 2019 at 12:16 | comment | added | user136077 | @LvW that way one can measure the transfer functions from the input to all parts (both voltages and currents) and the pole criterion can be used. Input voltage and current are not enough. | |
| Jun 11, 2019 at 12:08 | comment | added | LvW | Now, we are back at the beginning: How do we define resonance? Is it defined in the time domain only? What about the criterion zero phase (between V and I) ? Do we really need require complex poles for defining the resonance case? | |
| Jun 11, 2019 at 12:00 | comment | added | user136077 | @LvW 50 Ohm series resistor to L1 dampens the circuit to nonresonant, there doesn't exist decaying sinusoidal oscillation if one inputs a step or impulse. As you said, there's only real poles. There can still be a subcircuit (=L1, C1,R1) which would resonate if it was feed alone, but the whole circuit (=the test signal source, extra 50 Ohm resistor, L1, C1, R1) hasn't resonance at any frequency. | |
| Jun 11, 2019 at 11:45 | history | edited | user136077 | CC BY-SA 4.0 |
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| Jun 11, 2019 at 9:50 | comment | added | LvW | Regarding the example you have added: The situation changes drastically if you add a series resistor (50 ohms) to the inductor: (1) Zero phase between input voltage and current at 98000rad/s; (2) Current peaking at 130000 rad/s; (3) Two real poles at -41.826 and -478.100 rad/s. Question: Where is resonance? | |
| Jun 10, 2019 at 22:44 | comment | added | user136077 | @LvW it isn't a counter example. It's an example. I added something about it to the answer. | |
| Jun 10, 2019 at 22:42 | history | edited | user136077 | CC BY-SA 4.0 |
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| Jun 10, 2019 at 20:08 | comment | added | LvW | Yes - and thats the reason, you cannot use the complex pole pair ALONE for definig the case of resonance!! See my counter example. If I am wrong, the counter example must be wrong.Is it wrong? | |
| Jun 10, 2019 at 20:03 | comment | added | user136077 | What's the nominator? Zeros affect, too. | |
| Jun 10, 2019 at 19:57 | comment | added | LvW | Simple question: Don`t you agree that a conjugate-complex pole pair in the s-plane defines the "pole frequency" of a second-order filter with a phase shift of 90 deg? This is independend on realization alternatives (active or passiv, LC or RC) | |
| Jun 10, 2019 at 19:50 | comment | added | user136077 | @LvW That's definitely a resonance, a series resonant circuit+resistors, if it happens to be a LC filter. The same buildup can happen, of course, in an amp with RC feedback(=active filter) BTW In my ancient music synth the Q factor adjustment of the LOWpass filter had parameter name "Resonance" | |
| Jun 10, 2019 at 19:43 | comment | added | LvW | Quote: "...the resonance appears as a complex conjugate pole pair of the transfer function...." I think, this is not correct. Counter example: Each second-order lowpass with a Q-value Qp>0.5 has a conjugate-complex pole pair (defined by the pole frequency). But, of course, this property has nothing to do with the effect we call "resonance". In contrary, the phase shift between input and output at the pole frequency will be 90 deg. | |
| Jun 10, 2019 at 17:15 | history | undeleted | user136077 | ||
| Jun 10, 2019 at 17:15 | history | edited | user136077 | CC BY-SA 4.0 |
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| Jun 10, 2019 at 13:59 | history | edited | user136077 | CC BY-SA 4.0 |
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| Jun 8, 2019 at 23:33 | history | deleted | user136077 | via Vote | |
| Jun 8, 2019 at 23:33 | history | edited | user136077 | CC BY-SA 4.0 |
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| Jun 8, 2019 at 22:23 | history | edited | user136077 | CC BY-SA 4.0 |
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| Jun 8, 2019 at 16:37 | history | answered | user136077 | CC BY-SA 4.0 |