Series LC frequency/voltage dependance

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Discussion Overview

The discussion revolves around the frequency dependence of series and parallel LC circuits in relation to changes in voltage. Participants explore whether voltage affects the resonant frequency and the implications for circuit design, particularly in maintaining a constant frequency across varying voltage and current levels.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether changes in voltage affect the frequency of series or parallel LC circuits, suggesting that frequency may depend solely on capacitance and inductance.
  • Another participant argues that as long as voltage increases do not lead to saturation of the inductor or other non-linear effects, the resonant behavior should not depend on voltage amplitude.
  • A participant acknowledges a misunderstanding regarding impedance in series and parallel LC circuits, noting that series LC circuits have the least impedance at resonance, while parallel LC circuits behave oppositely.
  • One participant expresses a need for their series LC circuit to maintain a constant frequency despite varying voltage and current, indicating that the capacitor should be the primary means of frequency control.
  • Another participant advises ensuring the inductor does not approach saturation at high excitation levels to maintain frequency stability.

Areas of Agreement / Disagreement

Participants express differing views on the impact of voltage on frequency, with some suggesting it is independent while others imply that saturation effects could introduce complications. The discussion remains unresolved regarding the extent to which voltage affects frequency in practical applications.

Contextual Notes

Participants reference the need for observational evidence and practical design considerations, such as inductor saturation and core material properties, but do not reach a consensus on the theoretical implications.

artis
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I think I have mistaken something here but does changes in voltage affect the frequency of a series LC or parallel LC circuit or not?
Or is the frequency only dependent on capacitance and inductance of the circuit elements?

And if the fed in frequency matches the resonant frequency then the LC circuit reactance drops to zero ohms and only the ohmic wire resistance is left right?
 
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artis said:
I think I have mistaken something here but does changes in voltage affect the frequency of a series LC or parallel LC circuit or not?
Or is the frequency only dependent on capacitance and inductance of the circuit elements?
That depends. As long as the increase in amplitude of the voltage waveform does not cause an increase in current levels that result in saturation of the inductor (or cause some other non-linear effect), then the resonant behavior of the LC circuit will not depend on the amplitude of the voltages involved. Do you think you have observational evidence to the contrary?
artis said:
And if the fed in frequency matches the resonant frequency then the LC circuit reactance drops to zero ohms and only the ohmic wire resistance is left right?
What reading have you been doing to answer this question? You could use a simple Google Images search to help you see the impedance of series and parallel LC circuits, for example.
 
Ok, my bad , quick search reminded me that it was the series LC that had the least impedance as it approached it's resonant frequency while the parallel LC did exactly the opposite. Lucky for me my case involves the series LC.
I don't have any observational experience but part of what I'm making involves a series LC which would ideally have to hold it's frequency constant over a range or voltage/current values, ideally I should only be able to control the frequency with the help of the capacitor.

Think of the inductor in my case like a transformer winding and the capacitor being in series with it, now the strength of flux around my winding will change so the voltage in the winding and current will most likely change over some range but the circuit itself should be set so that it resonates with a certain frequency. The good thing is that my core flux is directly linked to my series LC resonant frequency whatever it will be.
 
artis said:
part of what I'm making involves a series LC which would ideally have to hold it's frequency constant over a range or voltage/current values
Then you need to ensure that the inductor does not get close to saturation at the highest excitation levels. You may need to make it a bit oversize (bigger core area, lower mu material) to ensure that.
 
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