# Re: LCLR Resonance...

```Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 09:21 PM 9/26/2006, you wrote:
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```Dear forum members,

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Yesterday, I tried to simulating the behavior of a LCLR circuit using PSPice. I connected a LCLR circuit to an AC source (sine wave generator). The analysis type was 'AC sweep'. Using PSpice, I plotted various graphs with Frequency on the x-axis and the following three parameters in Y-axis:
```1. Current through Parallel Inductor (inductor in tank circuit)
2. Current through Parallel Capacitor (capacitor in tank circuit)
3. Current through Series inductor.

My understanding is that at resonance:
1. The current through the tank circuit's L and C will be same.
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2. The tank circuit's (either through L or C) will be IN PHASE with the input sine wave source.
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I am not sure of the "exact" circuit you have, but the above is only true if the circuits are tuned to resonate exactly at the same frequency as the sine wave.
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```Question:
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I noticed that at resonant frequency the current through the Series inductor was not IN PHASE with the input AC (sine wave) source. The phase difference between the AC source and the current through the series inductor was approximately 90 degrees. Is that true?
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Yes, that will always be true.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/phase.html

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Also, I have read in some SSTC articles that explains the use of PLL to auto-tune the coil. Is it possible to use the current through the series inductor as the feedback signal?
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Certainly through the "primary" inductor.

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One thing I noticed is that at resonance, the series inductor current is not in phase with the ac sine wave source. I can use the current through the Tank circuit's L or C will be in phase at resonance and it can act as a feedback (either using an antenna or current transformer). But, I would like to use the series inductor's current to lock to the resonant frequency. Please let me know your suggestions.
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I am not sure where this "series" inductor is in the circuit.

Cheers,

Terry

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```Thanks and regards,
Raj.

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